INTERNET-DRAFT D. Meyer
draft-ietf-idr-bgp-analysis-04.txtdraft-ietf-idr-bgp-analysis-05.txt K. Patel Category Informational Expires: MarchDecember 2004 June 2004 September 2003BGP-4 Protocol Analysis <draft-ietf-idr-bgp-analysis-04.txt><draft-ietf-idr-bgp-analysis-05.txt> Status of this Document This document is an Internet-Draft and is in full conformance withsubject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txthttp://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.http://www.ietf.org/shadow.html This document is a product of the IDR Working Group.Group WG. Comments should be addressed to the authors, or the mailing list at email@example.com. Copyright Notice Copyright (C) The Internet Society (2003).(2004). All Rights Reserved. Abstract The purpose of this report is to document how the requirements for advancing a routing protocol from Draft Standard to full Standard have been satisfied by Border Gateway Protocol version 4 (BGP-4). This report satisfies the requirement for "the second report", as described in Section 6.0 of RFC 1264[RFC1264]. In order to fulfill the requirement, this report augments RFC 1774[RFC1774] and summarizes the key features of BGPBGP-4 protocol, and analyzes the protocol with respect to scaling and performance. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Key Features and algorithms of the BGP protocol. . . . . . . . 4 2.1. Key Features. . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. BGP Algorithms. . . . . . . . . . . . . . . . . . . . . . . 5 2.3. BGP Finite State Machine (FSM). . . . . . . . . . . . . . . 6 3. BGP Capabilities . . . . . . . . . . . . . . . . . . . . . . . 87 4. BGP Persistent Peer Oscillations . . . . . . . . . . . . . . . 87 5. Implementation Guidelines. . . . . . . . . . . . . . . . . . . 87 6. BGP Performance characteristics and Scalability. . . . . . . . 98 6.1. Link bandwidth and CPU utilization. . . . . . . . . . . . . 98 6.1.1. CPU utilization. . . . . . . . . . . . . . . . . . . . . 109 6.1.2. Memory requirements. . . . . . . . . . . . . . . . . . . 1110 7. BGP Policy Expressiveness and its Implications . . . . . . . . 1211 7.1. Existence of Unique Stable Routings . . . . . . . . . . . . 1312 7.2. Existence of Stable Routings. . . . . . . . . . . . . . . . 1513 8. Applicability. . . . . . . . . . . . . . . . . . . . . . . . . 1614 9. Intellectual Property. .Acknowledgments. . . . . . . . . . . . . . . . . . . . 17 10. Acknowledgments. . . . 15 10. Security Considerations . . . . . . . . . . . . . . . . . . . 1716 11. SecurityIANA Considerations . . . . . . . . . . . . . . . . . . . 18. . 17 12. IANA ConsiderationsReferences. . . . . . . . . . . . . . . . . . . . . . 18 13. References.. . . . 17 12.1. Informative References . . . . . . . . . . . . . . . . . . 17 13. Author's Addresses. . . . 18 13.1. Informative References. . . . . . . . . . . . . . . . . . 1819 14. Author's Addresses.Full Copyright Statement. . . . . . . . . . . . . . . . . . . 19 15. Intellectual Property . . . . 19 15. Full Copyright Statement.. . . . . . . . . . . . . . . . 20 16. Acknowledgement . . 19. . . . . . . . . . . . . . . . . . . . . 20 1. Introduction BGP-4 is an inter-autonomous system routing protocol designed for TCP/IP internets. Version 1 of the BGPBGP-4 protocol was published in RFC 1105[RFC1105]. Since then BGP versions 2, 3, and 4 have been developed. Version 2 was documented in RFC 1163[RFC1163]. Version 3 is documented in RFC 1267[RFC1267]. Version 4 is documented in the [BGP4] (version 4 of BGP will hereafter be referred to as BGP). The changes between versions are explained in Appendix A of [BGP4]. Possible applications of BGP in the Internet are documented in RFC 1772[RFC1772]. BGP introduced support for Classless InterDomain Routing [CIDR]. Since earlier versions of BGP lacked the support for CIDR, they are considered obsolete and unusable in today's Internet. 2. Key Features and algorithms of the BGP protocol This section summarizes the key features and algorithms of the BGP protocol. BGP is an inter-autonomous system routing protocol; it is designed to be used between multiple autonomous systems. BGP assumes that routing within an autonomous system is done by an intra- autonomous system routing protocol. BGP also assumes that data packets are routed from source towards destination independent of the source. BGP does not make any assumptions about intra-autonomous system routing protocols deployed within the various autonomous systems. Specifically, BGP does not require all autonomous systems to run the same intra-autonomous system routing protocol (i.e., interior gateway protocol or IGP). Finally, note that BGP is a real inter-autonomous system routing protocol, and as such it imposes no constraints on the underlying Internet topology.interconnect topology of the autonomous systems. The information exchanged via BGP is sufficient to construct a graph of autonomous systems connectivity from which routing loops may be pruned and many routing policy decisions at the autonomous system level may be enforced. 