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diff --git a/doc/rfc/rfc2432.txt b/doc/rfc/rfc2432.txt new file mode 100644 index 0000000..be58bba --- /dev/null +++ b/doc/rfc/rfc2432.txt @@ -0,0 +1,899 @@ + + + + + + +Network Working Group K. Dubray +Request for Comments: 2432 IronBridge Networks +Category: Informational October 1998 + + + Terminology for IP Multicast Benchmarking + +Status of this Memo + + This memo provides information for the Internet community. It does + not specify an Internet standard of any kind. Distribution of this + memo is unlimited. + +Copyright Notice + + Copyright (C) The Internet Society (1998). All Rights Reserved. + +Abstract + + The purpose of this document is to define terminology specific to the + benchmarking of multicast IP forwarding devices. It builds upon the + tenets set forth in RFC 1242, RFC 2285, and other IETF Benchmarking + Methodology Working Group (BMWG) efforts. This document seeks to + extend these efforts to the multicast paradigm. + + The BMWG produces two major classes of documents: Benchmarking + Terminology documents and Benchmarking Methodology documents. The + Terminology documents present the benchmarks and other related terms. + The Methodology documents define the procedures required to collect + the benchmarks cited in the corresponding Terminology documents. + +1. Introduction + + Network forwarding devices are being required to take a single frame + and support delivery to a number of destinations having membership to + a particular group. As such, multicast support may place a different + burden on the resources of these network forwarding devices than with + unicast or broadcast traffic types. + + Such burdens may not be readily apparent at first glance - the IP + multicast packet's Class D address may be the only noticeable + difference from an IP unicast packet. However, there are many + factors that may impact the treatment of IP multicast packets. + + Consider how a device's architecture may impact the handling of a + multicast frame. For example, is the multicast packet subject to the + same processing as its unicast analog? Or is the multicast packet + treated as an exeception and processed on a different data path? + + + +Dubray Informational [Page 1] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Consider, too, how a shared memory architecture may demonstrate a + different performance profile than an architecture which explicitly + passes each individual packet between the processing entities. + + In addition to forwarding device architecture, there are other + factors that may impact a device's or system's multicast related + performance. Protocol requirements may demand that routers and + switches consider destination and source addressing in its multicast + forwarding decisions. Capturing multicast source/destination + addressing information may impact forwarding table size and lengthen + lookups. Topological factors such as the degree of packet + replication, the number of multicast groups being supported by the + system, or the placement of multicast packets in unicast wrappers to + span non-multicast network paths may all potentially affect a + system's multicast related performance. For an overall understanding + of IP multicasting, the reader is directed to [Se98], [Hu95], and + [Mt98]. + + By clearly identifying IP multicast benchmarks and related + terminology in this document, it is hoped that detailed methodologies + can be generated in subsequent documents. Taken in tandem, these two + efforts endeavor to assist the clinical, empirical, and consistent + characterization of certain aspects of multicast technologies and + their individual implementations. Understanding the operational + profile of multicast forwarding devices may assist the network + designer to better deploy multicast in his or her networking + environment. + + Moreover, this document focuses on one source to many destinations + profiling. Elements of this document may require extension when + considering multiple source to multiple destination IP multicast + communication. + +2. Definition Format + + This section cites the template suggested by RFC 1242 in the + specification of a term to be defined. + + Term to be defined. + + Definition: + The specific definition for the term. + + Discussion: + A brief discussion of the term, its application, or other + information that would build understanding. + + + + + +Dubray Informational [Page 2] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Measurement units: + Units used to record measurements of this term, if applicable. + + [Issues:] + List of issues or conditions that affect this term. This field can + present items the may impact the term's related methodology or + otherwise restrict its measurement procedures. This field is + optional in this document. + + [See Also:] + List of other terms that are relevant to the discussion of this + term. This field is optional in this document. + +2.1 Existing Terminology + + This document draws on existing terminology defined in other BMWG + work. Examples include, but are not limited to: + + Throughput [RFC 1242, section 3.17] + Latency [RFC 1242, section 3.8] + Constant Load [RFC 1242, section 3.4] + Frame Loss Rate [RFC 1242, section 3.6] + Overhead behavior [RFC 1242, section 3.11] + Forwarding Rates [RFC 