[Idr] Few questions about Segment Routing extensions for BGP LS (draft-ietf-idr-bgp-ls-segment-routing-ext)

Boris Hassanov <bhassanov@yahoo.com> Wed, 21 July 2021 09:57 UTC

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Date: Wed, 21 Jul 2021 09:54:42 +0000 (UTC)
From: Boris Hassanov <bhassanov@yahoo.com>
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Subject: [Idr] Few questions about Segment Routing extensions for BGP LS (draft-ietf-idr-bgp-ls-segment-routing-ext)
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Hi all,
1) Need an advice, I might be missing something but I see that Anycasi SID (3333 in the example below)  is in BGP-LS update as regular Prefix SID TLV: Path Attribute - BGP-LS Attribute
            Flags: 0x80, Optional, Non-transitive, Complete
                1... .... = Optional: Set
                .0.. .... = Transitive: Not set
                ..0. .... = Partial: Not set
                ...0 .... = Extended-Length: Not set
                .... 0000 = Unused: 0x0
            Type Code: BGP-LS Attribute (29)
            Length: 12
            Link State
                Prefix SID TLV
                    Type: 1158
                    Length: 8
                    Flags: 0x40, Node-SID (N)
                        0... .... = Re-advertisement (R): Not set
                        .1.. .... = Node-SID (N): Set
                        ..0. .... = No-PHP (P): Not set
                        ...0 .... = Explicit-Null (E): Not set
                        .... 0... = Value (V): Not set
                        .... .0.. = Local (L): Not set
                    Algorithm: 0
                    SID/Index: 3333
Here is confusion, how, let's say, a controller, which receives such BGP-LS update, could  distinguish it from regular Prefix/Node SID?
Unfortunately draft-ietf-idr-bgp-ls-segment-routing-ext-18 does not clarify this issue because it only describes Prefix SID TLV type 1158. Any suggestions?
2)  draft-ietf-idr-bgp-ls-segment-routing-ext-18 has two types of labels TLV: SID/Label TLV type 1161 and Prefix SID  TLV type 1158.  I checked several vendors implementations of BGP-LS, all of them use only Prefix SID TLV.Why the draft does not have some conditions or clarifications when to use SID/Label TLV and when Prefix SID TLV?
Thank you.
SY,Boris