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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'IRR' is mentioned on line 93, but not defined == Unused Reference: 'RFC3547' is defined on line 557, but no explicit reference was found in the text == Unused Reference: 'RFC4271' is defined on line 560, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2385 (Obsoleted by RFC 5925) -- Obsolete informational reference (is this intentional?): RFC 2409 (Obsoleted by RFC 4306) -- Obsolete informational reference (is this intentional?): RFC 3547 (Obsoleted by RFC 6407) Summary: 4 errors (**), 0 flaws (~~), 4 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Routing Working Group M. Jethanandani 3 Internet-Draft Private 4 Intended status: Informational K. Patel 5 Expires: September 27, 2012 Cisco Systems, Inc 6 L. Zheng 7 Huawei 8 March 26, 2012 10 Analysis of BGP, LDP, PCEP, and MSDP Security According to KARP Design 11 Guide 12 draft-ietf-karp-routing-tcp-analysis-01.txt 14 Abstract 16 This document analyzes BGP, LDP, PCEP and MSDP according to 17 guidelines set forth in section 4.2 of Keying and Authentication for 18 Routing Protocols Design Guidelines [RFC6518]. 20 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 21 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 22 document are to be interpreted as described in RFC 2119 [RFC2119].. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on September 27, 2012. 41 Copyright Notice 43 Copyright (c) 2012 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. Contributing Authors . . . . . . . . . . . . . . . . . . . 3 60 1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 61 2. Current State of BGP, LDP, PCEP and MSDP . . . . . . . . . . . 5 62 2.1. Transport level . . . . . . . . . . . . . . . . . . . . . 5 63 2.2. Keying mechanisms . . . . . . . . . . . . . . . . . . . . 6 64 2.3. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 2.3.1. Spoofing attacks . . . . . . . . . . . . . . . . . . . 6 66 2.3.2. Privacy Issues . . . . . . . . . . . . . . . . . . . . 7 67 2.3.3. Denial of Service Attacks . . . . . . . . . . . . . . 7 68 2.4. PCEP . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 69 2.5. MSDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 70 3. Optimal State for BGP, LDP, PCEP, and MSDP . . . . . . . . . . 9 71 3.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 72 4. Gap Analysis for BGP, LDP, PCEP and MSDP . . . . . . . . . . . 10 73 4.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 74 4.2. PCEP . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 75 5. Transition and Deployment Considerations . . . . . . . . . . . 12 76 6. Security Requirements . . . . . . . . . . . . . . . . . . . . 13 77 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 78 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 79 8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 80 8.2. Informative References . . . . . . . . . . . . . . . . . . 15 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 83 1. Introduction 85 In March 2006 the Internet Architecture Board (IAB) in its "Unwanted 86 Internet Traffic" workshop documented in Report from the IAB workship 87 on Unwanted Traffic March 9-10, 2006 [RFC4948] described an attack on 88 core routing infrastructure as an ideal attack with the most amount 89 of damage. Four main steps were identified for that tightening: 91 1. Create secure mechanisms and practices for operating routers. 93 2. Clean up the Internet Routing Registry [IRR] repository, and 94 securing both the database and the access, so that it can be used 95 for routing verifications. 97 3. Create specifications for cryptographic validation of routing 98 message content. 100 4. Secure the routing protocols' packets on the wire. 102 This document looking at the last bullet performs the initial 103 analysis of the current state of BGP, LDP, PCEP and MSDP according to 104 the requirements of KARP Design Guidelines [RFC6518]. This draft 105 builds on several previous analysis efforts into routing security. 106 The OPSEC working group put together Issues with existing 107 Cryptographic Protection Methods for Routing Protocols 108 [draft-ietf-opsec-routing-protocols-crypto-issues-07] an analysis of 109 cryptographic issues with routing protocols and Analysis of OSPF 110 Security According to KARP Design Guide 111 [draft-ietf-karp-ospf-analysis-03]. 