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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group K. Patel 3 Internet-Draft R. Fernando 4 Intended status: Informational Cisco Systems 5 Expires: January 13, 2014 H. Gredler 6 Juniper Networks 7 S. Amante 8 Level 3 Communications, Inc. 9 July 12, 2013 11 Use Cases for an Interface to BGP Protocol 12 draft-keyupate-irs-bgp-usecases-02.txt 14 Abstract 16 A network routing protocol like BGP is typically configured and 17 results of its operation are analyzed through some form of Command 18 Line Interface (CLI) or NETCONF. These interactions to control BGP 19 and diagnose its operation encompass: configuration of protocol 20 parameters, display of protocol data, setting of certain protocol 21 state and debugging of the protocol. 23 Interface to the Routing System's (IRS) Programmatic interfaces, as 24 defined in [I-D.ward-irs-framework], provides an alternate way to 25 control the configuration and diagnose the operation of the BGP 26 protocol. IRS may be used for the configuration, manipulation, 27 polling or analyzing protocol data. This document describes set of 28 use cases for which IRS can be used for BGP protocol. It is intended 29 to provide a base for the solution draft describing a set of 30 interfaces to the BGP protocol. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at http://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on January 13, 2014. 49 Copyright Notice 51 Copyright (c) 2013 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 This document may contain material from IETF Documents or IETF 65 Contributions published or made publicly available before November 66 10, 2008. The person(s) controlling the copyright in some of this 67 material may not have granted the IETF Trust the right to allow 68 modifications of such material outside the IETF Standards Process. 69 Without obtaining an adequate license from the person(s) controlling 70 the copyright in such materials, this document may not be modified 71 outside the IETF Standards Process, and derivative works of it may 72 not be created outside the IETF Standards Process, except to format 73 it for publication as an RFC or to translate it into languages other 74 than English. 76 Table of Contents 78 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 79 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 80 2. BGP Configuration . . . . . . . . . . . . . . . . . . . . . . 3 81 2.1. BGP Protocol Configuration . . . . . . . . . . . . . . . 4 82 2.2. BGP Policy Configuration . . . . . . . . . . . . . . . . 5 83 3. BGP Protocol Operation . . . . . . . . . . . . . . . . . . . 7 84 3.1. BGP Error Handling for Internal BGP Sessions . . . . . . 7 85 4. BGP Route Manipulation . . . . . . . . . . . . . . . . . . . 8 86 4.1. Customized Best Path Selection Criteria . . . . . . . . . 8 87 4.2. Flowspec Routes . . . . . . . . . . . . . . . . . . . . . 8 88 4.3. Route Filter Routes for Legacy Routers . . . . . . . . . 9 89 4.4. Optimized Exit Control . . . . . . . . . . . . . . . . . 9 90 5. BGP Events . . . . . . . . . . . . . . . . . . . . . . . . . 9 91 5.1. Notification of Routing Events . . . . . . . . . . . . . 10 92 5.2. Tracing Dropped BGP Routes . . . . . . . . . . . . . . . 11 93 5.3. BGP Protocol Statistics . . . . . . . . . . . . . . . . . 12 94 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 95 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 96 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 97 8.1. Normative References . . . . . . . . . . . . . . . . . . 13 98 8.2. Informative References . . . . . . . . . . . . . . . . . 14 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 101 1. Introduction 103 Typically, a network routing protocol like BGP is configured and 104 results of its operation are analyzed through some form of Command 105 Line Interface (CLI) or NETCONF. These interactions to control BGP 106 and diagnose its operation encompass: configuration of protocol 107 parameters, display of protocol data, setting of certain protocol 108 state and debugging of the protocol. 110 The IRS Framework document [I-D.ward-irs-framework] describes a 111 mechanism to control network protocols like BGP using a set of 112 programmatic interfaces. These programmatic interfaces allow one to 113 control the BGP protocol by analyzing its operational state and 114 routing protocol data, plus manipulating BGP's configuration to 115 achieve various goals. The IRS is not intended to replace any 116 existing configuration mechanisms, (i.e.: Command Line Interface or 117 NETCONF). Instead, IRS is intended to augment those existing 118 mechanisms by defining a standardized set of programmatic interfaces 119 to enable easier configuration, interrogation and analysis of the BGP 120 protocol. 