2.1. Key Features The key features of the protocol are the notion of path attributes and aggregation of network layer reachability information (NLRI). Path attributes provide BGP with flexibility and extensibility. Path attributes are partitioned into well-known and optional. The provision for optional attributes allows experimentation that may involve a group of BGP routers without affecting the rest of the Internet. New optional attributes can be added to the protocol in much the same way that new options are added to, say, the Telnet protocol [RFC854]. One of the most important path attributes is the Autonomous System Path, or AS_PATH. ASAutonomous System's (AS) reachability information traverses the Internet, this information is augmented by the list of autonomous systems that have been traversed thus far, forming the AS_PATH. The AS_PATH allows straightforward suppression of the looping of routing information. In addition, the AS_PATH serves as a powerful and versatile mechanism for policy-based routing. BGP enhances the AS_PATH attribute to include sets of autonomous systems as well as lists via the AS_SET attribute. This extended format allows generated aggregate routes to carry path information from the more specific routes used to generate the aggregate. It should be noted however, that as of this writing, AS_SETs are rarely used in the Internet [ROUTEVIEWS]. 2.2. BGP Algorithms BGP uses an algorithm that is neither a pure distance vector algorithm or a pure link state algorithm. It is instead a modified distance vector algorithm referred to as a "Path Vector" algorithm that uses path information to avoid traditional distance vector problems. Each route within BGP pairs destination with path information to that destination. Path information (also known as AS_PATH information) is stored within the AS_PATH attribute in BGP. This allowsThe path information assist BGP to reconstruct large portions of overall topology whenever required.in detecting AS loops thereby allowing BGP speakers select loop free routes. BGP uses an incremental update strategy in order to conserve bandwidth and processing power. That is, after initial exchange of complete routing information, a pair of BGP routers exchanges only changes to that information. Such an incremental update design requires reliable transport between a pair of BGP routers to function correctly. BGP solves this problem by using TCP for reliable transport. TCP further assist BGP in limiting congestion to the advertised window limits. In addition to incremental updates, BGP has added the concept of route aggregation so that information about groups of networksdestinations that use hierarchical address assignment (e.g., CIDR) may be aggregated and sent as a single Network Layer Reachability (NLRI). Finally, note that BGP is a self-contained protocol. That is, BGP specifies how routing information is exchanged both between BGP speakers in different autonomous systems, and between BGP speakers within a single autonomous system. 2.3. BGP Finite State Machine (FSM) The BGP FSM is a set of rules that are applied to a BGP speaker's set of configured peers for the BGP operation. A BGP implementation requires that a BGP speaker must connect to and listen on TCP port 179 for accepting any new BGP connections from its peers. The BGP Finite State Machine, or FSM, must be initiated and maintained for each new incoming and outgoing peer connections. However, in steady state operation, there will be only one BGP FSM per connection per peer. There may exist a temporary period where in a BGP peer may have separate incoming and outgoing connections resulting into two different BGP FSMs for a peer (instead of one). This can be resolved following BGP connection collision rules defined in the [BGP4]. Following are different states of BGP FSM for its peers: IDLE: State when BGP peer refuses any incoming connections. CONNECT: State in which BGP peer is waiting for its TCP connection to be completed. ACTIVE: State in which BGP peer is trying to acquire a peer by listening