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diff --git a/doc/rfc/rfc4037.txt b/doc/rfc/rfc4037.txt new file mode 100644 index 0000000..050e145 --- /dev/null +++ b/doc/rfc/rfc4037.txt @@ -0,0 +1,3139 @@ + + + + + + +Network Working Group A. Rousskov +Request for Comments: 4037 The Measurement Factory +Category: Standards Track March 2005 + + + Open Pluggable Edge Services (OPES) Callout Protocol (OCP) Core + +Status of This Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (2005). + +Abstract + + This document specifies the core of the Open Pluggable Edge Services + (OPES) Callout Protocol (OCP). OCP marshals application messages + from other communication protocols: An OPES intermediary sends + original application messages to a callout server; the callout server + sends adapted application messages back to the processor. OCP is + designed with typical adaptation tasks in mind (e.g., virus and spam + management, language and format translation, message anonymization, + or advertisement manipulation). As defined in this document, the OCP + Core consists of application-agnostic mechanisms essential for + efficient support of typical adaptations. + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 1.2. OPES Document Map . . . . . . . . . . . . . . . . . . . 5 + 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . 6 + 2. Overall Operation . . . . . . . . . . . . . . . . . . . . . . 7 + 2.1. Initialization . . . . . . . . . . . . . . . . . . . . . 7 + 2.2. Original Dataflow . . . . . . . . . . . . . . . . . . . 8 + 2.3. Adapted Dataflow . . . . . . . . . . . . . . . . . . . . 8 + 2.4. Multiple Application Messages . . . . . . . . . . . . . 9 + 2.5. Termination . . . . . . . . . . . . . . . . . . . . . . 9 + 2.6. Message Exchange Patterns . . . . . . . . . . . . . . . 9 + 2.7. Timeouts . . . . . . . . . . . . . . . . . . . . . . . . 10 + 2.8. Environment . . . . . . . . . . . . . . . . . . . . . . 11 + 3. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 + + + +Rousskov Standards Track [Page 1] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + 3.1. Message Format . . . . . . . . . . . . . . . . . . . . . 12 + 3.2. Message Rendering . . . . . . . . . . . . . . . . . . . 13 + 3.3. Message Examples . . . . . . . . . . . . . . . . . . . . 14 + 3.4. Message Names . . . . . . . . . . . . . . . . . . . . . 15 + 4. Transactions . . . . . . . . . . . . . . . . . . . . . . . . . 15 + 5. Invalid Input . . . . . . . . . . . . . . . . . . . . . . . . 16 + 6. Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 6.1. Negotiation Phase . . . . . . . . . . . . . . . . . . . 17 + 6.2. Negotiation Examples . . . . . . . . . . . . . . . . . . 18 + 7. 'Data Preservation' Optimization . . . . . . . . . . . . . . . 20 + 8. 'Premature Dataflow Termination' Optimizations . . . . . . . . 21 + 8.1. Original Dataflow . . . . . . . . . . . . . . . . . . . 22 + 8.2. Adapted Dataflow . . . . . . . . . . . . . . . . . . . . 23 + 8.3. Getting Out of the Loop . . . . . . . . . . . . . . . . 24 + 9. Protocol Element Type Declaration Mnemonic (PETDM) . . . . . . 25 + 9.1 Optional Parameters . . . . . . . . . . . . . . . . . 27 + 10. Message Parameter Types . . . . . . . . . . . . . . . . . . . 28 + 10.1. uri. . . . . . . . . . . . . . . . . . . . . . . . . . 28 + 10.2. uni. . . . . . . . . . . . . . . . . . . . . . . . . . 28 + 10.3. size . . . . . . . . . . . . . . . . . . . . . . . . . 29 + 10.4. offset . . . . . . . . . . . . . . . . . . . . . . . . 29 + 10.5. percent . . . . . . . . . . . . . . . . . . . . . . . 29 + 10.6. boolean. . . . . . . . . . . . . . . . . . . . . . . . 30 + 10.7. xid . . . . . . . . . . . . . . . . . . . . . . . . . 30 + 10.8. sg-id. . . . . . . . . . . . . . . . . . . . . . . . . 30 + 10.9. modp. . . . . . . . . . . . . . . . . . . . . . . . . 30 + 10.10. result. . . . . . . . . . . . . . . . . . . . . . . . 30 + 10.11. feature . . . . . . . . . . . . . . . . . . . . . . . 32 + 10.12. features. . . . . . . . . . . . . . . . . . . . . . . 32 + 10.13. service . . . . . . . . . . . . . . . . . . . . . . . 32 + 10.14. services. . . . . . . . . . . . . . . . . . . . . . . 33 + 10.15. Dataflow Specializations. . . . . . . . . . . . . . . 33 + 11. Message Definitions . . . . . . . . . . . . . . . . . . . . . 33 + 11.1. Connection Start (CS) . . . . . . . . . . . . . . . . 34 + 11.2. Connection End (CE) . . . . . . . . . . . . . . . . . 35 + 11.3. Service Group Created (SGC) . . . . . . . . . . . . . 35 + 11.4. Service Group Destroyed (SGD) . . . . . . . . . . . . 36 + 11.5. Transaction Start (TS). . . . . . . . . . . . . . . . 36 + 11.6. Transaction End (TE). . . . . . . . . . . . . . . . . 36 + 11.7. Application Message Start (AMS) . . . . . . . . . . . 37 + 11.8. Application Message End (AME) . . . . . . . . . . . . 37 + 11.9. Data Use Mine (DUM) . . . . . . . . . . . . . . . . . 38 + 11.10. Data Use Yours (DUY). . . . . . . . . . . . . . . . . 39 + 11.11. Data Preservation Interest (DPI). . . . . . . . . . . 39 + 11.12. Want Stop Receiving Data (DWSR) . . . . . . . . . . . 40 + 11.13. Want Stop Sending Data (DWSS) . . . . . . . . . . . . 41 + 11.14. Stop Sending Data (DSS) . . . . . . . . . . . . . . . 41 + 11.15. Want Data Paused (DWP). . . . . . . . . . . . . . . . 42 + + + +Rousskov Standards Track [Page 2] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + 11.16. Paused My Data (DPM). . . . . . . . . . . . . . . . . 43 + 11.17. Want More Data (DWM). . . . . . . . . . . . . . . . . 43 + 11.18. Negotiation Offer (NO). . . . . . . . . . . . . . . . 44 + 11.19. Negotiation Response (NR) . . . . . . . . . . . . . . 45 + 11.20. Ability Query (AQ). . . . . . . . . . . . . . . . . . 46 + 11.21. Ability Answer (AA) . . . . . . . . . . . . . . . . . 46 + 11.22. Progress Query (PQ) . . . . . . . . . . . . . . . . . 47 + 11.23. Progress Answer (PA). . . . . . . . . . . . . . . . . 47 + 11.24. Progress Report (PR). . . . . . . . . . . . . . . . . 48 + 12. IAB Considerations . . . . . . . . . . . . . . . . . . . . . 48 + 13. Security Considerations . . . . . . . . . . . . . . . . . . . 48 + 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 + 15. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . 50 + 15.1. Extending OCP Core . . . . . . . . . . . . . . . . . . 51 + A. Message Summary . . . . . . . . . . . . . . . . . . . . . . . 52 + B. State Summary . . . . . . . . . . . . . . . . . . . . . . . 53 + C. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 54 + 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 54 + 16.1. Normative References . . . . . . . . . . . . . . . . . 54 + 16.2. Informative References . . . . . . . . . . . . . . . . 54 + Author's Address. . . . . . . . . . . . . . . . . . . . . . . . . 55 + Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . 56 + +1. Introduction + + The Open Pluggable Edge Services (OPES) architecture [RFC3835] + enables cooperative application services (OPES services) between a + data provider, a data consumer, and zero or more OPES processors. + The application services under consideration analyze and possibly + transform application-level messages exchanged between the data + provider and the data consumer. + + The OPES processor can delegate the responsibility of service + execution by communicating with callout servers. As described in + [RFC3836], an OPES processor invokes and communicates with services + on a callout server by using an OPES callout protocol (OCP). This + document specifies the core of that protocol ("OCP Core"). + + The OCP Core specification documents general application-independent + protocol mechanisms. A separate series of documents describes + application-specific aspects of OCP. For example, "HTTP Adaptation + with OPES" [OPES-HTTP] describes, in part, how HTTP messages and HTTP + meta-information can be communicated over OCP. + + Section 1.2 provides a brief overview of the entire OPES document + collection, including documents describing OPES use cases and + security threats. + + + + +Rousskov Standards Track [Page 3] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +1.1. Scope + + The OCP Core specification documents the behavior of OCP agents and + the requirements for OCP extensions. OCP Core does not contain + requirements or mechanisms specific for application protocols being + adapted. + + As an application proxy, the OPES processor proxies a single + application protocol or converts from one application protocol to + another. At the same time, OPES processor may be an OCP client, + using OCP to facilitate adaptation of proxied messages at callout + servers. It is therefore natural to assume that an OPES processor + takes application messages being proxied, marshals them over OCP to + callout servers, and then puts the adaptation results back on the + wire. However, this assumption implies that OCP is applied directly + to application messages that OPES processor is proxying, which may + not be the case. + + OPES processor scope callout server scope + +-----------------+ +-----------------+ + | pre-processing | OCP scope | | + | +- - - - - - - - - - - - - - - - - - -+ | + | iteration | <== ( application data ) ==> | adaptation | + | +- - - - - - - - - - - - - - - - - - -+ | + | post-processing | | | + +-----------------+ +-----------------+ + + An OPES processor may preprocess (or postprocess) proxied application + messages before (or after) they are adapted at callout servers. For + example, a processor may take an HTTP response being proxied and pass + it as-is, along with metadata about the corresponding HTTP + connection. Another processor may take an HTTP response, extract its + body, and pass that body along with the content-encoding metadata. + Moreover, to perform adaptation, the OPES processor may execute + several callout services, iterating over several callout servers. + Such preprocessing, postprocessing, and iterations make it impossible + to rely on any specific relationship between application messages + being proxied and application messages being sent to a callout + service. Similarly, specific adaptation actions at the callout + server are outside OCP Core scope. + + This specification does not define or require any specific + relationship among application messages being proxied by an OPES + processor and application messages being exchanged between an OPES + processor and a callout server via OCP. The OPES processor usually + provides some mapping among these application messages, but the + processor's specific actions are beyond OCP scope. In other words, + this specification is not concerned with the OPES processor role as + + + +Rousskov Standards Track [Page 4] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + an application proxy or as an iterator of callout services. The + scope of OCP Core is communication between a single OPES processor + and a single callout server. + + Furthermore, an OPES processor may choose which proxied application + messages or information about them to send over OCP. All proxied + messages on all proxied connections (if connections are defined for a + given application protocol), everything on some connections, selected + proxied messages, or nothing might be sent over OCP to callout + servers. OPES processor and callout server state related to proxied + protocols can be relayed over OCP as application message metadata. + +1.2. OPES Document Map + + This document belongs to a large set of OPES specifications produced + by the IETF OPES Working Group. Familiarity with the overall OPES + approach and typical scenarios is often essential when one tries to + comprehend isolated OPES documents. This section provides an index + of OPES documents to assist the reader with finding "missing" + information. + + o "OPES Use Cases and Deployment Scenarios" [RFC3752] describes a + set of services and applications that are considered in scope for + OPES and that have been used as a motivation and guidance in + designing the OPES architecture. + + o The OPES architecture and common terminology are described in "An + Architecture for Open Pluggable Edge Services (OPES)" [RFC3835]. + + o "Policy, Authorization, and Enforcement Requirements of OPES" + [RFC3838] outlines requirements and assumptions on the policy + framework, without specifying concrete authorization and + enforcement methods. + + o "Security Threats and Risks for OPES" [RFC3837] provides OPES risk + analysis, without recommending specific solutions. + + o "OPES Treatment of IAB Considerations" [RFC3914] addresses all + architecture-level considerations expressed by the IETF Internet + Architecture Board (IAB) when the OPES WG was chartered. + + o At the core of the OPES architecture are the OPES processor and + the callout server, two network elements that communicate with + each other via an OPES Callout Protocol (OCP). The requirements + for this protocol are discussed in "Requirements for OPES Callout + Protocols" [RFC3836]. + + + + + +Rousskov Standards Track [Page 5] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + o This document specifies an application agnostic protocol core to + be used for the communication between an OPES processor and a + callout server. + + o "OPES Entities and End Points Communications" [RFC3897] specifies + generic tracing and bypass mechanisms for OPES. + + o The OCP Core and communications documents are independent from the + application protocol being adapted by OPES entities. Their + generic mechanisms have to be complemented by application-specific + profiles. "HTTP Adaptation with OPES" [OPES-HTTP] is such an + application profile for HTTP. It specifies how + application-agnostic OPES mechanisms are to be used and augmented + in order to support adaptation of HTTP messages. + + o Finally, "P: Message Processing Language" [OPES-RULES] defines a + language for specifying what OPES adaptations (e.g., translation) + must be applied to what application messages (e.g., e-mail from + bob@example.com). P language is intended for configuring + application proxies (OPES processors). + +1.3. Terminology + + In this document, the keywords "MUST", "MUST NOT", "REQUIRED", + "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", + and "OPTIONAL" in this document are to be interpreted as described in + [RFC2119]. When used with the normative meanings, these keywords + will be all uppercase. Occurrences of these words in lowercase + constitute normal prose usage, with no normative implications. + + The OPES processor works with messages from application protocols and + may relay information about those application messages to a callout + server. OCP is also an application protocol. Thus, protocol + elements such as "message", "connection", or "transaction" exist in + OCP and other application protocols. In this specification, all + references to elements from application protocols other than OCP are + used with an