Re: [spring] Question on draft-ietf-spring-srv6-network-programming-12

Hi Chris,

They are the same thing. 

Section 3:
   ...
   Its processing is defined in [I-D.ietf-6man-segment-routing-header]
   section 4.3 and reproduced here as a reminder.

      Without constraining the details of an implementation, the SR
      segment endpoint node creates Forwarding Information Base (FIB)
      entries for its local SIDs.

      When an SRv6-capable node receives an IPv6 packet, it performs a
      longest-prefix-match lookup on the packets destination address.
      This lookup can return any of the following:

      - A FIB entry that represents a locally instantiated SRv6 SID

      - A FIB entry that represents a local interface, not locally
        instantiated as an SRv6 SID

      - A FIB entry that represents a non-local route

      - No Match

Section 4:
>   Each FIB entry indicates the behavior associated with a SID instance
>   and its parameters.

Thank you,
Pablo. 

-----Original Message-----
From: Christian Hopps <chopps@chopps.org>
Date: Tuesday, 10 March 2020 at 22:01
To: "Pablo Camarillo (pcamaril)" <pcamaril@cisco.com>
Cc: Christian Hopps <chopps@chopps.org>, "spring@ietf.org" <spring@ietf.org>
Subject: Re: [spring] Question on draft-ietf-spring-srv6-network-programming-12

    > On Mar 10, 2020, at 2:13 PM, Pablo Camarillo (pcamaril) <pcamaril=40cisco.com@dmarc.ietf.org> wrote:
    > 
    > Hi Chris,
    > 
    > Thanks for going through the document.
    > The behaviors 4.13 (End.B6.Encaps), 4.14 (End.B6.Encaps.Red) and 4.15 (End.BM) correspond to Binding SIDs [1].
    > 
    > As a result of 4.13 for example, the packet is encapsulated with a new IPv6 header and an SRH that contains the SR policy associated to the BSID.
    > Once the new IPv6 header is pushed into the packet, the NET-PGM pseudocode passes this packet to the IPv6 module of the router for transmission.
    > 
    > Normally the Upper-Layer Header should not be processed on a packet with a BSID, since you have just pushed an SR policy into the packet.
    > That said, when the ultimate destination is BSID, then the Upper Layer Header processing is the same to End (4.1).
    > 
    > Hope it clarifies.

    I'm still not clear on things I guess, but your answer leads me to a more basic question:

    Section 4.1 described the basic "FIB entry" "End" which says:

      "When N receives a packet whose IPv6 DA is S and S is a local End SID, N does..."

    So it's talking about a FIB entry for a "local End SID".

    Section 4.1.1 says:

      "When processing the Upper-layer Header of a packet matching a FIB
       entry locally instantiated as an SRv6 End SID"

    It's talking about a "FIB entry locally instantiated as an SRv6 END SID"

    I'm not understanding how these 2 things are different. 4.1s calling a FIB Entry a "local End SID" 4.1.1 is calling something (different?) a "FIB Entry locally instantiated as an SRv6 END SID".

    The terms seem too similar for me to make a distinction, where I feel the document expects me to make one.

    Thanks,
    Chris.

    > 
    > Thanks,
    > Pablo.
    > 
    > [1]. https://tools.ietf.org/html/rfc8402#section-5
    > 
    > 
    > -----Original Message-----
    > From: spring <spring-bounces@ietf.org> on behalf of Christian Hopps <chopps@chopps.org>
    > Date: Saturday, 7 March 2020 at 12:50
    > To: "spring@ietf.org" <spring@ietf.org>
    > Cc: Christian Hopps <chopps@chopps.org>
    > Subject: [spring] Question on draft-ietf-spring-srv6-network-programming-12
    > 
    >    In sections 4.13, (implicitly in 4.14) and 4.15 a set of steps is indicated. As far as I can tell the processing of the IPv6 header chain in all cases is terminated. e.g.,
    > 
    >    "
    >       When N receives a packet whose IPv6 DA is S and S is a local End.BM
    >       SID, does:
    > 
    >      S01. When an SRH is processed {
    >      S02.   If (Segments Left == 0) {
    >    ....
    >                   Interrupt packet processing and discard the packet.
    >      S04.   }
    >      S05.   If (IPv6 Hop Limit <= 1) {
    >    ....
    >                   Interrupt packet processing and discard the packet.
    >      S07.   }
    >      S09.   If ((Last Entry > max_LE) or (Segments Left > (Last Entry+1)) {
    >    ....
    >                   Interrupt packet processing and discard the packet.
    >      S11.   }
    >    ....
    >      S15.   Submit the packet to the MPLS engine for transmission to the
    >                topmost label.
    >      S16. }
    >    "
    > 
    >    The text then says:
    > 
    >       When processing the Upper-layer header of a packet matching a FIB
    >       entry locally instantiated as an SRv6 End.BM SID, process the packet
    >       as per Section 4.1.1.
    > 
    >    Why would I ever be processing the upper-layer header at this point?
    > 
    >    Thanks,
    >    Chris.
    >    _______________________________________________
    >    spring mailing list
    >    spring@ietf.org
    >    https://www.ietf.org/mailman/listinfo/spring
    > 
    > 
    > _______________________________________________
    > spring mailing list
    > spring@ietf.org
    > https://www.ietf.org/mailman/listinfo/spring