113 Section 2 looks at the current state of the four routing protocols. 114 Section 3 goes into what the optimal state would be for the three 115 routing protocols according to KARP Design Guidelines [RFC6518] and 116 Section 4 does a analysis of the gap between the existing state and 117 the optimal state of the protocols and suggest some areas where we 118 need to improve. 120 1.1. Contributing Authors 122 Anantha Ramaiah, Mach Chen 124 1.2. Abbreviations 126 BGP - Border Gateway Protocol 128 DoS - Denial of Service 130 KARP - Key and Authentication for Routing Protocols 131 KDF - Key Derivation Function 133 KEK - Key Encrypting Key 135 KMP - Key Management Protocol 137 LDP - Label Distribution Protocol 139 LSR - Label Switch Routers 141 MAC - Message Authentication Code 143 MKT - Master Key Tuple 145 MSDP - Multicast Source Distribution Protocol 147 MD5 - Message Digest algorithm 5 149 OSPF - OPen Shortest Path First 151 PCEP - Path Computation Element Protocol 153 TCP - Transmission Control Protocol 155 UDP - User Datagram Protocol 157 2. Current State of BGP, LDP, PCEP and MSDP 159 This section looks at the underlying transport protocol and key 160 mechanisms built for the protocol. It describes the security 161 mechanisms built into BGP, LDP, PCEP and MSDP. 163 2.1. Transport level 165 At a transport level, routing protocols are subject to a variety of 166 DoS attacks. Such attacks can cause the routing protocol to become 167 congested with the result that routing updates are supplied too 168 slowly to be useful or in extreme case prevent route convergence 169 after a change. 171 Routing protocols use several methods to protect themselves. Those 172 that run on TCP use access list to permit packets only from know 173 sources. These access lists also help edge routers from attacks 174 originating from outside the protected cloud. In addition for edge 175 routers running eBGP, TCP LISTEN is run only on interfaces on which 176 its peers have been discovered or that are configured to expect 177 sessions on. 179 GTSM [RFC5082] describes a generalized Time to Live (TTL) security 180 mechanism to protect a protocol stack from CPU-utilization based 181 attacks.TCP Robustness [RFC5961] recommends some TCP level 182 mitigations against spoofing attacks targeted towards long lived 183 routing protocol sessions. 185 Even when BGP, LDP, PCEP and MSDP sessions use access list they are 186 subject to spoofing and man in the middle attacks. Authentication 187 and integrity checks allow the receiver of a routing protocol update 188 to know that the message genuinely comes from the node that purports 189 to have sent it and to know whether the message has been modified. 190 Sometimes routers can be subjected to a large number of 191 authentication and integrity checks which can result in genuine 192 requests failing. 194 TCP MD5 [RFC2385] specifies a mechanism to protect BGP and other TCP 195 based routing protocols via the TCP MD5 option. TCP MD5 option 196 provides a way for carrying an MD5 digest in a TCP segment. This 197 digest acts like a signature for that segment, incorporating 198 information known only to the connection end points. The MD5 key 199 used to compute the digest is stored locally on the router. This 200 option is used by routing protocols to provide for session level 201 protection against the introduction of spoofed TCP segments into any 202 existing TCP streams, in particular TCP Reset segments. TCP MD5 does 203 not provide a generic mechanism to support key roll-over. 205 However, the Message Authentication Codes (MACs) used by MD5 to 206 compute the signature are considered to be too weak. TCP-AO 207 [RFC5925] and its companion document Crypto Algorithms for TCP-AO 208 [RFC5926] is a step towards correcting both the MAC weakness and KMP. 209 For MAC it specifies two MAC algorithms that MUST be supported. They 210 are HMAC-SHA-1-96 as specified in HMAC [RFC2104] and AES-128-CMAC-96 211 as specified in NIST-SP800-38B [NIST-SP800-38B]. Cryptographic 212 research suggests that both these MAC algorithms defined are fairly 213 secure and are not known to be broken in any ways. It also provides 214 for additional MACs to be added in the future. 