How are BSIDs used to reduce MSD?

Reducing MSD with BSIDs

The NSP supports draft-ietf-pce-binding-label-sid for the advertisement of binding segment identifiers (BSIDs) for both PCC-initiated and PCE-initiated SR-TE LSPs in order to avoid exceeding their maximum stack depth (MSD). If and how this is accomplished is determined by the configuration of the path profile policy associated with a given LSP. See Path profile policy parameters for more information.

The NSP is able to discover LSPs with pre-existing BSIDs, and can use these BSIDs when attempting to reduce MSD. Alternatively, BSIDs can be created during either PCE-initiated LSP creation, or SR policy creation. See How do I create PCE-initiated LSPs? or How do I create an SR policy? for more information.

The NSP is also capable of auto-generating BSIDs of either type (PCEP LSP or BGP SR policy) when the configuration of a path profile policy indicates that they are required but none are available. Whether or not BSIDs can be auto-generated - and which type will be auto-generated - is specified via the bsid-generation-config API, which includes the following options:

enabled — specifies whether BSIDs can be auto-generated
tunnel-type-preference — specifies the type of tunnel that will be used for BSID generation (LSP or SR policy)
allow-reroute — specifies whether or not auto-generated BSIDs can be rerouted
pcep-bsid-retry-duration — specifies the retry duration (in seconds) for deploying PCEP BSID. After this period, it will be assumed that the PCC does not support PCEP BSID, and this will persist until the PCEP session reconnects or the pcep-bsid-not-supported-ttl expires. The default is 60 seconds.
pcep-bsid-not-supported-ttl — Specifies the Time-To-Live (in seconds) before PCEP-BSID-NOT-SUPPORTED states become stale. The default is 3600 seconds.

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