122 This document describes set of use cases for which IRS's programmatic 123 interfaces can be used to control and analyze the operation of BGP. 124 The use cases described in this document cover the following aspects 125 of BGP: protocol parameter configuration, configuration of routing 126 policies, protocol route manipulation and tracking of protocol 127 events. The goal is to inform the community's understanding of where 128 the IRS BGP extensions fit within the overall IRS architecture. It 129 is intended to provide a basis for the solutions draft describing the 130 set of Interfaces to the BGP protocol. 132 1.1. Requirements Language 134 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 135 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 136 document are to be interpreted as described in RFC 2119 [RFC2119]. 138 2. BGP Configuration 140 The configuration of BGP is arduous to establish and maintain, 141 particularly on networks whose services have a requirement for 142 complex routing policies. This need is magnified by the need to 143 routinely perform changes to large numbers of BGP routers to, for 144 example: add or remove customer's BGP sessions, announce or withdraw 145 (customer) IP prefixes in BGP, modify BGP policies to effect changes 146 in Traffic Engineering, audit BGP routers to ensure they have 147 consistent and appropriate BGP policies, etc. 149 There are three categories of BGP configuration: 151 1. Local BGP routing protocol configuration: local Autonomous System 152 Number (ASN), BGP path selection properties of the router, 153 injection of (aggregate) routes into BGP, etc. 155 2. Local BGP policies: policies designed to filter and then 156 manipulate BGP attributes associated with BGP routes learned 157 through BGP sessions. These policies typically live in the 158 global configuration of a BGP router, but are applied on a per- 159 BGP neighbor basis (or, group of BGP neighbors); and, 161 3. BGP neighbor sessions: remote ASN, remote IP address, address 162 families, BGP policies to applied to routes, max-prefix limits, 163 etc. 165 The sum total of BGP configuration on a BGP router is typically the 166 largest quantify of configuration on Service Provider's BGP routers, 167 by a fairly large margin. When that is combined with the large set 168 of routine configuration changes, mentioned above, it should be 169 fairly clear that systematic reading, configuration and control of 170 BGP routers through a mechanism like IRS would greatly benefit all 171 operators of BGP routers. 173 While it may not be possible to provide programmatic APIs for 174 esoteric vendor-specific policy configuration, it is possible to 175 provide such API's for BGP protocol specific configuration and the 176 more commonly used BGP routing policies. 178 2.1. BGP Protocol Configuration 180 Ability to enable and disable new address families within a BGP 181 protocol for a network of BGP speaking routers is a challenge. The 182 challenge is mainly in keeping track of BGP speaker's feature 183 capabilities and then configuration of new address families on a 184 multiple BGP speakers within a given network. With the necessary 185 information, IRS controllers allow a network operator to push 186 configuration information for enabling and disabling of new address 187 families on a partial or entire set of BGP speakers within a given 188 network. This would assist in building BGP overlay networks as 189 needed. 191 For VPN address families, the main challenge lies in the complex VPN 192 configuration required to setup the control plane for Customer VPNs. 194 The configuration involves creating a Virtual Routing and Forwarding 195 instance (VRF), a Route Distinguisher (RD) that ensures each customer 196 prefixes remains unique across VPNs, and Route Targets (RT) that help 197 ensure that the Customer prefixes are segregated appropriately so 198 that they do not cross the VPN boundaries. IRS would allow a network 199 operator to push such configuration from a central location where a 200 global VPN provisioning information could be stored. This helps 201 avoid manual configuration of a VPN on multiple routers. Instead the 202 configuration is controlled and pushed though a central IRS 203 controller using a programmatic set of APIs on targeted set of BGP 204 speakers. 