216 2.2. Keying mechanisms 218 For TCP-AO [RFC5925] there is no Key Management Protocol (KMP) used 219 to manage the keys that are used for generating the Message 220 Authentication Code (MAC). It allows for a master key to be 221 configured manually or for it to be managed from a out of band 222 mechanism. Most routers are configured with a static key that does 223 not change over the life of the session. 225 It should also be mentioned that those routers that have been 226 configured with static keys have not seen the key changed. The 227 common reason given for not changing the key is because it triggers a 228 TCP reset, and thus bounces links/adjacencies thus undermining 229 Service Level Agreements (SLAs). It is well known that longer the 230 same key is used, higher is the chance that it can be guessed, 231 particularly if it is not a strong key. 233 For point-to-point key management IKE [RFC2409] tries to solve the 234 issue of key exchange under a SA. 236 2.3. LDP 238 Section 5 of LDP [RFC5036] states that LDP is subject to three 239 different types of attacks. These are spoofing, protection of 240 privacy of label distribution and denial of service attacks. 242 2.3.1. Spoofing attacks 244 Spoofing attack for LDP occur both during the discovery phase and 245 during the session communication phase. 247 2.3.1.1. Discovery exchanges using UDP 249 Label Switching Routers (LSRs) indicate their willingness to 250 establish and maintain LDP sessions by periodically sending Hello 251 messages. Receipt of a Hello message serves to create a new "Hello 252 adjacency", if one does not already exist, or to refresh an existing 253 one. 255 Unlike all other LDP messages, the Hello messages are sent using UDP 256 not TCP. This means that they cannot benefit from the security 257 mechanisms available with TCP. LDP [RFC5036] does not provide any 258 security mechanisms for use with Hello messages except to note that 259 some configuration may help protect against bogus discovery events. 261 Spoofing a Hello packet for an existing adjacency can cause the 262 adjacency to time out and that can result in termination of the 263 associated session. This can occur when the spoofed Hello message 264 specifies a small Hold Time, causing the receiver to expect Hello 265 messages within this interval, while the true neighbor continues 266 sending Hello messages at the lower, previously agreed to, frequency. 268 Spoofing a Hello packet can also cause the LDP session to be 269 terminated directly. This can occur when the spoofed Hello specifies 270 a different Transport Address from the previously agreed one between 271 neighbors. Spoofed Hello messages are observed and reported as real 272 problem in production networks. 274 2.3.1.2. Session communication using TCP 276 LDP like other TCP based routing protocols specifies use of the TCP 277 MD5 Signature Option to provide for the authenticity and integrity of 278 session messages. As stated above, some assert that MD5 279 authentication is now considered by some to be too weak for this 280 application. A stronger hashing algorithm e.g SHA1, could be 281 deployed to take care of the weakness. 283 2.3.2. Privacy Issues 285 LDP provides no mechanism for protecting the privacy of label 286 distribution. The security requirements of label distribution are 287 similar to other routing protocols that need to distribute routing 288 information. 290 2.3.3. Denial of Service Attacks 292 LDP is subject to Denial of Service (DoS) attacks both in its 293 discovery mode as well as during the session mode. 295 The discovery mode attack is similar to the spoofing attack except 296 that when the spoofed Hello messages are sent with a high enough 297 frequency can cause the adjacency to time out. 299 2.4. PCEP 301 Attacks on PCEP [RFC5440] may result in damage to active networks. 302 This may include computation responses, which if changed can cause 303 protocols like LDP to setup sub-optimal or inappropriate LSPs. In 304 addition, PCE itself can be attacked by a variety of DoS attacks. 305 Such attacks can cause path computations to be supplied too slowly to 306 be of any value particularly as it relates to recovery or 307 establishment of LSPs. 309 As the RFC states, PCEP could be the target of the following attacks. 311 o Spoofing (PCC or PCE implementation) 313 o Snooping (message interception) 315 o Falsification 317 o Denial of Service 319 According to the RFC, inter-AS scenarios when PCE-to-PCE 320 communication is required, attacks may be particularly significant 321 with commercial as well as service-level implications. 