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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Benchmarking Methodology Working Group G. Trotter 3 Internet Draft Agilent Technologies 4 Document: draft-ietf-bmwg-fib-term-03.txt September 2001 5 Category: Informational 7 Terminology for Forwarding Information Base (FIB) based Router 8 Performance 10 Status of this Memo 12 This document is an Internet-Draft and is in full conformance with 13 all provisions of Section 10 of RFC2026 [1]. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that 17 other groups may also distribute working documents as Internet- 18 Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six 21 months and may be updated, replaced, or obsoleted by other documents 22 at any time. It is inappropriate to use Internet- Drafts as 23 reference material or to cite them other than as "work in progress." 25 The list of current Internet-Drafts can be accessed at 26 http://www.ietf.org/ietf/1id-abstracts.txt. 28 The list of Internet-Draft Shadow Directories can be accessed at 29 http://www.ietf.org/shadow.html. 31 Abstract 33 The forwarding performance of an IP router may be dependent upon or 34 may be linked to the composition and size of the forwarding 35 information base installed within a router. This document describes 36 the terms to be used in a methodology that determines the IP packet 37 forwarding performance of IP routers as a function of the forwarding 38 information base installed within a router. 40 Table of Contents 42 1. Introduction....................................................2 43 2. Overview........................................................2 44 3. Existing Definitions............................................3 45 4. Definition Format...............................................3 46 5. Definitions - parameters........................................3 47 5.1 Network Prefix.................................................3 48 5.2 Network Prefix Length..........................................4 49 5.3 Forwarding Information Base (FIB)..............................4 50 5.4 Forwarding Information Base Entry..............................5 51 5.5 Forwarding Information Base Size...............................5 52 5.6 Longest Length Prefix Match Algorithm..........................6 53 5.7 Forwarding Information Base Prefix Distribution................6 54 5.8 Per-Interface or Per-Card Forwarding Information Base..........7 55 Terminology for FIB based Router Performance Sept., 2001 57 5.9 Per-Interface Forwarding Information Base Cache................8 58 5.10 Route Aggregation.............................................9 59 6. Definitions - metrics...........................................9 60 6.1 Maximum Forwarding Information Base Size.......................9 61 6.2 Forwarding Information Base Learning Time.....................10 62 6.3 Forwarding Information Base-dependent Throughput..............11 63 6.4 Forwarding Information Base-dependent Latency.................11 64 6.5 Forwarding Information Base-dependent Frame Loss Rate.........11 65 7. Security Considerations........................................12 66 8. References.....................................................12 67 9. Acknowledgments................................................12 68 10. Author's Addresses............................................12 70 1. Introduction 72 This document defines terms that are to be used in a methodology 73 that determines the IP packet forwarding performance of IP routers 74 as a function of the forwarding information base installed within 75 the router. 77 This document is restricted to IPv4 routers. 79 The objective of this methodology is to evaluate the performance 80 levels of IP routers as forwarding information bases continue to 81 grow in size and complexity of structure. 83 This methodology utilizes the packet forwarding performance 84 measurements described in [2]; reference will also be made to the 85 associated terminology document [3] for these terms. 87 2. Overview 89 In order to measure the forwarding information base-based router 90 performance, different forwarding information bases (5.3) are 91 installed in the router. The two key elements describing the FIB 92 are the FIB size (5.5) and FIB prefix distribution (5.6). The 93 forwarding performance of a router may be dependent upon these two 94 primary factors, particularly if FIB prefix distributions tend 95 towards longer network prefixes (3). The FIB-dependent throughput, 96 latency and frame loss rate (6.3, 6.4, 6.5), measured with fully 97 meshed traffic flows [2], will reflect the change in performance of 98 the router. Tests may need to be performed up to the maximum FIB 99 size (6.1). 101 When configuring the router for these measurements, the routes need 102 to be manually entered into the router, or advertised via a routing 103 protocol. It may take some period of time (the FIB learning time 104 (6.2)) before the router learns all the routes. 106 When routes are advertised into the router, the routes should be 107 advertised in such a way so that route aggregation (5.10) does not 108 Terminology for FIB based Router Performance Sept., 2001 110 occur. Also, the effect of a per-interface FIB cache (5.9) needs to 111 be taken into account. 113 3. Existing Definitions 115 [3] should be consulted before attempting to make use of this 116 document. [2] contains discussions of a number of terms relevant to 117 the benchmarking of network interconnect devices and should also be 118 consulted. 