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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: '137' is mentioned on line 403, but not defined == Missing Reference: '139' is mentioned on line 403, but not defined ** Obsolete normative reference: RFC 793 (ref. '1') (Obsoleted by RFC 9293) Summary: 4 errors (**), 0 flaws (~~), 4 warnings (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group P. Marques 3 Internet-Draft N. Sheth 4 Expires: February 15, 2008 R. Raszuk 5 Juniper Networks 6 B. Greene 7 Cisco Systems, Inc. 8 J. Mauch 9 NTT/Verio 10 D. McPherson 11 Arbor Networks 12 August 14, 2007 14 Dissemination of flow specification rules 15 draft-ietf-idr-flow-spec-00 17 Status of this Memo 19 By submitting this Internet-Draft, each author represents that any 20 applicable patent or other IPR claims of which he or she is aware 21 have been or will be disclosed, and any of which he or she becomes 22 aware will be disclosed, in accordance with Section 6 of BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF), its areas, and its working groups. Note that 26 other groups may also distribute working documents as Internet- 27 Drafts. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 The list of current Internet-Drafts can be accessed at 35 http://www.ietf.org/ietf/1id-abstracts.txt. 37 The list of Internet-Draft Shadow Directories can be accessed at 38 http://www.ietf.org/shadow.html. 40 This Internet-Draft will expire on February 15, 2008. 42 Copyright Notice 44 Copyright (C) The IETF Trust (2007). 46 Abstract 48 This document defines a new BGP NLRI encoding format that can be used 49 to distribute traffic flow specifications. This allows the routing 50 system to propagate information regarding more-specific components of 51 the traffic aggregate defined by an IP destination prefix. 53 Additionally it defines two applications of that encoding format. 54 One that can be used to automate inter-domain coordination of traffic 55 filtering, such as what is required in order to mitigate 56 (distributed) denial of service attacks. And a second application to 57 traffic filtering in the context of a BGP/MPLS VPN service. 59 The information is carried via the Border Gateway Protocol (BGP), 60 thereby reusing protocol algorithms, operational experience and 61 administrative processes such as inter-provider peering agreements. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 66 2. Flow specifications . . . . . . . . . . . . . . . . . . . . . 6 67 3. Dissemination of Information . . . . . . . . . . . . . . . . . 7 68 4. Traffic filtering . . . . . . . . . . . . . . . . . . . . . . 13 69 4.1. Order of traffic filtering rules . . . . . . . . . . . . . 14 70 5. Validation procedure . . . . . . . . . . . . . . . . . . . . . 15 71 6. Traffic Filtering Actions . . . . . . . . . . . . . . . . . . 16 72 7. Traffic filtering in RFC2547bis networks . . . . . . . . . . . 18 73 8. Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . 19 74 9. Security considerations . . . . . . . . . . . . . . . . . . . 20 75 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 76 11. Normative References . . . . . . . . . . . . . . . . . . . . . 22 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 78 Intellectual Property and Copyright Statements . . . . . . . . . . 25 80 1. Introduction 82 Modern IP routers contain both the capability to forward traffic 83 according to aggregate IP prefixes as well as to classify, shape, 84 limit filter or redirect packets based on administratively defined 85 policies. 87 While forwarding information is, typically, dynamically signaled 88 across the network via routing protocols, there is no agreed upon 89 mechanism to dynamically signal flows across autonomous-systems. 91 For several applications, it may be necessary to exchange control 92 information pertaining to aggregated traffic flow definitions which 93 cannot be expressed using destination address prefixes only. 95 An aggregated traffic flow is considered to be an n-tuple consisting 96 of several matching criteria such as source and destination address 97 prefixes, IP protocol and transport protocol port numbers. 99 The intention of this document is to define a general procedure to 100 encode such flow specification rules as a BGP [2] NLRI which can be 101 reused for several different control applications. Additionally, we 102 define the required mechanisms to utilize this definition to the 103 problem of immediate concern to the authors: intra and inter provider 104 distribution of traffic filtering rules to filter (Distributed) 105 Denial of Service (DoS) attacks. 