explicit "application" qualifier. References without + the "application" qualifier refer to OCP elements. + + OCP message: A basic unit of communication between an OPES processor + and a callout server. The message is a sequence of octets + formatted according to syntax rules (section 3.1). Message + semantics is defined in section 11. + + application message: An entity defined by OPES processor and callout + server negotiation. Usually, the negotiated definition would + match the definition from an application protocol (e.g., [RFC2616] + definition of an HTTP message). + + + +Rousskov Standards Track [Page 6] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + application message data: An opaque sequence of octets representing a + complete or partial application message. OCP Core does not + distinguish application message structures (if there are any). + Application message data may be empty. + + data: Same as application message data. + + original: Referring to an application message flowing from the OPES + processor to a callout server. + + adapted: Referring to an application message flowing from an OPES + callout server to the OPES processor. + + adaptation: Any kind of access by a callout server, including + modification, generation, and copying. For example, translating + or logging an SMTP message is adaptation of that application + message. + + agent: The actor for a given communication protocol. The OPES + processor and callout server are OCP agents. An agent can be + referred to as a sender or receiver, depending on its actions in a + particular context. + + immediate: Performing the specified action before reacting to new + incoming messages or sending any new messages unrelated to the + specified action. + + OCP extension: A specification extending or adjusting this document + for adaptation of an application protocol (a.k.a., application + profile; e.g., [OPES-HTTP]), new OCP functionality (e.g., + transport encryption and authentication), and/or new OCP Core + version. + +2. Overall Operation + + The OPES processor may use the OPES callout protocol (OCP) to + communicate with callout servers. Adaptation using callout services + is sometimes called "bump in the wire" architecture. + +2.1. Initialization + + The OPES processor establishes transport connections with callout + servers to exchange application messages with the callout server(s) + by using OCP. After a transport-layer connection (usually TCP/IP) is + established, communicating OCP agents exchange Connection Start (CS) + messages. Next, OCP features can be negotiated between the processor + and the callout server (see section 6). For example, OCP agents may + negotiate transport encryption and application message definition. + + + +Rousskov Standards Track [Page 7] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + When enough settings are negotiated, OCP agents may start exchanging + application messages. + + OCP Core provides negotiation and other mechanisms for agents to + encrypt OCP connections and authenticate each other. OCP Core does + not require OCP connection encryption or agent authentication. + Application profiles and other OCP extensions may document and/or + require these and other security mechanisms. OCP is expected to be + used, in part, in closed environments where trust and privacy are + established by means external to OCP. Implementations are expected + to demand necessary security features via the OCP Core negotiation + mechanism, depending on agent configuration and environment. + +2.2. Original Dataflow + + When the OPES processor wants to adapt an application message, it + sends a Transaction Start (TS) message to initiate an OCP transaction + dedicated to that application message. The processor then sends an + Application Message Start (AMS) message to prepare the callout server + for application data that will follow. Once the application message + scope is established, application data can be sent to the callout + server by using Data Use Mine (DUM) and related OCP message(s). All + of these messages correspond to the original dataflow. + +2.3. Adapted Dataflow + + The callout server receives data and metadata sent by the OPES + processor (original dataflow). The callout server analyses metadata + and adapts data as it comes in. The server usually builds its + version of metadata and responds to the OPES processor with an + Application Message Start (AMS) message. Adapted application message + data can be sent next, using Data Use Mine (DUM) OCP message(s). The + application message is then announced to be "completed" or "closed" + by using an Application Message End (AME) message. The transaction + may be closed by using a Transaction End (TE) message, as well. All + these messages correspond to adapted data flow. + + +---------------+ +-------+ + | OPES | == (original data flow) ==> |callout| + | processor | <== (adapted data flow) === |server | + +---------------+ +-------+ + + The OPES processor receives the adapted application message sent by + the callout server. Other OPES processor actions specific to the + application message received are outside scope of this specification. + + + + + + +Rousskov Standards Track [Page 8] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +2.4. Multiple Application Messages + + OCP Core specifies a transactions interface dedicated to exchanging a + single original application message and a single adapted application + message. Some application protocols may require multiple adapted + versions for a single original application message or even multiple + original messages to be exchanged as a part of a single OCP + transaction. For example, a single original e-mail message may need + to be transformed into several e-mail messages, with one custom + message for each recipient. + + OCP extensions MAY document mechanisms for exchanging multiple + original and/or multiple adapted application messages within a single + OCP transaction. + +2.5. Termination + + Either OCP agent can terminate application message delivery, + transaction, or connection by sending an appropriate OCP message. + Usually, the callout server terminates adapted application message + delivery and the transaction. Premature and abnormal terminations at + arbitrary times are supported. The termination message includes a + result description. + +2.6. Message Exchange Patterns + + In addition to messages carrying application data, OCP agents may + also exchange messages related to their configuration, state, + transport connections, application connections, etc. A callout + server may remove itself from the application message processing + loop. A single OPES processor can communicate with many callout + servers and vice versa. Though many OCP exchange patterns do not + follow a classic client-server model, it is possible to think of an + OPES processor as an "OCP client" and of a callout server as an "OCP + server". The OPES architecture document [RFC3835] describes + configuration possibilities. + + The following informal rules illustrate relationships between + connections, transactions, OCP messages, and application messages: + + o An OCP agent may communicate with multiple OCP agents. This is + outside the scope of this specification. + + o An OPES processor may have multiple concurrent OCP connections to + a callout server. Communication over multiple OCP connections is + outside the scope of this specification. + + + + + +Rousskov Standards Track [Page 9] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + o A connection may carry multiple concurrent transactions. A + transaction is always associated with a single connection (i.e., a + transaction cannot span multiple concurrent connections). + + o A connection may carry at most one message at a time, including + control messages and transaction-related messages. A message is + always associated with a single connection (i.e., a message cannot + span multiple concurrent connections). + + o A transaction is a sequence of messages related to application of + a given set of callout services to a single application message. + + A sequence of transaction messages from an OPES processor to a + callout server is called original flow. A sequence of transaction + messages from a callout server to an OPES processor is called + adapted flow. The two flows may overlap in time. + + o In OCP Core, a transaction is associated with a single original + and a single adapted application message. OCP Core extensions may + extend transaction scope to more application messages. + + o An application message (adapted or original) is transferred by + using a sequence of OCP messages. + +2.7. Timeouts + + OCP violations, resource limits, external dependencies, and other + factors may lead to states in which an OCP agent is not receiving + required messages from the other OCP agent. OCP Core defines no + messages to address such situations. In the absence of any extension + mechanism, OCP agents must implement timeouts for OCP operations. An + OCP agent MUST forcefully terminate any OCP connection, negotiation, + transaction, etc. that is not making progress. This rule covers + both dead- and livelock situations. + + In their implementation, OCP agents MAY rely on transport-level or + other external timeouts if such external timeouts are guaranteed to + happen for a given OCP operation. Depending on the OCP operation, an + agent may benefit from "pinging" the other side with a Progress Query + (PQ) message before terminating an OCP transaction or connection. + The latter is especially useful for adaptations that may take a long + time at the callout server before producing any adapted data. + + + + + + + + + +Rousskov Standards Track [Page 10] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +2.8. Environment + + OCP communication is assumed usually to take place over TCP/IP + connections on the Internet (though no default TCP port is assigned + to OCP in this specification). This does not preclude OCP from being + implemented on top of other transport protocols, or on other + networks. High-level transport protocols such as BEEP [RFC3080] may + be used. OCP Core requires a reliable and message-order-preserving + transport. Any protocol with these properties can be used; the + mapping of OCP message structures onto the transport data units of + the protocol in question is outside the scope of this specification. + + OCP Core is application agnostic. OCP messages can carry + application-specific information as a payload or as + application-specific message parameters. + + OCP Core overhead in terms of extra traffic on the wire is about 100 + - 200 octets per small application message. Pipelining, preview, + data preservation, and early termination optimizations, as well as + as-is encapsulation of application data, make fast exchange of + application messages possible. + +3. Messages + + As defined in section 1.3, an OCP message is a basic unit of + communication between an OPES processor and a callout server. A + message is a sequence of octets formatted according to syntax rules + (section 3.1). Message semantics is defined in section 11. Messages + are transmitted on top of OCP transport. + + OCP messages deal with transport, transaction management, and + application data exchange between a single OPES processor and a + single callout server. Some messages can be emitted only by an OPES + processor; some only by a callout server; and some by both OPES + processor and callout server. Some messages require responses (one + could call such messages "requests"); some can only be used in + response to other messages ("responses"); some may be sent without + solicitation; and some may not require a response. + + + + + + + + + + + + + +Rousskov Standards Track [Page 11] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +3.1. Message Format + + An OCP message consists of a message name followed by optional + parameters and a payload. The exact message syntax is defined by the + following Augmented Backus-Naur Form (ABNF) [RFC2234]: + + message = name [SP anonym-parameters] + [CRLF named-parameters CRLF] + [CRLF payload CRLF] + ";" CRLF + + anonym-parameters = value *(SP value) ; space-separated + named-parameters = named-value *(CRLF named-value) ; CRLF-separated + list-items = value *("," value) ; comma-separated + + payload = data + + named-value = name ":" SP value + + value = structure / list / atom + structure = "{" [anonym-parameters] [CRLF named-parameters CRLF] "}" + list = "(" [ list-items ] ")" + atom = bare-value / quoted-value + + name = ALPHA *safe-OCTET + bare-value = 1*safe-OCTET + quoted-value = DQUOTE data DQUOTE + data = size ":" *OCTET ; exactly size octets + + safe-OCTET = ALPHA / DIGIT / "-" / "_" + size = dec-number ; 0-2147483647 + dec-number = 1*DIGIT ; no leading zeros or signs + + Several normative rules accompany the above ABNF: + + o There is no "implied linear space" (LWS) rule. LWS rules are + common to MIME-based grammars but are not used here. The + whitespace syntax is restricted to what is explicitly allowed by + the above ABNF. + + o All protocol elements are case sensitive unless it is specified + otherwise. In particular, message names and parameter names are + case sensitive. + + o Sizes are interpreted as decimal values and cannot have leading + zeros. + + o Sizes do not exceed 2147483647. + + + +Rousskov Standards Track [Page 12] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + o The size attribute in a quoted-value encoding specifies the exact + number of octets following the column (':') separator. If size + octets are not followed by a quote ('"') character, the encoding + is syntactically invalid. + + o Empty quoted values are encoded as a 4-octet sequence "0:". + + o Any bare value can be encoded as a quoted value. A quoted value + is interpreted after the encoding is removed. For example, number + 1234 can be encoded as four octets 1234 or as eight octets + "4:1234", yielding exactly the same meaning. + + o Unicode UTF-8 is the default encoding. Note that ASCII is a UTF-8 + subset, and that the syntax prohibits non-ASCII characters outside + of the "data" element. + + Messages violating formatting rules are, by definition, invalid. See + section 5 for rules governing processing of invalid messages. + +3.2. Message Rendering + + OCP message samples in this specification and its extensions may not + be typeset to depict minor syntactical details of OCP message format. + Specifically, SP and CRLF characters are not shown explicitly. No + rendering of an OCP message can be used to infer message format. The + message format definition above is the only normative source for all + implementations. + + On occasion, an OCP message line exceeds text width allowed by this + specification format. A backslash ("\"), a "soft line break" + character, is used to emphasize a protocol-violating + presentation-only linebreak. Bare backslashes are prohibited by OCP + syntax. Similarly, an "\r\n" string is sometimes used to emphasize + the presence of a CRLF sequence, usually before OCP message payload. + Normally, the visible end of line corresponds to the CRLF sequence on + the wire. + + The next section (section 3.3) contains specific OCP message + examples, some of which illustrate the above rendering techniques. + + + + + + + + + + + + +Rousskov Standards Track [Page 13] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +3.3. Message Examples + + OCP syntax provides for compact representation of short control + messages and required parameters while allowing for parameter + extensions. Below are examples of short control messages. The + required CRLF sequence at the end of each line is not shown + explicitly (see section 3.2). + + PQ; + TS 1 2; + DWM 22; + DWP 22 16; + x-doit "5:xyzzy"; + + The above examples contain atomic anonymous parameter values, such as + number and string constants. OCP messages sometimes use more + complicated parameters such as item lists or structures with named + values. As both messages below illustrate, structures and lists can + be nested: + + NO ({"32:http://www.iana.org/assignments/opes/ocp/tls"}); + NO ({"54:http://www.iana.org/assignments/opes/ocp/http/response" + Optional-Parts: (request-header) + },{"54:http://www.iana.org/assignments/opes/ocp/http/response" + Optional-Parts: (request-header,request-body) + Transfer-Encodings: (chunked) + }); + + Optional parameters and extensions are possible with a named + parameters approach, as illustrated by the following example. The + DWM (section 11.17) message in the example has two anonymous + parameters (the last one being an extension) and two named parameters + (the last one being an extension). + + DWM 1 3 + Size-Request: 16384 + X-Need-Info: "26:twenty six octet extension"; + + Finally, any message may have a payload part. For example, the Data + Use Mine (DUM) message below carries 8865 octets of raw data. + + DUM 1 13 + Modp: 75 + \r\n + 8865:... 