and accepting TCP connection. OPENSENT: BGP peer is waiting for OPEN message from its peer. OPENCONFIRM: BGP peer is waiting for KEEPALIVE or NOTIFICATION message from its peer. ESTABLISHED: BGP peer connection is established and exchanges UPDATE, NOTIFICATION, and KEEPALIVE messages with its peer. There are different BGP events that operate on above mentioned states of BGP FSM for itsBGP peers. These BGP events are used for initiating and terminating peer connections.either mandatory or optional. They also assist BGP in identifying any persistent peer connection oscillations and provide a mechanism for controlling them. Followingare different BGP events: Manual Start: Manually start the peer connection. Manual Stop: Manually stoptriggered by the peer connection. Automatic Start: Local system automatically startsprotocol logic as part of the peer connection. Manual start with passive TCP flag: Local system administrator manually startsBGP or using an operator intervention via a configuration interface to the peer connection with peer in passive mode. Automatic start with passiveBGP protocol. These BGP events are of following types: Optional events linked to Optional Session attributes, Administrative Events, Timer Events, TCP flag: Local system administrator automatically starts the peer connection with peer in passive mode. Automatic start with bgp_stop_flap option set: Local system administrator automatically starts the peer connection with peer oscillation damping enabled. Automatic start with bgp_stop_flap option setConnection based Events, and passive TCP establishment option set: Local system administrator automatically startsBGP Message-based Events. Both, the peer connection with peer oscillation damping enabledFSM and with peer in passive mode. Automatic stop: Local system automatically stopsthe BGP connection. Both, Manual Start and Manual Stop are mandatory BGP events. All otherevents are optional.explained in details in [BGP4]. 3. BGP Capabilities The BGP Capability mechanism [RFC2842] provides an easy and flexible way to introduce new features within the protocol. In particular, the BGP capability mechanism allows peersa BGP speaker to advertise to negotiateits peers during startup various optional features during startup.supported by the speaker (and receive similar information from the peers). This allows the base BGP protocol to contain only essential functionality, while at the same time providing a flexible mechanism for signaling protocol extensions. 4. BGP Persistent Peer Oscillations Ideally, whenever a BGP speaker detects an error in any peer connection, it shuts down the peer and changes its FSM state to IDLE. BGP speaker requires a Start event to re-initiate its idle peer connection. If the error remains persistent and BGP speaker generates Start event automatically then it may result in persistent peer flapping. However, although peer oscillation is found to be wide-spreadwide- spread in BGP implementations, methods for preventing persistent peer oscillations are outside the scope of base BGP protocol specification. 5. Implementation Guidelines A robust BGP implementation is work conserving. This means that if the number of prefixes is bound, arbitrarily high levels of route change can be tolerated with bounded impact on route convergence for occasionallyoccasional changes in generally stable routes. A BGP implementation under high load conditions should empty as much inbound routing updates from its input streams, processing only the most recent route if the route for a given NLRI changes multiple times. TCP also provides blocking on the writes on the sender side. A BGP implementation under load should expect blocks on write calls and send only the most recent routes when sockets unblock rather than sending entire history. Arobust implementation of BGP should have the following characteristics: 1. It is able to operate in almost arbitrarily high levels of route flap without loosing peerings (failing to send keepalives) or loosing other protocol adjacencies as a result of BGP load. 2. Instability of a subset of routes should not affect the route advertisements or forwarding associated with the set of stable routes. 3. High levels of instability and peers of different CPU speed or load resulting in faster or slower processing of routes should not cause instability and should have a bounded impact on the convergence time for generally stable routes. Numerous robust BGP implementations exist. Producing a robust implementation is not a trivial matter but clearly achievable. 