Re: [spring] [Lsr] clarification of locator block and locator node in draft-ietf-spring-srv6-network-programming and draft-ietf-lsr-isis-srv6-extensions

"Acee Lindem (acee)" <acee@cisco.com> Wed, 22 April 2020 14:24 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: Derek Yeung <derek@arrcus.com>, Peter Psenak <ppsenak=40cisco.com@dmarc.ietf.org>, Chris Bowers <chrisbowers.ietf@gmail.com>
CC: "lsr@ietf.org" <lsr@ietf.org>, SPRING WG List <spring@ietf.org>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>, Bruno Decraene <bruno.decraene@orange.com>
Thread-Topic: [Lsr] clarification of locator block and locator node in draft-ietf-spring-srv6-network-programming and draft-ietf-lsr-isis-srv6-extensions
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Date: Wed, 22 Apr 2020 14:21:51 +0000
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Subject: Re: [spring] [Lsr] clarification of locator block and locator node in draft-ietf-spring-srv6-network-programming and draft-ietf-lsr-isis-srv6-extensions
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Speaking as WG member:

In the past, we developed protocol encodings that afforded future extendibility. I don't see the problem with the including the SID structure sub-sub-TLV and would support progression.

Thanks,
Acee

On 4/10/20, 2:45 AM, "Lsr on behalf of Derek Yeung" <lsr-bounces@ietf.org on behalf of derek@arrcus.com> wrote:

    Hi,

    We at Arrcus have implemented support for this draft including the SID Structure sub-sub-TLV.
    The proposed encodings for the SID Structure sub-sub-TLV is flexible and works fine.

    Thanks,
    Derek

    Derek Yeung
    Derek@arrcus.com
    Main: 408.884.1965



    2077 Gateway Place, Suite 400
    San Jose, CA.  95110

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    On 4/6/20, 4:03 AM, "Lsr on behalf of Peter Psenak" <lsr-bounces@ietf.org on behalf of ppsenak=40cisco.com@dmarc.ietf.org> wrote:

        Chris,

        On 01/04/2020 21:58, Chris Bowers wrote:
        > Peter,
        > 
        > There seem to be two disconnects in this discussion.
        > 
        > 1) The response below implies that the encodings in 
        > draft-ietf-lsr-isis-srv6-extensions are supposed represent the case 
        > where the locators are allocated from several different IPv6 address 
        > blocks (for example, blocks S1/s1 through Sn/sn). However, 
        > draft-ietf-spring-srv6-network-programming and 
        > draft-ietf-6man-segment-routing-header only discuss the case where the 
        > locators are allocated from a single block (S/s).  If an implementation 
        > is expected to properly encode the case where locators are allocated 
        > from several different IPv6 address blocks, then I think that case 
        > should be explicitly described in these documents.


        There is no statement in draft-ietf-spring-srv6-network-programming that 
        the block is unique. As an example, Iliad authorized me to indicate that 
        their SRv6 deployment involves several blocks.


        > 
        > 2)   The response below says "To be able to find out where the func and 
        > arg are located, you need to know the LOC length, e.g. Block and Node 
        > length."  However, the SRv6 SID Structure Sub-Sub-TLV is carried within 
        > the SRv6 End SID, SRv6 End.X SID, and the SRv6 LAN End.X SID Sub-TLVs, 
        > which are carried within the SRv6 Locator TLV.  

        not really. SRv6 End.X SID, and the SRv6 LAN End.X SID Sub-TLVs are 
        advertised in the IS Reachability TLVs (22, 23, 222, 223, 141), not in 
        SRv6 Locator TLV.