8865 octets of raw data ...; + + + + + + +Rousskov Standards Track [Page 14] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +3.4. Message Names + + Most OCP messages defined in this specification have short names, + formed by abbreviating or compressing a longer but human-friendlier + message title. Short names without a central registration system + (such as this specification or the IANA registry) are likely to cause + conflicts. Informal protocol extensions should avoid short names. + To emphasize what is already defined by message syntax, + implementations cannot assume that all message names are very short. + +4. Transactions + + An OCP transaction is a logical sequence of OCP messages processing a + single original application message. The result of the processing + + may be zero or more application messages, adapted from the original. + A typical transaction consists of two message flows: a flow from the + OPES processor to the callout server (sending the original + application message), and a flow from the callout server to the OPES + processor (sending adapted application messages). The number of + application messages produced by the callout server and whether the + callout server actually modifies the original application message may + depend on the requested callout service and other factors. The OPES + processor or the callout server can terminate the transaction by + sending a corresponding message to the other side. + + An OCP transaction starts with a Transaction Start (TS) message sent + by the OPES processor. A transaction ends with the first Transaction + End (TE) message sent or received, explicit or implied. A TE message + can be sent by either side. Zero or more OCP messages associated + with the transaction can be exchanged in between. The figure below + illustrates a possible message sequence (prefix "P" stands for the + OPES processor; prefix "S" stands for the callout server). Some + message details are omitted. + + P: TS 10; + P: AMS 10 1; + ... processor sending application data to the callout server + S: AMS 10 2; + ... callout server sending application data to the processor + ... processor sending application data to the callout server + P: AME 10 1 result; + S: AME 10 2 result; + P: TE 10 result; + + + + + + + +Rousskov Standards Track [Page 15] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +5. Invalid Input + + This specification contains many criteria for valid OCP messages and + their parts, including syntax rules, semantics requirements, and + relationship to agents state. In this context, "Invalid input" means + messages or message parts that violate at least one of the normative + rules. A message with an invalid part is, by definition, invalid. + If OCP agent resources are exhausted while parsing or interpreting a + message, the agent MUST treat the corresponding OCP message as + invalid. + + Unless explicitly allowed to do otherwise, an OCP agent MUST + terminate the transaction if it receives an invalid message with + transaction scope and MUST terminate the connection if it receives an + invalid message with a connection scope. A terminating agent MUST + use the result status code of 400 and MAY specify termination cause + information in the result status reason parameter (see section + 10.10). If an OCP agent is unable to determine the scope of an + invalid message it received, the agent MUST treat the message as + having connection scope. + + OCP usually deals with optional but invasive application message + manipulations for which correctness ought to be valued above + robustness. For example, a failure to insert or remove certain + optional web page content is usually far less disturbing than + corrupting (making unusable) the host page while performing that + insertion or removal. Most OPES adaptations are high level in + nature, which makes it impossible to assess correctness of the + adaptations automatically, especially if "robustness guesses" are + involved. + +6. Negotiation + + The negotiation mechanism allows OCP agents to agree on the mutually + acceptable set of features, including optional and + application-specific behavior and OCP extensions. For example, + transport encryption, data format, and support for a new message can + be negotiated. Negotiation implies intent for a behavioral change. + For a related mechanism allowing an agent to query capabilities of + its counterpart without changing the counterpart's behavior, see the + Ability Query (AQ) and Ability Answer (AA) message definitions. + + Most negotiations require at least one round trip time delay. In + rare cases when the other side's response is not required + immediately, negotiation delay can be eliminated, with an inherent + risk of an overly optimistic assumption about the negotiation + response. + + + + +Rousskov Standards Track [Page 16] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + A detected violation of negotiation rules leads to OCP connection + termination. This design reduces the number of negotiation scenarios + resulting in a deadlock when one of the agents is not compliant. + + Two core negotiation primitives are supported: negotiation offer and + negotiation response. A Negotiation Offer (NO) message allows an + agent to specify a set of features from which the responder has to + select at most one feature that it prefers. The selection is sent by + using a Negotiation Response (NR) message. If the response is + positive, both sides assume that the selected feature is in effect + immediately (see section 11.19 for details). If the response is + negative, no behavioral changes are assumed. In either case, further + offers may follow. + + Negotiating OCP agents have to take into account prior negotiated + (i.e., already enabled) features. OCP agents MUST NOT make and MUST + reject offers that would lead to a conflict with already negotiated + features. For example, an agent cannot offer an HTTP application + profile for a connection that already has an SMTP application profile + enabled, as there would be no way to resolve the conflict for a given + transaction. Similarly, once TLSv1 connection encryption is + negotiated, an agent must not offer and must reject offers for SSLv2 + connection encryption (unless a negotiated feature explicitly allows + for changing an encryption scheme on the fly). + + Negotiation Offer (NO) messages may be sent by either agent. OCP + extensions documenting negotiation MAY assign the initiator role to + one of the agents, depending on the feature being negotiated. For + example, negotiation of transport security feature should be + initiated by OPES processors to avoid situations where both agents + wait for the other to make an offer. + + As either agent may make an offer, two "concurrent" offers may be + made at the same time, by the two communicating agents. Unmanaged + concurrent offers may lead to a negotiation deadlock. By giving OPES + processor a priority, offer-handling rules (section 11.18) ensure + that only one offer per OCP connection is honored at a time, and that + the other concurrent offers are ignored by both agents. + +6.1. Negotiation Phase + + A Negotiation Phase is a mechanism ensuring that both agents have a + chance to negotiate all features they require before proceeding + further. Negotiation Phases have OCP connection scope and do not + overlap. For each OCP agent, the Negotiation Phase starts with the + first Negotiation Offer (NO) message received or the first + Negotiation Response (NR) message sent, provided the message is not a + part of an existing Phase. For each OCP agent, Negotiation Phase + + + +Rousskov Standards Track [Page 17] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + ends with the first Negotiation Response (NR) message (sent or + received), after which the agent expects no more negotiations. Agent + expectation rules are defined later in this section. + + During a Negotiation Phase, an OCP agent MUST NOT send messages other + than the following "Negotiation Phase messages": Negotiation Offer + (NO), Negotiation Response (NR), Ability Query (AQ), Ability Answer + (AA), Progress Query (PQ), Progress Answer (PA), Progress Report + (PR), and Connection End (CE). + + Multiple Negotiation Phases may happen during the lifespan of a + single OCP connection. An agent may attempt to start a new + Negotiation Phase immediately after the old Phase is over, but it is + possible that the other agent will send messages other than + "Negotiation Phase messages" before receiving the new Negotiation + Offer (NO). The agent that starts a Phase has to be prepared to + handle those messages while its offer is reaching the recipient. + + An OPES processor MUST make a negotiation offer immediately after + sending a Connection Start (CS) message. If the OPES processor has + nothing to negotiate, the processor MUST send a Negotiation Offer + (NO) message with an empty features list. These two rules bootstrap + the first Negotiation Phase. Agents are expected to negotiate at + least the application profile for OCP Core. Thus, these + bootstrapping requirements are unlikely to result in any extra work. + + Once a Negotiation Phase starts, an agent MUST expect further + negotiations if and only if the last NO sent or the last NR received + contained a true "Offer-Pending" parameter value. Informally, an + agent can keep the phase open by sending true "Offer-Pending" + parameters with negotiation offers or responses. Moreover, if there + is a possibility that the agent may need to continue the Negotiation + Phase, the agent must send a true "Offer-Pending" parameter. + +6.2. Negotiation Examples + + Below is an example of the simplest negotiation possible. The OPES + processor is offering nothing and is predictably receiving a + rejection. Note that the NR message terminates the Negotiation Phase + in this case because neither of the messages contains a true + "Offer-Pending" value: + + P: NO (); + S: NR; + + The next example illustrates how a callout server can force + negotiation of a feature that an OPES processor has not negotiated. + Note that the server sets the "Offer-Pending" parameter to true when + + + +Rousskov Standards Track [Page 18] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + responding to the processor Negotiation Offer (NO) message. The + processor chooses to accept the feature: + + P: NO (); + S: NR + Offer-Pending: true + ; + S: NO ({"22:ocp://feature/example/"}) + Offer-Pending: false + ; + P: NR {"22:ocp://feature/example/"}; + + If the server seeks to stop the above negotiations after sending a + true "Offer-Pending" value, its only option would be send an empty + negotiation offer (see the first example above). If the server does + nothing instead, the OPES processor would wait for the server and + would eventually time out the connection. + + The following example shows a dialog with a callout server that + insists on enabling two imaginary features: strong transport + encryption and volatile storage for responses. The server is + designed not to exchange sensitive messages until both features are + enabled. Naturally, the volatile storage feature has to be + negotiated securely. The OPES processor supports one of the strong + encryption mechanisms but prefers not to offer (to volunteer support + for) strong encryption, perhaps for performance reasons. The server + has to send a true "Offer-Pending" parameter to get a chance to offer + strong encryption (which is successfully negotiated in this case). + Any messages sent by either agent after the (only) successful NR + response are encrypted with "strongB" encryption scheme. The OPES + processor does not understand the volatile storage feature, and the + last negotiation fails (over a strongly encrypted transport + connection). + + P: NO ({"29:ocp://example/encryption/weak"}) + ; + S: NR + Offer-Pending: true + ; + S: NO ({"32:ocp://example/encryption/strongA"},\ + {"32:ocp://example/encryption/strongB"}) + Offer-Pending: true + ; + P: NR {"32:ocp://example/encryption/strongB"} + ; + ... all traffic below is encrypted using strongB ... + + + + + +Rousskov Standards Track [Page 19] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + S: NO ({"31:ocp://example/storage/volatile"}) + Offer-Pending: false + ; + P: NR + Unknowns: ({"31:ocp://example/storage/volatile"}) + ; + S: CSE { 400 "33:lack of VolStore protocol support" } + ; + + The following example from [OPES-HTTP] illustrates successful HTTP + application profile negotiation: + + P: NO ({"54:http://www.iana.org/assignments/opes/ocp/http/response" + Aux-Parts: (request-header,request-body) + }) + SG: 5; + S: NR {"54:http://www.iana.org/assignments/opes/ocp/http/response" + Aux-Parts: (request-header) + Pause-At-Body: 30 + Wont-Send-Body: 2147483647 + Content-Encodings: (gzip) + } + SG: 5; + +7. 