A Border Gateway Protocol 4 (BGP-4), January Canonical URL: https:// ; File formats: Plain Text PDF; Status: DRAFT. Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to RFC corrected errors, clarified ambiguities and updated the. RFC (part 1 of 4): A Border Gateway Protocol 4 (BGP-4).

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A BGP router used only for a network with a single point of entry to the Internet may have a much smaller routing table size and hence RAM and CPU requirement than a multihomed network. These devices, however, may be perfectly frc and useful when used for BGP routing of some smaller part of the network, such as a confederation-AS representing one of several smaller enterprises that are linked, by a BGP backbone of backbonesor a small enterprise that announces routes to an ISP but only accepts a default route and perhaps a small number of aggregated routes.

The exact nature of this policy information, and the computation involved, is a local matter. Therefore, in addition to local Routing Table stability, this check also improves behavior of the protocol in the network. The techniques specified in RFC for random number generation provide a guide for generation of values that could be used as keys.

Definition of Commonly Used Terms On the other hand, BGP can support any policy conforming to the destination-based forwarding paradigm. The tie-breaking algorithm begins by considering all equally preferable routes to the same destination, and then selects routes to be removed from consideration.

BGP neighbors, called peers, are established by manual configuration among routers to create a TCP session on port An implementation may choose any algorithm that conforms to these rules. For example, it distributes the routes chosen by the Decision Process to other BGP speakers, which may be located in either the same autonomous system or a neighboring autonomous system.

RFC – part 1 of 4

Route Selection Criteria Generally, additional rules for comparing routes among several alternatives are outside the scope of this document. An alternative to full mesh IBGP. Because the mechanism defined in the RFC does not provide peer-entity authentication, these connections may be subject to some forms of replay attacks that will not be detected at the TCP layer. However, absent a standard mechanism for effecting such changes in a coordinated fashion between peers, one cannot assume that BGP-4 implementations complying with this RFC will support frequent key changes.


Products marketed as switches may or may not have a size limitation on BGP tables, such as 20, routes, far smaller than a full Internet table plus internal routes. Frequency of Route Origination The routing tables managed by a BGP implementation are adjusted continually to reflect actual changes in the network, such as links breaking and being restored or routers going down and coming back up. These mechanisms include support for advertising a set of destinations as an IP prefix and eliminating the concept of network “class” within BGP.

Once the interface goes down, and there are no more preferred routes, the Loc-RIB route would be installed in the main routing table. Increasingly, BGP is used as a generalized signaling protocol to carry information about routes that may not be part of the global Internet, such as VPNs.

Supported Standards for BGP

Such policies cannot be enforced using BGP either. Multiple Networks Per Message Rffc BGP protocol allows for multiple address prefixes with the same path attributes to be specified in one message.

This procedure does not limit the rate of route selection, but only the rate of route advertisement. Bg; manipulation is outside the scope of the standard but is commonly used. In the “OpenSent” state, the router sends an Open message and waits for one in return in order to transition to the “OpenConfirm” state.

The concept of network classes, or subnetting, is foreign to BGP As long as that directly connected route’s interface is active, the BGP route 42711 the destination will not be put into the routing table. A compliant implementation must support this mechanism, and must allow a network administrator to activate it on a per-peer basis.

The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. The Marker field has been expanded and its role broadened to support authentication. The initial data flow is the portion of the BGP routing table that is allowed by the export policy, called the Adj-Ribs-Out see 3.

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Information on RFC ยป RFC Editor

This requires a 44271 on most routers. Finally, we would like to thank all the members of the IDR Working Group for their ideas and the support they have given to this document.

Until recently, it was a common mistake to say BGP carries policies. This network reachability information includes information on the list of Autonomous Systems ASes that reachability information traverses.

Border Gateway Protocol

These mechanisms include support for advertising a set of destinations as an IP prefix, and eliminating the concept of network “class” within BGP. Retrieved 13 April A better method would be to read all received messages before sending updates. One method of doing this is to limit the rate of updates.

The current standard however specifies that missing MEDs are to be treated as the lowest possible value. IGP Interior Gateway Protocol – a routing protocol used to exchange routing information among routers within a single Autonomous System.

Feasible route An advertised route that is available for use by the recipient. Retrieved from ” https: Both confederations and route reflectors bbgp be subject to persistent oscillation unless specific design rules, affecting both BGP and the interior routing protocol, are followed.

Static routes can specify the outbound interface, the intermediate address, or both.

Please refer to the current edition of the “Internet Official Protocol Standards” STD 1 for the standardization state and status of this protocol. Optional Parameter Type 1 Authentication Information has been deprecated. If an optional transitive attribute is unrecognized, the Partial bit the third high-order bit in the attribute flags octet is set to 1, and the attribute is retained for propagation to other BGP speakers.