6. BGP Performance characteristics and Scalability In this section, we provide "order of magnitude" answers to the questions of how much link bandwidth, router memory and router CPU cycles the BGP protocol will consume under normal conditions. In particular, we will address the scalability of BGP and its limitations. 6.1. Link bandwidth and CPU utilization Immediately after the initial BGP connection setup, BGP peers exchange complete set of routing information. If we denote the total number of routes in the Internet by N, the mean AS distance of the Internet by M (distance at the level of an autonomous system, expressed in terms of the number of autonomous systems), thetotal number of unique AS paths bypath attributes (for all N routes) received from a peer as A, and assume that the networks are uniformly distributed among the autonomous systems, then the worst case amount of bandwidth consumed during the initial exchange between a pair of BGP speakers (P) is BW = O(NO((N + (MA) * A))P) The following table illustrates the typical amount of bandwidth consumed during the initial exchange between a pair of BGPBGP-4 speakers based on the above assumptions (ignoring bandwidth consumed by the BGPBGP-4 Header). For purposes of the estimates here, we will calculate BW = 4(((4 * (NN) + (MA) * A)). # NLRI Mean AS Distance # AS's Bandwidth (MR) ---------- ---------------- ------ ---------------- 40,000 15 400 184,000 bytes 100,000 10 10,000 800,000 bytes 120,000 10 15,000 1,080,000 bytes 140,000 15 20,000 1,760,000 bytes [note that most of this bandwidth is consumed by the NLRI exchange] BGPP). BGP-4 was created specifically to reduce the size of the set of NLRI entries which have to be carried and exchanged by border routers. The aggregation scheme, defined in RFC 1519 [RFC1519], describes[RFC1519],describes the provider-basedprovider- based aggregation scheme in use in today's Internet. Due to the advantages of advertising a few large aggregate blocks instead of many smaller class-based individual networks, it is difficult to estimate the actual reduction in bandwidth and processing that BGPBGP-4 has provided over BGP-3. If we simply enumerate all aggregate blocks into their individual class-based networks, we would not take into account "dead" space that has been reserved for future expansion. The best metric for determining the success of BGP's aggregation is to sample the number NLRI entries in the globally connected Internet today and compare it to projected growth rates before BGP was deployed. At the time of this writing, the full set of exterior routes carried by BGP is approximately 120,000 network entries [ROUTEVIEWS]. 6.1.1. CPU utilization An important and fundamental feature of BGP is that BGP's CPU utilization depends only on the stability of the Internet.its network which relates to BGP in terms of BGP UPDATE message announcments. If the InternetBGP network is stable,stable: all the BGP routers within its network are in the steady state; then the only link bandwidth and router CPU cycles consumed by BGP are due to the exchange of the BGP KEEPALIVE messages. The KEEPALIVE messages are exchanged only between peers. The suggested frequency of the exchange is 30 seconds. The KEEPALIVE messages are quite short (19 octets), and require virtually no processing. As a result, the bandwidth consumed by the KEEPALIVE messages is about 5 bits/sec. Operational experience confirms that the overhead (in terms of bandwidth and CPU) associated with the KEEPALIVE messages should be viewed as negligible. During the periods of Internetnetwork instability, changes toBGP routers within the reachability informationnetwork are passed between routers ingenerating routing updates that are exchanged using the BGP UPDATE messages. The greatest overhead per UPDATE message occurs when each UPDATE message contains only a single network. It should bepointed out that in practice routing changes exhibit strong locality with respect to the AS path.route attributes. That is, routes that change are likely to have common AS path.route attributes. In this case, multiple networks can be grouped into a single UPDATE message, thus significantly reducing the amount of bandwidth required (see also Appendix F.1 of [BGP4]). Since6.1.2. Memory requirements To quantify the worst case memory requirements for BGP, we denote the total number of networks in the steady state the link bandwidth and router CPU cycles consumed by the BGP protocol are dependent only on the stability of the Internet, it follows that BGP should have