'Data Preservation' Optimization + + Many adaptations do not require any data modifications (e.g., message + logging or blocking). Some adaptations modify only a small portion + of application message content (e.g., HTTP cookies filtering or ad + insertion). Yet, in many cases, the callout service has to see + complete data. By default, unmodified data would first travel from + the OPES processor to the callout server and then back. The "data + preservation" optimization in OCP helps eliminate the return trip if + both OCP agents cooperate. Such cooperation is optional: OCP agents + MAY support data preservation optimization. + + To avoid sending back unmodified data, a callout service has to know + that the OPES processor has a copy of the data. As data sizes can be + very large and the callout service may not know in advance whether it + will be able to use the processor copy, it is not possible to require + the processor to keep a copy of the entire original data. Instead, + it is expected that a processor may keep some portion of the data, + depending on processor settings and state. + + When an OPES processor commits to keeping a data chunk, it announces + its decision and the chunk parameters via a Kept parameter of a Data + Use Mine (DUM) message. The callout server MAY "use" the chunk by + sending a Data Use Yours (DUY) message referring to the preserved + + + +Rousskov Standards Track [Page 20] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + chunk. That OCP message does not have payload and, therefore, the + return trip is eliminated. + + As the mapping between original and adapted data is not known to the + processor, the processor MUST keep the announced-as-preserved chunk + until the end of the corresponding transaction, unless the callout + server explicitly tells the processor that the chunk is not needed. + As implied by the above requirement, the processor cannot assume that + a data chunk is no longer needed just because the callout server sent + a Data Use Yours (DUY) message or adapted data with, for instance, + the same offset as the preserved chunk. + + For simplicity, preserved data is always a contiguous chunk of + original data, described by an (offset, size) pair using a "Kept" + parameter of a Data Use Mine (DUM) message. An OPES processor may + volunteer to increase the size of the kept data. An OPES processor + may increase the offset if the callout server indicated that the kept + data is no longer needed. + + Both agents may benefit from data reuse. An OPES processor has to + allocate storage to support this optimization, but a callout server + does not. On the other hand, it is the callout server that is + responsible for relieving the processor from data preservation + commitments. There is no simple way to resolve this conflict of + interest on a protocol level. Some OPES processors may allocate a + relatively small buffer for data preservation purposes and stop + preserving data when the buffer becomes full. This technique would + benefit callout services that can quickly reuse or discard kept data. + Another processor strategy would be to size the buffer based on + historical data reuse statistics. To improve chances of beneficial + cooperation, callout servers are strongly encouraged to immediately + notify OPES processors of unwanted data. The callout server that + made a decision not to send Data Use Yours (DUY) messages (for a + specific data ranges or at all) SHOULD immediately inform the OPES + processor of that decision with the corresponding Data Preservation + Interest (DPI) message(s) or other mechanisms. + +8. 'Premature Dataflow Termination' Optimizations + + Many callout services adapt small portions of large messages and + would preferably not to be in the loop when that adaptation is over. + Some callout services may not seek data modification and would + preferably not send data back to the OPES processor, even if the OPES + processor is not supporting the data preservation optimization + (Section 7). By OCP design, unilateral premature dataflow + termination by a callout server would lead to termination of an OCP + transaction with an error. Thus, the two agents must cooperate to + allow for error-free premature termination. + + + +Rousskov Standards Track [Page 21] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + This section documents two mechanisms for premature termination of + original or adapted dataflow. In combination, the mechanisms allow + the callout server to get out of the processing loop altogether. + +8.1. Original Dataflow + + There are scenarios where a callout server is not interested in the + remaining original dataflow. For example, a simple access blocking + or "this site is temporary down" callout service has to send an + adapted (generated) application message but would preferably not + receive original data from the OPES processor. + + OCP Core supports premature original dataflow termination via the + Want Stop Receiving Data (DWSR) message. A callout server that does + not seek to receive additional original data (beyond a certain size) + sends a DWSR message. The OPES processor receiving a DWSR message + terminates original dataflow by sending an Application Message End + (AME) message with a 206 (partial) status code. + + The following figure illustrates a typical sequence of events. The + downward lines connecting the two dataflows illustrate the + transmission delay that allows for more OCP messages to be sent while + an agent waits for the opposing agent reaction. + + OPES Callout + Processor Server + DUM> <DUM + DUM> <DWSR <-- Server is ready to stop receiving + ... _____/<DUM <-- Server continues as usual + DUM>______/ <DUM + AME> ... <-- Processor stops sending original data + \_____ <DUM + \______<DUM + <DUM <-- Server continues to send adapted data + ... + <AME + + The mechanism described in this section has no effect on the adapted + dataflow. Receiving an Application Message End (AME) message with + 206 (partial) result status code from the OPES processor does not + introduce any special requirements for the adapted dataflow + termination. However, it is not possible to terminate adapted + dataflow prematurely after the original dataflow has been prematurely + terminated (see section 8.3). + + + + + + + +Rousskov Standards Track [Page 22] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +8.2. Adapted Dataflow + + There are scenarios where a callout service may want to stop sending + adapted data before a complete application message has been sent. + For example, a logging-only callout service has to receive all + application messages but would preferably not send copies back to the + OPES processor. + + OCP Core supports premature adapted dataflow termination via a + combination of Want Stop Sending Data (DWSS) and Stop Sending Data + (DSS) messages. A callout service that seeks to stop sending data + sends a DWSS message, soliciting an OPES processor permission to + stop. While waiting for the permission, the server continues with + its usual routine. + + An OPES processor receiving a Want Stop Sending Data message responds + with a Stop Sending Data (DSS) message. The processor may then pause + to wait for the callout server to terminate the adapted dataflow or + may continue sending original data while making a copy of it. Once + the server terminates the adapted dataflow, the processor is + responsible for using original data (sent or paused after sending + DSS) instead of the adapted data. + + The callout server receiving a DSS message terminates the adapted + dataflow (see the Stop Sending Data (DSS) message definition for the + exact requirements and corner cases). + + The following figure illustrates a typical sequence of events, + including a possible pause in original dataflow when the OPES + processor is waiting for the adapted dataflow to end. The downward + lines connecting the two dataflows illustrate the transmission delay + that allows for more OCP messages to be sent while an agent waits for + the opposing agent reaction. + + + + + + + + + + + + + + + + + + +Rousskov Standards Track [Page 23] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + OPES Callout + Processor Server + DUM> <DUM + DUM> <DWSS <-- Server is ready to stop sending + ... _____/<DUM <-- Server continues as usual, + DUM>______/ <DUM waiting for DSS + DSS> ... + \_____ <DUM + possible \______<DUM + org-dataflow <AME 206 <-- Server terminates adapted dataflow + pause _____/ upon receiving the DSS message + ______/ + DUM> <-- Processor resumes original dataflow + DUM> to the server and starts using + ... original data without adapting it + AME> + + Premature adapted dataflow preservation is not trivial, as the OPES + processor relies on the callout server to provide adapted data + (modified or not) to construct the adapted application message. If + the callout server seeks to quit its job, special care must be taken + to ensure that the OPES processor can construct the complete + application message. On a logical level, this mechanism is + equivalent to switching from one callout server to another + (non-modifying) callout server in the middle of an OCP transaction. + + Other than a possible pause in the original dataflow, the mechanism + described in this section has no effect on the original dataflow. + Receiving an Application Message End (AME) message with 206 (partial) + result status code from the callout server does not introduce any + special requirements for the original dataflow termination. + +8.3. Getting Out of the Loop + + Some adaptation services work on application message prefixes and do + not seek to be in the adaptation loop once their work is done. For + example, an ad insertion service that did its job by modifying the + first fragment of a web "page" would not seek to receive more + original data or to perform further adaptations. The 'Getting Out of + the Loop' optimization allows a callout server to get completely out + of the application message processing loop. + + The "Getting Out of the Loop" optimization is made possible by + terminating the adapted dataflow (section 8.2) and then by + terminating the original dataflow (section 8.1). The order of + termination is very important. + + + + + +Rousskov Standards Track [Page 24] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + If the original dataflow is terminated first, the OPES processor + would not allow the adapted dataflow to be terminated prematurely, as + the processor would not be able to reconstruct the remaining portion + of the adapted application message. The processor would not know + which suffix of the remaining original data has to follow the adapted + parts. The mapping between original and adapted octets is known only + to the callout service. + + An OPES processor that received a DWSS message followed by a DWSR + message MUST NOT send an AME message with a 206 (partial) status code + before sending a DSS message. Informally, this rule means that a + callout server that wants to get out of the loop fast should send a + DWSS message immediately followed by a DWSR message; the server does + not have to wait for the OPES processor's permission to terminate + adapted dataflow before requesting that the OPES processor terminates + original dataflow. + +9. Protocol Element Type Declaration Mnemonic (PETDM) + + A protocol element type is a named set of syntax and semantics rules. + This section defines a simple, formal declaration mnemonic for + protocol element types, labeled PETDM. PETDM simplicity is meant to + ease type declarations in this specification. PETDM formality is + meant to improve interoperability among implementations. Two + protocol elements are supported by PETDM: message parameter values + and messages. + + All OCP Core parameter and message types are declared by using PETDM. + OCP extensions SHOULD use PETDM when declaring new types. + + Atom, list, structure, and message constructs are four available base + types. Their syntax and semantics rules are defined in section 3.1. + New types can be declared in PETDM to extend base types semantics by + using the following declaration templates. The new semantics rules + are meant to be attached to each declaration using prose text. + + Text in angle brackets "<>" are template placeholders, to be + substituted with actual type names or parameter name tokens. Square + brackets "[]" surround optional elements such as structure members or + message payload. + + o Declaring a new atomic type: + <new-type-name>: extends atom; + + o Declaring a new list with old-type-name items: + <new-type-name>: extends list of <old-type-name>; + Unless it is explicitly noted otherwise, empty lists are valid and + have the semantics of an absent parameter value. + + + +Rousskov Standards Track [Page 25] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + o Declaring a new structure with members: + <new-type-name>: extends structure with { + <old-type-nameA> <old-type-nameB> [<old-type-nameC>] ...; + <member-name1>: <old-type-name1>; + <member-name2>: <old-type-name2>; + [<member-name3>: <old-type-name3>]; + ... + }; + + The new structure may have anonymous members and named members. + Neither group has to exist. Note that it is always possible for + extensions to add more members to old structures without affecting + type semantics because unrecognized members are ignored by compliant + agents. + + o Declaring a new message with parameters: + <new-type-name>: extends message with { + <old-type-nameA> <old-type-nameB> [<old-type-nameC>] ...; + <parameter-name1>: <old-type-name1>; + <parameter-name2>: <old-type-name2>; + [<parameter-name3>: <old-type-name3>]; + ... + }; + + The new type name becomes the message name. Just as when a structure + is extended, the new message may have anonymous parameters and named + parameters. Neither group has to exist. Note that it is always + possible for extensions to add more parameters to old messages + without affecting type semantics because unrecognized parameters are + ignored by compliant agents. + + o Extending a type with more semantics details: + + <new-type-name>: extends <old-type-name>; + + o Extending a structure- or message-base type: + <new-type-name>: extends <old-type-name> with { + <old-type-nameA> <old-type-nameB> [<old-type-nameC>] ...; + <member-name1>: <old-type-name1>; + <member-name2>: <old-type-name2>; + [<member-name3>: <old-type-name3>]; + ... + }; + New anonymous members are appended to the anonymous members of the + old type, and new named members are merged with named members of the + old type. + + + + + +Rousskov Standards Track [Page 26] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + o Extending a message-base type with payload semantics: + <new-type-name>: extends <old-type-name> with { + ... + } and payload; + Any any OCP message can have payload, but only some message types + have known payload semantics. Like any parameter, payload may be + required or optional. + + o Extending type semantics without renaming the type: + <old-type-name>: extends <namespace>::<old-type-name>; + The above template can be used by OCP Core extensions that seek to + change the semantics of OCP Core types without renaming them. This + technique is essential for extending OCP messages because the message + name is the same as the message type name. For example, an SMTP + profile for OCP might use the following declaration to extend an + Application Message Start (AMS) message with Am-Id, a parameter + defined in that profile: + + AMS: extends Core::AMS with { + Am-Id: am-id; + }; + + All extended types may be used as replacements of the types they + extend. For example, a Negotiation Offer (NO) message uses a + parameter of type Features. Features (section 10.12) is a list of + feature (section 10.11) items. A Feature is a structure-based type. + An OCP extension (e.g., an HTTP application profile) may extend the + feature type and use a value of that extended type in a negotiation + offer. Recipients that are aware of the extension will recognize + added members in feature items and negotiate accordingly. Other + recipients will ignore them. + + The OCP Core namespace tag is "Core". OCP extensions that declare + types MUST define their namespace tags (so that other extensions and + documentation can use them in their PETDM declarations). + +9.1. Optional Parameters + + Anonymous parameters are positional: The parameter's position (i.e., + the number of anonymous parameters to the left) is its "name". Thus, + when a structure or message has multiple optional anonymous + parameters, parameters to the right can be used only if all + parameters to the left are present. The following notation + + [name1] [name2] [name3] ... [nameN] + + is interpreted as + + + + +Rousskov Standards Track [Page 27] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + [name1 [ name2 [ name3 ... [nameN] ... ]]] + + When an anonymous parameter is added to a structure or message that + has optional anonymous parameters, the new parameter has to be + optional and can only be used if all old optional parameters are in + use. Named parameters do not have these limitations, as they are not + positional, but associative; they are identified by their explicit + and unique names. + +10. Message Parameter Types + + This section defines parameter value types that are used for message + definitions (section 11). Before using a parameter value, an OCP + agent MUST check whether the value has the expected type (i.e., + whether it complies with all rules from the type definition). A + single rule violation means that the parameter is invalid. See + Section 5 for rules on processing invalid input. + + OCP extensions MAY define their own types. If they do, OCP + extensions MUST define types with exactly one base format and MUST + specify the type of every new protocol element they introduce. + +10.1. uri + + uri: extends atom; + + Uri (universal resource identifier) is an atom formatted according to + URI rules in [RFC2396]. + + Often, a uri parameter is used as a unique (within a given scope) + identifier. Uni semantics is incomplete without the scope + specification. Many uri parameters are URLs. Unless it is noted + otherwise, URL identifiers do not imply the existence of a + serviceable resource at the location they specify. For example, an + HTTP request for an HTTP-based URI identifier may result in a 404 + (Not Found) response. + +10.2. uni + + uni: extends atom; + + Uni (unique numeric identifier) is an atom formatted as dec-number + and with a value in the [0, 2147483647] range, inclusive. + + A uni parameter is used as a unique (within a given scope) + identifier. Uni semantics is incomplete without the scope + specification. Some OCP messages create identifiers (i.e., bring + them into scope). Some OCP messages destroy them (i.e, remove them + + + +Rousskov Standards Track [Page 28] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + from scope). An OCP agent MUST NOT create the same uni value more + than once within the same scope. When creating a new identifier of + the same type and within the same scope as some old identifier, an + OCP agent MUST use a higher numerical value for the new identifier. + The first rule makes uni identifiers suitable for cross-referencing + logs and other artifacts. The second rule makes efficient checks of + the first rule possible. + + For example, a previously used transaction identifier "xid" must not + be used for a new Transaction Start (TS) message within the same OCP + transaction, even if a prior Transaction End (TE) message was sent + for the same transaction. + + An OCP agent MUST terminate the state associated with uni uniqueness + scope if all unique values have been used up. + +10.3. size + + size: extends atom; + + Size is an atom formatted as dec-number and with a value in the [0, + 2147483647] range, inclusive. + + Size value is the number of octets in the associated data chunk. + + OCP Core cannot handle application messages that exceed 2147483647 + octets in size, that require larger sizes as a part of OCP marshaling + process, or that use sizes with granularity other than 8 bits. This + limitation can be addressed by OCP extensions, as hinted in section + 15.1. + +10.4. offset + + offset: extends atom; + + Offset is an atom formatted as dec-number and with a value in the [0, + 2147483647] range, inclusive. + + Offset is an octet position expressed in the number of octets + relative to the first octet of the associated dataflow. The offset + of the first data octet has a value of zero. + +10.5. percent + + percent: extends atom; + + Percent is an atom formatted as dec-number and with a value in the + [0, 100] range, inclusive. + + + +Rousskov Standards Track [Page 29] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + Percent semantics is incomplete unless its value is associated with a + boolean statement or assertion. The value of 0 indicates absolute + impossibility. The value of 100 indicates an absolute certainty. In + either case, the associated statement can be relied upon as if it + were expressed in boolean rather than probabilistic terms. Values in + the [1,99] inclusive range indicate corresponding levels of certainty + that the associated statement is true. + +10.6. boolean + + boolean: extends atom; + + Boolean type is an atom with two valid values: true and false. A + boolean parameter expresses the truthfulness of the associated + statement. + +10.7. xid + + xid: extends uni; + + Xid, an OCP transaction identifier, uniquely identifies an OCP + transaction within an OCP connection. + +10.8. sg-id + + sg-id: extends uni; + + Sg-id, a service group identifier, uniquely identifies a group of + services on an OCP connection. + +10.9. modp + + modp: extends percent; + + Modp extends the percent type to express the sender's confidence that + application data will be modified. The boolean statement associated + with the percentage value is "data will be modified". Modification + is defined as adaptation that changes the numerical value of at least + one data octet. + +10.10. result + + result: extends structure with { + atom [atom]; + }; + + The OCP processing result is expressed as a structure with two + documented members: a required Uni status code and an optional + + + +Rousskov Standards Track [Page 30] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + reason. The reason member contains informative textual information + not intended for automated processing. For example: + + { 200 OK } + { 200 "6:got it" } + { 200 "27:27 octets in UTF-8 encoding" } + + This specification defines the following status codes: + + Result Status Codes + + +--------+--------------+-------------------------------------------+ + | code | text | semantics | + +--------+--------------+-------------------------------------------+ + | 200 | OK | Overall success. This specification does | + | | | not contain any general actions for a 200 | + | | | status code recipient. | + | 206 | partial | Partial success. This status code is | + | | | documented for Application Message End | + | | | (AME) messages only. The code indicates | + | | | that the agent terminated the | + | | | corresponding dataflow prematurely (i.e., | + | | | more data would be needed to reconstruct | + | | | a complete application message). | + | | | Premature termination of one dataflow | + | | | does not introduce any special | + | | | requirements for the other dataflow | + | | | termination. See dataflow termination | + | | | optimizations (section 8) for use cases. | + | 400 | failure | An error, exception, or trouble. A | + | | | recipient of a 400 (failure) result of an | + | | | AME, TE, or CE message MUST destroy any | + | | | state or data associated with the | + | | | corresponding dataflow, transaction, or | + | | | connection. For example, an adapted | + | | | version of the application message data | + | | | must be purged from the processor | + | | | cache if the OPES processor receives an | + | | | Application Message End (AME) message | + | | | with result code of 400. | + +--------+--------------+-------------------------------------------+ + + Specific OCP messages may require code-specific actions. + + Extending result semantics is made possible by adding new "result" + structure members or by negotiating additional result codes (e.g., as + a part of a negotiated profile). A recipient of an unknown (in + + + + +Rousskov Standards Track [Page 31] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + then-current context) result code MUST act as if code 400 (failure) + were received. + + The recipient of a message without the actual result parameter, but + with an optional formal result parameter, MUST act as if code 200 + (OK) were received. + + Textual information (the second anonymous parameter of the result + structure) is often referred to as "reason" or "reason phrase". To + assist manual troubleshooting efforts, OCP agents are encouraged to + include descriptive reasons with all results indicating a failure. + + In this specification, an OCP message with result status code of 400 + (failure) is called "a message indicating a failure". + +10.11. feature + + feature: extends structure with { + uri; + }; + + The feature type extends structure to relay an OCP feature identifier + and to reserve a "place" for optional feature-specific parameters + (sometimes called feature attributes). Feature values are used to + declare support for and to negotiate use of OCP features. + + This specification does not define any features. + +10.12. features + + features: extends list of feature; + + Features is a list of feature values. Unless it is noted otherwise, + the list can be empty, and features are listed in decreasing + preference order. + +10.13. service + + service: extends structure with { + uri; + }; + + Service structure has one anonymous member, an OPES service + identifier of type uri. Services may have service-dependent + parameters. An OCP extension defining a service for use with OCP + MUST define service identifier and service-dependent parameters, if + there are any, as additional "service" structure members. For + example, a service value may look like this: + + + +Rousskov Standards Track [Page 32] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + {"41:http://www.iana.org/assignments/opes/ocp/tls" "8:blowfish"} + +10.14. services + + services: extends list of service; + + Services is a list of service values. Unless it is noted otherwise, + the list can be empty, and the order of the values is the requested + or actual service application order. + +10.15. Dataflow Specializations + + Several parameter types, such as offset apply to both original and + adapted dataflow. It is relatively easy to misidentify a type's + dataflow affiliation, especially when parameters with different + affiliations are mixed together in one message declaration. The + following statements declare new dataflow-specific types by using + their dataflow-agnostic versions (denoted by a <type> placeholder). + + The following new types refer to original data only: + + org-<type>: extends <type>; + + The following new types refer to adapted data only: + + adp-<type>: extends <type>; + + The following new types refer to the sender's dataflow only: + + my-<type>: extends <type>; + + The following new types refer to the recipient's dataflow only: + + your-<type>: extends <type>; + + OCP Core uses the above type-naming scheme to implement dataflow + specialization for the following types: offset, size, and sg-id. OCP + extensions SHOULD use the same scheme. + +11. Message Definitions + + This section describes specific OCP messages. Each message is given + a unique name and usually has a set of anonymous and/or named + parameters. The order of anonymous parameters is specified in the + message definitions below. No particular order for named parameters + is implied by this specification. OCP extensions MUST NOT introduce + order-dependent named parameters. No more than one named-parameter + + + + +Rousskov Standards Track [Page 33] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + with a given name can appear in the message; messages with multiple + equally named parameters are semantically invalid. + + A recipient MUST be able to parse any message in valid format (see + section 3.1), subject to the limitations of the recipient's + resources. + + Unknown or unexpected message names, parameters, and payloads may be + valid extensions. For example, an "extra" named parameter may be + used for a given message, in addition to what is documented in the + message definition below. A recipient MUST ignore any valid but + unknown or unexpected name, parameter, member, or payload. + + Some message parameter values use uni identifiers to refer to various + OCP states (see section 10.2 and Appendix B). These identifiers are + created, used, and destroyed by OCP agents via corresponding + messages. Except when creating a new identifier, an OCP agent MUST + NOT send a uni identifier that corresponds to an inactive state + (i.e., that was either never created or already destroyed). Such + identifiers invalidate the host OCP message (see section 5). For + example, the recipient must terminate the transaction when the xid + parameter in a Data Use Mine (DUM) message refers to an unknown or + already terminated OCP transaction. + +11.1. Connection Start (CS) + + CS: extends message; + + A Connection Start (CS) message indicates the start of an OCP + connection. An OCP agent MUST send this message before it sends any + other message on the connection. If the first message an OCP