120 4. Definition Format 122 The definition format is the equivalent to that defined in [3], and 123 is repeated here for convenience: 125 X.x Term to be defined. (e.g., Latency) 127 Definition: 128 The specific definition for the term. 130 Discussion: 131 A brief discussion about the term, it's application and any 132 restrictions on measurement procedures. 134 Measurement units: 135 The units used to report measurements of this term, if 136 applicable. 138 Issues: 139 List of issues or conditions that effect this term. 141 See Also: 142 List of other terms that are relevant to the discussion of 143 this term. 145 5. Definitions - parameters 147 This section defines parameters that would dictate the execution of 148 methodology to determine the FIB based forwarding performance of a 149 router. 151 5.1 Network Prefix 153 Definition: 155 "A network prefix is . . . a contiguous set of bits at the 156 more significant end of the address that defines a set of 157 systems; host numbers select among those systems." 159 (This definition is taken directly from section 2.2.5, 160 "Addressing Architecture", in [4].) 162 Discussion: 164 Terminology for FIB based Router Performance Sept., 2001 166 In the CIDR context, the network prefix is the network 167 component of an IP address. A common alternative to using a 168 bitwise mask to communicate this component is the use of 169 "slash (/) notation." Slash notation binds the notion of 170 network prefix length (see 5.2) in bits to an IP address. 171 E.g., 141.184.128.0/17 indicates the network component of 172 this IPv4 address is 17 bits wide. 174 Measurement units: 175 177 Issues: 179 See Also: 180 Network Prefix Length (5.2) 182 5.2 Network Prefix Length 184 Definition: 185 The number of bits used to define the network prefix. 186 Network prefixes, using CIDR terminology, are typically 187 referred to as 15.35.128.0 /17, indicating that the network 188 prefix is 17 bits long. 190 Discussion: 191 When referring to groups of addresses, the network prefix 192 length is often used as a means of describing groups of 193 addresses as an equivalence class. For example, 100 /16 194 addresses refers to 100 addresses whose network prefix length 195 is 16 bits. 197 Measurement units: 198 bits 200 Issues: 202 See Also: 203 network prefix (5.1) 204 forwarding information base prefix distribution (5.6) 206 5.3 Forwarding Information Base (FIB) 208 Definition: 209 As according to the definition in [4]: 211 "The table containing the information necessary to forward IP 212 Datagrams, in this document, is called the Forwarding 213 Information Base. At minimum, this contains the interface 214 identifier and next hop information for each reachable 215 destination network prefix." 217 Discussion: 219 Terminology for FIB based Router Performance Sept., 2001 221 The forwarding information base describes a database indexing 222 network prefixes versus router port identifiers. 224 A forwarding information base consists of [FIB size (6.1)] 225 FIB entries (5.4). 227 The forwarding information base is distinct from the "routing 228 table" (or, the Routing Information Base), which holds all 229 routing information received from routing peers. 231 The forwarding information base contains unique paths only 232 (i.e. does not contain secondary paths). 234 Measurement units: 235 237 Issues: 239 See Also: 240 forwarding information base entry (5.4) 241 forwarding information base size (5.5) 242 forwarding information base prefix distribution (5.6) 243 maximum forwarding information base size (6.1) 245 5.4 Forwarding Information Base Entry 247 Definition: 248 A single entry within a forwarding information base. This 249 entry consists of the minimum amount of information necessary 250 to make a forwarding decision on a particular packet. The 251 typical components within a forwarding information base entry 252 are a network prefix, a router port identifier and next hop 253 information. This is an entry that the router can and does 254 use to forward packets. 256 Discussion: 257 See (5.3). 259 Measurement units: 260 262 Issues: 264 See Also: 265 forwarding information base (5.3) 266 forwarding information base size (5.5) 267 forwarding information base prefix distribution (5.6) 268 maximum forwarding information base size (6.1) 270 5.5 Forwarding Information Base Size 272 Definition: 274 Terminology for FIB based Router Performance Sept., 2001 276 Refers to the number of forwarding information base entries 277 within a forwarding information base. 279 Discussion: 280 The number of entries within a forwarding information base is 281 one of the key elements that may influence the forwarding 282 performance of a router. Generally, the more entries within 283 the forwarding information base, the longer it could take to 284 find the longest matching network prefix within the 285 forwarding information base. 287 Measurement units: 288 Number of routes 290 Issues: 292 See Also: 293 forwarding information base (5.3) 294 forwarding information base entry (5.4) 295 forwarding information base prefix distribution (5.6) 296 maximum forwarding information base size (6.1) 298 5.6 Longest Length Prefix Match Algorithm 300 Definition: 301 An algorithm that a router uses to quickly match destination 302 addresses within received IP packets to exit interfaces on 303 the router. 305 Discussion: 307 Measurement Units: 308 310 Issues: 312 See Also: 314 5.7 Forwarding Information Base Prefix Distribution 316 Definition: 317 The distribution of network prefix lengths within the 318 forwarding information base. 320 Discussion: 321 Network prefixes within the forwarding information base could 322 be all of a single network prefix length, but, more 323 realistically, the network prefix lengths will be distributed 324 across some range. 