107 By expanding routing information with flow specifications, the 108 routing system can take advantage of the ACL/firewall capabilities in 109 the router's forwarding path. Flow specifications can be seen as 110 more specific routing entries to an unicast prefix and are expected 111 to depend upon the existing unicast data information. 113 A flow specification received from a external autonomous-system will 114 need to be validated against unicast routing before being accepted. 115 If the aggregate traffic flow defined by the unicast destination 116 prefix is forwarded to a given BGP peer, then the local system can 117 safely install more specific flow rules which result in different 118 forwarding behavior, as requested by this system. 120 The choice of BGP as the carrier of this control information is also 121 justifiable by the fact that the key issues in terms of complexity 122 are problems which are common to unicast route distribution and have 123 already been solved in the current environment. 125 From an algorithmic perspective, the main problem that presents 126 itself is the loop-free distribution of pairs from 127 one originator to N ingresses. The key, in this particular instance, 128 being a flow specification. 130 From an operational perspective, the utilization of BGP as the 131 carrier for this information, allows a network service provider to 132 reuse both internal route distribution infrastructure (e.g.: route 133 reflector or confederation design) and existing external 134 relationships (e.g.: inter-domain BGP sessions to a customer 135 network). 137 While it is certainly possible to address this problem using other 138 mechanisms, the authors believe that this solution offers the 139 substantial advantage of being an incremental addition to deployed 140 mechanisms. 142 2. Flow specifications 144 A flow specification is an n-tuple consisting on several matching 145 criteria that can be applied to IP traffic. A given IP packet is 146 said to match the defined flow if it matches all the specified 147 criteria. 149 A given flow may be associated with a set of attributes, depending on 150 the particular application, such attributes may or may not include 151 reachability information (i.e. NEXT_HOP). Well-known or AS-specific 152 community attributes can be used to encode a set of predeterminate 153 actions. 155 A particular application is identified by a specific (AFI, SAFI) pair 156 [3] and corresponds to a distinct set of RIBs. Those RIBs should be 157 treated independently from each other in order to assure non- 158 interference between distinct applications. 160 BGP itself treats the NLRI as an opaque key to an entry in its 161 databases. Entries that are placed in the Loc-RIB are then 162 associated with a given set of semantics which is application 163 dependent. This is consistent with existing BGP applications. For 164 instance IP unicast routing (AFI=1, SAFI=1) and IP multicast reverse- 165 path information (AFI=1, SAFI=2) are handled by BGP without any 166 particular semantics being associated with them until installed in 167 the Loc-RIB. 169 Standard BGP policy mechanisms, such as UPDATE filtering by NLRI 170 prefix and community matching, SHOULD apply to the newly defined 171 NLRI-type. Network operators can also control propagation of such 172 routing updates by enabling or disabling the exchange of a particular 173 (AFI, SAFI) pair on a given BGP peering session. 175 3. Dissemination of Information 177 We define a "Flow Specification" NLRI type that may include several 178 components such as destination prefix, source prefix, protocol, 179 ports, etc. This NLRI is treated as an opaque bit string prefix by 180 BGP. Each bit string identifies a key to a database entry which a 181 set of attributes can be associated with. 183 This NLRI information is encoded using MP_REACH_NLRI and 184 MP_UNREACH_NLRI attributes as defined in RFC4760 [3]. Whenever the 185 corresponding application does not require Next Hop information, this 186 shall be encoded as a 0 octet length Next Hop in the MP_REACH_NLRI 187 attribute and ignored on receipt. 189 The NLRI field of the MP_REACH_NLRI and MP_UNREACH_NLRI is encoded as 190 a 1 or 2 octet NLRI length field followed by a variable length NLRI 191 value. The NLRI length is expressed in octets. 