no scaling problems in the areas of link bandwidth and router CPU utilization. This assumes that as the Internet grows, the overall stability of the inter-AS connectivity of the Internet can be controlled. In particular, while the size of the IPv4 Internet routing table is bounded by O(232 * M), (where M is a slow-moving function describing the AS interconnectivity of the network), no such bound can be formulated for the dynamic properties (i.e., stability) of BGP. Although, the dynamic properties of the network cannot be quantitatively bounded, they can be controlled within BGP. Beyond certain changes in the network, BGP can start to suppress such changes using BGP Route Flap Damping [RFC2439], pacing of its route updates, or BGP would be unable to keep up with the changes and force suppression of multiple changes over very short periods by causing the BGP peer socket to block on the sender. 6.1.2. Memory requirements To quantify the worst case memory requirements for BGP, we denote the total number of networks in the Internet by N,Internet by N, the mean AS distance of the Internet by M (distance at the level of an autonomous system, expressed in terms of the number of autonomous systems), the total number of unique AS paths as A. Then the worst case memory requirements (MR) can be expressed as MR = O(N + (M * A)) Since a mean AS distance M is a slow moving function of the interconnectivity ("meshiness") of the Internet, for all practical purposes the worst case router memory requirements are on the order of the total number of networks in the Internet times the number of peers the local system is peering with. We expect that the total number of networks in the Internet will grow much faster than the average number of peers per router. As a result, BGP's memory scaling properties are linearly related to the total number of networks in the Internet. The following table illustrates typical memory requirements of a router running BGP. We denote average number of routes advertised by each peer as N, the total number of unique AS paths as A, the mean AS distance of the Internet as M (distance at the level of an autonomous system, expressed in terms of the number of autonomous systems), number of bytes required to store a routenetwork as R, and number of bytes required to store one AS in an AS path as P. It is assumed that each network is encoded as four bytes, each AS is encoded as two bytes, and each networks is reachable via some fraction of all of the peers (# BGP peers/per net). For purposes of the estimates here, we will calculate MR = ((N(((N * R) + (M * A) * P) * S). # Networks Mean AS Distance # AS's # BGP peers/per net Memory Req (N) (M) (A) (P) (MR) ---------- ---------------- ------ ------------------- -------------- 100,000 20 3,000 20 1,040,00010,400,000 100,000 20 15,000 20 1,040,00020,000,000 120,000 10 15,000 100 75,000,00078,000,000 140,000 15 20,000 100 116,000,000 In analyzing BGP's memory requirements, we focus on the size of the forwardingBGP RIB table (and ignoring implementation details). In particular, we derive upper bounds for the size of the forwardingBGP RIB table. For example, at the time of this writing, the forwardingBGP RIB tables of a typical backbone router carry on the order of 120,000 entries. Given this number, one might ask whether it would be possible to have a functional router with a table that will have 1,000,000 entries. Clearly the answer to this question is more related to how BGP is implemented. A robust BGP implementation with a reasonable CPU and memory should not have issues scaling to such limits. 7. BGP Policy Expressiveness and its Implications BGP is unique among deployed IP routing protocols in that routing is determined using semantically rich routing policies. Although routing policies are usually the first thing that comes to a network operator's mind concerning BGP, it is important to note that the languages and techniques for specifying BGP routing policies are not actually a part of the protocol specification (see RFC 2622 [RFC2622]([RFC2622] for an example of such a policy language). In addition, the BGP specification contains few restrictions, either explicitly or implicitly, on routing policy languages. These languages have typically been developed by vendors and have evolved through interactions with network engineers in an environment lacking vendor- independent standards. The complexity of typical BGP configurations, at least in provider networks, has been steadily increasing. Router vendors typically provided hundreds of special