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INTERNET-DRAFT                                      D. Meyer
draft-ietf-idr-bgp-analysis-07.txt                  K. Patel
Category                                       Informational
Expires: June 2005                             December 2004

                        BGP-4 Protocol Analysis
                  <draft-ietf-idr-bgp-analysis-07.txt>



Status of this Memo


   Status of this Memo

   This document is an Internet-Draft and is subject to all
   provisions of section 3 of RFC 3667.  By submitting this
   Internet-Draft, each author represents that any applicable patent
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   disclosed, in accordance with RFC 3668.

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   This document is a product of the IDR Working Group
   WG. Comments should be addressed to the authors, or the
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Copyright Notice

   Copyright (C) The Internet Society (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 [RFC1264]. In order to fulfill the
   requirement, this report augments [RFC1774] and summarizes the key
   features of BGP-4 protocol, and analyzes the protocol with respect
   to scaling and performance.



































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                           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 . . . . . . . . . . . . . . . . . . . . . . .   7
   4. BGP Persistent Peer Oscillations . . . . . . . . . . . . . . .   7
   5. Implementation Guidelines. . . . . . . . . . . . . . . . . . .   7
   6. BGP Performance characteristics and Scalability. . . . . . . .   8
    6.1. Link bandwidth and CPU utilization. . . . . . . . . . . . .   8
     6.1.1. CPU utilization. . . . . . . . . . . . . . . . . . . . .   9
     6.1.2. Memory requirements. . . . . . . . . . . . . . . . . . .  10
   7. BGP Policy Expressiveness and its Implications . . . . . . . .  11
    7.1. Existence of Unique Stable Routings . . . . . . . . . . . .  12
    7.2. Existence of Stable Routings. . . . . . . . . . . . . . . .  13
   8. Applicability. . . . . . . . . . . . . . . . . . . . . . . . .  14
   9. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . .  15
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   12. References. . . . . . . . . . . . . . . . . . . . . . . . . .  17
    12.1. Normative References . . . . . . . . . . . . . . . . . . .  17
    12.2. Informative References . . . . . . . . . . . . . . . . . .  18
   13. Author's Addresses. . . . . . . . . . . . . . . . . . . . . .  19


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1.  Introduction


   BGP-4 is an inter-autonomous system routing protocol designed for
   TCP/IP internets. Version 1 of the BGP-4 protocol was published in
   [RFC1105]. Since then BGP versions 2, 3, and 4 have been developed.
   Version 2 was documented in [RFC1163]. Version 3 is documented in
   [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 [RFC1772].

   BGP introduced support for Classless Inter-Domain Routing
   [RFC1519]. 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 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).



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   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. As the reachability information
   traverses the Internet, this (AS_PATH) 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. The path information assists BGP 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.

   In addition to incremental updates, BGP has added the concept
   of route aggregation so that information about groups of
   destinations


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   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 be a short period during which a BGP peer may have
   separate incoming and outgoing connections resulting in the
   creation of two different BGP FSMs relating to a peer (instead
   of one). This can be resolved by following the BGP connection
   collision rules defined in the [BGP4] specification.

   The BGP FSM has the following states associated with each of 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



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                   its peer.

   There are an number of BGP events that operate on above
   mentioned states of the BGP FSM for BGP peers. Support of
   these BGP events are either mandatory or optional. They are
   triggered by the protocol logic as part of the BGP or using an
   operator intervention via a configuration interface to the BGP
   protocol.

   These BGP events are of following types: Optional events
   linked to Optional Session attributes, Administrative Events,
   Timer Events, TCP Connection based Events, and BGP
   Message-based Events. Both the FSM and the BGP events are
   explained in detail 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 a BGP speaker to advertise to its
   peers during startup various optional features 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


   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-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 bounded, arbitrarily high levels of route



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   change can be tolerated with bounded impact on route convergence for
   occasional changes in generally stable routes.


   A robust implementation of BGP should have the following
   characteristics:
         1.  It is able to operate in almost arbitrarily high levels
             of route flap without losing 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 total path 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




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           BW = O((N + A) * P)

   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 [RFC1519],
   describes the provider-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 BGP-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 134,000 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 its network which
   relates to BGP in terms of BGP UPDATE message announcements.  If the
   BGP network is 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 periods of network instability, BGP routers within the network
   are generating 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 be
   pointed out that in practice routing changes exhibit strong locality
   with respect to the route attributes.  That is, routes that change
   are likely to have common 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



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   Appendix F.1 of [BGP4]).