323 Additionally, snooping of PCEP requests and responses may give an 324 attacker information about the operation of the network. Simply by 325 viewing the PCEP messages someone can determine the pattern of 326 service establishment in the network and can know where traffic is 327 being routed, thereby making the network susceptible to targeted 328 attacks and the data within specific LSPs vulnerable. 330 Ensuring PCEP communication privacy is of key importance, especially 331 in an inter-AS context, where PCEP communication end-points do not 332 reside in the same AS, as an attacker that intercepts a PCE message 333 could obtain sensitive information related to computed paths and 334 resources. 336 2.5. MSDP 338 Similar to BGP and LDP, TCP MD5 [RFC2385] specifies a mechanism to 339 protect TCP sessions via the TCP MD5 option. But with a weak MD5 340 authentication, TCP MD5 is considered too weak for this application. 342 MSDP also advocates imposing a limit on number of source address and 343 group addresses (S,G) that can be stored within the protocol and 344 thereby mitigate state explosion due to any denial of service and 345 other attacks. 347 3. Optimal State for BGP, LDP, PCEP, and MSDP 349 The ideal state for BGP, LDP and MSDP protocols are when they can 350 withstand any of the known types of attacks. 352 Additionally, Key Management Protocol (KMP) for the routing sessions 353 should help negotiate unique, pair wise random keys without 354 administrator involvement. It should also negotiate Security 355 Association (SA) parameter required for the session connection, 356 including key life times. It should keep track of those lifetimes 357 and negotiate new keys and parameters before they expire and do so 358 without administrator involvement. In the event of a breach, the 359 keys should be changed immediately. 361 The DoS attacks for BGP, LDP, PCEP and MSDP are attacks to the 362 transport protocol, TCP in this case. TCP should be able to 363 withstand any of DoS scenarios by dropping packets that are attack 364 packets in a way that does not impact legitimate packets. 366 The routing protocols should provide a mechanism to determine 367 authenticate and validate the routing information carried within the 368 payload. 370 3.1. LDP 372 For the spoofing kind of attacks that LDP is vulnerable to during the 373 discovery phase, it should be able to determine the authenticity of 374 the neighbors sending the Hello message. 376 There is currently no requirement to protect the privacy of label 377 distribution as labels are carried in the clear like other routing 378 information. 380 4. Gap Analysis for BGP, LDP, PCEP and MSDP 382 This section outlines the differences between the current state of 383 the routing protocol and the desired state as outlined in section 4.2 384 of KARP Design Guidelines [RFC6518]. As that document states, these 385 routing protocols fall into the category of the one-to-one peering 386 messages and will use peer keying protocol. It covers issues that 387 are common to the four protocols leaving protocol specific issues to 388 sub-sections. 390 At a transport level the routing protocols are subject to some of the 391 same attacks that TCP applications are subject to. These include but 392 are not limited to DoS attacks. Recommendations to make the 393 transport protocol should be followed and implemented. An example of 394 such a draft is Improving TCP's Robustness to Blind In-Window 395 Attacks. [RFC5961] 397 From a security perspective there is a lack of comprehensive KMP. As 398 an example TCP-AO [RFC5925] talks about coordinating keys derived 399 from MKT between endpoints, but the MKT itself has to be configured 400 manually or through a out of band mechanism. Even when keys are 401 configured manually, a method for their rollover has not been 402 defined. This leads to keys not being updated regularly which in 403 itself increases the security risk. Also TCP-AO does not address the 404 issue of connectionless reset. 406 Authentication, tamper protection, and encryption all require the use 407 of keys by sender and receiver. An automated KMP therefore has to 408 include a way to distribute MKT between two end points with little or 409 no administration overhead. It has to cover automatic key rollover. 