suehares
commented
3 months ago Jeffrey: When should the BGP update [stop] being propagated if RT is used? Never? or should a matching RT be removed by each matching receiver and then the propagation stops when there is no RT left?
Ketan: Yes, it can do that using local configuration. See the next paragraph (from section 4.2.3)
A BGP node advertises a received SR Policy NLRI to its IBGP neighbors according to normal IBGP propagation rules.
By default, a BGP node receiving an SR Policy NLRI SHOULD NOT remove route target extended community before propagation. An implementation MAY provide support for configuration to filter and/or remove route target extended community before propagation.
Jeffrey: Isn't the above applicable to any AFI/SAFI? Why do we need to specify that?
Ketan: It goes with the previous paragraph - hence required to clarify.
Jeffrey: I think it SHOULD remove the RT that matches its BGP identifier and stop propagating if there are no more RTs left, w/o relying on configuration. (reference: https://mailarchive.ietf.org/arch/msg/rtg-dir/pzT0P9XId3qV3iCd-mgpZUvul7A/)
Ketan: I can understand where you are coming from and IIRC this option was discussed at some point of time during the draft's life as a WG document. The decision at that point was to keep it as an explicit policy option and to not create an exception in the base BGP propagation mechanism. The way it works today is that the BGP Identifier matching is done during "import" into SRPM that is specific to the BGP SR Policy SAFI.
RTG-DIR Issue 26: 4.2.3 Eligibility for Local Use of an SR Policy NLRI
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Jeffrey: Isn't the above applicable to any AFI/SAFI? Why do we need to specify that?