206 Use of IRS controllers to announce protocol configuration information 207 would simplify and automate configuration of BGP protocol in IBGP 208 deployments where the protocol based policies are seldom used. To 209 facilitate such a centralized configuration model, BGP speakers could 210 be extended to use programmatic APIs to announce their feature 211 capabilities as part of protocol initialization to the centralize IRS 212 controllers. This would assist IRS controllers to auto-discover BGP 213 protocol capabilities of various BGP speakers in a given network. 214 IRS controllers in turn would use the information towards enabling/ 215 disabling of BGP specific features on BGP speakers. 217 2.2. BGP Policy Configuration 219 Filtering of BGP routes is strongly recommended to control the 220 announcements of BGP prefixes across the internet. Most providers 221 make extensive use of BGP prefix filtering policies at the edge of 222 their networks. The reasons for filtering BGP prefixes are: 224 o Avoid Unwanted Route Announcements. Filter prefixes that MUST not 225 be routed [RFC5735], [RFC5156]. Filter prefixes that are not 226 allocated by Internet Routing Registries. 228 o Facilitate Route Summarization. Filter prefixes beyond certain 229 agreed prefix mask length between providers. Route Summarization 230 helps control BGP RIB and FIB table size. 232 o Defensive Security. Filter prefixes from Stub customer ASes that 233 are not owned by the customers. Filter customer prefixes 234 announced by other providers. This helps avoid prefix hijacking. 236 A set of standards-based schemas to enable configuration of Local BGP 237 policies and BGP neighbor sessions was realized through the Routing 238 Policy Specification Language (RSPL) [RFC2622]. The RPSL defined a 239 standards-based schemas, or 'objects' as it called them, that 240 defined: 242 o binding of IP prefixes to (one or more) Origin AS, (route 243 objects); 245 o collections of routes (route-set objects); 247 o collections of Autonomous Systems (as-set objects); and, 249 o routing policy of an Autonomous System to/from its adjacent 250 neighbor AS'es, (aut-num objects) 252 Each ASN is responsible for creation, modification and deletion of 253 its RPSL objects in an Internet Routing Registry (IRR). IRR's are 254 typically operated by Regional Internet Registries (RIR's) and a few 255 dozen larger ISP's and independent organizations. The IRR's provide 256 a well-known location for all organizations attached to the Internet 257 to retrieve or update RPSL objects. 259 While still widely and actively used by Internet Service Providers, 260 the prevailing belief is that the data contained in the IRR's is 261 inaccurate, primarily due to a lack of deployed authorization method 262 with respect to the creation of modification of RPSL objects. It 263 should be noted that this criticism is not directed at the previously 264 defined RPSL schemas, but rather at the data contained in RPSL 265 schemas by end-users of the IRR system. Please refer to the IRR And 266 Routing Policy Configuration Considerations 267 [I-D.mcpherson-irr-routing-policy-considerations] document for a more 268 thorough discussion of the history and present state of the IRR's. 270 Currently, RPSL schemas are exchanged between non-routing systems 271 (servers) used within the IRR system. In addition, open-source and 272 proprietary applications create or modify RPSL schemas, as necessary, 273 to signal the announcement (or, withdrawal) of an IP prefix from an 274 ASN or the creation (or, teardown) of a neighbor relationship between 275 two adjacent ASN's. Most importantly, these RPSL schemas are 276 consumed by similar applications to automatically build routing 277 policies, (i.e.: lists of IP prefixes, corresponding Origin ASN's and 278 /or AS_PATH's), that then get translated to device-specific syntax 279 (i.e.: CLI) before being pushed into individual BGP routers to effect 280 routing policy on the network. It is common for Internet Service 281 Providers to perform updates to these routing policies across their 282 entire network on a daily basis. 284 With IRS it would be desirable to change the last step in the above 285 process so that BGP policies derived from RPSL schemas, and other 286 information sources, are translated into standards-based schemas that 287 are then pushed, or pulled, into individual BGP routers. More 288 generally, IRS controllers could use API's to gather information 289 required to build various types of BGP routing policies plus the 290 corresponding set of Autonomous System Border Routers (ASBR's) where 291 such policies need to be applied in the network and, finally, making 292 those changes to individual network elements so those BGP policies 293 take effect in the network. In doing so, a network operator now has 294 a centralized way of building and making these policies take effect 295 across the network in a coordinated manner. 