410 It is expected that authentication will cover the packet, i.e. the 411 payload and the TCP header and will not cover the frame i.e. the link 412 layer 2 header. 414 There are two methods of automatic key rollover. Implicit key 415 rollover can be initiated after certain volume of data gets exchanged 416 or when a certain time has elapsed. This does not require explicit 417 signaling nor should it result in a reset of the TCP connection in a 418 way that the links/adjacencies are affected. On the other hand, 419 explicit key rollover requires a out of band key signaling mechanism. 420 It can be triggered by either side and can be done anytime a security 421 parameter changes e.g. an attack has happened, or a system 422 administrator with access to the keys has left the company. An 423 example of this is IKE [RFC2409] but it could be any other new 424 mechanisms also. 426 As stated earlier TCP-AO [RFC5925] and its accompanying document 427 Crypto Algorithms for TCP-AO [RFC5926] suggest that two MAC 428 algorithms that MUST be supported are HMAC-SHA-1-96 as specified in 429 HMAC [RFC2104] and AES-128-CMAC-96 as specified in NIST-SP800-38B 430 [NIST-SP800-38B]. 432 There is a need to protect authenticity and validity of the routing/ 433 label information that is carried in the payload of the sessions. 434 However, we believe that is outside the scope of this document at 435 this time and is being addressed by SIDR WG. Similar mechanisms 436 could be used for intra-domain protocols. 438 4.1. LDP 440 As described in LDP [RFC5036], the threat of spoofed Basic Hellos can 441 be reduced by accepting Basic Hellos on interfaces that LSRs trust, 442 employing GTSM [RFC5082] and ignoring Basic Hellos not addressed to 443 the "all routers on this subnet" multicast group. Spoofing attacks 444 via Extended Hellos are potentially a more serious threat. An LSR 445 can reduce the threat of spoofed Extended Hellos by filtering them 446 and accepting Hellos from sources permitted by an access list. 447 However, performing the filtering using access lists requires LSR 448 resource, and the LSR is still vulnerable to the IP source address 449 spoofing. Spoofing attacks can be solved by being able to 450 authenticate the Hello messages, and an LSR can be configured to only 451 accept Hello messages from specific peers when authentication is in 452 use. 454 LDP Hello Cryptographic Authentication 455 [draft-zheng-mpls-ldp-hello-crypto-auth-01] suggest a new 456 Cryptographic Authentication TLV that can be used as an 457 authentication mechanism to secure Hello messages. 459 4.2. PCEP 461 PCE discovery according to its RFC is a significant feature for the 462 successful deployment of PCEP in large networks. This mechanism 463 allows a PCC to discover the existence of suitable PCEs within the 464 network without the necessity of configuration. It should be obvious 465 that, where PCEs are discovered and not configured, the PCC cannot 466 know the correct key to use. There are different approaches to 467 retain some aspect of security, but all of them require use of a keys 468 and a keying mechanism, the need for which has been discussed above. 470 5. Transition and Deployment Considerations 472 As stated in KARP Design Guidelines [RFC6518] it is imperative that 473 the new authentication and security mechanisms defined support 474 incremental deployment, as it is not feasible to deploy the new 475 routing protocol authentication mechansim overnight. 477 Typically authentication and security in a peer-to-peer protocol 478 requires that both parties agree to the mechanisms that will be used. 479 If an agreement is not reached the setup of the new mechanism will 480 fail. Upon failure, the routing protocols can fallback to the 481 mechanisms that were already in place e.g. use static keys if that 482 was the mechanism in place. It is usually not possible for one end 483 to use the new mechanism while the other end uses the old. Policies 484 can be put in place to retry upgrading after a said period of time, 485 so a manual coordiantion is not required. 