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diff --git a/doc/rfc/rfc7497.txt b/doc/rfc/rfc7497.txt new file mode 100644 index 0000000..f14dccd --- /dev/null +++ b/doc/rfc/rfc7497.txt @@ -0,0 +1,787 @@ + + + + + + +Internet Engineering Task Force (IETF) A. Morton +Request for Comments: 7497 AT&T Labs +Category: Informational April 2015 +ISSN: 2070-1721 + + + Rate Measurement Test Protocol Problem Statement and Requirements + +Abstract + + This memo presents a problem statement for access rate measurement + for test protocols to measure IP Performance Metrics (IPPM). Key + rate measurement test protocol aspects include the ability to control + packet characteristics on the tested path, such as asymmetric rate + and asymmetric packet size. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7497. + +Copyright Notice + + Copyright (c) 2015 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + + + + + +Morton Informational [Page 1] + +RFC 7497 Rate Problem Statement April 2015 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 + 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 + 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3 + 3. Active Rate Measurement . . . . . . . . . . . . . . . . . . . 6 + 4. Measurement Method Categories . . . . . . . . . . . . . . . . 7 + 5. Test Protocol Control and Generation Requirements . . . . . . 9 + 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 + 7. Operational Considerations . . . . . . . . . . . . . . . . . 11 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 + 8.2. Informative References . . . . . . . . . . . . . . . . . 13 + Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 13 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 + +1. Introduction + + There are many possible rate measurement scenarios. This memo + describes one rate measurement problem and presents a rate + measurement problem statement for test protocols to measure IP + Performance Metrics (IPPM). + + When selecting a form of access to the Internet, subscribers are + interested in the performance characteristics of the various + alternatives. Standardized measurements can be a basis for + comparison between these alternatives. There is an underlying need + to coordinate measurements that support such comparisons and to test + control protocols to fulfill this need. The figure below depicts + some typical measurement points of access networks. + + User /====== Fiber ======= Access Node \ + Device -|------ Copper ------- Access Node -|-- Infrastructure -- GW + or Host \------ Radio ------- Access Node / + + GW = Gateway + + The access rate scenario or use case has received widespread + attention of Internet-access subscribers and seemingly all Internet- + industry players, including regulators. This problem is being + approached with many different measurement methods. The eventual + protocol solutions to this problem (and the systems that utilize the + protocol) may not directly involve users, such as when tests reach + from the infrastructure to a service-specific device, such as a + residential gateway. However, no aspect of the problem precludes + users from developing a test protocol controlled via command line + + + + + +Morton Informational [Page 2] + +RFC 7497 Rate Problem Statement April 2015 + + + interfaces on both ends. Thus, a very wide range of test protocols, + active measurement methods, and system solutions are the possible + outcomes of this problem statement. + +1.1. Requirements Language + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in RFC 2119 [RFC2119]. + +2. Purpose and Scope + + The scope and purpose of this memo is to define the measurement + problem statement for test protocols conducting access rate + measurement on production networks. Relevant test protocols include + [RFC4656] and [RFC5357], but the problem is stated in a general way + so that it can be addressed by any existing test protocol, such as + [RFC6812]. + + This memo discusses possible measurement methods but does not specify + exact methods that would normally be part of the solution. + + We are interested in access measurement scenarios with the following + characteristics: + + o The access portion of the network is the focus of this problem + statement. The user typically subscribes to a service with + bidirectional access partly described by rates in bits per second. + The rates may be expressed as raw capacity or restricted capacity, + as described in [RFC6703]. These are the quantities that must be + measured according to one or more standard metrics and for which + measurement methods must also be agreed on as a part of the + solution. + + o Referring to the reference path illustrated below and defined in + [RFC7398], possible measurement points include a subscriber's + host, the access service demarcation point, intra IP access (where + a globally routable address is present), or the gateway between + the measured access network and other networks. + + Subsc. -- Private -- Private -- Access -- Intra IP -- GRA -- Transit + device Net #1 Net #2 Demarc. Access GW GRA GW + + GRA = Globally Routable Address, GW = Gateway + + o Rates at some links near the edge of the provider's network can + often be several orders of magnitude less than link rates in the + aggregation and core portions of the network. + + + +Morton Informational [Page 3] + +RFC 7497 Rate Problem Statement April 2015 + + + o Asymmetrical access rates on ingress and egress are prevalent. + + o In many scenarios of interest, services of extremely