agent + receives is not Connection Start (CS), the agent MUST terminate the + connection with a Connection End (CE) message having 400 (failure) + result status code. An OCP agent MUST send Connection Start (CS) + message exactly once. An OCP agent MUST ignore repeated Connection + Start (CS) messages. + + At any time, a callout server MAY refuse further processing on an OCP + connection by sending a Connection End (CE) message with the status + code 400 (failure). Note that the above requirement to send a CS + message first still applies. + + With TCP/IP as transport, raw TCP connections (local and remote peer + IP addresses with port numbers) identify an OCP connection. Other + transports may provide OCP connection identifiers to distinguish + logical connections that share the same transport. For example, a + single BEEP [RFC3080] channel may be designated as a single OCP + connection. + + + +Rousskov Standards Track [Page 34] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +11.2. Connection End (CE) + + CE: extends message with { + [result]; + }; + + A Connection End (CE) Indicates the end of an OCP connection. The + agent initiating closing or termination of a connection MUST send + this message immediately prior to closing or termination. The + recipient MUST free associated state, including transport state. + + Connection termination without a Connection End (CE) message + indicates that the connection was prematurely closed, possibly + without the closing-side agent's prior knowledge or intent. When an + OCP agent detects a prematurely closed connection, the agent MUST act + as if a Connection End (CE) message indicating a failure was + received. + + A Connection End (CE) message implies the end of all transactions, + negotiations, and service groups opened or active on the connection + being ended. + +11.3. Service Group Created (SGC) + + SGC: extends message with { + my-sg-id services; + }; + + A Service Group Created (SGC) message informs the recipient that a + list of adaptation services has been associated with the given + service group identifier ("my-sg-id"). Following this message, the + sender can refer to the group by using the identifier. The recipient + MUST maintain the association until a matching Service Group + Destroyed (SGD) message is received or the corresponding OCP + connection is closed. + + Service groups have a connection scope. Transaction management + messages do not affect existing service groups. + + Maintaining service group associations requires resources (e.g., + storage to keep the group identifier and a list of service IDs). + Thus, there is a finite number of associations an implementation can + maintain. Callout servers MUST be able to maintain at least one + association for each OCP connection they accept. If a recipient of a + Service Group Created (SGC) message does not create the requested + association, it MUST immediately terminate the connection with a + Connection End (CE) message indicating a failure. + + + + +Rousskov Standards Track [Page 35] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +11.4. Service Group Destroyed (SGD) + + SGD: extends message with { + my-sg-id; + }; + + A Service Group Destroyed (SGD) message instructs the recipient to + forget about the service group associated with the specified + identifier. The recipient MUST destroy the identified service group + association. + +11.5. Transaction Start (TS) + + TS: extends message with { + xid my-sg-id; + }; + + Sent by an OPES processor, a Transaction Start (TS) message indicates + the start of an OCP transaction. Upon receiving this message, the + callout server MAY refuse further transaction processing by + responding with a corresponding Transaction End (TE) message. A + callout server MUST maintain the state until it receives a message + indicating the end of the transaction or until it terminates the + transaction itself. + + The required "my-sg-id" identifier refers to a service group created + with an a Service Group Created (SGC) message. The callout server + MUST apply the list of services associated with "my-sg-id", in the + specified order. + + This message introduces the transaction identifier (xid). + +11.6. Transaction End (TE) + + TE: extends message with { + xid [result]; + }; + + A Transaction End (TE) indicates the end of the identified OCP + transaction. + + An OCP agent MUST send a Transaction End (TE) message immediately + after it makes a decision to send no more messages related to the + corresponding transaction. Violating this requirement may cause, for + + + + + + + +Rousskov Standards Track [Page 36] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + example, unnecessary delays, rejection of new transactions, and even + timeouts for agents that rely on this end-of-file condition to + proceed. + + This message terminates the life of the transaction identifier (xid). + +11.7. Application Message Start (AMS) + + AMS: extends message with { + xid; + [Services: services]; + }; + + An Application Message Start (AMS) message indicates the start of the + original or adapted application message processing and dataflow. The + recipient MAY refuse further processing by sending an Application + Message End (AME) message indicating a failure. + + When an AMS message is sent by the OPES processor, the callout server + usually sends an AMS message back, announcing the creation of an + adapted version of the original application message. This + announcement may be delayed. For example, the callout server may + wait for more information from the OPES processor. + + When an AMS message is sent by the callout server, an optional + "Services" parameter describes OPES services that the server MAY + apply to the original application message. Usually, the "services" + value matches what was asked by the OPES processor. The callout + server SHOULD send a "Services" parameter if its value would differ + from the list of services requested by the OPES processor. As the + same service may be known under many names, the mismatch does not + necessarily imply an error. + +11.8. Application Message End (AME) + + AME: extends message with { + xid [result]; + }; + + An Application Message End (AME) message indicates the end of the + original or adapted application message processing and dataflow. The + recipient should expect no more data for the corresponding + application message. + + An Application Message End (AME) message ends any data preservation + commitments and any other state associated with the corresponding + application message. + + + + +Rousskov Standards Track [Page 37] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + An OCP agent MUST send an Application Message End (AME) message + immediately after it makes a decision to stop processing of its + application message. Violating this requirement may cause, for + example, unnecessary delays, rejection of new transactions, and even + timeouts for agents that rely on this end-of-file condition to + proceed. + +11.9. Data Use Mine (DUM) + + DUM: extends message with { + xid my-offset; + [As-is: org-offset]; + [Kept: org-offset org-size ]; + [Modp: modp]; + } and payload; + + A Data Use Mine (DUM) message carries application data. It is the + only OCP Core message with a documented payload. The sender MUST NOT + make any gaps in data supplied by Data Use Mine (DUM) and Data Use + Yours (DUY) messages (i.e., the my-offset of the next data message + must be equal to the my-offset plus the payload size of the previous + data message). Messages with gaps are invalid. The sender MUST send + payload and MAY use empty payload (i.e., payload with zero size). A + DUM message without payload is invalid. Empty payloads are useful + for communicating meta-information about the data (e.g., modification + predictions or preservation commitments) without sending data. + + An OPES processor MAY send a "Kept" parameter to indicate its current + data preservation commitment (section 7) for original data. When an + OPES processor sends a "Kept" parameter, the processor MUST keep a + copy of the specified data (the preservation commitment starts or + continues). The Kept offset parameter specifies the offset of the + first octet of the preserved data. The Kept size parameter is the + size of preserved data. Note that data preservation rules allow + (i.e., do not prohibit) an OPES processor to decrease offset and to + specify a data range not yet fully delivered to the callout server. + OCP Core does not require any relationship between DUM payload and + the "Kept" parameter. + + If the "Kept" parameter value violates data preservation rules but + the recipient has not sent any Data Use Yours (DUY) messages for the + given OCP transaction yet, then the recipient MUST NOT use any + preserved data for the given transaction (i.e., must not sent any + Data Use Yours (DUY) messages). If the "Kept" parameter value + violates data preservation rules and the recipient has already sent + Data Use Yours (DUY) messages, the DUM message is invalid, and the + rules of section 5 apply. These requirements help preserve data + integrity when "Kept" optimization is used by the OPES processor. + + + +Rousskov Standards Track [Page 38] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + A callout server MUST send a "Modp" parameter if the server can + provide a reliable value and has not already sent the same parameter + value for the corresponding application message. The definition of + "reliable" is entirely up to the callout server. The data + modification prediction includes DUM payload. That is, if the + attached payload has been modified, the modp value cannot be 0%. + + A callout server SHOULD send an "As-is" parameter if the attached + data is identical to a fragment at the specified offset in the + original dataflow. An "As-is" parameter specifying a data fragment + that has not been sent to the callout server is invalid. The + recipient MUST ignore invalid "As-is" parameters. Identical means + that all adapted octets have the same numeric value as the + corresponding original octets. This parameter is meant to allow for + partial data preservation optimizations without a preservation + commitment. The preserved data still crosses the connection with the + callout server twice, but the OPES processor may be able to optimize + its handling of the data. + + The OPES processor MUST NOT terminate its data preservation + commitment (section 7) in reaction to receiving a Data Use Mine (DUM) + message. + +11.10. Data Use Yours (DUY) + + DUY: extends message with { + xid org-offset org-size; + }; + + The callout server tells the OPES processor to use the "size" bytes + of preserved original data, starting at the specified offset, as if + that data chunk came from the callout server in a Data Use Mine (DUM) + message. + + The OPES processor MUST NOT terminate its data preservation + commitment (section 7) in reaction to receiving a Data Use Yours + (DUY) message. + +11.11. Data Preservation Interest (DPI) + + DPI: extends message with { + xid org-offset org-size; + }; + + The Data Preservation Interest (DPI) message describes an original + data chunk by using the first octet offset and size as parameters. + The chunk is the only area of original data that the callout server + may be interested in referring to in future Data Use Yours (DUY) + + + +Rousskov Standards Track [Page 39] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + messages. This data chunk is referred to as "reusable data". The + rest of the original data is referred to as "disposable data". Thus, + disposable data consists of octets below the specified offset and at + or above the (offset + size) offset. + + After sending this message, the callout server MUST NOT send Data Use + Yours (DUY) messages referring to disposable data chunk(s). If an + OPES processor is not preserving some reusable data, it MAY start + preserving that data. If an OPES processor preserves some disposable + data, it MAY stop preserving that data. If an OPES processor does + not preserve some disposable data, it MAY NOT start preserving that + data. + + A callout server MUST NOT indicate reusable data areas that overlap + with disposable data areas indicated in previous Data Preservation + Interest (DPI) messages. In other words, reusable data must not + grow, and disposable data must not shrink. If a callout server + violates this rule, the Data Preservation Interest (DPI) message is + invalid (see section 5). + + The Data Preservation Interest (DPI) message cannot force the OPES + processor to preserve data. In this context, the term reusable + stands for callout server interest in reusing the data in the future, + given the OPES processor cooperation. + + For example, an offset value of zero and the size value of 2147483647 + indicate that the server may want to reuse all the original data. + The size value of zero indicates that the server is not going to send + any more Data Use Yours (DUY) messages. + +11.12. Want Stop Receiving Data (DWSR) + + DWSR: extends message with { + xid org-size; + }; + + The Want Stop Receiving Data (DWSR) message informs OPES processor + that the callout server wants to stop receiving original data any + time after receiving at least an org-size amount of an application + message prefix. That is, the server is asking the processor to + terminate original dataflow prematurely (see section 8.1) after + sending at least org-size octets. + + An OPES processor receiving a Want Stop Receiving Data (DWSR) message + SHOULD terminate original dataflow by sending an Application Message + End (AME) message with a 206 (partial) status code. + + + + + +Rousskov Standards Track [Page 40] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + An OPES processor MUST NOT terminate its data preservation commitment + (section 7) in reaction to receiving a Want Stop Receiving Data + (DWSR) message. Just like with any other message, an OPES processor + may use information supplied by Want Stop Receiving Data (DWSR) to + decide on future preservation commitments. + +11.13. Want Stop Sending Data (DWSS) + + DWSS: extends message with { + xid; + }; + + The Want Stop Sending Data (DWSS) message informs the OPES processor + that the callout server wants to stop sending adapted data as soon as + possible; the server is asking the processor for permission to + terminate adapted dataflow prematurely (see section 8.2). The OPES + processor can grant this permission by using a Stop Sending Data + (DSS) message. + + Once the DWSS message is sent, the callout server MUST NOT + prematurely terminate adapted dataflow until the server receives a + DSS message from the OPES processor. If the server violates this + rule, the OPES processor MUST act as if no DWSS message were + received. The latter implies that the OCP transaction is terminated + by the