297 3. BGP Protocol Operation 299 It is increasingly common for services facilitated via BGP to be 300 subject to severe, widespread disruptions (outages), primarily due to 301 the destructive teardown of BGP sessions as a result of receiving 302 malformed BGP attributes. The document Operational Requirements for 303 Enhanced Error Handling Behaviour in BGP-4 304 [I-D.ietf-grow-ops-reqs-for-bgp-error-handling] outlines requirements 305 to try to minimize the scope of the impact attributed to such errors. 306 Unfortunately, more fine-grained BGP error handling solutions, which 307 would result in little to no impact on the operation of BGP protocol, 308 remain elusive. 310 3.1. BGP Error Handling for Internal BGP Sessions 312 It is possible that IRS could enable enhanced error handling 313 techniques for Internal BGP sessions. At a minimum, IRS-capable BGP 314 routers could signal an event such as "Malformed Attribute Received" 315 toward an IRS controller(s). IRS controller(s) may already have a 316 real-time view of BGP routes, and corresponding BGP attributes, or 317 may dynamically interrogate BGP routers in the network to identify 318 the present propagation scope of the BGP route(s) that are affected. 319 Finally, the IRS controller(s) could then signal back to BGP routers 320 to apply a filter that would block propagation of the BGP attribute 321 or BGP route, as necessary, in order to temporarily aid in 322 consistency of BGP routing information across the entire network 323 until a permanent fix can be developed and deployed within BGP 324 routers. 326 IRS would enable the global visibility and global control over the 327 operational state of BGP, within a given Autonomous System, that is 328 necessary to facilitate the learning of, rapid response to and more 329 fine-grained isolation/scoping of BGP protocol events that currently 330 cause a destructive tear-down of BGP sessions that lead to widespread 331 disruptions of services. 333 4. BGP Route Manipulation 335 Multiprotocol BGP [RFC4760] provides support to carry routing 336 information for different BGP address families. Route manipulation 337 is heavily done across these different address families for different 338 reasons. BGP IPv4 and IPv6 address families use BGP Communities 339 [RFC1997] and other IBGP and EBGP attributes to manipulate BGP routes 340 for Traffic Engineering purpose. BGP VPN adddress families use 341 Extended Communities [RFC4360] to filter unwanted BGP routes. BGP 342 Flowspec address family [RFC5575] is used to install Flow based 343 filters to filter unwanted data traffic. The following sub-sections 344 describe the use of IRS towards BGP Route Manipulation for different 345 BGP address families. 347 4.1. Customized Best Path Selection Criteria 349 The BGP customized Bestpath facilitates custom bestpath computations 350 within a BGP speaking network. It is usually used within an IBGP 351 network. Customized bestpaths use special extended communities known 352 as cost communities. Cost communities carry enough information; 353 Point of Insertion (POI) and the cost value to signal where in BGP 354 bestpath the customize checks need to be done. Both, the traffic 355 engineering as well as backdoor (SHAM) links use customized bestpath 356 computation. 358 With IRS, it would be possible for an IRS controller to push routes 359 with custom cost communities on the BGP routers for Traffic 360 Engineering purpose. IRS controller now can act as a central entity 361 keeping track of all Traffic engineering data that get applied to BGP 362 routes within an IBGP network. 364 4.2. Flowspec Routes 366 The BGP flowspec address family is used to disseminate the traffic 367 flow specification to the BGP Autonomous System Border Routers 368 (ASBRs) and Provider Edge (PE) routers. Both, the BGP ASBRs and the 369 PEs would translate the received BGP traffic flow specification into 370 an Access Control List (ACL) and install it in router's forwarding 371 path. Using such ACLs routers can now classify, shape, rate limit, 372 filter, or redirect traffic flows. 