193 +------------------------------+ 194 | length (0xnn or 0xfn nn) | 195 +------------------------------+ 196 | NLRI value (variable) | 197 +------------------------------+ 199 flow-spec NLRI 201 If the NLRI length value is smaller than 240 (0xf0 hex), the length 202 field can be encoded as a single octet. Otherwise, it is encoded as 203 a extended length 2 octet value in which the most significant nibble 204 of the first byte is all ones. 206 The Flow Specification NLRI-type consists of several optional 207 subcomponents. A specific packet is considered to match the flow 208 specification when it matches the intersection (AND) of all the 209 components present in the specification. 211 The following component types are defined: 213 Type 1 - Destination Prefix 215 Encoding: 217 Defines the destination prefix to match. Prefixes are encoded 218 as in BGP UPDATE messages, a length in bits is followed by 219 enough octets to contain the prefix information. 221 Type 2 - Source Prefix 223 Encoding: 225 Defines the source prefix to match. 227 Type 3 - IP Protocol 229 Encoding: 231 Contains a set of {operator, value} pairs that are used to 232 match IP protocol value byte in IP packets. 234 The operator byte is encoded as: 236 7 6 5 4 3 2 1 0 237 +---+---+---+---+---+---+---+---+ 238 | e | a | len | 0 |lt |gt |eq | 239 +---+---+---+---+---+---+---+---+ 241 Numeric operator 243 + End of List bit. Set in the last {op, value} pair in the 244 list. 246 + And bit. If unset the previous term is logically ORed with 247 the current one. If set the operation is a logical AND. It 248 should be unset in the first operator byte of a sequence. 249 The AND operator has higher priority than OR for the 250 purposes of evaluating logical expressions. 252 + The length of value field for this operand is given as (1 << 253 len). 255 + Lt - less than comparison between data and value. 257 + gt - greater than comparison between data and value. 259 + eq - equality between data and value. 261 The bits lt, gt, and eq can be combined to produce "less or 262 equal", "greater or equal" and inequality values. 264 Type 4 - Port 266 Encoding: 267 Defines a list of {operation, value} pairs that matches source 268 OR destination TCP/UDP ports. This list is encoded using the 269 numeric operand format defined above. Values are encoded as 1 270 or 2 byte quantities. 272 Type 5 - Destination port 274 Encoding: 276 Defines a list of {operation, value} pairs used to match the 277 destination port of a TCP or UDP packet. Values are encoded as 278 1 or 2 byte quantities. 280 Type 6 - Source port 282 Encoding: 284 Defines a list of {operation, value} pairs used to match the 285 source port of a TCP or UDP packet. Values are encoded as 1 or 286 2 byte quantities. 288 Type 7 - ICMP type 290 Encoding: 292 Defines a list of {operation, value} pairs used to match the 293 type field of an icmp packet. Values are encoded using a 294 single byte. 296 Type 8 - ICMP code 298 Encoding: 300 Defines a list of {operation, value} pairs used to match the 301 code field of an icmp packet. Values are encoded using a 302 single byte. 304 Type 9 - TCP flags 306 Encoding: 308 Bitmask values are encoded using a single byte, using the bit 309 definitions specified in the TCP header format [1]. 311 This type uses the bitmask operand format, which differs from 312 the numeric operator format in the lower nibble. 314 7 6 5 4 3 2 1 0 315 +---+---+---+---+---+---+---+---+ 316 | e | a | len | 0 | 0 |not| m | 317 +---+---+---+---+---+---+---+---+ 319 + Top nibble: (End of List bit, And bit and Length field), as 320 defined for in the numeric operator format. 322 + Not bit. If set, logical negation of operation. 324 + Match bit. If set this is a bitwise match operation defined 325 as "(data & value) == value"; if unset (data & value) 326 evaluates to true if and of the bits in the value mask are 327 set in the data. 329 Type 10 - Packet length 331 Encoding: 333 Match on the total IP packet length (excluding L2 but including 334 IP header). Values are encoded using as 1 or 2 byte 335 quantities. 337 Type 11 - DSCP 339 Encoding: 341 Defines a list of {operation, value} pairs used to match the IP 342 TOS octet. 344 Type 12 - Fragment 346 Encoding: 348 Uses bitmask operand format defined above. 350 Bitmask values: 352 + Bit 0 - Dont fragment 354 + Bit 1 - Is a fragment 356 + Bit 2 - First fragment 358 + Bit 3 - Last fragment 360 Flow specification components must follow strict type ordering. A 361 given component type may or may not be present in the specification, 362 but if present it MUST precede any component of higher numeric type 363 value. 