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Redundancy Policy in BGPHuawei156 Beiqing Rd.Beijing100095Chinashirley.yangfan@huawei.comHuawei156 Beiqing Rd.Beijing100095Chinagengxuesong@huawei.comHuawei156 Beiqing Rd.Beijing100095Chinazhoutianran@huawei.comIDR Working GroupRedundancy Protection is a generalized protection mechanism by
replicating and transmitting copies of flow packets on redundancy node
over multiple different and disjoint paths, and further eliminating the
redundant packets at merging node. In order to support the replication
behavior of redundancy protection, Redundancy Policy is used to instruct
the replication of service packets and assign more than one redundancy
forwarding paths. This document defines the extensions to BGP to
advertise the redundancy policy.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 .Redundancy protection is a generalized
protection mechanism by replicating and transmitting copies of flow
packets on redundancy node over multiple different and disjoint paths,
and further eliminating the redundant packets at merging node. To
support the replication on the redundancy node, Redundancy Segment and Redundancy
Policy are specified
respectively. Redundancy Segment is the variation of Binding SID to
associate with a Redundancy Policy, instantiation of which provides
segment lists of more than one disjoint paths. Redundancy Policy is a
variant of SR Policy , and shares the basic
structure and elements with SR Policy. Different from SR policy, a new
attribute Flag is added to indicate the type of the Candidate Path as
redundancy type, which means all the Segment-Lists in this candidate
path are used to forward the different copies of service traffics.This document defines the extensions to Border Gateway Protocol (BGP)
to distribute the redundancy policy information. As a variant of SR
policy, Redundancy Policy reuses the BGP extensions to SR policy
candidate path and other information distribution specified in . In addition, a new
sub-TLV is defined in this document to support the distribution of new
attribute of redundancy policy.The 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.As a variant of SR policy, redundancy policy uses the same Subsequent
Address Family Identifier (SAFI) whose NLRI identifies an SR Policy
candidate path. The Tunnel Type identifier for SR Policy and a set of
sub-TLVs specifying segment lists of the SR Policy candidate path, as
well as other information about the SR Policy are reused. The content of
Redundancy Policy Candidate Path is encoded in the Tunnel Encapsulation
Attribute by using the same Tunnel-Type of SR
Policy Type.The redundancy policy encoding structure is as follows:Redundancy policy introduces a new attribute Flag to indicate the
type of Candidate Path as redundancy type. Correspondingly, a new Flag
sub-TLV is defined to be attached at the candidate path level as a
sub-TLV. The Flag sub-TLV is optional and MUST NOT appear more than
once in the Redundancy Policy encoding.where:Type: to be allocated by IANA.Length: specifies the length of the value field not including
Type and Length fields.Flags: 1 octet of flags. It is requested to IANA to create a
new registry "SR Policy Candidate Path Flags" . One flag is
defined at this writing:R-Flag: This flag encodes the redundancy policy behaviorU-Flag: Unused and unassignedRESERVED: 1 octet of reserved bits. SHOULD be set to zero on
transmission and MUST be ignored on receipt.Redundancy Policy can be optionally associated with a Binding
Segment, which can only be Redundancy Segment. When there is a
Redundancy Segment associated with Redundancy Policy, Redundancy
Segment is required to be distributed by the Binding SID Sub-TLV or
SRv6 Binding SID Sub-TLV defined in section 2.4.2 and 2.4.3 of respectively. In
SRv6, the endpoint behavior End.R of Redundancy Segment is required to
be distributed with SRv6 Binding SID at the same time.This document defines new sub-TLVs in the registry "BGP Tunnel
Encapsulation Attribute sub-TLVs" that has been assigned codepoints by
IANA as follows via the early allocation process:TBD