large-scale + access require low-complexity devices participating at the user + end of the path, and those devices place limits on clock and + control timing accuracy. + + This problem statement assumes that the most likely bottleneck device + or link is adjacent to the remote (user-end) measurement device or is + within one or two router/switch hops of the remote measurement + device. + + Other use cases for rate measurement involve situations where the + packet switching and transport facilities are leased by one operator + from another, and the link capacity available cannot be directly + determined (e.g., from device-interface utilization). These + scenarios could include mobile backhaul, Ethernet service access + networks, and/or extensions of layer 2 or layer 3 networks. The + results of rate measurements in such cases could be employed to + select alternate routing, investigate whether capacity meets some + previous agreement, and/or adapt the rate of traffic sources if a + capacity bottleneck is found via the rate measurement. In the case + of aggregated leased networks, available capacity may also be + asymmetric. In these cases, the tester is assumed to have a sender + and receiver location under their control. We refer to this scenario + below as the aggregated leased-network case. + + This memo describes protocol support for active measurement methods + consistent with the IPPM working group's traditional charter. Active + measurements require synthetic traffic streams dedicated to testing + and do not make measurements on user traffic. See Section 2 of + [RFC2679], where the concept of a stream is first introduced in IPPM + literature as the basis for collecting a sample (defined in + Section 11 of [RFC2330]). + + As noted in [RFC2330], the focus of access traffic management may + influence the rate measurement results for some forms of access, as + it may differ between user and test traffic if the test traffic has + different characteristics, primarily in terms of the packets + themselves (see Section 13 of [RFC2330] for the considerations on + packet type, or Type-P). + + There are several aspects of Type-P where user traffic may be + examined and selected for special treatment that may affect + transmission rates. Various aspects of Type-P are known to influence + + + + + + +Morton Informational [Page 4] + +RFC 7497 Rate Problem Statement April 2015 + + + Equal-Cost Multipath (ECMP) routing with possible rate measurement + variability across parallel paths. Without being exhaustive, the + possibilities include: + + o Packet length + + o IP addresses + + o Transport protocol (e.g., where TCP packets may be routed + differently from UDP) + + o Transport-protocol port numbers + + This issue requires further discussion when specific solutions/ + methods of measurement are proposed; for this problem statement, it + is sufficient to identify the problem and indicate that the solution + may require an extremely close emulation of user traffic, in terms of + one or more factors above. + + Although the user may have multiple instances of network access + available to them, the primary problem scope is to measure one form + of access at a time. It is plausible that a solution for the single + access problem will be applicable to simultaneous measurement of + multiple access instances, but treatment of this scenario is beyond + the current scope this document. + + A key consideration is whether or not active measurements will be + conducted with user traffic present. In-Service testing takes place + with user traffic present. Out-of-Service testing occurs during pre- + service assessment or during maintenance that interrupts service + temporarily. Out-of-Service testing includes activities described as + "service commissioning", "service activation", and "planned + maintenance". Opportunistic In-Service testing (when there is no + user traffic present throughout the test interval, such as outside + normal business hours) is essentially equivalent to Out-of-Service + testing. Both In-Service and Out-of-Service testing are within the + scope of this problem. + + It is a non-goal to solve the measurement protocol specification + problem in this memo. + + It is a non-goal to standardize methods of measurement in this memo. + However, the problem statement mandates support for one category of + rate measurement methods in the test protocol and adequate control + features for the methods in the control protocol (assuming the + control and test protocols are separate). + + + + + +Morton Informational [Page 5] + +RFC 7497 Rate Problem Statement April 2015 + + +3. Active Rate Measurement + + This section lists features of active measurement methods needed to + measure access rates in production networks. + + Coordination between source and destination devices through control + messages and other basic capabilities described in the methods of + IPPM RFCs [RFC2679] [RFC2680], and assumed for test protocols such as + [RFC5357] and [RFC4656], are taken as given. + + Most forms of active testing intrude on user performance to some + degree, especially In-Service testing. One key tenet of IPPM methods + is to minimize test traffic effects on user traffic in the production + network. Section 5 of [RFC2680] lists the problems with high + measurement traffic rates ("too much" traffic); the most relevant for + rate measurement is the tendency for measurement traffic to skew the + results, followed by the possibility of introducing congestion on the + access