365 If a given component type within a prefix in unknown, the prefix in 366 question cannot be used for traffic filtering purposes by the 367 receiver. Since a Flow Specification as the semantics of a logical 368 AND of all components, if a component is FALSE by definition it 369 cannot be applied. However for the purposes of BGP route propagation 370 this prefix should still be transmitted since BGP route distribution 371 is independent on NLRI semantics. 373 Flow specification components are to be interpreted as a bit match at 374 a given packet offset. When more than one component in a flow 375 specification tests the same packet offset the behavior is 376 undetermined. 378 The encoding is chosen in order to account for future 379 extensibility. 381 An example of a Flow Specification encoding for: "all packets to 382 10.0.1/24 and TCP port 25". 384 +------------------+----------+----------+ 385 | destination | proto | port | 386 +------------------+----------+----------+ 387 | 0x01 18 0a 00 01 | 03 81 06 | 04 81 19 | 388 +------------------+----------+----------+ 390 Decode for protocol: 392 +-------+----------+------------------------------+ 393 | Value | | | 394 +-------+----------+------------------------------+ 395 | 0x03 | type | | 396 | | | | 397 | 0x81 | operator | end-of-list, value size=1, = | 398 | | | | 399 | 0x06 | value | | 400 +-------+----------+------------------------------+ 402 An example of a Flow Specification encoding for: "all packets to 403 10.0.1/24 from 192/8 and port {range [137, 139] or 8080}". 405 +------------------+----------+-------------------------+ 406 | destination | source | port | 407 +------------------+----------+-------------------------+ 408 | 0x01 18 0a 01 01 | 02 08 c0 | 04 03 89 45 8b 91 1f 90 | 409 +------------------+----------+-------------------------+ 410 Decode for port: 412 +--------+----------+------------------------------+ 413 | Value | | | 414 +--------+----------+------------------------------+ 415 | 0x04 | type | | 416 | | | | 417 | 0x03 | operator | size=1, >= | 418 | | | | 419 | 0x89 | value | 137 | 420 | | | | 421 | 0x45 | operator | &, value size=1, <= | 422 | | | | 423 | 0x8b | value | 139 | 424 | | | | 425 | 0x91 | operator | end-of-list, value-size=2, = | 426 | | | | 427 | 0x1f90 | value | 8080 | 428 +--------+----------+------------------------------+ 430 This constitutes a NLRI with an NLRI length of 16 octets. 432 Implementations wishing to exchange flow specification rules MUST use 433 BGP's Capability Advertisement facility to exchange the Multiprotocol 434 Extension Capability Code (Code 1) as defined in RFC4760 [3]. The 435 (AFI, SAFI) pair carried in the Multiprotocol Extension capability 436 MUST be the same as the one used to identify a particular application 437 that uses this NLRI-type. 439 4. Traffic filtering 441 Traffic filtering policies have been traditionally considered to be 442 relatively static. 444 The popularity of traffic-based denial of service (DoS) attacks, 445 which often requires the network operator to be able to use traffic 446 filters for detection and mitigation, brings with it requirements 447 that are not fully satisfied by existing tools. 449 Increasingly, DoS mitigation, requires coordination among several 450 Service Providers, in order to be able to identify traffic source(s) 451 and because the volumes of traffic may be such that they will 452 otherwise significantly affect the performance of the network. 454 Several techniques are currently used to control traffic filtering of 455 DoS attacks. Among those, one of the most common is to inject 456 unicast route advertisements corresponding to a destination prefix 457 being attacked. One variant of this technique marks such route 458 advertisements with a community that gets translated into a discard 459 next-hop by the receiving router. Other variants, attract traffic to 460 a particular node that serves as a deterministic drop point. 462 Using unicast routing advertisements to distribute traffic filtering 463 information has the advantage of using the existing infrastructure 464 and inter-as communication channels. This can allow, for instance, 465 for a service provider to accept filtering requests from customers 466 for address space they own. 468 There are several drawbacks, however. An issue that is immediately 469 apparent is the granularity of filtering control: only destination 470 prefixes may be specified. Another area of concern is the fact that 471 filtering information is intermingled with routing information. 473 The mechanism defined in this document is designed to address these 474 limitations. We use the flow specification NLRI defined above to 475 convey information about traffic filtering rules for traffic that 476 should be discarded. 