commands for use in the configuration of BGP, and this command set is continually expanding. For example, BGP communities [RFC1997] allow policy writers to selectively attach tags to routes and use these to signal policy information to other BGP- speaking routers. Many providers allow customers, and sometimes peers, to send communities that determine the scope and preference of their routes. These developments have more and more given the task of writing BGP configurations aspects associated with open-ended programming. This has allowed network operators to encode complex policies in order to address many unforeseen situations, and has opened the door for a great deal of creativity and experimentation in routing policies. This policy flexibility is one of the main reasons why BGP is so well suited to the commercial environment of the current Internet. However, this rich policy expressiveness has come with a cost that is often not recognized. In particular, it is possible to construct locally defined routing policies that can lead to unexpected global routing anomalies such as (unintended) nondeterminism and to protocol divergence. If the interacting policies causing such anomalies are defined in different autonomous systems, then these problems can be very difficult to debug and correct. In the following sections, we describe two such cases relating to the existence (or lack thereof) of stable routings. 7.1. Existence of Unique Stable Routings One can easily construct sets of policies for which BGP can not guarantee that stable routings are unique. This can be illustrated by the following simple example. Consider the example of four Autonomous Systems, AS1, AS2, AS3, and AS4. AS1 and AS2 are peers, and they provide transit for AS3 and AS4 respectively, Suppose further that AS3 provides transit for AS4 (in this case AS3 is a customer of AS1, and AS4 is a multihomed customer of both AS3 and AS2). AS4 may want to use the link to AS3 as a "backup" link, and sends AS3 a community value that AS3 has configured to lower the preference of AS4's routes to a level below that of its upstream provider, AS1. The intended "backup routing" to AS4 is illustrated here: AS1 ------> AS2 /|\ | | | | | | \|/ AS3 ------- AS4 That is, the AS3-AS4 link is intended to be used only when the AS2-AS4 link is down (for outbound traffic, AS4 simply gives routes from AS2 a higher local preference). This is a common scenario in today's Internet. But note that this configuration has another stable solution: AS1 ------- AS2 | | | | | | \|/ \|/ AS3 ------> AS4 In this case, AS3 does not translate the "depref my route" community received from AS4 into a "depref my route" community for AS1, and so if AS1 hears the route to AS4 that transits AS3 it will prefer that route (since AS3 is a customer). This state could be reached, for example, by starting in the "correct" backup routing shown first, bringing down the AS2-AS4 BGP session, and then bringing it back up. In general, BGP has no way to prefer the "intended" solution over the anomalous one, and which is picked will depend on the unpredictable order of BGP messages. While this example is relatively simple, many operators may fail to recognize that the true source of the problem is that the BGP policies of ASes can interact in unexpected ways, and that these interactions can result in multiple stable routings. One can imagine that the interactions could be much more complex in the real Internet. We suspect that such anomalies will only become more common as BGP continues to evolve with richer policy expressiveness. For example, extended communities provide an even more flexible means of signaling information within and between autonomous systems than is possible with RFC 1997[RFC1997] communities. At the same time, applications of communities by network operators are evolving to address complex issues of inter-domain traffic engineering. 7.2. Existence of Stable Routings One can also construct a set of policies for which BGP can not guarantee that a stable routing exists (or worse, that a stable routing will ever be found). For example, RFC 3345[RFC3345] documents several scenarios that lead to route oscillations associated with the use of the Multi-Exit Discriminator or MED, attribute. Route oscillation will happen in BGP when a set of policies has no solution. That is, when there is no stable routing that satisfies the constraints imposed by policy, then BGP has no choice by to keep trying. In addition, BGP configurations can have a stable routing, yet the protocol may not be able to find it; BGP can "get trapped" down a blind alley that has no solution. Protocol divergence is not, however, a problem associated solely with use of the MED attribute. This potential exists in BGP even without the use of the MED attribute. Hence, like the unintended nondeterminism described in the previous section, this type of protocol divergence is an unintended consequence of the unconstrained nature of BGP policy languages. 