374 With IRS, it would be possible for an IRS controller to push traffic 375 flow specifications to the BGP ASBRs and the PE routers. IRS 376 controller can act as a central entity tracking all the traffic flow 377 specifications that are installed within an IBGP network. IRS 378 controller could also prioritize and control the announcement of 379 traffic flow specifications according to various ASRBs and PE 380 router's capacity. BGP ASBRs and PE routers MAY forward traffic flow 381 specifications received from EBGP speakers to IRS Controllers. This 382 would allow IRS controllers to centrally manage and track any 383 externally received traffic flow specifications. 385 4.3. Route Filter Routes for Legacy Routers 387 The BGP Route Filter address family is used to disseminate the Route 388 Target filter information between VPN BGP speakers. This information 389 is then used to build a route distribution graph that helps in 390 limiting the propagation of VPN NLRI within a VPN network. However, 391 it requires that all the BGP VPN routers are upgraded to support this 392 functionality. Otherwise, the graph information is incomplete when a 393 VPN network consists of legacy routers that participates in VPN but 394 does not implement the BGP route filter address family. 396 With IRS, it would be possible for an IRS controller to push router 397 filter information to BGP RR routers on behalf of all legacy routers 398 that participates in VPN but does not support or implement the BGP 399 route filter address family. IRS controller can act as a central 400 entity tracking all the configured Route Filters for legacy routers 401 and push them on appropriate RRs who in turn would push it to ASBRs 402 and PE routers. In this way, IRS controllers help build an optimal 403 route distribution graph that would assist in filtering of VPN NLRIs 404 in a VPN network. 406 4.4. Optimized Exit Control 408 Optimized Exit Control is used to provide route optimization and load 409 distribution for multiple network connections between networks. 410 Network operators can monitor IP traffic flows and then could define 411 policies and rules based on traffic class performance, link bandwidth 412 monetary costs, link load distribution, traffic types, link failures, 413 etc. 415 With IRS, it would be possible for an IRS controller to manipulate 416 BGP routes and its parameters that influence BGP bestpath decisions. 417 IRS controller could act as a central entity that would monitor and 418 manipulate BGP routes based on central network based policies. Such 419 routes would then be injected by a IRS controller into the network so 420 as to get the load distribution for multiple network connections. 422 5. BGP Events 423 Given the extremely large number of BGP Routes in networks, it is 424 critical to have scalable mechanisms that can be used to monitor for 425 events affecting routing state and, consequently, reachability. In 426 addition, similar tools are needed in order to monitor BGP protocol 427 statistics, which help operators and developers better understand 428 scalability of software and hardware that BGP utilizes. 430 IRS could provide a publish-subscribe capability to applications to: 432 o request monitoring of BGP routes and related events; and, 434 o subscribe to the IRS controller to receive events related to BGP 435 routes or other protocol-related events of interest. 437 5.1. Notification of Routing Events 439 There are certain IP prefixes, for example those that are arbitrarily 440 classified by a given network operator as "high visibility" by its 441 end-users, for which immediate notification of changes in their state 442 are extremely useful to know about. Upon notification of such 443 events, a Network Operations Center (NOC) could respond to customer 444 inquiries in a more timely fashion; alternatively, the NOC may decide 445 to perform Traffic Engineering to restore service, etc. 447 Currently, the only way to learn of such events is for a BGP 448 monitoring system to establish a BGP session with a multitude of BGP 449 routers in an AS. Then, the BGP monitoring system needs to look 450 through all BGP UPDATE's in order to identify those events that are 451 of interest to it. Note, this doesn't account for the fact that 452 there are several applications that might be simultaneously 453 interested in learning of events to a given IP prefix nor the fact 454 that some applications may want to dynamically insert or remove "IP 455 prefixes of interest", depending on the needs of their constituent 456 applications. 