478 This mechanism is designed to, primarily, allow an upstream 479 autonomous system to perform inbound filtering, in their ingress 480 routers of traffic that a given downstream AS wishes to drop. 482 In order to achieve that goal, we define an application specific NLRI 483 identifier (AFI=1, SAFI=133) along with specific semantic rules. 485 BGP routing updates containing this identifier use the flow 486 specification NLRI encoding to convey particular aggregated flows 487 that require special treatment. 489 Flow routing information received via this (afi, safi) pair is 490 subject to the validation procedure detailed bellow. 492 4.1. Order of traffic filtering rules 494 With traffic filtering rules, more than one rule may match a 495 particular traffic flow. Thus it is necessary to define the order at 496 which rules get matched and applied to a particular traffic flow. 497 This ordering function must be such that it must not depend on the 498 arrival order of the flow specifications rules and must be constant 499 in the network. 501 We choose to order traffic filtering rules such that the order of two 502 flow specifications is given by the comparison of NLRI key byte 503 strings as defined by the memcmp() function is the ISO C standard. 505 Given the way that flow specifications are encoded this results in a 506 flow with a less-specific destination IP prefix being considered 507 less-than (and thus match before) a flow specification with a more- 508 specific destination IP prefix. 510 This matches an application model where the user may want to define a 511 restriction that affects an aggregate of traffic and a subsequent 512 rule that applies only to a subset of that. 514 A flow-specification without a destination IP prefix is considered to 515 match after all flow-specifications that contain an IP destination 516 prefix. 518 5. Validation procedure 520 Flow specifications received from a BGP peer and which are accepted 521 in the respective Adj-RIB-In are used as input to the route selection 522 process. Although the forwarding attributes of two routes for the 523 same Flow Specification prefix may be the same, BGP is still required 524 to perform its path selection algorithm in order to select the 525 correct set of attributes to advertise. 527 The first step of the BGP Route Selection procedure (section 9.1.2) 528 is to exclude from the selection procedure routes that are considered 529 non-feasible. In the context of IP routing information this step is 530 used to validate that the NEXT_HOP attribute of a given route is 531 resolvable. 533 The concept can be extended, in the case of Flow Specification NLRI, 534 to allow other validation procedures. 536 A flow specification NLRI must be validated such that it is 537 considered feasible if and only if: 539 a) The originator of the flow specification matches the originator of 540 the best-match unicast route for the destination prefix embedded 541 in the flow specification. 543 b) There are no more-specific unicast routes, when compared with the 544 flow destination prefix, that have been received from a different 545 neighboring AS than the best-match unicast route, which has been 546 determined in step a). 548 By originator of a BGP route, we mean either the BGP originator path 549 attribute, as used by route reflection, or the transport address of 550 the BGP peer, if this path attribute is not present. 552 The underlying concept is that the neighboring AS that advertises the 553 best unicast route for a destination is allowed to advertise flow- 554 spec information that conveys a more or equally specific destination 555 prefix. This, as long as there are no more-specific unicast routes, 556 received from a different neighbor AS, which would be affected by 557 that filtering rule. 559 The neighboring AS is the immediate destination of the traffic 560 described by the Flow Specification. If it requests these flows to 561 be dropped that request can be honored without concern that it 562 represents a denial of service in itself. Supposedly, the traffic is 563 being dropped by the downstream autonomous-system and there is no 564 added value in carrying the traffic to it. 566 6. Traffic Filtering Actions 568 This specification defines a minimum set of filtering actions that it 569 standardizes as BGP extended community values [4]. This is not ment 570 to be an inclusive list of all the possible actions but only a subset 571 that can be interpreted consistently across the network. 