One document matched: draft-ietf-idr-bgp-analysis-01.txt
Differences from draft-ietf-idr-bgp-analysis-00.txt
INTERNET-DRAFT David Meyer
draft-ietf-idr-bgp-analysis-01.txt Keyur Patel
Category Informational
Expires: October 2003 April 2003
BGP-4 Protocol Analysis
<draft-ietf-idr-bgp-analysis-01.txt>
Status of this Document
This document is an Internet-Draft and is in full conformance with
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-
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Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at
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This document is a product of an individual. Comments are solicited
and should be addressed to the author(s).
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
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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 BGP 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 . . . . . . . . . . . . . . . 8
5. BGP Performance characteristics and Scalability. . . . . . . . 8
5.1. Link bandwidth and CPU utilization. . . . . . . . . . . . . 8
5.1.1. CPU utilization. . . . . . . . . . . . . . . . . . . . . 9
5.1.2. Memory requirements. . . . . . . . . . . . . . . . . . . 11
6. BGP Policy Expressiveness and its Implications . . . . . . . . 12
6.1. Existence of Unique Stable Routings . . . . . . . . . . . . 13
6.2. Existence of Stable Routings. . . . . . . . . . . . . . . . 14
7. Applicability. . . . . . . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10. Author's Address. . . . . . . . . . . . . . . . . . . . . . . 18
11. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 18
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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 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].
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 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. 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
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protocol [RFC854].
One of the most important path attributes is the AS_PATH. 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 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 allows BGP to reconstruct large
portions of overall topology whenever required.
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 networks 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.
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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 it's 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 operates on above mentioned states
of BGP FSM for its peers. These BGP events are used for initiating and
terminating peer connections. They also assist BGP in identifying any
persistent peer connection oscillations and provides mechanism
for controlling it.
Following are different BGP events:
Manual Start: Manually start the peer connection.
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Manual Stop: Manually stop the peer connection.
Automatic Start: Local system automatically starts the peer
connection.
Manual start with
passive TCP flag: Local system administrator manually starts the
peer connection with peer in passive mode.
Automatic start
with passive 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
set and passive TCP
establishment
option set: Local system administrator automatically starts
the peer connection with peer oscillation
damping enabled and with peer in passive mode.
Automatic stop: Local system automatically stops the
BGP connection.
Both, Manual Start and Manual Stop are mandatory BGP events. All
other events are optional.
3. BGP Capabilities
The BGP Capability mechanism [RFC2842] provides easy and flexible way
to introduce new features within the protocol. In particular, the BGP
capability mechanism allows peers to negotiate various optional
features during startup. This allows the base BGP protocol to contain
only essential functionality, while at the same time providing a
flexible mechanism for signaling protocol extensions.
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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 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. 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.
It is important to note that BGP does not require all the routers
within an autonomous system to participate in the BGP protocol. In
particular, only the border routers that provide connectivity between
the local autonomous system and their adjacent autonomous systems
need participate in BGP. The ability to constraint the set of BGP
speakers is one way to address scaling issues.
5.1. 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), the total
number of autonomous systems in the Internet by 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 is
MR = O(N + M * A)
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The following table illustrates the typical amount of bandwidth
consumed during the initial exchange between a pair of BGP speakers
based on the above assumptions (ignoring bandwidth consumed by the
BGP Header). For purposes of the estimates here, we will calculate MR
= 4 * (N + (M * 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]
BGP 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 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 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 approximately 120,000 network entries [ROUTEVIEWS].
5.1.1. CPU utilization
An important and fundamental feature of BGP is that BGP's CPU
utilization depends only on the stability of the Internet. If the
Internet is stable, 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
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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 Internet instability, changes to the reachability
information are passed between routers in UPDATE messages. If we
denote the number of routing changes per second by C, then in the
worst case the amount of bandwidth consumed by the BGP can be
expressed as O(C * M). 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 AS path. That is routes that change are
likely to have common AS path. 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]).
Since 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(2^32 *
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. Finally, since
the dynamic properties of the network cannot be quantitatively
bounded, stability must be addressed via heuristics such as BGP
Route Flap Dampening [RFC2439]. Due to the nature of BGP, such
dampening should be viewed as a local to an autonomous system matter
(see also Appendix F.2 of [BGP4]).
It may also be instructive to compare bandwidth and CPU requirements
of BGP with EGP. While with BGP the complete information is exchanged
only at the connection establishment time, with EGP the complete
information is exchanged periodically (usually every 3 minutes). Note
that both for BGP and for EGP the amount of information exchanged is
roughly on the order of the networks reachable via a peer that sends
the information. Therefore, even if one assumes extreme instabilities
of BGP, its worst case behavior will be the same as the steady state
behavior of it's predecessor, EGP.