2285, section 3.6] + Loads [RFC 2285, section 3.5] + Device Under Test (DUT) [RFC 2285, section 3.1.1] + System Under Test (SUT) [RFC 2285, section 3.1.2] + + Note: "DUT/SUT" refers to a metric that may be applicable to a DUT or + SUT. + +3. Table of Defined Terms + + 3.1 General Nomenclature + + 3.1.1 Traffic Class. (TC) + 3.1.2 Group Class. (GC) + 3.1.3 Service Class. (SC) + + 3.2 Forwarding and Throughput + 3.2.1 Mixed Class Throughput (MCT). + 3.2.2 Scaled Group Forwarding Matrix (SGFM). + 3.2.3 Aggregated Multicast Throughput (AMT) + 3.2.4 Encapsulation Throughput (ET) + 3.2.5 Decapsulation Throughput (DT) + 3.2.6 Re-encapsulation Throughput (RET) + + + + + +Dubray Informational [Page 3] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + 3.3 Forwarding Latency + 3.3.1 Multicast Latency (ML) + 3.3.2 Min/Max Multicast Latency (Min/Max ML) + + 3.4 Overhead + 3.4.1 Group Join Delay. (GJD) + 3.4.2 Group Leave Delay. (GLD) + + 3.5 Capacity + 3.5.1 Multicast Group Capacity. (MGC) + + 3.6 Interaction + 3.6.1 Burdened Response + 3.6.2 Forwarding Burdened Multicast Latency (FBML) + 3.6.3 Forwarding Burdened Join Delay (FBJD) + +3.1 General Nomenclature + + This section will present general terminology to be used in this and + other documents. + +3.1.1 Traffic Class. (TC) + + Definition: + An equivalence class of packets comprising one or more data + streams. + + Discussion: + In the scope of this document, Traffic Class will be considered a + logical identifier used to discriminate between a set or sets of + packets offered the DUT. + + For example, one Traffic Class may identify a set of unicast + packets offered to the DUT. Another Traffic Class may + differentiate the multicast packets destined to multicast group X. + Yet another Class may distinguish the set of multicast packets + destined to multicast group Y. + + Unless otherwise qualified, the usage of the word "Class" in this + document will refer simply to a Traffic Class. + + Measurement units: + Not applicable. + + + + + + + + +Dubray Informational [Page 4] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +3.1.2 Group Class. (GC) + + Definition: + A specific type of Traffic Class where the packets comprising the + Class are destined to a particular multicast group. + + Discussion: + + Measurement units: + Not applicable. + +3.1.3 Service Class. (SC) + + Definition: + A specific type of Traffic Class where the packets comprising the + Class require particular treatment or treatments by the network + forwarding devices along the path to the packets' destination(s). + + Discussion: + + Measurement units: + Not applicable. + +3.2 Forwarding and Throughput. + + This section presents terminology related to the characterization of + the packet forwarding ability of a DUT/SUT in a multicast + environment. Some metrics extend the concept of throughput presented + in RFC 1242. The notion of Forwarding Rate is cited in RFC 2285. + +3.2.1 Mixed Class Throughput (MCT). + + Definition: + The maximum rate at which none of the offered frames, comprised + from a unicast Class and a multicast Class, to be forwarded are + dropped by the device across a fixed number of ports. + + Discussion: + Often times, throughput is collected on a homogenous traffic class + - the offered load to the DUT is either singularly unicast or + singularly multicast. In most networking environments, the + traffic mix is seldom so uniformly distributed. + + Based on the RFC 1242 definition for throughput, the Mixed Class + Throughput benchmark attempts to characterize the DUT's ability to + process both unicast and multicast frames in the same aggregated + traffic stream. + + + + +Dubray Informational [Page 5] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Measurement units: + Frames per second + + Issues: + Related methodology may have to address the ratio of unicast + packets to multicast packets. + + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.2.2 Scaled Group Forwarding Matrix (SGFM). + + Definition: + A table that demonstrates Forwarding Rate as a function of tested + multicast groups for a fixed number of tested DUT/SUT ports. + + Discussion: + A desirable attribute of many Internet mechanisms is the ability + to "scale." This benchmark seeks to demonstrate the ability of a + SUT to forward as the number of multicast groups is scaled + upwards. + + Measurement units: + Packets per second, with corresponding tested multicast group and + port configurations. + + Issues: + The corresponding methodology may have to reflect the impact that + the pairing (source, group) has on many multicast routing + protocols. + + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.2.3 Aggregated Multicast Throughput (AMT) + + Definition: + The maximum rate at which none of the offered frames to be + forwarded through N destination interfaces of the same multicast + group are dropped. + + Discussion: + Another "scaling" type of exercise, designed to identify the + DUT/SUT's ability to handle traffic as a function of the multicast + destination ports it is required to support. + + + + +Dubray Informational [Page 6] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Measurement units: + The ordered pair (N,t) where, + + N = the number of destination ports of the multicast group. + t = the throughput, in frames per second, relative to the + source