573 Implementations should provide mechanisms that map an arbitrary bgp 574 community value (normal or extended) to filtering actions that 575 require different mappings in different systems in the network. For 576 instance, providing packets with a worse than best-effort per-hop 577 behavior is a functionality that is likely to be implemented 578 differently in different systems and for which no standard behavior 579 is currently known. Rather than attempting to define it here, this 580 can be accomplished by mapping a user defined community value to 581 platform / network specific behavior via user configuration. 583 The default action for a traffic filtering flow specification is to 584 accept IP traffic that matches that particular rule. 586 The following extended community values can be used to specify 587 particular actions. 589 +--------+--------------------+--------------------------+ 590 | type | extended community | encoding | 591 +--------+--------------------+--------------------------+ 592 | 0x8006 | traffic-rate | 2-byte as#, 4-byte float | 593 | | | | 594 | 0x8007 | traffic-action | bitmask | 595 | | | | 596 | 0x8008 | redirect | 6-byte Route Target | 597 +--------+--------------------+--------------------------+ 599 Traffic-rate The traffic-rate extended community uses the same 600 encoding as the "Link Bandwidth" [4] extended community. The rate 601 is is expressed as 4 octets in IEEE floating point format, units 602 being bytes per second. A traffic-rate of 0 should result on all 603 traffic for the particular flow to be discarded. 605 Traffic-action The traffic-action extended community consists of 6 606 bytes of which only the 2 least significant bits of the 6th byte 607 (from left to right) are currently defined. 609 * Terminal action (bit 0). When this bit is set the traffic 610 filtering engine will apply any subsequent filtering rules (as 611 defined by the ordering procedure). If not set the evaluation 612 of the traffic filter stops when this rule is applied. 614 * Sample (bit 1). Enables traffic sampling and logging for this 615 flow specification. 617 Redirect The redirect extended community allows the traffic to be 618 redirected to a VRF routing instance that list the specified 619 route-target in its import policy. If several local instances 620 match this criteria, the choice between them is a local matter 621 (for example, the instance with the lowest Route Distinguisher 622 value can be elected). The traffic marking extended community 623 instruct a system to modify the DSCP bits of a transiting IP 624 packet to the corresponding value. This extended community is 625 encoded as a sequence of 5 zero bytes followed by the DSCP value. 627 7. Traffic filtering in RFC2547bis networks 629 Provider-based layer 3 VPN networks, such as the ones using an BGP/ 630 MPLS IP VPN [5] control plane, have different traffic filtering 631 requirements than internet service providers. 633 In these environments, the VPN customer network often has traffic 634 filtering capabilities towards their external network connections 635 (e.g. firewall facing public network connection). Less common is the 636 presence of traffic filtering capabilities between different VPN 637 attachment sites. In an any-to-any connectivity model, which is the 638 default, this means that site to site traffic is unfiltered. 640 In circumstances where a security threat does get propagated inside 641 the VPN customer network, there may not be readily available 642 mechanisms to provide mitigation via traffic filter. 644 This document proposes an additional BGP NLRI type (afi=1, safi=134) 645 value, which can be used to propagate traffic filtering information 646 in a BGP/MPLS VPN environment. 648 The NLRI format for this address family consists of a fixed length 649 Route Distinguisher field (8 bytes) followed by a flow specification, 650 following the encoded defined in this document. The NLRI length 651 field shall includes the both 8 bytes of the Route Distinguisher as 652 well as the subsequent flow specification. 654 Propagation of this NLRI is controlled by matching Route Target 655 extended communities associated with the BGP path advertisement with 656 the VRF import policy, using the same mechanism as described in "BGP/ 657 MPLS IP VPNs" [5] . 659 Flow specification rules received via this NLRI apply only to traffic 660 that belongs to the VRF(s) in which it is imported. By default, 661 traffic received from a remote PE is switched via an mpls forwarding 662 decision and is not subject to filtering. 664 Contrary to the behavior specified for the non-VPN NLRI, flow rules 665 are accepted by default, when received from remote PE routers. 