326 Individual performance measurements will be made against FIBs 327 populated with the same network prefix length, as well as 328 Terminology for FIB based Router Performance Sept., 2001 330 against FIBs with some distribution of network prefix 331 lengths. 333 The distribution of network prefix lengths may have an impact 334 on the forwarding performance of a router. The longer the 335 network prefix length, the longer it will take for a router 336 to perform the longest length prefix match algorithm, and 337 potentially the lower the performance of the router. 339 Measurement units: 340 The forwarding information base prefix distribution is 341 expressed by a list of network prefix lengths and the 342 percentage of entries within the forwarding information base 343 with a particular network prefix length. For example, a 344 forwarding information base prefix distribution is 345 represented as: 347 {[/16, 100], [/20, 360], [/24, 540]} 349 This indicates that 100 of the entries within the forwarding 350 information base have a 16 bit network prefix length, 360 351 have a 20 bit network prefix length, and 540 have a 24 bit 352 network prefix length. 354 Issues: 356 See Also: 357 forwarding information base (5.3) 358 forwarding information base entry (5.4) 359 forwarding information base size (5.5) 360 maximum forwarding information base size (6.1) 362 5.8 Per-Interface or Per-Card Forwarding Information Base 364 Definition: 365 A complete copy of the forwarding information base, installed 366 on a router's card or individual physical interface to speed 367 the destination address to network prefix lookup process. 369 Discussion: 370 Router manufacturers have developed many optimizations for 371 routers, of which one optimization is to copy the forwarding 372 information base to every interface or interface card on the 373 router. By doing this, destination address / network prefix 374 lookups can be performed on the interface or card, unloading 375 a router's CPU. 377 Measurement units: 378 380 Issues: 382 See Also: 384 Terminology for FIB based Router Performance Sept., 2001 386 forwarding information base (5.3) 387 per-interface forwarding information base cache (5.9) 389 5.9 Per-Interface Forwarding Information Base Cache 391 Definition: 392 A subset of a forwarding information base, installed on a 393 router's interface card to speed the destination address / 394 network prefix lookup process. 396 Discussion: 397 Prior to installing a complete copy of the forwarding 398 information base on each interface of a router, a popular 399 technique for speeding destination address lookups is to 400 install a cache of frequently used routes on a router's 401 interface. 403 The most frequently used routes are placed in the forwarding 404 information base cache. IP packets whose destination address 405 does not match a network prefix within the per-interface 406 forwarding information base cache are forwarded to a router's 407 central processor for lookup in the complete forwarding 408 information base. 410 The implication for benchmarking the performance of a router 411 as a function of the forwarding information base is 412 significant. IP packets whose destination address matches an 413 entry within the per-interface forwarding information base 414 cache could be forwarded more quickly than packets whose 415 destination address does not match an entry within the per- 416 interface forwarding information base cache. 418 To create useful benchmarks, the role of a per-interface 419 forwarding cache needs to be considered. The nature of 420 benchmarking tests to measure the impact of the forwarding 421 performance of a router requires that the destination 422 addresses within IP packets transmitted into the router be 423 distributed amongst the total set of network prefixes 424 advertised into the router. This negates the role of a per- 425 interface forwarding information base cache, but serves to 426 stress the forwarding information base-based packet 427 forwarding performance of the router. 429 Measurement units: 430 432 Issues: 434 See Also: 435 forwarding information base (5.3) 436 per-interface forwarding information base (5.8) 437 Terminology for FIB based Router Performance Sept., 2001 439 5.10 Route Aggregation 441 Definition: 442 The ability of a router to collapse many forwarding 443 information base entries into a single entry. 445 Discussion: 446 A router may aggregate routes in a forwarding information 447 base into a single entry to conserve space. 449 When advertising routes into a router to perform benchmarking 450 tests as a function of the forwarding information base 451 installed within the router, it is necessary to ensure that a 452 router does not aggregate routes. 454 Thus, when routes are advertised to the router or installed 455 statically, care must be taken to ensure that the router does 456 not aggregate routes. 458 For example, if advertising a set of /24 network prefixes 459 into a particular port on the router, 256 consecutive /24 460 routes, sharing a common leading 16 bits, should not be 461 advertised on a single port. If this is done, then the 462 router will install a single entry within the forwarding 463 information base indicating that all networks matching a 464 particular /16 network prefix are accessible through one 465 particular entry. 