[Idr] [IDR] Questions regarding draft-ietf-idr-bgpls-srv6-ext

"Wanghaibo (Rainsword)" <rainsword.wang@huawei.com> Tue, 06 August 2019 10:19 UTC

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From: "Wanghaibo (Rainsword)" <rainsword.wang@huawei.com>
To: "draft-ietf-idr-bgpls-srv6-ext@ietf.org" <draft-ietf-idr-bgpls-srv6-ext@ietf.org>
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Date: Tue, 6 Aug 2019 10:13:29 +0000
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Subject: [Idr] [IDR] Questions regarding draft-ietf-idr-bgpls-srv6-ext
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Hi authors,
     I have some questions about this draft, comment with blue words.



2.  BGP-LS Extensions for SRv6

   o  SRv6 End.X SID of the link state routing adjacency or the BGP EPE

      Peer Adjacency is advertised via a new SRv6 End.X SID TLV
// No doubt about this
   o  The BGP EPE Peer Node and Peer Set SID context is advertised via a
      new SRv6 BGP EPE Peer Node SID TLV
// Here use a new TLV to descripe peer node & peer set


7.2.  SRv6 BGP Peer Node SID TLV

   The BGP Peer Node SID and Peer Set SID for SR with MPLS dataplane are

   specified in [I-D.ietf-idr-bgpls-segment-routing-epe].  The similar

   Peer Node and Peer Set SID functionality can be realized with SRv6

   using the END.X SRv6 SID.  The SRv6 BGP Peer Node SID TLV is an

   optional TLV for use in the BGP-LS Attribute for an SRv6 SID NLRI

   corresponding to BGP protocol.  This TLV MUST be included along with

   SRv6 End.X SID that is associated with the BGP Peer Node or Peer Set

   functionality.
// Here said the peer node sid followed by the SRv6 SID NLRI


6.  SRv6 SID NLRI



   A new "Link-State NLRI Type" is defined for SRv6 SID information as

   following:



   o  Link-State NLRI Type: SRv6 SID NLRI (value TBD see IANA

      Considerations Section 8.1).


     0                   1                   2                   3

     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

    +-+-+-+-+-+-+-+-+

    |  Protocol-ID  |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    |                        Identifier                             |

    |                        (64 bits)                              |

    ++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|

    |               Local Node Descriptors (variable)              //

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    |               SRv6 SID Descriptors (variable)                //

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





                      Figure 11: SRv6 SID NLRI Format
     // Here defined the SRv6 SID NLRI. If we use this NLRI, when we have more than one peer node,
   We may construct routes with:
   Route1: SRv6 SID NLRI1 (Local Node Desc + SID1) + Peer Node SID (peer1) + other Attr Tlv
   Route2: SRv6 SID NLRI2 (Local Node Desc + SID2) + Peer Node SID (peer2) + other Attr Tlv
   Why do we have to change to this? What are the benefits of this change?

   For draft draft-ietf-idr-bgpls-segment-routing-epe, the route will be
   Route1: Link NLRI1(Local Node Desc + peer1) + Peer Node SID (peer1) + other Attr Tlv
   Route2: Link NLRI2(Local Node Desc + peer2) + Peer Node SID (peer2) + other Attr Tlv

     Also in this format, when a peer join a peer set, how to create the route? Perhaps:
   Route1: SRv6 SID NLRI1 (Local Node Desc + SID1) + Peer Node SID (peer1) + other Attr Tlv
   Route2: SRv6 SID NLRI1 (Local Node Desc + SID2) + Peer Node SID (S-flag) + other Attr Tlv
   What’s the relationship about the two routes ?
   If there exist a route3:
   Route3: SRv6 SID NLRI1 (Local Node Desc + SID3) + Peer Node SID (S-flag) + other Attr Tlv
   Now the Peer node route1 belongs to route2’s Peer Set or route3’s Peer Set?

   But it’s clear for old mpls epe draft:
   Route1: Link NLRI1(Local Node Desc + peer1) + Peer Node SID (peer1) + Peer Set Sid(set1)+other Attr Tlv
   Route2: Link NLRI2(Local Node Desc + peer2) + Peer Node SID (peer2) + Peer Set Sid(set1)+ other Attr Tlv



Best Regards
Haibo