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, 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 octets required to store a network 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 * 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           10,400,000
     100,000           20        15,000         20           20,000,000
     120,000           10        15,000        100           78,000,000



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     140,000           15        20,000        100           116,000,000


   In analyzing BGP's memory requirements, we focus on the size of the
   BGP RIB table (ignoring implementation details).  In particular, we
   derive upper bounds for the size of the BGP RIB table.  For example,
   at the time of this writing, the BGP 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 ([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
   provide 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
   increasingly 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.



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   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)
   non-determinism 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
















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   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 [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, [RFC3345] documents
   several scenarios that lead to route oscillations associated
   with the use of the Multi-Exit Discriminator or MED,
   attribute.  Route



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   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  identify the environments for which 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 allows 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.



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   To summarize, BGP is well suited as an inter-autonomous system
   routing protocol for any internet that is based on IP [RFC791]
   as the internet protocol and "hop-by-hop" routing paradigm.



9.  Acknowledgments


   We would like to thank Paul Traina for authoring previous
   versions of this document.  Elwyn Davies, Tim Griffin, Randy
   Presuhn, Curtis Villamizar and Atanu Ghosh also provided many
   insightful comments on earlier versions of this document.






































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10.  Security Considerations


   BGP provides flexible mechanisms with varying 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 exchanged between its sessions.  The usage
   of TCP MD5 option for BGP is described at length in [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 BGP data).  The IPsec mechanism can
   be used in both, 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 BGP in today's Internet and hence it is difficult to gauge their
   real performance impact when using with BGP.  However, since both the
   mechanisms 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 protect its External BGP (EBGP) sessions
   from any TCP (or IP) based CPU intensive attacks.  It is a simple
   mechanism which suggests the use of filtering BGP (TCP) segments
   using the IP TTL value carried within the IP header of BGP (TCP)
   segments exchanged between the EBGP sessions.  The BGP TTL mechanism
   is described in [RFC3682]. Usage of [RFC3682] impacts performance in
   a similar way as using any ACL policies for BGP.

   Such flexible TCP and IP based security mechanisms, allow BGP to
   prevent  insertion/deletion/modification of BGP data, any snooping of
   the data, session stealing, etc.  However, BGP is vulnerable to the
   same security attacks that are present in TCP.  The [BGP-VUL]
   explains in depth about the BGP security vulnerability. At the time
   of this writing, several efforts are underway for creating and
   defining an appropriate security infrastructure  within the BGP
   protocol to provide authentication and security for its  routing
   information; some of which include [SBGP] and [SOBGP].









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11.  IANA Considerations


   This document presents an analysis of the BGP protocol and hence
   presents no new IANA considerations.



12.  References

12.1.  Normative References



   [BGP4]          Rekhter, Y., T. Li., and S. Hares, Editors, "A
                   Border Gateway Protocol 4 (BGP-4)",
                   draft-ietf-idr-bgp4-2.txt. Work in progress.

   [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.

   [RFC791]        "INTERNET PROTOCOL", DARPA INTERNET PROGRAM
                   PROTOCOL SPECIFICATION, RFC 791, September,
                   1981.

   [RFC1997]       Chandra. R, and T. Li, "BGP Communities
                   Attribute",  RFC 1997, August, 1996.

   [RFC2385]       Heffernan, A., "Protection of BGP Sessions via
                   the TCP MD5 Signature Option", RFC 2385,
                   August, 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.

   [RFC3562]       Leech, M., "Key Management Considerations for
                   the TCP MD5 Signature Option", RFC 3562,
                   July, 2003.






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   [RFC3682]       Gill, V., Heasley, J., and D. Meyer, "The
                   Generalized TTL Security Mechanism (GTSM)", RFC
                   3682, February, 2004.
   [SOBGP]         White, R., "Architecture and Deployment
                   Considerations for Secure Origin BGP (soBGP)",
                   draft-white-sobgp-architecture-00.txt.  Work in
                   Progress.

   [BGP_VULN]      Murphy, S., "BGP Security Vulnerabilities Analysis",
                   draft-ietf-idr-bgp-vuln-01.txt. Work in progress

   [SBGP]          Lynn, C., Mikkelson, J., and K. Seo, "Secure BGP S-BGP",
                   Internet-Draft, Work in Progress.



12.2.  Informative References



   [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.

   [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.

   [RFC2622]       Alaettinoglu, C., et. al., "Routing Policy
                   Specification Language (RPSL)" RFC 2622, May,
                   1998.



Meyer and Patel                                 Section 12.2.  [Page 18]

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   [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



13.  Author's Addresses



   David Meyer
   Email: dmm@1-4-5.net

   Keyur Patel
   Cisco Systems
   Email: keyupate@cisco.com


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Meyer and Patel                                   Section 13.  [Page 19]

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   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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Meyer and Patel                                   Section 13.  [Page 20]


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