link. Section 4 of [RFC3148] provides additional + considerations. The user of protocols for In-Service testing MUST + respect these traffic constraints. Obviously, categories of rate + measurement methods that use less active test traffic than others + with similar accuracy are preferred for In-Service testing, and the + specifications of this memo encourage traffic reduction through + asymmetric control capabilities. + + Out-of-Service tests where the test path shares no links with In- + Service user traffic, have none of the congestion or skew concerns. + Both types should address practical matters common to all test + efforts, such as conducting measurements within a reasonable time + from the tester's point of view and ensuring that timestamp accuracy + is consistent with the precision needed for measurement [RFC2330]. + Out-of-Service tests where some part of the test path is shared with + In-Service traffic MUST respect the In-Service constraints described + above. + + The intended metrics to be measured have strong influence over the + categories of measurement methods required. For example, using the + terminology of [RFC5136], it may be possible to measure a path + capacity metric while In-Service if the level of background (user) + traffic can be assessed and included in the reported result. + + The measurement architecture MAY be either of one-way (e.g., + [RFC4656]) or two-way (e.g., [RFC5357]), but the scale and complexity + aspects of end-user or aggregated access measurement clearly favor + two-way (with a low-complexity user-end device and round-trip results + collection, as found in [RFC5357]). However, the asymmetric rates of + many access services mean that the measurement system MUST be able to + evaluate performance in each direction of transmission. In the two- + + + +Morton Informational [Page 6] + +RFC 7497 Rate Problem Statement April 2015 + + + way architecture, both end devices MUST include the ability to launch + test streams and collect the results of measurements in both (one- + way) directions of transmission (this requirement is consistent with + previous protocol specifications, and it is not a unique problem for + rate measurements). + + The following paragraphs describe features for the roles of test + packet SENDER, RECEIVER, and results REPORTER. + + SENDER: + + Generate streams of test packets with various characteristics as + desired (see Section 4). The SENDER MAY be located at the user end + of the access path or elsewhere in the production network, such as at + one end of an aggregated leased-network segment. + + RECEIVER: + + Collect streams of test packets with various characteristics (as + described above), and make the measurements necessary to support rate + measurement at the receiving end of an access or aggregated leased- + network segment. + + REPORTER: + + Use information from test packets and local processes to measure + delivered packet rates and prepare results in the required format + (the REPORTER role may be combined with another role, most likely the + SENDER). + +4. Measurement Method Categories + + A protocol that addresses the rate measurement problem MUST serve the + test stream generation and measurement functions (SENDER and + RECEIVER). The follow-up phase of analyzing the measurement results + to produce a report is outside the scope of this problem and memo + (REPORTER). + + For the purposes of this problem statement, we categorize the many + possibilities for rate measurement stream generation as follows: + + 1. Packet pairs, with fixed intra-pair packet spacing and fixed or + random time intervals between pairs in a test stream. + + 2. Multiple streams of packet pairs, with a range of intra-pair + spacing and inter-pair intervals. + + + + + +Morton Informational [Page 7] + +RFC 7497 Rate Problem Statement April 2015 + + + 3. One or more packet ensembles in a test stream, using a fixed + ensemble size in packets and one or more fixed intra-ensemble + packet spacings (including zero spacing, meaning that back-to- + back burst ensembles and constant rate ensembles fall in this + category). + + 4. One or more packet chirps (a set of packets with specified + characteristics), where inter-packet spacing typically decreases + between adjacent packets in the same chirp and each pair of + packets represents a rate for testing purposes. + + The test protocol SHALL support test packet ensemble generation + (category 3), as this appears to minimize the demands on measurement + accuracy. Other stream generation categories are OPTIONAL. + + For all supported categories, the following is a list of additional + variables that the protocol(s) MUST be able to specify, control, and + generate: + + a. variable payload lengths among packet streams; + + b. variable length (in packets) among packet streams or ensembles; + + c. variable IP header markings among packet streams; + + d. choice of UDP transport and variable port numbers, or choice of + TCP transport and variable port numbers for two-way architectures + only, or both (see below for additional requirements on TCP + transport generation); and + + e. variable number of packet pairs, ensembles, or streams used in a + test session. + + The ability to revise these variables during an established test + session is OPTIONAL, as multiple test sessions could serve the same + purpose. Another OPTIONAL feature is the ability to generate streams + with VLAN tags and other markings. + + For measurement systems employing TCP as the transport protocol, the + ability