8. Applicability In this section we answer the question of which environments is BGP well suited, and for which environments it is not suitable. This question is partially answered in Section 2 of BGP [BGP4], which states: "To characterize the set of policy decisions that can be enforced using BGP, one must focus on the rule that an AS advertises to its neighbor ASs only those routes that it itself uses. This rule reflects the "hop-by-hop" routing paradigm generally used throughout the current Internet. Note that some policies cannot be supported by the "hop-by-hop" routing paradigm and thus require techniques such as source routing to enforce. For example, BGP does not enable one AS to send traffic to a neighbor AS intending that the traffic take a different route from that taken by traffic originating in the neighbor AS. On the other hand, BGP can support any policy conforming to the "hop-by-hop" routing paradigm. Since the current Internet uses only the "hop-by-hop" routing paradigm and since BGP can support any policy that conforms to that paradigm, BGP is highly applicable as an inter-AS routing protocol for the current Internet." One of the important points here is that the BGP protocol contains only the functionality that is essential, while at the same time providing a flexible mechanism within the protocol that allow us to extend its functionality. For example, BGP capabilities provide an easy and flexible way to introduce new features within the protocol. Finally, since BGP was designed with flexibility and extensibility in mind, new and/or evolving requirements can be addressed via existing mechanisms. To summarize, BGP is well suitable as an inter-autonomous system routing protocol for the IPv4 Internetany internet that is based on IP [RFC791] as the Internet Protocolinternet protocol and "hop-by-hop" routing paradigm. 9. Intellectual Property The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertainAcknowledgments We would like to the implementation or usethank Paul Traina for authoring previous versions of the technology described inthis document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Informationdocument. Tim Griffin, Randy Presuhn, Curtis Villamizar and Atanu Ghosh also provided many insightful comments on the IETF's proceduresearlier versions of this document. 10. Security Considerations BGP provides flexible mechanisms with respect to rightsvarying levels of complexity for security purposes. BGP sessions are authenticated using BGP session addresses and the assigned AS number. Since BGP sessions use TCP (and IP) for reliable transport, BGP sessions are further authenticated and secured by any authentication and security mechanisms used by TCP and IP. BGP uses TCP MD5 option for validating data and protecting against spoofing of TCP segments exhanged between its sessions. The usage of TCP MD5 option for BGP is described at length in standards-track[RFC 2385]. The TCP MD5 Key management is discussed in [RFC 3562]. BGP data encryption is provided using IPsec mechanism which encrypts the IP payload data (including TCP and standards-related documentationBGP data). The IPsec mechanism can be foundused in BCP-11. Copies of claims of rights made availableboth, the transport mode as well as the tunnel mode. The IPsec mechanism is described in [RFC 2406]. Both, the TCP MD5 option and the IPsec mechanism are not widely deployed security mechanisms for publicationBGP in today's Internet and any assurances of licenseshence it is difficult to be made available, orguage their real performance impact when using with BGP. However, since both the result of an attempt mademechanisms are TCP and IP based security mechanisms, the Link Bandwidth, CPU utilization and router memory consumed by BGP protocol using it would be same as any other TCP and IP based protocols. BGP uses IP TTL value to obtainprotect its EBGP sessions from any TCP (or IP) based CPU intensive attacks. It is a general license or permission forsimple mechanism which suggests the use of such proprietary rights by implementors or usersfiltering BGP (TCP) segments using the IP TTL value carried within the IP header of this specification can be obtained fromBGP (TCP) segments exchanged between the IETF Secretariat.EBGP sessions. The IETF invitesBGP TTL mechanism is described in [BTSH]. Usage of [BTSH] impacts performance in a similar way as using any interested party to bringACL policies for BGP. Such flexible TCP and IP based security mechanisms, allow BGP to its attentionprevent insertion/deletion/modification of BGP data, any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please addresssnooping of the informationdata, session stealing, etc. However, BGP is vulnerable to the IETF Executive Director. 