As per Relevance of the word implementation, we have this rfc below:
Network Working Group P.
Request for Comments: 1656 cisco
Category: Informational July 1994
BGP-4 Protocol Document Roadmap and Implementation
Status of this
This memo provides information for the Internet community. This
does not specify an Internet standard of any kind. Distribution
this memo is unlimited
Border Gateway Protocol v4 (BGP-4) [1] is an inter-Autonomous
routing protocol. It is built on experience gained with BGP
defined in RFC-1267 [2] and BGP usage in the connected Internet
described in RFC-1268 [3].
The primary function of a BGP speaking system is to exchange
reachability information with other BGP systems. This
reachability information includes information on the list
Autonomous Systems (ASs) that reachability information traverses
This information is sufficient to construct a graph of
connectivity from which routing loops may be pruned and some
decisions at the AS level may be enforced
BGP-4 provides a new set of mechanisms for supporting
inter-domain routing. These mechanisms include support
advertising an IP prefix and eliminates the concept of
"class" within BGP. BGP-4 also introduces mechanisms which
aggregation of routes, including aggregation of AS paths.
changes provide support for the proposed supernetting scheme [4].
The management information base has been defined [5] and
considerations are discussed in the protocol definition document [1].
Applicability Statement for BGP-4
BGP-4 is explicitly designed for carrying reachability
between Autonomous Systems. BGP-4 is not intended to
interior gateway protocols such as OSPF [7] or RIP [6].
Four vendors have developed independent implementations at the
of this memo
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RFC 1656 BGP-4 Implementation July 1994
ANS (gated
3
The complete interoperability matrix between all
implementations of various versions of BGP is available
separate cover [9].
Implementation
One implementation has been extensively tested in a network
to mirror the complex connectivity present at many major
borders. This network consists of multiple BGP-3 and BGP-4
carrying full routing information injected from Alternet, EBone
Sprint, CERFnet, and cisco. In many cases additional AS
are simulated via the use of IP over IP tunnels to increase
complexity of the routing topology
The primary feature of BGP-4 is the ability to carry
reachability information without regard to classfull routing.
addition to canonical routing information, CIDR prefixes (
supernets and subnets) are being injected from IGP information
aggregated using the methods described in BGP-4. AS set
and policy decisions based upon AS sets have been tested
Secondary extensions incorporated as part of version 4 of
protocol include enhancements to use of the INTER_AS_METRIC (
called MULTI_EXIT_DISC), the addition of a LOCAL_PREF parameter
influence route selection within an AS, and a specified method
damping route fluctuations. All of these features have been
in at least one implementation
All implementations, are able to carry and exchange
reachability information
Not all implementations are capable of generating
information based upon the existence of more specific routes
No implementation supports automatic deaggregation (enumeration
all networks in an aggregate block for backwards compatibility
routing protocols that do not carry mask information (e.g. BGP-3)).
However, most implementations do allow for staticly
controlled deaggregation for minimal backwards compatibility
non-CIDR capable routers
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RFC 1656 BGP-4 Implementation July 1994
At least one implementation capable of running earlier versions
BGP deliberately does not automaticly negotiate to earlier versions
Connections to BGP-4 peers must be explicitly configured as such
The ability to carry and inject natural networks and CIDR
is the immediate requirement for BGP-4. The ability to carry
information (useful when reassigning parts of class A networks
organizations with different routing policies) is of
concern
The ability to conditionally aggregate routing information may
worked around by injecting static or IGP network information
BGP, or aggregation may be performed by an upstream router that
capable
Deaggregation is dangerous. It leads to information loss and
tightly controlled by a manual mechanism, will create a
information explosion
Automatic version negotiation is dangerous due to the state-
nature. Given packet losses or spontaneous restarts, it is
for two BGP peers capable of BGP-4 to negotiate a BGP-3 or BGP-2
connection, which is incapable of carrying super/subnet
information and AS set information
The author would like to acknowledge Yakov Rekhter (IBM) and Tony
(cisco) for their advice, encouragement and insightful comments
[1] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4),
1654, cisco Systems, T.J. Watson Research Center, IBM Corp.,
1994.
[2] Lougheed K., and Y. Rekhter, "A Border Gateway Protocol 3 (BGP
3)", RFC 1267, cisco Systems, T.J. Watson Research Center,
Corp., October 1991.
[3] Gross P., and Y. Rekhter, "Application of the Border
Protocol in the Internet", RFC 1268, T.J. Watson Research Center
IBM Corp., ANS, October 1991.
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RFC 1656 BGP-4 Implementation July 1994
[4] Fuller V., Li. T, Yu J., and K. Varadhan, "Supernetting:
Address Assignment and Aggregation Strategy", Work in Progress
[Note: This is an expired draft, and is also referred to
BGP4.6.]
[5] Willis S., Burruss J., and J. Chu, "Definitions of
Objects for the Border Gateway Protocol (Version 4) using SMIv2",
RFC 1657, Wellfleet Communications Inc., IBM Corp., July 1994.
[6] Hedrick, C., "Routing Information Protocol", RFC 1058,
University, June 1988.
[7] Moy J., "Open Shortest Path First Routing Protocol (Version 2)",
RFC 1583, Proteon, March 1994.
[8] Varadhan, K., Hares S., and Y. Rekhter, "BGP4/IDRP for IP---
Interaction", Work in Progress, September 1993.
[9] Li, T., and P. Traina, "BGP Interoperabilty Matrix", Work
Progress, November 1993.
Security
Security issues are not discussed in this memo
Author's
Paul
cisco Systems, Inc
1525 O'Brien
Menlo Park, CA 94025
EMail: pst@cisco.
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if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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