458 With IRS, it is conceivable that applications could tell an IRS 459 controller, through a North-Bound API, their "IP prefixes" (or, 460 AS_PATH's, BGP communities, etc.) that are of interest. For example, 461 a NOC application may be interested in changes to high visibility 462 content or service-provider Web sites; alternatively, a security 463 application may be interested in events associated with a different 464 set of IP prefixes. The IRS controller would then consolidate the 465 list of IP prefixes, and associated characteristics, to be monitored 466 and program BGP routers in an AS to observe this subset of routes for 467 changes. Some examples of changes in routing state might include: 469 o an IP prefix being announced or withdrawn 470 o an IP prefix being suppressed, due to route flap dampening 472 o an alternative best-path being chosen for a given IP prefix 474 When the requisite events for a BGP Route are observed by a BGP 475 router, it would notify IRS controllers. 477 The IRS controllers would have a publish/subscribe mechanism whereby 478 various sets of applications may subscribe to events of interest. 479 The IRS controller would then publish these events so applications 480 would immediately receive them and take the appropriate domain- 481 specific action necessary. 483 5.2. Tracing Dropped BGP Routes 485 It is extremely useful to operators to be able to rapidly identify 486 instances where a BGP route is not being propagated within an 487 Autonomous System. At a minimum, this could result in sub-optimal 488 performance when attempting to reach such destinations. 490 There are two instances when this scenario will occur. First, when a 491 Service Provider is using "Soft Reconfiguration Inbound", it allows 492 their ASBR routers to receive a copy of a BGP route, but show that 493 route was not permitted into the Adj-RIB-In most likely as a result 494 of the inbound BGP policy not permitting that IP prefix. Thus, this 495 BGP route is not even eligible for BGP Path Selection. The second 496 instance is where the BGP route is permitted by the inbound BGP 497 policy into the Adj-RIB-In, but due to BGP Path Selection (i.e.: 498 lower LOCAL_PREF, longer AS_PATH length, etc.) was not chosen as the 499 best path and, subsequently, this particular BGP route is not 500 forwarded on to other internal BGP speakers in the AS. In both 501 instances, the BGP route is only visible within the ASBR on which 502 that BGP route was first learned. Needless to say, in large Service 503 Provider networks with a numerous interconnects to a single customer 504 it can be very time-consuming to discover where such a BGP route is 505 learned before ultimately determining why the route was blocked or 506 not preferred. 508 With IRS, it would be possible for an IRS controller to rapidly 509 gather information from across a large set of BGP routers in the 510 network to determine at what ASBR's the BGP route is being learned. 511 Next, the IRS controller could interrogate those routers BGP policies 512 to determine the root cause of why the route was either not learned 513 or not preferred in BGP. Finally, if necessary, the IRS 514 controller(s) could amend BGP policies and push them out to BGP 515 routers to permit the BGP route or make it a preferred route 516 according to the BGP path selection algorithm. 518 5.3. BGP Protocol Statistics 520 There are a variety of statistics related to the operation of BGP 521 that are invaluable to network operators. These statistics generally 522 help operators, and developers, understand the present state and 523 future scalability of BGP. 525 One statistic that is invaluable to operators is the current number 526 of BGP routes learned through an eBGP session. Operators then apply 527 a command against each eBGP session to limit the maximum number of 528 BGP routes that may be learned through that eBGP session before a 529 warning message is triggered and/or the eBGP session is torn down 530 completely. This configuration capability is often referred to as a 531 "max-prefix limit". This command must be routinely audited and, if 532 necessary, adjusted in order to not trigger a false warning or 533 teardown due to the natural organic growth in BGP routes learned from 534 a given BGP neighbor. 