to generate specific stream characteristics requires a sender + with the ability to establish and prime the connection such that the + desired stream characteristics are allowed. See [IPPM-METRICS] for + more background. + + + + + + + + +Morton Informational [Page 8] + +RFC 7497 Rate Problem Statement April 2015 + + + Beyond a simple connection handshake and the options establishment, + an "open-loop" TCP sender requires the SENDER ability to: + + o generate TCP packets with well-formed headers (all fields valid), + including Acknowledgement aspects; + + o produce packet streams at controlled rates and variable inter- + packet spacings, including packet ensembles (back-to-back at + server rate); and + + o continue the configured sending stream characteristics despite all + control indications except receive-window exhaust. + + The corresponding TCP RECEIVER performs normally, having some ability + to configure the receive window sufficiently large so as to allow the + SENDER to transmit at will (up to a configured target). + + It may also be useful (for diagnostic purposes) to provide a control + for the bulk transfer capacity measurement with fully-specified (and + congestion-controlled) TCP senders and receivers, as envisioned in + [RFC3148], but this would be a brute-force assessment, which does not + follow the conservative tenets of IPPM measurement [RFC2330]. + + Measurements for each UDP test packet transferred between SENDER and + RECEIVER MUST be compliant with the singleton measurement methods + described in IPPM RFCs [RFC2679][RFC2680]. The timestamp information + or loss/arrival status for each packet MUST be available for + communication to the REPORTER function. + +5. Test Protocol Control and Generation Requirements + + In summary, the test protocol must support the measurement features + described in the sections above. This requires: + + 1. Communicating all test variables to the SENDER and RECEIVER; + + 2. Results collection in a one-way architecture; + + 3. Remote device control for both one-way and two-way architectures; + and + + 4. Asymmetric packet rates in a two-way measurement architecture, or + coordinated one-way test capabilities with the same effect + (asymmetric rates may be achieved through directional control of + packet rate or packet size). + + + + + + +Morton Informational [Page 9] + +RFC 7497 Rate Problem Statement April 2015 + + + The ability to control and generate asymmetric rates in a two-way + architecture is REQUIRED. Two-way architectures are RECOMMENDED to + include control and generation capability for both asymmetric and + symmetric packet sizes because packet size often matters in the scope + of this problem and test systems SHOULD be equipped to detect + directional size dependency through comparative measurements. + + Asymmetric packet size control is indicated when the result of a + measurement may depend on the size of the packets used in each + direction, i.e., when any of the following conditions hold: + + o there is a link in the path with asymmetrical capacity in opposite + directions (in combination with one or more of the conditions + below, but their presence or specific details may be unknown to + the tester); + + o there is a link in the path that aggregates (or divides) packets + into link-level frames and may have a capacity that depends on + packet size, rate, or timing; + + o there is a link in the path where transmission in one direction + influences performance in the opposite direction; + + o there is a device in the path where transmission capacity depends + on packet header processing capacity (in other words, the capacity + is sensitive to packet size); + + o the target application stream is nominally MTU size packets in one + direction versus ACK stream in the other (noting that there are a + vanishing number of symmetrical rate application streams for which + rate measurement is wanted or interesting but such streams might + have some relevance at this time); + + o the distribution of packet losses is critical to rate assessment; + + and possibly other circumstances revealed by measurements comparing + streams with symmetrical size and asymmetrical size. + + Implementations may support control and generation for only symmetric + packet sizes when none of the above conditions hold. + + The test protocol SHOULD enable measurement of the capacity metric + [RFC5136] either Out-of-Service, In-Service, or both; other metrics + [RFC5136] are OPTIONAL. + + + + + + + +Morton Informational [Page 10] + +RFC 7497 Rate Problem Statement April 2015 + + +6. Security Considerations + + The security considerations that apply to any active measurement of + live networks are relevant here as well. See [RFC4656] and + [RFC5357]. + + Privacy considerations for measurement systems, particularly when + Internet users participate in the tests in some way, are described in + [LMAP-FRAMEWORK]. + + There may be a serious issue if a proprietary service level agreement + involved with the access network segment provider were somehow leaked + in the process of rate measurement. To address this, test protocols + SHOULD NOT convey this information in a way that could be discovered + by unauthorized parties. + +7. Operational Considerations + + All forms of testing originate network traffic, either through their + communications for control and results collection, from dedicated + measurement packet streams, or from a combination of both types of + traffic. Testing traffic primarily falls in one of two categories: + subscriber traffic or network management traffic. There is an + ongoing need to engineer networks so that various forms of traffic + are adequately served, and publication of this memo does not change + this need. Service subscribers and authorized users SHOULD obtain + their network operator's or service provider's permission before + conducting tests. Likewise, a service provider or third party SHOULD + obtain the subscriber's permission to conduct tests, since they might + temporarily reduce service quality. The protocol SHOULD communicate + the permission status once the overall system has obtained it, either + explicitly or through other means. + + Subscribers, their service providers and network operators, and + sometimes third parties, all seek to measure network performance. + Capacity testing with active traffic often affects the packet + transfer performance of streams traversing shared components of the + test path, to some degree. The degradation can be minimized by + scheduling such tests infrequently and restricting the amount of + measurement traffic required to assess capacity metrics. As a + result, occasional short-duration estimates with minimal traffic are + preferred to measurements based on frequent file transfers of many + megabytes with similar accuracy. New measurement methodologies + intended for standardization should be evaluated individually for + potential operational issues. However, the scheduled frequency of + testing is as important as the methods used (and schedules are not + typically submitted for standardization). + + + + +Morton Informational [Page 11] + +RFC 7497 Rate Problem Statement April 2015 + + + The new test protocol feature of asymmetrical packet size generation + in two-way testing is recommended in this memo. It can appreciably + reduce the load and packet processing demands of each test and + therefore reduce the likelihood of degradation in one direction of + the tested path. Current IETF standardized test protocols (e.g., + [RFC5357] and [RFC6812]) do not possess the asymmetric size + generation capability with two-way testing. + +8. References + +8.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997, + <http://www.rfc-editor.org/info/rfc2119>. + + [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, + "Framework for IP Performance Metrics", RFC 2330, May + 1998, <http://www.rfc-editor.org/info/rfc2330>. + + [RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way + Delay Metric for IPPM", RFC 2679, September 1999, + <http://www.rfc-editor.org/info/rfc2679>. + + [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way + Packet Loss Metric for IPPM", RFC 2680, September 1999, + <http://www.rfc-editor.org/info/rfc2680>. + + [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. + Zekauskas, "A One-way Active Measurement Protocol + (OWAMP)", RFC 4656, September 2006, + <http://www.rfc-editor.org/info/rfc4656>. + + [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. + Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", + RFC 5357, October 2008, + <http://www.rfc-editor.org/info/rfc5357>. + + [RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting + IP Network Performance Metrics: Different Points of View", + RFC 6703, August 2012, + <http://www.rfc-editor.org/info/rfc6703>. + + + + + + + + + +Morton Informational [Page 12] + +RFC 7497 Rate Problem Statement April 2015 + + +8.2. Informative References + + [IPPM-METRICS] + Mathis, M. and A. Morton, "Model Based Bulk Performance + Metrics", Work in Progress, draft-ietf-ippm-model-based- + metrics-04, March 2015. + + [LMAP-FRAMEWORK] + Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., + Aitken, P., and A. Akhter, "A framework for Large-Scale + Measurement of Broadband Performance (LMAP)", Work in + Progress, draft-ietf-lmap-framework-12, March 2015. + + [RFC3148] Mathis, M. and M. Allman, "A Framework for Defining + Empirical Bulk Transfer Capacity Metrics", RFC 3148, July + 2001, <http://www.rfc-editor.org/info/rfc3148>. + + [RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity", + RFC 5136, February 2008, + <http://www.rfc-editor.org/info/rfc5136>. + + [RFC6812] Chiba, M., Clemm, A., Medley, S., Salowey, J., Thombare, + S., and E. Yedavalli, "Cisco Service-Level Assurance + Protocol", RFC 6812, January 2013, + <http://www.rfc-editor.org/info/rfc6812>. + + [RFC7398] Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and + A. Morton, "A Reference Path and Measurement Points for + Large-Scale Measurement of Broadband Performance", RFC + 7398, February 2015, + <http://www.rfc-editor.org/info/rfc7398>. + +Acknowledgements + + Dave McDysan provided comments and text for the aggregated leased use + case. Yaakov Stein suggested many considerations to address, + including the In-Service vs. Out-of-Service distinction and its + implication on test traffic limits and protocols. Bill Cerveny, + Marcelo Bagnulo, Kostas Pentikousis (a persistent reviewer), and + Joachim Fabini have contributed insightful, clarifying comments that + made this a better document. Barry Constantine also provided + suggestions for clarification. + + + + + + + + + +Morton Informational [Page 13] + +RFC 7497 Rate Problem Statement April 2015 + + +Author's Address + + Al Morton + AT&T Labs + 200 Laurel Avenue South + Middletown, NJ 07748 + United States + + Phone: +1 732 420 1571 + Fax: +1 732 368 1192 + EMail: acmorton@att.com + URI: http://home.comcast.net/~acmacm/ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Morton Informational [Page 14] + |