Supplement of BGP-LS Distribution for SR Policies and State ZTE
Nanjing China liu.yao71@zte.com.cn
ZTE
Nanjing China peng.shaofu@zte.com.cn
Routing IDR Working Group SR Policy BGP-LS Segment List This document supplements some additional information of the segment list in the BGP-LS advertisement for SR Policy state information .
Introduction SR Policy architecture details are specified in . An SR Policy comprises one or more candidate paths (CP) of which at a given time one and only one may be active. Each CP in turn may have one or more SID-List of which one or more may be active; when multiple are active then traffic is load balanced over them. proposes extensions to PCEP to specify the protection relationship among segment lists within the candidate path. There would be segment lists in the CP acting as backup for one or more primary segment lists, the backup lists only carry rerouted traffic after the protected path fails. describes a mechanism to collect the SR policy information that is locally available in a node and advertise it into BGP Link State (BGP-LS) updates. Various TLVs are defined to enable the headend to report the state at the SR Policy CP level. For example, there's a B Flag in the SR Candidate Path State TLV indicating the CP is in an administrative shut state when set. Currently, a few segment list-related information is not included in . One is the information to indicate that the segment list is a backup path as described in . And the segment list may be shut by the administrator, this information may also needed and reported via BGP-LS. This document supplements some additional information of the segment list in the BGP-LS advertisement for SR Policy state information .
Requirements Language 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 when, and only when, they appear in all capitals, as shown here.
BGP-LS Extensions for Distributing Segment List States SR Segment List TLV is defined in to to report the SID-List(s) of a candidate path.As show in Figure 1,this document introduces two new flags in the flag field of SR Segment List TLV, where,
Flag Field of SR Segment List TLV
  • S-Flag: Indicates the segment list is in administrative shut state when set.
  • B-Flag: Indicates the segment list is a backup path described in when set, otherwise it is the primary path.
IANA Considerations This document requests bit 9 and bit 10 in the flag field of "SR Segment List TLV" under the "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs" registry.
Security Considerations Procedures and protocol extensions defined in this document do not affect the security considerations discussed in .
References Normative References Informative References