10. Acknowledgments We would like to thank Paul Traina for authoring previous versionssame security attacks that are present in TCP. The [BGP-VUL] explains in depth about the BGP security vulneribility. At the time of this document. Tim Griffin, Randy Presuhn, Curtis Villamizarwriting, several efforts are underway for creating and Atanu Ghosh also provided many insightful comments on earlier versions of this document. 11. Security Considerations This document presentsdefining an analysis ofappropriate security infrastructure within the BGP protocol to provide authentication and as such presents no newsecurity implicationsfor BGP. 12.its routing information; some of which include [SBGP] and [SOBGP]. 11. IANA Considerations This document presents an analysis of the BGP protocol and hence presents no new IANA considerations. 13.12. References 126.96.36.199. Informative References [BGP4] Rekhter, Y., T. Li., and S. Hares, Editors, "A Border Gateway Protocol 4 (BGP-4)", draft-ietf-idr-bgp4-20.txt. Work in progress. [CIDR] Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy", RFC 1519, September, 1993. [RFC791] "INTERNET PROTOCOL", DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION, RFC 791, September, 1981. [RFC854] Postel, J. and J. Reynolds, "TELNET PROTOCOL SPECIFICATION", RFC 854, May, 1983. [RFC1105] Lougheed, K., and Y. Rekhter, "Border Gateway Protocol BGP", RFC 1105, June 1989. [RFC1163] Lougheed, K., and Rekhter, Y, "Border Gateway Protocol BGP", RFC 1105, June 1990. [RFC1264] Hinden, R., "Internet Routing Protocol Standardization Criteria", RFC 1264, October 1991. [RFC1267] Lougheed, K., and Rekhter, Y, "Border Gateway Protocol 3 (BGP-3)", RFC 1105, October 1991. [RFC1519] Fuller, V., Li. T., Yu J., and K. Varadhan, "Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy", RFC 1519, September 1993. [RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995. [RFC1772] Rekhter, Y., and P. Gross, Editors, "Application of the Border Gateway Protocol in the Internet", RFC 1772, March 1995. [RFC1774] Traina, P., "BGP-4 protocol analysis", RFC 1774, March, 1995. [RFC1997] Chandra. R, and T. Li, "BGP Communities Attribute", RFC 1997, August, 1996. [RFC2439] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route Flap Damping", RFC 2439, November 1998.August, 1996. [RFC2622] Alaettinoglu, C., et. al., "Routing Policy Specification Language (RPSL)" RFC 2622, May, 1998. [RFC2842] Chandra, R. and J. Scudder, "Capabilities Advertisement with BGP-4", RFC 2842, May 2000. [RFC3345] McPherson, D., Gill, V., Walton, D., and A. Retana, "Border Gateway Protocol (BGP) Persistent Route Oscillation Condition", RFC 3345, August, 2002. [BTSH] Gill, V., Heasley, J., and D. Meyer, "The BGP TTL Security Hack (BTSH)", draft-gill-btsh-02.txt. Work in progress. [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 Signature Option", RFC 2385, August, 1998. [RFC3562] Leech, M., "Key Management Considerations for the TCP MD5 Signature Option", RFC 3562, July, 2003. [RFC2406] Kent, S., Atkinson, R., "IP Encapsulating Security Payload (ESP)", RFC 2406, November, 1998. [ROUTEVIEWS] Meyer, D., "The Route Views Project", http://www.routeviews.org 14.[SBGP] Lynn, C., Mikkelson, J., and K. Seo, "Secure BGP S-BGP", Internet-Draft, Work in Progress. [soBGP] White, R., "Architecture and Deployment Considerations for Secure Origin BGP (soBGP)", Internet-Draft, Work in Progress. [BGP_VULN] Murphy, S., "BGP Security Vulnerabilities Analysis", draft-ietf-idr-bgp-vuln-00.txt. work in progress 13. Author's Addresses David Meyer Email: firstname.lastname@example.org Keyur Patel Cisco Systems Email: email@example.com 15.14. Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved.(2004). This document is subject to the rights, licenses and restrictions contained in BCP 78 and except as set forth therein, the authors retain all their rights. 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