Hi Eduard, BGP Prefix-SID is actually a BGP Path Attribute (refer https://www.iana.org/assignments/bgp-parameters/bgp-parameters.xhtml#bgp-parameters-2). I hope that explains the correlation between the path and what's carried in the BGP Prefix-SID attribute TLVs for SRv6.
That said, I am not sure if I've understood and answered your question. Thanks, Ketan On Wed, Jan 12, 2022 at 10:12 PM Vasilenko Eduard < vasilenko.edu...@huawei.com> wrote: > Dear Authors, > > Ordinary BGP services use “BGP Path Attributes” (with MP_REACH_NLRI and > Extended Communities inside Path Attribute). > > SRv6 needs additionally to explain the structure of SID. ”BGP Prefix SID > TLV” was chosen for this task. This TLV is at the same BGP level, not > inside Path Attribute. > > So far so good. > > > > I am trying to understand how the correlation should be done between > routes sent inside “Path Attributes” and SID structure sent inside “Prefix > SID TLV”. > > 1. Potentially it is possible to send the SID structure 1 time. > Remote PE could calculate “Label Filed” by transposition scheme out of full > SID and put it in some table. > Then for every route received in Path Attribute it would be possible to > check that such “Label Filed” is already known from this next hop. > If known then it is possible to reconstruct full SID and use it for SRH or > whatever. > > 2. The alternative solution is to always supply ”BGP Prefix SID > TLV” together with every route in “BGP Path Attributes”. (chatty approach) > Then a separate table is not needed – it is possible to derive SID > directly out of ”BGP Prefix SID TLV” that is always attached to the route. > > > > I have not understood what strategy is assumed by > “draft-ietf-bess-srv6-services”. I have not found any recommendation on > this matter. > > Potentially it could create an interoperability issue if one side would > choose option 1, but the remote side would be capable only to option 2. > > > > [image: cid:image001.png@01D3A7DF.E7D86320] > > Best Regards > > Eduard Vasilenko > > Senior Architect > > Europe Standardization & Industry Development Department > > Tel: +7(985) 910-1105, +7(916) 800-5506 > > >
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