667 8. Monitoring 669 Traffic filtering applications require monitoring and traffic 670 statistics facilities. While this is an implementation specific 671 choice, implementations SHOULD provide: 673 o A mechanism to log the packet header of filtered traffic, 675 o A mechanism to count the number of matches for a given Flow 676 Specification rule. 678 9. Security considerations 680 Inter-provider routing is based on a web of trust. Neighboring 681 autonomous-systems are trusted to advertise valid reachability 682 information. If this trust model is violated, a neighboring 683 autonomous system may cause a denial of service attack by advertising 684 reachability information for a given prefix for which it does not 685 provide service. 687 As long as traffic filtering rules are restricted to match the 688 corresponding unicast routing paths for the relevant prefixes, the 689 security characteristics of this proposal are equivalent to the 690 existing security properties of BGP unicast routing. 692 Where it not the case, this would open the door to further denial of 693 service attacks. 695 10. Acknowledgments 697 The authors would like to thank Yakov Rekhter, Dennis Ferguson and 698 Chris Morrow for their comments. 700 Chaitanya Kodeboyina helped design the flow validation procedure. 702 Steven Lin and Jim Washburn ironed out all the details necessary to 703 produce a working implementation. 705 11. Normative References 707 [1] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, 708 September 1981. 710 [2] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 711 (BGP-4)", RFC 4271, January 2006. 713 [3] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol 714 Extensions for BGP-4", RFC 4760, January 2007. 716 [4] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 717 Communities Attribute", RFC 4360, February 2006. 719 [5] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks 720 (VPNs)", RFC 4364, February 2006. 722 Authors' Addresses 724 Pedro Marques 725 Juniper Networks 726 1194 N. Mathilda Ave. 727 Sunnyvale, CA 94089 728 US 730 Email: roque@juniper.net 732 Nischal Sheth 733 Juniper Networks 734 1194 N. Mathilda Ave. 735 Sunnyvale, CA 94089 736 US 738 Email: nsheth@juniper.net 740 Robert Raszuk 741 Juniper Networks 742 1194 N. Mathilda Ave. 743 Sunnyvale, CA 94089 744 US 746 Email: raszuk@juniper.net 748 Barry Greene 749 Cisco Systems, Inc. 750 170 West Tasman Dr 751 San Jose, CA 95134 752 US 754 Email: bgreene@cisco.com 756 Jared Mauch 757 NTT/Verio 758 8285 Reese Lane 759 Ann Arbor, MI 48103-9753 760 US 761 Danny McPherson 762 Arbor Networks 764 Email: danny@arbor.net 766 Full Copyright Statement 768 Copyright (C) The IETF Trust (2007). 770 This document is subject to the rights, licenses and restrictions 771 contained in BCP 78, and except as set forth therein, the authors 772 retain all their rights. 774 This document and the information contained herein are provided on an 775 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 776 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 777 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 778 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 779 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 780 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 782 Intellectual Property 784 The IETF takes no position regarding the validity or scope of any 785 Intellectual Property Rights or other rights that might be claimed to 786 pertain to the implementation or use of the technology described in 787 this document or the extent to which any license under such rights 788 might or might not be available; nor does it represent that it has 789 made any independent effort to identify any such rights. Information 790 on the procedures with respect to rights in RFC documents can be 791 found in BCP 78 and BCP 79. 793 Copies of IPR disclosures made to the IETF Secretariat and any 794 assurances of licenses to be made available, or the result of an 795 attempt made to obtain a general license or permission for the use of 796 such proprietary rights by implementers or users of this 797 specification can be obtained from the IETF on-line IPR repository at 798 http://www.ietf.org/ipr. 800 The IETF invites any interested party to bring to its attention any 801 copyrights, patents or patent applications, or other proprietary 802 rights that may cover technology that may be required to implement 803 this standard. Please address the information to the IETF at 804 ietf-ipr@ietf.org. 806 Acknowledgment 808 Funding for the RFC Editor function is provided by the IETF 809 Administrative Support Activity (IASA).