Operational experience with BGP showed that the incremental update
approach employed by BGP provides qualitative improvement in both
bandwidth and CPU utilization when compared with complete periodic
updates used by EGP (see also presentation by Dennis Ferguson at the
Twentieth IETF, March 11-15, 1991, St.Louis).
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5.1.2. 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 autonomous systems in the Internet by A, and the total
number of BGP speakers that a system is peering with by K (note that
K will usually be dominated by the total number of the BGP speakers
within a single autonomous system). Then the worst case memory
requirements (MR) can be expressed as
MR = O((N + M * A) * K)
It is interesting to note that prior to the introduction of BGP in
the NSFNET Backbone, memory requirements on the NSFNET Backbone
routers running EGP were on the order of O(N *K). Therefore, the
extra overhead in memory incurred by modern routers running BGP is
less than 7 percent.
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. 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*4) + (M*A)*2) * K.
# Networks Mean AS Distance # AS's # BGP peers/per net Memory Req (MR)
---------- ---------------- ------ ------------------- --------------
100,000 20 3,000 20 1,040,000
100,000 20 15,000 20 1,040,000
120,000 10 15,000 100 75,000,000
140,000 15 20,000 100 116,000,000
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In analyzing BGP's memory requirements, we focus on the size of the
forwarding table (and ignoring implementation details). In
particular, we derive upper bounds for the size of the forwarding
table. For example, at the time of this writing, the forwarding
tables of a typical backbone router carries 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 independent
of BGP. Interestingly, in his review of the BGP protocol for the BGP
review committee in March of 1990, Paul Tsuchiya noted that "BGP does
not scale well. This is not really the fault of BGP. It is the fault
of the flat IP address space. Given the flat IP address space, any
routing protocol must carry network numbers in its updates." The
introduction of the provider based aggregation schemes (e.g., CIDR
[RFC1519]) have sought to address this issue, to the extent possible,
within the context of current addressing architectures.
6. 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]
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
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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.
6.1. 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 AS4). 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 RFC 1997 communities. At the same time, applications of
communities by network operators are evolving to address complex
issues of inter-domain traffic engineering.
6.2. 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 MEDs. Route oscillation will happen in BGP
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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.
7. 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 RFC 1771 [RFC1771],
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.
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To summarize, BGP is well suitable as an inter-autonomous system
routing protocol for the IPv4 Internet that is based on IP [RFC791]
as the Internet Protocol and "hop-by-hop" routing paradigm. Finally,
BGP is equally applicable to IPv6 [RFC2460] internets.
8. Acknowledgments
We would like to thank Paul Traina for authoring previous versions of
this document. Tim Griffin also provided many insightful comments on
earlier versions of this document.
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9. References
[BGP4] Rekhter, Y., T. Li., and Hares. S, Editors, "A
Border Gateway Protocol 4 (BGP-4)",
draft-ietf-idr-bgp4-19.txt. Work in progress.
[RFC791] "INTERNET PROTOCOL", DARPA INTERNET PROGRAM
PROTOCOL SPECIFICATION, RFC 791, September,
1981.
[RFC854] Postel, J. and Reynolds, J., "TELNET PROTOCOL
SPECIFICATION", RFC 854, May, 1983.
[RFC1105] Lougheed, K., and Rekhter, Y, "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.
[RFC1997] Chandra. R, and T. Li, "BGP Communities
Attribute", RFC 1997, August, 1996.
[RFC2439] Villamizar, C., Chandra, R., and Govindan, R.,
"BGP Route Flap Damping", RFC 2439, November
1998.
Meyer and Patel Section 9. [Page 17]
INTERNET-DRAFT Expires: October 2003 April 2003
[RFC2460] Deering, S, and R. Hinden, "Internet Protocol,
Version 6 (IPv6) Specification", RFC 2460,
December, 1998.
[RFC2622] C. Alaettinoglu, 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
Retana, A, "Border Gateway Protocol (BGP) Persistent
Route Oscillation Condition", RFC 3345,
August, 2002.
[ROUTEVIEWS] Meyer, David, "The Route Views Project",
http://www.routeviews.org
10. Author's Address
David Meyer
Email: dmm@maoz.com
Keyur Patel
Cisco Systems
Email: keyupate@cisco.com
11. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
Meyer and Patel Section 11. [Page 18]
INTERNET-DRAFT Expires: October 2003 April 2003
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Meyer and Patel Section 11. [Page 19]
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