467 Route aggregation on a router can be turned off, but routes 468 should still be advertised into the router in such a manner 469 as to avoid route aggregation. 471 Measurement units: 472 474 Issues: 476 See Also: 478 6. Definitions - metrics 480 This section defines the metrics, or results, that would 481 characterized the FIB based forwarding performance of a router. 483 6.1 Maximum Forwarding Information Base Size 485 Definition: 486 The maximum number of forwarding information base entries 487 that can be supported within the forwarding information base. 488 The Maximum Forwarding Information Base Size is the size over 489 which all entries can and are used to forward traffic. 491 Discussion: 493 Terminology for FIB based Router Performance Sept., 2001 495 It is useful to know the maximum forwarding information base 496 size for a router as it will be an indicator of the ability 497 of the router to function within the given application space, 498 and whether the router will be able to handle projected 499 network growth. 501 As a benchmarking value, it is necessary to discover this 502 value so that performance measurements can be made up to the 503 maximum possible forwarding information base size. 505 Measurement units: 506 Number of routes 508 Issues: 509 Could this value vary with the forwarding information base 510 prefix distribution? 512 See Also: 513 forwarding information base (5.3) 514 forwarding information base entry (5.4) 515 forwarding information base size (5.5) 516 forwarding information base prefix distribution (5.6) 518 6.2 Forwarding Information Base Learning Time 520 Definition: 521 The time a router takes to process received routing messages, 522 and to construct (and, possibly to distribute amongst the 523 interface cards in the router) the forwarding information 524 base. This is measured from the time at which a router is 525 presented with the first routing message, through to when it 526 can forward packets using any entry in the forwarding 527 information base. 529 Discussion: 530 It takes time for a router to construct its forwarding 531 information base. A router needs to process received routing 532 packets, build the routing information database, select the 533 best paths, build the forwarding information base and then 534 possibly distribute the forwarding information base or a 535 subset thereof to the interface cards. This entire process 536 can take several minutes with very large forwarding 537 information bases. 539 When performing benchmarking tests that take the forwarding 540 information base into account, time must be allocated for the 541 router to process the routing information and to install the 542 complete forwarding information base within itself, before 543 performance measurements are made. 545 Measurement units: 546 Prefixes per second. 548 Terminology for FIB based Router Performance Sept., 2001 550 Issues: 552 See Also: 553 forwarding information base (5.3) 555 6.3 Forwarding Information Base-dependent Throughput 557 Definition: 558 Throughput, as defined in [3], used in a context where the 559 forwarding information base influences the throughput. 561 Discussion: 562 This definition for FIB-dependent throughput is added to 563 distinguish the context of this measurement from that defined 564 in [3]. 566 Measurement units: 567 See [3]. 569 Issues: 571 See Also: 572 forwarding information base-dependent latency (6.4) 573 forwarding information base-dependent frame loss rate (6.5) 575 6.4 Forwarding Information Base-dependent Latency 577 Definition: 578 Latency, as defined in [3], used in a context where the 579 forwarding information base influences the throughput. 581 Discussion: 582 This definition for FIB-dependent latency is added to 583 distinguish the context of this measurement from that defined 584 in [3]. 586 Measurement units: 587 See [3]. 589 Issues: 591 See Also: 592 forwarding information base-dependent throughput (6.3) 593 forwarding information base-dependent frame loss rate (6.5) 595 6.5 Forwarding Information Base-dependent Frame Loss Rate 597 Definition: 598 Frame Loss Rate, as defined in [3], used in a context where 599 the forwarding information base influences the throughput. 601 Discussion: 603 Terminology for FIB based Router Performance Sept., 2001 605 This definition for FIB-dependent frame loss rate is added to 606 distinguish the context of this measurement from that defined 607 in [3]. 609 Measurement units: 610 See [3]. 612 Issues: 614 See Also: 615 forwarding information base-dependent throughput (6.3) 616 forwarding information base-dependent latency (6.4) 618 7. Security Considerations 620 As this document is solely for the purpose of providing metric 621 methodology and describes neither a protocol nor a protocols 622 implementation, there are no security considerations associated with 623 this document. 625 8. References 627 1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 628 9, RFC 2026, October 1996. 629 2 Bradner, S., McQuaid, J., "Benchmarking Methodology for Network 630 Interconnect Devices", RFC 2544, March 1999 631 3 Bradner, S., "Benchmarking Terminology for Network 632 Interconnection Devices", RFC 1242, July 1991 633 4 Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, 634 June 1995 636 9. Acknowledgments 638 10. Author's Addresses 640 Guy Trotter 641 Agilent Technologies (Canada) Inc. 642 #2500 4710 Kingsway 643 Burnaby, British Columbia 644 Canada 645 V5H 4M2 646 Phone: +1 604 454 3516 647 Email: Guy_Trotter@agilent.com 649 Full Copyright Statement 651 "Copyright (C) The Internet Society (2001). 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