BGP Capability for IPv6 BGP
IdentifierChina MobileCNlizhenqiang@chinamobile.comChina MobileCNsongguangchenjc@chinamobile.com
Routing
Inter-Domain RoutingBGPBGP IdentifierCapabilityThis document defines a new BGP Capability that enables an IPv6 BGP
Speaker to use its global unicast IPv6 address as its BGP Identifier. This mechanism
simplifies configuration in IPv6-only networks by leveraging the
inherent uniqueness of IPv6 addresses, while maintaining full backward
compatibility with existing BGP implementations.
IntroductionA router that runs the Border Gateway Protocol (BGP) is referred to as
a BGP Speaker, and each BGP Speaker is uniquely identified by a BGP
Identifier (BGP ID). The BGP ID is a critical parameter in the BGP protocol,
used for establishing peering sessions, resolving connection collisions,
and participating in best-path selection.
specifies that the BGP ID is a 4-byte unsigned integer
and should be configured as a valid IPv4 address assigned to one of the BGP
Speaker's interfaces. However, in IPv6-only network environments, devices are
typically not configured with any IPv4 addresses, making it impossible to fulfill
this requirement and thereby preventing BGP from operating correctly.
addresses this limitation by allowing the BGP ID
to be any 4-byte unsigned integer, independent of interface addresses.
Nevertheless, in IPv6-only deployments, operators must still manually assign
a unique 4-byte BGP ID to each BGP Speaker and ensure that all BGP IDs within
the same Autonomous System (AS) are distinct. This imposes additional operational
complexity, particularly in large-scale or automated network scenarios.
defines an Optional Parameter called Capabilities,
which facilitates the introduction of new capabilities into the
Border Gateway Protocol (BGP) by providing a graceful capability advertisement
mechanism—eliminating the need to terminate BGP peering sessions
when new capabilities are introduced.
This document proposes an operationally friendly solution for IPv6-only
networks: allowing a BGP Speaker to use one of its own global unicast IPv6
addresses as its BGP Identifier, referred to as the IPv6 BGP ID. To this end,
a new BGP Capability is defined.
The solution proposed in this document fully preserves compatibility with
existing BGP implementations. The IPv6 BGP ID is used only between BGP Speakers
that establish a BGP session over IPv6 and mutually support the new capability.
Peers that do not support this capability will ignore the new option and continue
to operate using the traditional 4-byte BGP Identifier as specified in
and .
Requirements LanguageThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD
NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in BCP 14
when, and only when, they appear in all capitals, as shown here.IPv6 BGP IdentifierThis document defines a new BGP capability, the IPv6 BGP Identifier
(IPv6 BGP ID). An IPv6 BGP Speaker advertises its support for the IPv6 BGP ID
to its peer by including this capability in the Optional Parameters of
the BGP OPEN message.
specifies the format of the OPEN message as follows:OPEN messageThe Optional Parameters field, as shown below, contains a list of optional parameters.Optional Parameters defines the Capabilities Optional Parameter with Parameter Type 2. This parameter contains one or more triples <Capability Code, Capability Length, Capability Value>, where each triple is encoded as shown below:Capabilities Optional ParameterThe IPv6 BGP Identifier defined in this document is encapsulated in one triple of the Capabilities Optional Parameter, as shown below.
Capability Code：
1 octet. The specific value will be assigned by IANA and is used to indicate that this capability option represents the IPv6 BGP Identifier capability.
Capability Length:
1 octet. It has a value of 16, indicating that the Capability Value is 16 bytes (the IPv6 BGP Identifier).
Capability Value:
16 octets. This field contains the global unicast IPv6 address of the BGP Speaker that is used as its BGP Identifier.
In an OPEN message carrying the IPv6 BGP Identifier, the BGP Identifier field MUST be set to all zeros to indicate that the actual BGP Identifier is carried within the Capabilities Optional Parameter. Open Message ProcessingConstructing the OPEN MessageA BGP Speaker that supports the IPv6 BGP Identifier MUST set the BGP Identifier
field in the OPEN message to zero and include the IPv6 BGP Identifier
defined in this document as a capability option, where the Capability Value
is a global unicast IPv6 address of the BGP Speaker.One and only one IPv6 BGP Identifier SHOULD be carried in the OPEN message.Receiving the OPEN MessageA BGP Speaker that supports the IPv6 BGP Identifier capability MUST examine
the BGP Identifier field in the received OPEN message.If this field is not set to zero, the speaker MUST process the OPEN message
as if the peer does not support the IPv6 BGP Identifier capability. In this case,
any instance of the IPv6 BGP Identifier capability carried in the Capabilities
Optional Parameter MUST be ignored.If the BGP Identifier field is zero, the speaker MUST inspect the Capabilities
Optional Parameter for the presence of the IPv6 BGP Identifier capability defined
in this document. If the capability is absent, the speaker MUST send a
NOTIFICATION message with Error Code 2 (OPEN Message Error) and Error Subcode 3
(Bad BGP Identifier).If the capability is present but the Capability Value does not represent a
valid global unicast IPv6 address, the speaker MUST also send a NOTIFICATION
message with Error Code 2 (OPEN Message Error) and Error Subcode 3 (Bad BGP
Identifier).If the IPv6 BGP Identifier capability is present in the OPEN message and
its Capability Value is a valid global unicast IPv6 address, the BGP speaker
proceeds to evaluate potential connection collision in accordance with
Section 6.8 of , with the following modification:For the purpose of collision resolution, the IPv6 BGP Identifier carried in
the capability (not the 4-byte BGP Identifier field in the OPEN message,
which is zero) is used as the BGP Identifier of the peer. The local system MUST
compare its own IPv6 BGP Identifier with that of the remote peer.
Each IPv6 BGP Identifier SHALL be interpreted as a 128-bit unsigned integer
in host byte order. The connection initiated by the BGP speaker with the
numerically larger IPv6 BGP Identifier MUST be retained.If the OPEN message contains more than one IPv6 BGP Identifier, it MUST be treated as malformed. The speaker MUST send a NOTIFICATION
message with Error Code 2 (OPEN Message Error) and Error Subcode 3 (Bad BGP Identifier) to its peer.The format of the NOTIFICATION message follows the definition in Section 4.5
of RFC .AGGREGATOR Attribute ProcessingSince the BGP Identifier is also used in the AGGREGATOR path attribute of the BGP protocol, this document extends that attribute accordingly. A BGP Speaker that supports the IPv6 BGP Identifier SHALL include its AS number and IP address in the attribute, and the included IP address SHOULD be identical
to the speaker's IPv6 BGP Identifier.Route Decision ProcessFor a BGP speaker that supports the IPv6 BGP Identifier, the same route decision process defined in applies, with the following extension to step f of the Phase 2 tie‑breaking procedure specified in Section 9.1.2.2 of .f) Remove from consideration all routes other than the route that was advertised by the BGP speaker with the lowest BGP Identifier value.If routes are advertised by both IPv4 BGP Speakers and IPv6 BGP Speakers, the routes from IPv6 BGP Speakers are preferred.If routes are advertised by multiple IPv6 BGP Speakers, the routes from the Speaker with the numerically smallest IPv6 BGP Identifier are preferred.IANA ConsiderationsIANA is requested to assign new code points from the "BGP Capability Codes"
registry for the following capability defined in this document:
New BGP Capability for IPv6 BGP ID
Code Point
Description
Reference
TBD
IPv6 BGP ID
This document
Security ConsiderationsThis extension to BGP does not introduce new security considerations. BGP security considerations are discussed in .Normative ReferencesAcknowledgementsThe authors would like to acknowledge the supports from Cheng Chang, Bo Liu.