536 IRS controllers could provide an invaluable capability to help audit 537 and re-program the "max-prefix limit" on a periodic basis, which is 538 generally once per day. Specifically, the first task would be for an 539 IRS controller to validate that there is a "max-prefix limit" applied 540 to every eBGP session. (If there is not, that should either trigger 541 a red alarm to the NOC to manually fix this condition or for the IRS 542 controller to automatically apply a "max-prefix limit" that would 543 alleviate this hazardous condition). Assuming there is a "max-prefix 544 limit" already in place, the IRS controller would simultaneously 545 retrieve, from each BGP router, the current number of BGP routes 546 learned through a BGP session and value used for the "max-prefix 547 limit" on that same BGP session. These two values could then be 548 handed off to an application that determines if adjustments in the 549 "max-prefix limit" value are required for each BGP session. The 550 application would then notify the IRS controller of the subset of 551 eBGP sessions and their associated change in "max-prefix limit" 552 value, whereby the IRS controller would then adjust the BGP protocol 553 configuration on each requisite BGP router in the network. Finally, 554 it should be noted that the above is just one method whereby "max- 555 prefix limit" values are adjusted. It's similarly possible that the 556 BGP routers may, through the IRS, pull the "max-prefix limit" values 557 for each eBGP neighbor they have onboard on a periodic basis and 558 validate their accuracy. 560 The above is just one use case related to BGP protocol statistics. 561 There are wealth of other BGP protocol statistics or state 562 informatioin that would be invaluable to have programmatic visibility 563 into that operators do not have today. 565 6. Security Considerations 567 The BGP use cases described in this document assumes use of IRS's 568 programmatic interfaces described in the IRS framework mentioned in 569 [I-D.ward-irs-framework]. This document does not change the 570 underlying security issues inherent in the existing 571 [I-D.ward-irs-framework]. 573 7. Acknowledgements 575 TBD. 577 8. References 579 8.1. Normative References 581 [I-D.ward-irs-framework] 582 Atlas, A., Nadeau, T., and D. Ward, "Interface to the 583 Routing System Framework", draft-ward-irs-framework-00 584 (work in progress), July 2012. 586 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 587 Communities Attribute", RFC 1997, August 1996. 589 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 590 Requirement Levels", BCP 14, RFC 2119, March 1997. 592 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, 593 June 1999. 595 [RFC3392] Chandra, R. and J. Scudder, "Capabilities Advertisement 596 with BGP-4", RFC 3392, November 2002. 598 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 599 Text on Security Considerations", BCP 72, RFC 3552, July 600 2003. 602 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 603 Protocol 4 (BGP-4)", RFC 4271, January 2006. 605 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 606 Communities Attribute", RFC 4360, February 2006. 608 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, 609 "Multiprotocol Extensions for BGP-4", RFC 4760, January 610 2007. 612 8.2. Informative References 614 [I-D.ietf-grow-ops-reqs-for-bgp-error-handling] 615 Shakir, R., "Operational Requirements for Enhanced Error 616 Handling Behaviour in BGP-4", draft-ietf-grow-ops-reqs- 617 for-bgp-error-handling-05 (work in progress), July 2012. 619 [I-D.mcpherson-irr-routing-policy-considerations] 620 McPherson, D., Amante, S., Osterweil, E., and L. Blunk, 621 "IRR & Routing Policy Configuration Considerations", 622 draft-mcpherson-irr-routing-policy-considerations-01 (work 623 in progress), September 2012. 625 [RFC2622] Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D., 626 Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra, 627 "Routing Policy Specification Language (RPSL)", RFC 2622, 628 June 1999. 630 [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, 631 "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. 633 [RFC5156] Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156, 634 April 2008. 636 [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., 637 and D. McPherson, "Dissemination of Flow Specification 638 Rules", RFC 5575, August 2009. 640 [RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses", 641 RFC 5735, January 2010. 643 Authors' Addresses 645 Keyur Patel 646 Cisco Systems 647 170 W. Tasman Drive 648 San Jose, CA 95134 649 USA 651 Email: keyupate@cisco.com 652 Rex Fernando 653 Cisco Systems 654 170 W. Tasman Drive 655 San Jose, CA 95134 656 USA 658 Email: rex@cisco.com 660 Hannes Gredler 661 Juniper Networks 662 1194 N. Mathilda Ave 663 Sunnyvale, CA 94089 664 USA 666 Email: hannes@juniper.net 668 Shane Amante 669 Level 3 Communications, Inc. 670 1025 Eldorado Blvd 671 Broomfield, CO 80021 672 USA 674 Email: shane@level3.net