processor, with an error. + + An OPES processor receiving a DWSS message SHOULD respond with a Stop + Sending Data (DSS) message, provided the processor would not violate + DSS message requirements by doing so. The processor SHOULD respond + immediately once DSS message requirements can be satisfied. + +11.14. Stop Sending Data (DSS) + + DSS: extends message with { + xid; + }; + + The Stop Sending Data (DSS) message instructs the callout server to + terminate adapted dataflow prematurely by sending an Application + Message End (AME) message with a 206 (partial) status code. A + callout server is expected to solicit the Stop Sending Data (DSS) + message by sending a Want Stop Sending Data (DWSS) message (see + section 8.2). + + A callout server receiving a solicited Stop Sending Data (DSS) + message for a yet-unterminated adapted dataflow MUST immediately + terminate dataflow by sending an Application Message End (AME) + message with a 206 (partial) status code. If the callout server + + + +Rousskov Standards Track [Page 41] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + already terminated adapted dataflow, the callout server MUST ignore + the Stop Sending Data (DSS) message. A callout server receiving an + unsolicited DSS message for a yet-unterminated adapted dataflow MUST + either treat that message as invalid or as solicited (i.e., the + server cannot simply ignore unsolicited DSS messages). + + The OPES processor sending a Stop Sending Data (DSS) message MUST be + able to reconstruct the adapted application message correctly after + the callout server terminates dataflow. This requirement implies + that the processor must have access to any original data sent to the + callout after the Stop Sending Data (DSS) message, if there is any. + Consequently, the OPES processor either has to send no data at all or + has to keep a copy of it. + + If a callout server receives a DSS message and, in violation of the + above rules, waits for more original data before sending an + Application Message End (AME) response, a deadlock may occur: The + OPES processor may wait for the Application Message End (AME) message + to send more original data. + +11.15. Want Data Paused (DWP) + + DWP: extends message with { + xid your-offset; + }; + + The Want Data Paused (DWP) message indicates the sender's temporary + lack of interest in receiving data starting with the specified + offset. This disinterest implies nothing about sender's intent to + send data. + + The "your-offset" parameter refers to dataflow originating at the OCP + agent receiving the parameter. + + If, at the time the Want Data Paused (DWP) message is received, the + recipient has already sent data at the specified offset, the message + recipient MUST stop sending data immediately. Otherwise, the + recipient MUST stop sending data immediately after it sends the + specified offset. Once the recipient stops sending more data, it + MUST immediately send a Paused My Data (DPM) message and MUST NOT + send more data until it receives a Want More Data (DWM) message. + + As are most OCP Core mechanisms, data pausing is asynchronous. The + sender of the Want Data Paused (DWP) message MUST NOT rely on the + data being paused exactly at the specified offset or at all. + + + + + + +Rousskov Standards Track [Page 42] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +11.16. Paused My Data (DPM) + + DPM: extends message with { + xid; + }; + + The Paused My Data (DPM) message indicates the sender's commitment to + send no more data until the sender receives a Want More Data (DWM) + message. + + The recipient of the Paused My Data (DPM) message MAY expect the data + delivery being paused. If the recipient receives data despite this + expectation, it MAY abort the corresponding transaction with a + Transaction End (TE) message indicating a failure. + +11.17. Want More Data (DWM) + + DWM: extends message with { + xid; + [Size-request: your-size]; + }; + + The Want More Data (DWM) message indicates the sender's need for more + data. + + Message parameters always refer to dataflow originating at the other + OCP agent. When sent by an OPES processor, your-size is adp-size; + when sent by a callout server, your-size is org-size. + + The "Size-request" parameter refers to dataflow originating at the + OCP agent receiving the parameter. If a "Size-request" parameter is + present, its value is the suggested minimum data size. It is meant + to allow the recipient to deliver data in fewer chunks. The + recipient MAY ignore the "Size-request" parameter. An absent + "Size-request" parameter implies "any size". + + The message also cancels the Paused My Data (DPM) message effect. If + the recipient was not sending any data because of its DPM message, + the recipient MAY resume sending data. Note, however, that the Want + More Data (DWM) message can be sent regardless of whether the + dataflow in question has been paused. The "Size-request" parameter + makes this message a useful stand-alone optimization. + + + + + + + + + +Rousskov Standards Track [Page 43] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +11.18. Negotiation Offer (NO) + + NO: extends message with { + features; + [SG: my-sg-id]; + [Offer-Pending: boolean]; + }; + + A Negotiation Offer (NO) message solicits a selection of a single + "best" feature out of a supplied list, using a Negotiation Response + (NR) message. The sender is expected to list preferred features + first when it is possible. The recipient MAY ignore sender + preferences. If the list of features is empty, the negotiation is + bound to fail but remains valid. + + Both the OPES processor and the callout server are allowed to send + Negotiation Offer (NO) messages. The rules in this section ensure + that only one offer is honored if two offers are submitted + concurrently. An agent MUST NOT send a Negotiation Offer (NO) + message if it still expects a response to its previous offer on the + same connection. + + If an OPES processor receives a Negotiation Offer (NO) message while + its own offer is pending, the processor MUST disregard the server + offer. Otherwise, it MUST respond immediately. + + + If a callout server receives a Negotiation Offer (NO) message when + its own offer is pending, the server MUST disregard its own offer. + In either case, the server MUST respond immediately. + + If an agent receives a message sequence that violates any of the + above rules in this section, the agent MUST terminate the connection + with a Connection End (CE) message indicating a failure. + + An optional "Offer-Pending" parameter is used for Negotiation Phase + maintenance (section 6.1). The option's value defaults to "false". + + An optional "SG" parameter is used to narrow the scope of + negotiations to the specified service group. If SG is present, the + negotiated features are negotiated and enabled only for transactions + that use the specified service group ID. Connection-scoped features + are negotiated and enabled for all service groups. The presence of + scope does not imply automatic conflict resolution common to + programming languages; no conflicts are allowed. When negotiating + connection-scoped features, an agent MUST check for conflicts within + each existing service group. When negotiating group-scoped features, + an agent MUST check for conflicts with connection-scoped features + + + +Rousskov Standards Track [Page 44] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + already negotiated. For example, it must not be possible to + negotiate a connection-scoped HTTP application profile if one service + group already has an SMTP application profile, and vice versa. + + OCP agents SHOULD NOT send offers with service groups used by pending + transactions. Unless it is explicitly noted otherwise in a feature + documentation, OCP agents MUST NOT apply any negotiations to pending + transactions. In other words, negotiated features take effect with + the new OCP transaction. + + As with other protocol elements, OCP Core extensions may document + additional negotiation restrictions. For example, specification of a + transport security feature may prohibit the use of the SG parameter + in negotiation offers, to avoid situations where encryption is + enabled for only a portion of overlapping transactions on the same + transport connection. + +11.19. Negotiation Response (NR) + + NR: extends message with { + [feature]; + [SG: my-sg-id]; + [Rejects: features]; + [Unknowns: features]; + [Offer-Pending: boolean]; + }; + + A Negotiation Response (NR) message conveys recipient's reaction to a + Negotiation Offer (NO) request. An accepted offer (a.k.a., positive + response) is indicated by the presence of an anonymous "feature" + parameter, containing the selected feature. If the selected feature + does not match any of the offered features, the offering agent MUST + consider negotiation failed and MAY terminate the connection with a + Connection End (CE) message indicating a failure. + + A rejected offer (negative response) is indicated by omitting the + anonymous "feature" parameter. + + The successfully negotiated feature becomes effective immediately. + The sender of a positive response MUST consider the corresponding + feature enabled immediately after the response is sent; the recipient + of a positive response MUST consider the corresponding feature + enabled immediately after the response is received. Note that the + scope of the negotiated feature application may be limited to a + specified service group. The negotiation phase state does not affect + enabling of the feature. + + + + + +Rousskov Standards Track [Page 45] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + If negotiation offer contains an SG parameter, the responder MUST + include that parameter in the Negotiation Response (NR) message. The + recipient of an NR message without the expected SG parameter MUST + treat negotiation response as invalid. + + If the negotiation offer lacks an SG parameter, the responder MUST + NOT include that parameter in the Negotiation Response (NR) message. + The recipient of an NR message with an unexpected SG parameter MUST + treat the negotiation response as invalid. + + An optional "Offer-Pending" parameter is used for Negotiation Phase + maintenance (section 6.1). The option's value defaults to "false". + + When accepting or rejecting an offer, the sender of the Negotiation + Response (NR) message MAY supply additional details via Rejects and + Unknowns parameters. The Rejects parameter can be used to list + features that were known to the Negotiation Offer (NO) recipient but + could not be supported given negotiated state that existed when NO + message was received. The Unknowns parameter can be used to list + features that were unknown to the NO recipient. + +11.20. Ability Query (AQ) + + AQ: extends message with { + feature; + }; + + An Ability Query (AQ) message solicits an immediate Ability Answer + (AA) response. The recipient MUST respond immediately with an AA + message. This is a read-only, non-modifying interface. The + recipient MUST NOT enable or disable any features due to an AQ + request. + + OCP extensions documenting a feature MAY extend AQ messages to supply + additional information about the feature or the query itself. + + The primary intended purpose of the ability inquiry interface is + debugging and troubleshooting and not automated fine-tuning of agent + behavior and configuration. The latter may be better achieved by the + OCP negotiation mechanism (section 6). + +11.21. Ability Answer (AA) + + AA: extends message with { + boolean; + }; + + + + + +Rousskov Standards Track [Page 46] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + An Ability Answer (AA) message expresses the sender's support for a + feature requested via an Ability Query (AQ) message. The sender MUST + set the value of the anonymous boolean parameter to the truthfulness + of the following statement: "At the time of this answer generation, + the sender supports the feature in question". The meaning of + "support" and additional details are feature specific. OCP + extensions documenting a feature MUST document the definition of + "support" in the scope of the above statement and MAY extend AA + messages to supply additional information about the feature or the + answer itself. + +11.22. Progress Query (PQ) + + PQ: extends message with { + [xid]; + }; + + A Progress Query (PQ) message solicits an immediate Progress Answer + (PA) response. The recipient MUST immediately respond to a PQ + request, even if the transaction identifier is invalid from the + recipient's point of view. + +11.23. Progress Answer (PA) + + PA: extends message with { + [xid]; + [Org-Data: org-size]; + }; + + A PA message carries the sender's state. The "Org-Data" size is the + total original data size received or sent by the agent so far for the + identified application message (an agent can be either sending or + receiving original data, so there is no ambiguity). When referring + to received data, progress information does not imply that the data + has otherwise been processed in some way. + + The progress inquiry interface is useful for several purposes, + including keeping idle OCP connections "alive", gauging the agent + processing speed, verifying the agent's progress, and debugging OCP + communications. Verifying progress, for example, may be essential to + implement timeouts for callout servers that do not send any adapted + data until the entire original application message is received and + processed. + + A recipient of a PA message MUST NOT assume that the sender is not + working on any transaction or application message not identified in + the PA message. A PA message does not carry information about + multiple transactions or application messages. + + + +Rousskov Standards Track [Page 47] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + If an agent is working on the transaction identified in the Progress + Query (PQ) request, the agent MUST send the corresponding transaction + ID (xid) when answering the PQ with a PA message. Otherwise, the + agent MUST NOT send the transaction ID. If an agent is working on + the original application message for the specified transaction, the + agent MUST send the Org-Data parameter. If the agent has already + sent or received the Application Message End (AME) message for the + original dataflow, the agent MUST NOT send the Org-data parameter. + + Informally, the PA message relays the sender's progress with the + transaction and original dataflow identified by the Progress Query + (PQ) message, provided the transaction identifier is still valid at + the time of the answer. Absent information in the answer indicates + invalid, unknown, or closed transaction and/or original dataflow from + the query recipient's point of view. + +11.24. Progress Report (PR) + + PR: extends message with { + [xid]; + [Org-Data: org-size]; + }; + + A Progress Report (PR) message carries the sender's state. The + message semantics and associated requirements are identical to those + of a Progress Answer (PA) message except that the PR message, is sent + unsolicited. The sender MAY report progress at any time. The sender + MAY report progress unrelated to any transaction or original + application message or related to any valid (current) transaction or + original dataflow. + + Unsolicited progress reports are especially useful for OCP extensions + dealing with "slow" callout services that introduce significant + delays for the final application message recipient. The report may + contain progress information that will make that final recipient more + delay tolerant. + +12. IAB Considerations + + OPES treatment of IETF Internet Architecture Board (IAB) + considerations [RFC3238] are documented in [RFC3914]. + +13. Security Considerations + + This section examines security considerations for OCP. OPES threats + are documented in [RFC3837] + + + + + +Rousskov Standards Track [Page 48] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + OCP relays application messages that may contain sensitive + information. Appropriate transport encryption can be negotiated to + prevent information leakage or modification (see section 6), but OCP + agents may support unencrypted transport by default. These + configurations will expose application messages to third-party + recording and modification, even if OPES proxies themselves are + secure. + + OCP implementation bugs may lead to security vulnerabilities in OCP + agents, even if OCP traffic itself remains secure. For example, a + buffer overflow in a callout server caused by a malicious OPES + processor may grant that processor access to information from other + (100% secure) OCP connections, including connections with other OPES + processors. + + Careless OCP implementations may rely on various OCP identifiers to + be unique across all OCP agents. A malicious agent can inject an OCP + message that matches identifiers used by other agents, in an attempt + to gain access to sensitive data. OCP implementations must always + check an identifier for being "local" to the corresponding connection + before using that identifier. + + OCP is a stateful protocol. Several OCP commands increase the amount + of state that the recipient has to maintain. For example, a Service + Group Created (SGC) message instructs the recipient to maintain an + association between a service group identifier and a list of + services. + + Implementations that cannot correctly handle resource exhaustion + increase security risks. The following are known OCP-related + resources that may be exhausted during a compliant OCP message + exchange: + + OCP message structures: OCP message syntax does not limit the nesting + depth of OCP message structures and does not place an upper limit + on the length (number of OCTETs) of most syntax elements. + + concurrent connections: OCP does not place an upper limit on the + number of concurrent connections that a callout server may be + instructed to create via Connection Start (CS) messages. + + service groups: OCP does not place an upper limit on the number of + service group associations that a callout server may be instructed + to create via Service Group Created (SGC) messages. + + concurrent transactions: OCP does not place an upper limit on the + number of concurrent transactions that a callout server may be + instructed to maintain via Transaction Start (TS) messages. + + + +Rousskov Standards Track [Page 49] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + concurrent flows: OCP Core does not place an upper limit on the + number of concurrent adapted flows that an OPES processor may be + instructed to maintain via Application Message Start (AMS) + messages. + +14. IANA Considerations + + The IANA maintains a list of OCP features, including application + profiles (section 10.11). For each feature, its uri parameter value + is registered along with the extension parameters (if there are any). + Registered feature syntax and semantics are documented with PETDM + notation (section 9). + + The IESG is responsible for assigning a designated expert to review + each standards-track registration prior to IANA assignment. The OPES + working group mailing list may be used to solicit commentary for both + standards-track and non-standards-track features. + + Standards-track OCP Core extensions SHOULD use + http://www.iana.org/assignments/opes/ocp/ prefix for feature uri + parameters. It is suggested that the IANA populate resources + identified by such "uri" parameters with corresponding feature + registrations. It is also suggested that the IANA maintain an index + of all registered OCP features at the + http://www.iana.org/assignments/opes/ocp/ URL or on a page linked + from that URL. + + This specification defines no OCP features for IANA registration. + +15. Compliance + + This specification defines compliance for the following compliance + subjects: OPES processors (OCP client implementations), callout + servers (OCP server implementations), and OCP extensions. An OCP + agent (a processor or callout server) may also be referred to as the + "sender" or "recipient" of an OCP message. + + A compliance subject is compliant if it satisfies all applicable + "MUST" and "SHOULD" requirements. By definition, to satisfy a "MUST" + requirement means to act as prescribed by the requirement; to satisfy + a "SHOULD" requirement means either to act as prescribed by the + requirement or to have a reason to act differently. A requirement is + applicable to the subject if it instructs (addresses) the subject. + + Informally, OCP compliance means that there are no known "MUST" + violations, and that all "SHOULD" violations are deliberate. In + other words, "SHOULD" means "MUST satisfy or MUST have a reason to + violate". It is expected that compliance claims be accompanied by a + + + +Rousskov Standards Track [Page 50] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + list of unsupported SHOULDs (if any), in an appropriate format, + explaining why the preferred behavior was not chosen. + + Only normative parts of this specification affect compliance. + Normative parts are those parts explicitly marked with the word + "normative", definitions, and phrases containing unquoted capitalized + keywords from [RFC2119]. Consequently, examples and illustrations + are not normative. + +15.1. Extending OCP Core + + OCP extensions MUST NOT change the OCP Core message format, as + defined by ABNF and accompanying normative rules in Section 3.1. + This requirement is intended to allow OCP message viewers, + validators, and "intermediary" software to at least isolate and + decompose any OCP message, even a message with semantics unknown to + them (i.e., extended). + + OCP extensions are allowed to change normative OCP Core requirements + for OPES processors and callout servers. However, OCP extensions + SHOULD NOT make these changes and MUST require on a "MUST"-level that + these changes are negotiated prior to taking effect. Informally, + this specification defines compliant OCP agent behavior until changes + to this specification (if any) are successfully negotiated. + + For example, if an RTSP profile for OCP requires support for offsets + exceeding 2147483647 octets, the profile specification can document + appropriate OCP changes while requiring that RTSP adaptation agents + negotiate "large offsets" support before using large offsets. This + negotiation can be bundled with negotiating another feature (e.g., + negotiating an RTSP profile may imply support for "large offsets"). + + As implied by the above rules, OCP extensions may dynamically alter + the negotiation mechanism itself, but such an alternation would have + to be negotiated first, using the negotiation mechanism defined by + this specification. For example, successfully negotiating a feature + might change the default "Offer-Pending" value from false to true. + + + + + + + + + + + + + + +Rousskov Standards Track [Page 51] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +Appendix A. Message Summary + + This appendix is not normative. The table below summarizes key OCP + message properties. For each message, the table provides the + following information: + + name: Message name as seen on the wire. + + title: Human-friendly message title. + + P: Whether this specification documents message semantics as sent by + an OPES processor. + + S: Whether this specification documents message semantics as sent by + a callout server. + + tie: Related messages such as associated request, response message, + or associated state message. + + +-------+----------------------------+-------+-------+--------------+ + | name | title | P | S | tie | + +-------+----------------------------+-------+-------+--------------+ + | CS | Connection Start | X | X | CE | + | CE | Connection End | X | X | CS | + | SGC | Service Group Created | X | X | SGD TS | + | SGD | Service Group Destroyed | X | X | SGC | + | TS | Transaction Start | X | | TE SGC | + | TE | Transaction End | X | X | TS | + | AMS | Application Message Start | X | X | AME | + | AME | Application Message End | X | X | AMS DSS | + | DUM | Data Use Mine | X | X | DUY DWP | + | DUY | Data Use Yours | | X | DUM DPI | + | DPI | Data Preservation Interest | | X | DUY | + | DWSS | Want Stop Sending Data | | X | DWSR DSS | + | DWSR | Want Stop Receiving Data | | X | DWSS | + | DSS | Stop Sending Data | X | | DWSS | + | DWP | Want Data Paused | X | X | DPM | + | DPM | Paused My Data | X | X | DWP DWM | + | DWM | Want More Data | X | X | DPM | + | NO | Negotiation Offer | X | X | NR SGC | + | NR | Negotiation Response | X | X | NO | + | PQ | Progress Query | X | X | PA | + | PA | Progress Answer | X | X | PQ PR | + | PR | Progress Report | X | X | PA | + | AQ | Ability Query | X | X | AA | + | AA | Ability Answer | X | X | AQ | + +-------+----------------------------+-------+-------+--------------+ + + + + +Rousskov Standards Track [Page 52] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +Appendix B. State Summary + + This appendix is not normative. The table below summarizes OCP + states. Some states are maintained across multiple transactions and + application messages. Some correspond to a single request/response + dialog; the asynchronous nature of most OCP message exchanges + requires OCP agents to process other messages while waiting for a + response to a request and, hence, while maintaining the state of the + dialog. + + For each state, the table provides the following information: + + state: Short state label. + + birth: Messages creating this state. + + death: Messages destroying this state. + + ID: Associated identifier, if any. + + +-------------------------------+-------------+-------------+-------+ + | state | birth | death | ID | + +-------------------------------+-------------+-------------+-------+ + | connection | CS | CE | | + | service group | SGC | SGD | sg-id | + | transaction | TS | TE | xid | + | application message and | AMS | AME | | + | dataflow | | | | + | premature org-dataflow | DWSR | AME | | + | termination | | | | + | premature adp-dataflow | DWSS | DSS AME | | + | termination | | | | + | paused dataflow | DPM | DWM | | + | preservation commitment | DUM | DPI AME | | + | negotiation | NO | NR | | + | progress inquiry | PQ | PA | | + | ability inquiry | PQ | PA | | + +-------------------------------+-------------+-------------+-------+ + + + + + + + + + + + + + +Rousskov Standards Track [Page 53] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +Appendix C. Acknowledgements + + The author gratefully acknowledges the contributions of Abbie Barbir + (Nortel Networks), Oskar Batuner (Independent Consultant), Larry + Masinter (Adobe), Karel Mittig (France Telecom R&D), Markus Hofmann + (Bell Labs), Hilarie Orman (The Purple Streak), Reinaldo Penno + (Nortel Networks), and Martin Stecher (Webwasher), as well as an + anonymous OPES working group participant. + + Special thanks to Marshall Rose for his xml2rfc tool. + +16. References + +16.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax + Specifications: ABNF", RFC 2234, November 1997. + + [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform + Resource Identifiers (URI): Generic Syntax", RFC 2396, + August 1998. + + [RFC3835] Barbir, A., Penno, R., Chen, R., Hofmann, M., and H. + Orman, "An Architecture for Open Pluggable Edge Services + (OPES)", RFC 3835, August 2004. + +16.2. Informative References + + [RFC3836] Beck, A., Hofmann, M., Orman, H., Penno, R., and A. + Terzis, "Requirements for Open Pluggable Edge Services + (OPES) Callout Protocols", RFC 3836, August 2004. + + [RFC3837] Barbir, A., Batuner, O., Srinivas, B., Hofmann, M., and + H. Orman, "Security Threats and Risks for Open Pluggable + Edge Services (OPES)", RFC 3837, August 2004. + + [RFC3752] Barbir, A., Burger, E., Chen, R., McHenry, S., Orman, + H., and R. Penno, "Open Pluggable Edge Services (OPES) + Use Cases and Deployment Scenarios", RFC 3752, April + 2004. + + [RFC3838] Barbir, A., Batuner, O., Beck, A., Chan, T., and H. + Orman, "Policy, Authorization, and Enforcement + Requirements of the Open Pluggable Edge Services + (OPES)", RFC 3838, August 2004. + + + +Rousskov Standards Track [Page 54] + +RFC 4037 OPES Callout Protocol Core March 2005 + + + [RFC3897] Barbir, A., "Open Pluggable Edge Services (OPES) + Entities and End Points Communication", RFC 3897, + September 2004. + + [OPES-RULES] Beck, A. and A. Rousskov, "P: Message Processing + Language", Work in Progress, October 2003. + + [RFC3914] Barbir, A. and A. Rousskov, "Open Pluggable Edge + Services (OPES) Treatment of IAB Considerations", RFC + 3914, October 2004. + + [OPES-HTTP] Rousskov, A. and M. Stecher, "HTTP adaptation with + OPES", Work in Progress, January 2004. + + [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., + Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext + Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. + + [RFC3080] Rose, M., "The Blocks Extensible Exchange Protocol + Core", RFC 3080, March 2001. + + [RFC3238] Floyd, S. and L. Daigle, "IAB Architectural and Policy + Considerations for Open Pluggable Edge Services", RFC + 3238, January 2002. + +Author's Address + + Alex Rousskov + The Measurement Factory + + EMail: rousskov@measurement-factory.com + URI: http://www.measurement-factory.com/ + + + + + + + + + + + + + + + + + + + +Rousskov Standards Track [Page 55] + +RFC 4037 OPES Callout Protocol Core March 2005 + + +Full Copyright Statement + + Copyright (C) The Internet Society (2005). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at ietf- + ipr@ietf.org. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + +Rousskov Standards Track [Page 56] + |