stream. + + Issues: + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.2.4 Encapsulation Throughput (ET) + + Definition: + The maximum rate at which frames offered a DUT are encapsulated + and correctly forwarded by the DUT without loss. + + Discussion: + A popular technique in presenting a frame to a device that may not + support a protocol feature is to encapsulate, or tunnel, the + packet containing the unsupported feature in a format that is + supported by that device. + + More specifically, encapsulation refers to the act of taking a + frame or part of a frame and embedding it as a payload of another + frame. This benchmark attempts to characterize the overhead + behavior associated with that translational process. + + Measurement units: + Frames per second. + + Issues: + Consideration may need to be given with respect to the impact of + different frame formats on usable bandwidth. + + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.2.5 Decapsulation Throughput (DT) + + Definition: + The maximum rate at which frames offered a DUT are decapsulated + and correctly forwarded by the DUT without loss. + + + + + + +Dubray Informational [Page 7] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Discussion: + A popular technique in presenting a frame to a device that may not + support a protocol feature is to encapsulate, or tunnel, the + packet containing the unsupported feature in a format that is + supported by that device. At some point, the frame may be required + to be returned its orginal format from its encapsulation wrapper + for use by the frame's next destination. + + More specifically, decapsulation refers to the act of taking a + frame or part of a frame embedded as a payload of another frame + and returning it to the payload's appropriate format. This + benchmark attempts to characterize the overhead behavior + associated with that translational process. + + Measurement units: + Frames per second. + + Issues: + Consideration may need to be given with respect to the impact of + different frame formats on usable bandwidth. + + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.2.6 Re-encapsulation Throughput (RET) + + Definition: + The maximum rate at which frames of one encapsulated format + offered a DUT are converted to another encapsulated format and + correctly forwarded by the DUT without loss. + + Discussion: + A popular technique in presenting a frame to a device that may not + support a protocol feature is to encapsulate, or tunnel, the + packet containing the unsupported feature in a format that is + supported by that device. At some point, the frame may be required + to be converted from one encapsulation format to another + encapsulation format. + + More specifically, re-encapsulation refers to the act of taking an + encapsulated payload of one format and replacing it with another + encapsulated format - all the while preserving the original + payload's contents. This benchmark attempts to characterize the + overhead behavior associated with that translational process. + + Measurement units: + Frames per second. + + + +Dubray Informational [Page 8] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Issues: + Consideration may need to be given with respect to the impact of + different frame formats on usable bandwidth. + + Since frame size can sometimes be a factor in frame forwarding + benchmarks, the corresponding methodology for this metric will + need to consider frame size distribution(s). + +3.3 Forwarding Latency. + + This section presents terminology relating to the characterization of + the forwarding latency of a DUT/SUT in a multicast environment. It + extends the concept of latency presented in RFC 1242. + +3.3.1 Multicast Latency. (ML) + + Definition: + The set of individual latencies from a single input port on the + DUT or SUT to all tested ports belonging to the destination + multicast group. + + Discussion: + This benchmark is based on the RFC 1242 definition of latency. + While it is useful to collect latency between a pair of source and + destination multicast ports, it may be insightful to collect the + same type of measurements across a range of ports supporting that + Group Class. + + A variety of statistical exercises can be applied to the set of + latencies measurements. + + Measurement units: + Time units with enough precision to reflect a latency measurement. + +3.3.2 Min/Max Multicast Latency. (Min/Max ML) + + Definition: + The difference between the maximum latency measurement and the + minimum latency measurement from the set of latencies produced by + the Multicast Latency benchmark. + + Discussion: + This statistic may yield some insight into how a particular + implementation handles its multicast traffic. This may be useful + to users of multicast synchronization types of applications. + + Measurement units: + Time units with enough precision to reflect latency measurement. + + + +Dubray Informational [Page 9] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +3.4 Overhead + + This section presents terminology relating to the characterization of + the overhead delays associated with explicit operations found in + multicast environments. + +3.4.1 Group Join Delay. (GJD) + + Definition: + The time duration it takes a DUT to start forwarding multicast + packets from the time a successful IGMP group membership