487 If the automatic KMP requires use of public/private keys to exchange 488 key material, the required CA root certificates may need to be 489 installed to verify authenticity of requests initiated by a peer. 490 Such a step does not require coordination with the peer except to 491 agree on what CA authority will be used. 493 6. Security Requirements 495 This section describes requirements for BGP, LDP, PCEP and MSDP 496 security that should be met within the routing protocol. 498 As with all routing protocols, they need protection from both on-path 499 and off-path blind attacks. A better way to protect them would be 500 with per-packet protection using a cryptographic MAC. In order to 501 provide for the MAC, keys are needed. 503 Once keys are used, mechanisms are required to support key rollover. 504 This should cover both manual and automatic key rollover. Multiple 505 approaches could be used. However since the existing mechanisms 506 provide a protocol field to identify the key as well as management 507 mechanisms to introduce and retire new keys, focusing on the existing 508 mechanism as a starting point is prudent. 510 Finally, replay protection is required. The replay mechanism needs 511 to be sufficient to prevent an attacker from creating a denial of 512 service or disrupting the integrity of the routing protocol by 513 replaying packets. It is important that an attacker not be able to 514 disrupt service by capturing packets and waiting for replay state to 515 be lost. 517 7. Acknowledgements 519 We would like to thank Brian Weis for encouraging us to write this 520 draft and providing comments on it. 522 8. References 524 8.1. Normative References 526 [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 527 Signature Option", RFC 2385, August 1998. 529 [RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms 530 for the TCP Authentication Option (TCP-AO)", RFC 5926, 531 June 2010. 533 [RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 534 Routing Protocols (KARP) Design Guidelines", RFC 6518, 535 February 2012. 537 [draft-ietf-karp-threats-reqs] 538 Lebovitz, G. and M. Bhatia, "KARP Threats and 539 Requirements", March 2012. 541 8.2. Informative References 543 [NIST-SP800-38B] 544 Dworking, "Recommendation for Block Cipher Modes of 545 Operation: The CMAC Mode for Authentication", May 2005. 547 [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- 548 Hashing for Message Authentication", RFC 2104, 549 February 1997. 551 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 552 Requirement Levels", BCP 14, RFC 2119, March 1997. 554 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange 555 (IKE)", RFC 2409, November 1998. 557 [RFC3547] Baugher, M., Weis, B., Hardjono, T., and H. Harney, "The 558 Group Domain of Interpretation", RFC 3547, July 2003. 560 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 561 Protocol 4 (BGP-4)", RFC 4271, January 2006. 563 [RFC4948] Andersson, L., Davies, E., and L. Zhang, "Report from the 564 IAB workshop on Unwanted Traffic March 9-10, 2006", 565 RFC 4948, August 2007. 567 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP 568 Specification", RFC 5036, October 2007. 570 [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C. 571 Pignataro, "The Generalized TTL Security Mechanism 572 (GTSM)", RFC 5082, October 2007. 574 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 575 (PCE) Communication Protocol (PCEP)", RFC 5440, 576 March 2009. 578 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 579 Authentication Option", RFC 5925, June 2010. 581 [RFC5961] Ramaiah, A., Stewart, R., and M. Dalal, "Improving TCP's 582 Robustness to Blind In-Window Attacks", RFC 5961, 583 August 2010. 585 [draft-ietf-karp-ospf-analysis-03] 586 Hartman, S., "Analysis of OSPF Security According to KARP 587 Design Guide", March 2012. 589 [draft-ietf-opsec-routing-protocols-crypto-issues-07] 590 Bhatia, M., "Issues with Existing Cryptographic Protection 591 Methods for Routing Protocols", October 2010. 593 [draft-zheng-mpls-ldp-hello-crypto-auth-01] 594 Zheng, "LDP Hello Cryptographic Authentication", 595 March 2011. 597 Authors' Addresses 599 Mahesh Jethanandani 600 Private 601 USA 603 Phone: 604 Email: mjethanandani@gmail.com 606 Keyur Patel 607 Cisco Systems, Inc 608 170 Tasman Drive 609 San Jose, CA 95134 610 USA 612 Phone: +1 (408) 526-7183 613 Email: keyupate@cisco.com 615 Lianshu Zheng 616 Huawei 617 No. 3 Xinxi Road, Hai-Dian District 618 Beijing, 100085 619 China 621 Phone: +86 (10) 82882008 622 Fax: 623 Email: verozheng@huawei.com 624 URI: