rfc3392.CapabilitiesAdvertimentwithBGP-4
Network Working Group R. Chandra Request for Comments: 3392 Redback Networks Obsoletes: 2842 J. Scudder Category: Standards Track Cisco Systems November 2002 Capabilities Advertiment with BGP-4
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for
improvements. Plea refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Rerved.
Abstract
同心多元化This document defines a new Optional Parameter, called Capabilities, that is expected to facilitate the introduction of new capabilities
in the Border Gateway Protocol (BGP) by providing graceful capability advertiment without requiring that BGP peering be terminated.
This document obsoletes RFC 2842.
1. Introduction
Currently BGP-4 requires that when a BGP speaker receives an OPEN
message with one or more unrecognized Optional Parameters, the
speaker must terminate BGP peering. This complicates introduction of new capabilities in BGP.
2. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Chandra, et. al. Standards Track [Page 1]
3. Overview of Operations
When a BGP speaker [BGP-4] that supports capabilities advertiment
nds an OPEN message to its BGP peer, the message MAY include an
Optional Parameter, called Capabilities. The parameter lists the
capabilities supported by the speaker.
A BGP speaker determines the capabilities supported by its peer by
examining the list of capabilities prent in the Capabilities
五角星折法
Optional Parameter carried by the OPEN message that the speaker
receives from the peer.
A BGP speaker that supports a particular capability may u this
capability with its peer after the speaker determines (as described
above) that the peer supports this capability.
A BGP speaker determines that its peer doesn’t support capabilities费马定理证明
advertiment, if in respon to an OPEN message that carries the
Capabilities Optional Parameter, the speaker receives a NOTIFICATION message with the Error Subcode t to Unsupported Optional Parameter. In this ca the speaker SHOULD attempt to re-establish a BGP
所以用英语怎么说connection with the peer without nding to the peer the Capabilities Optional Parameter.
If a BGP speaker that supports a certain capability determines that
its peer doesn’t support this capability, the speaker MAY nd a
NOTIFICATION message to the peer, and terminate peering (e Section "Extensions to Error Handling" for more details). The Error Subcode in the message is t to Unsupported Capability. The message SHOULD contain the capability (capabilities) that caus the speaker to nd the message. The decision to nd the message and terminate peering is local to the speaker. If terminated, such peering SHOULD NOT be
re-established automatically.
Chandra, et. al. Standards Track [Page 2]
4. Capabilities Optional Parameter (Parameter Type 2):
This is an Optional Parameter that is ud by a BGP speaker to convey to its BGP peer the list of capabilities supported by the speaker.
昆明旅游路线The parameter contains one or more triples <="" p="">
Capability Length, Capability Value>, where each triple is encoded as shown below:
+------------------------------+
| Capability Code (1 octet) |
+------------------------------+
| Capability Length (1 octet) |
+------------------------------+
| Capability Value (variable) |史记是我国第一部什么
+------------------------------+
The u and meaning of the fields are as follows:宝的成语
Capability Code:
Capability Code is a one octet field that unambiguously
时间管理表identifies individual capabilities.
Capability Length:
Capability Length is a one octet field that contains the length of the Capability Value field in octets.
Capability Value:
Capability Value is a variable length field that is interpreted according to the value of the Capability Code field.
BGP speakers SHOULD NOT include more than one instance of a