report + has been issued to the DUT. + + Discussion: + Many factors can contribute to different results, such as the + number or type of multicast-related protocols configured on the + device under test. Other factors are physical topology and "tree" + configuration. + + Because of the number of variables that could impact this metric, + the metric may be a better characterization tool for a device + rather than a basis for comparisons with other devices. + + Issues: + A consideration for the related methodology: possible need to + differentiate a specifically-forwarded multicast frame from those + sprayed by protocols implementing a flooding tactic to solicit + prune feedback. + + While this metric attempts to identify a simple delay, the + underlying and contributing delay components (e.g., propagation + delay, frame processing delay, etc.) make this a less than simple + measurement. The corresponding methodology will need to consider + this and similar factors to ensure a consistent and precise metric + result. + + Measurement units: + Microseconds. + +3.4.2 Group Leave Delay. (GLD) + + Definition: + The time duration it takes a DUT to cease forwarding multicast + packets after a corresponding IGMP "Leave Group" message has been + successfully offered to the DUT. + + + + + + +Dubray Informational [Page 10] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Discussion: + While it is important to understand how quickly a device can + process multicast frames; it may be beneficial to understand how + quickly that same device can stop the process as well. + + Because of the number of variables that could impact this metric, + the metric may be a better characterization tool for a device + rather than a basis for comparisons with other devices. + + Measurement units: + Microseconds. + + Issues: + The Methodology may need to consider protocol-specific timeout + values. + + While this metric attempts to identify a simple delay, the + underlying and contributing delay components (e.g., propagation + delay, frame processing delay, etc.) make this a less than simple + measurement. Moreover, the cessation of traffic is a rather + unobservable event (i.e., at what point is the multicast forwarded + considered stopped on the DUT interface processing the Leave?). + The corresponding methodology will need to consider this and + similar factors to ensure a consistent and precise metric result. + +3.5 Capacity + + This section offers terms relating to the identification of multicast + group limits of a DUT/SUT. + +3.5.1 Multicast Group Capacity. (MGC) + + Definition: + The maximum number of multicast groups a SUT/DUT can support while + maintaining the ability to forward multicast frames to all + multicast groups registered to that SUT/DUT. + + Discussion: + + Measurement units: + Multicast groups. + + Issues: + The related methodology may have to consider the impact of + multicast sources per group on the ability of a SUT/DUT to "scale + up" the number of supportable multicast groups. + + + + + +Dubray Informational [Page 11] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +3.6 Interaction + + Network forwarding devices are generally required to provide more + functionality than than the forwarding of traffic. Moreover, network + forwarding devices may be asked to provide those functions in a + variety of environments. This section offers terms to assist in the + charaterization of DUT/SUT behavior in consideration of potentially + interacting factors. + +3.6.1 Burdened Response. + + Definition: + A measured response collected from a DUT/SUT in light of + interacting, or potentially interacting, distinct stimulii. + + Discussion: + Many metrics provide a one dimensional view into an operating + characteristic of a tested system. For example, the forwarding + rate metric may yield information about the packet processing + ability of a device. Collecting that same metric in view of + another control variable can oftentimes be very insightful. Taking + that same forwarding rate measurement, for instance, while the + device's address table is injected with an additional 50,000 + entries may yield a different perspective. + + Measurement units: + A burdened response is a type of metric. Metrics of this this + type must follow guidelines when reporting results. + + The metric's principal result MUST be reported in conjunction with + the contributing factors. + + For example, in reporting a Forwarding Burdened Latency, the + latency measurement should be reported with respect to + corresponding Offered Load and Forwarding Rates. + + Issues: A Burdened response may be very illuminating when trying to + characterize a single device or system. Extreme care must be + exercised when attempting to use that characterization as a basis + of comparison with other devices or systems. Test agents must + ensure that the measured response is a function of the controlled + stimulii, and not secondary factors. An example of of such an + interfering factor would be configuration mismatch of a timer + impacting a response process. + + + + + + + +Dubray Informational [Page 12] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +3.6.2 Forwarding Burdened Multicast Latency. (FBML) + + Definition: + A multicast latency taken from a DUT/SUT in the presence of a + traffic forwarding requirement. + + Discussion: + This burdened response metric builds on the Multicast Latency + definition offered in section 3.3.1. It mandates that the DUT be + subjected to an additional measure of traffic not required by the + non-burdened metric. + + This metric attempts to provide a means by which to evaluate how + traffic load may or may not impact a device's or system's packet + processing delay. + + Measurement units: + Time units with enough precision to reflect the latencies + measurements. + + Latency measurements MUST be reported with the corresponding + sustained Forwarding Rate and associated Offered Load. + +3.6.3 Forwarding Burdened Group Join Delay. (FBGJD) + + Definition: + A multicast Group Join Delay taken from a DUT in the presence of a + traffic forwarding requirement. + + Discussion: + This burdened response metric builds on the Group Join Delay + definition offered in section 3.4.1. It mandates that the DUT be + subjected to an additional measure of traffic not required by the + non-burdened metric. + + Many factors can contribute to different results, such as the + number or type of multicast-related protocols configured on the + device under test. Other factors could be physical topology or the + logical multicast "tree" configuration. + + Because of the number of variables that could impact this metric, + the metric may be a better characterization tool for a device + rather than a basis for comparisons with other devices. + + Measurement units: + Time units with enough precision to reflect the delay + measurements. + + + + +Dubray Informational [Page 13] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + + Delay measurements MUST be reported with the corresponding + sustained Forwarding Rate and associated Offered Load. + + Issues: + While this metric attempts to identify a simple delay, the + underlying and contributing delay components (e.g., propagation + delay, frame processing delay, etc.) make this a less than simple + measurement. The corresponding methodology will need to consider + this and similar factors to ensure a consistent and precise metric + result. + +4. Security Considerations + + This document addresses metrics and terminology relating to the + performance benchmarking of IP Multicast forwarding devices. The + information contained in this document does not impact the security + of the Internet. + + Methodologies regarding the collection of the metrics described + within this document may need to cite security considerations. This + document does not address methodological issues. + +5. Acknowledgments + + The IETF BMWG participants have made several comments and suggestions + regarding this work. Particular thanks goes to Harald Alvestrand, + Scott Bradner, Brad Cain, Eric Crawley, Bob Mandeville, David Newman, + Shuching Sheih, Dave Thaler, Chuck Winter, Zhaohui Zhang, and John + Galgay for their insightful review and assistance. + + + + + + + + + + + + + + + + + + + + + + +Dubray Informational [Page 14] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +6. References + + [Br91] Bradner, S., "Benchmarking Terminology for Network + Interconnection Devices", RFC 1242, July 1991. + + [Br96] Bradner, S., and J. McQuaid, "Benchmarking Methodology for + Network Interconnect Devices", RFC 1944, May 1996. + + [Hu95] Huitema, C. "Routing in the Internet." Prentice-Hall, 1995. + + [Se98] Semeria, C. and Maufer, T. "Introduction to IP Multicast + Routing." http://www.3com.com/nsc/501303.html 3Com Corp., + 1998. + + [Ma98] Mandeville, R., "Benchmarking Terminology for LAN Switching + Devices", RFC 2285, February 1998. + + [Mt98] Maufer, T. "Deploying IP Multicast in the Enterprise." + Prentice-Hall, 1998. + +7. Author's Address + + Kevin Dubray + IronBridge Networks + 55 Hayden Avenue + Lexington, MA 02421 + USA + + Phone: 781 372 8118 + EMail: kdubray@ironbridgenetworks.com + + + + + + + + + + + + + + + + + + + + + +Dubray Informational [Page 15] + +RFC 2432 Terminology for IP Multicast Benchmarking October 1998 + + +8. Full Copyright Statement + + Copyright (C) The Internet Society (1998). All Rights Reserved. + + This document and translations of it may be copied and furnished to + others, and derivative works that comment on or otherwise explain it + or assist in its implementation may be prepared, copied, published + and distributed, in whole or in part, without restriction of any + kind, provided that the above copyright notice and this paragraph are + included on all such copies and derivative works. However, this + document itself may not be modified in any way, such as by removing + the copyright notice or references to the Internet Society or other + Internet organizations, except as needed for the purpose of + developing Internet standards in which case the procedures for + copyrights defined in the Internet Standards process must be + followed, or as required to translate it into languages other than + English. + + The limited permissions granted above are perpetual and will not be + revoked by the Internet Society or its successors or assigns. + + This document and the information contained herein is provided on an + "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING + TASK FORCE DISCLAIMS 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. + + + + + + + + + + + + + + + + + + + + + + + + +Dubray Informational [Page 16] + |