        thanks,
        Peter


        > The  SRv6 Locator TLV 
        > has a Loc-Size field.  Why would the value of the LOC length computed as 
        > the sum of the Block and Node length ever be different from the value in 
        > the Loc-Size field?
        > 
        > Chris
        > 
        > 
        > On Wed, Mar 25, 2020 at 9:49 AM Peter Psenak <ppsenak@cisco.com 
        > <mailto:ppsenak@cisco.com>> wrote:
        > 
        >     Chris,
        > 
        >     please see inline:
        > 
        > 
        >     On 23/03/2020 17:39, Chris Bowers wrote:
        >      > Peter,
        >      >
        >      > The proposed SRv6 SID Structure Sub-Sub-TLV has several problems.
        >      >
        >      > 1) As discussed in item#3 below, it is not clear that flooding LB
        >      > Length, LN Length, Fun. Length, and Arg. Length to all ISIS
        >     speakers is
        >      > really the right approach.  However, if the WG determines that it
        >     is the
        >      > right approach, the current encodings of this information in the
        >      > proposed SRv6 SID Structure Sub-Sub-TLV are problematic.  As
        >     discussed
        >      > earlier in this thread, a network operator may choose to not
        >     allocate
        >      > all locators from a single block, so LB Length and LN Length may
        >     not be
        >      > well-defined.
        > 
        >     I'm not sure what do you mean by not "well defined". For every SID you
        >     need to know the LOC (B+N) part. If you guarantee that it is the
        >     same on
        >     all nodes, you know it from the local config, otherwise, you advertise
        >     it with a SID.
        > 
        >      > The current encoding of the SRv6 SID Structure
        >      > Sub-Sub-TLV makes it difficult to represent this situation.  The
        >     simple
        >      > thing to do for nodes that don't have a well-defined value of LB
        >     Length
        >      > and LN Length would be to not advertise a value for LB Length and LN
        >      > Length.  However, since the currently proposed SRv6 SID Structure
        >      > Sub-Sub-TLV combines LB Length, LN Length, Fun. Length, and Arg.
        >     Length
        >      > into a single sub-sub-TLV, if a node wants to advertise values
        >     for Fun.
        >      > Length and Arg. Length, it also has to advertise values for LB
        >     Length
        >      > and LN Length.  It seems like a better approach would be to have
        >      > different sub-sub-TLVs, one for  LB Length and LN Length, and a
        >     separate
        >      > one for Fun. Length and Arg. Length to be able to better
        >     represent this
        >      > situation.
        > 
        > 
        >     I'm afraid you are missing an important point.
        > 
        >     SRv6 SID is defined as LOC:FUNCT:ARG, where LOC is represented as B:N.
        >     To be able to find out where the func and arg are located, you need to
        >     know the LOC length, e.g. Block and Node length. Advertising just Func
        >     and Arg length does not help.
        > 
        > 
        >      >
        >      > 2) Now consider the situation where a network operator chooses to
        >      > allocate all locators from a single block, so that LB Length and LN
        >      > Length are well-defined across the network.  A given node should
        >      > presumably advertise its own understanding of LB Length and LN
        >     Length.
        >      > A given node's understanding of LB Length and LN Length is a
        >     property of
        >      > the node.  It is not a property of a given End SID.  The currently
        >      > proposed SRv6 SID Structure Sub-Sub-TLV however is carried within
        >     each
        >      > End SID Sub-TLV.  With the currently proposed encoding,
        >     presumably an
        >      > implementation is expected to send the exact same values of LB
        >     Length
        >      > and LN Length for all of the End SIDs that it advertises.  Not
        >     only is
        >      > this inefficient, but it creates the need for logic to decide
        >     what to do
        >      > when different End SIDs advertised by the same node carry different
        >      > values of LB Length and LN Length in their sub-sub-TLVs.  It
        >     seems like
        >      > a better approach would be for a given node to advertise its
        >      > understanding of the value of LB Length and LN Length in a
        >     sub-TLV of
        >      > the Router Capability TLV.
        > 
        >     When we design the encoding, we have to define it such, that it
        >     supports
        >     all possible use cases. We can not design the encoding that works for
        >     single use case (allocate all locators from a single block) and does
        >     not
        >     work for others - different block from different node, multiple blocks
        >     on a single node (e.g. border node), which are all valid.
        > 
        >      >
        >      > 3) At this point, the only use case that has been proposed for
        >     flooding
        >      > the LB Length, LN Length, Fun. Length, and Arg. Length to all ISIS
        >      > speakers is to make it more convenient for BGP-LS to get those
        >     values to
        >      > an external controller as part of a topology feed from any ISIS
        >     node.
        >      > No use case has been proposed for ISIS speakers themselves to
        >     make use
        >      > of the information.  It seems like a more scalable approach would
        >     be to
        >      > use BGP-LS sessions to collect the information from the subset of
        >     nodes
        >      > that actually produce the relevant information.  So far there are
        >     no End
        >      > SIDs defined that are advertised in ISIS that have a non-zero Arg.
        >      > Length.  If an End SID with non-zero Arg. Length were to be
        >     proposed in
        >      > the future as needing to be flooded to all ISIS nodes, it seems
        >     likely
        >      > that the new End SID would also be advertised using the BGP
        >     IP/VPN/EVPN
        >      > control plane.   So it seems like a viable alternative for this
        >      > hypothetical future End SID would be to have the subset of nodes
        >     that
        >      > have non-zero Arg. Length values communicate to an external
        >     controller
        >      > via  BGP sessions. I think the WG needs a more detailed
        >     discussion of a
        >      > concrete use case in order to determine whether flooding LB
        >     Length, LN
        >      > Length, Fun. Length, and Arg. Length to all ISIS speakers is
        >     really the
        >      > right approach.
        > 
        >     there are networks, where BGP is not deployed on all nodes, only on a
        >     few nodes that re-distribute the information to BGP-LS. In such case we
        >     need the IGP to distribute this data.
        > 
        >     Argument that "it seems likely that the new End SID would also be
        >     advertised using the BGP IP/VPN/EVPN" is a wishful thinking that we can
        >     not based our encoding on.
        > 
        > 
        >      >
        >      > Given the lack of a compelling use case for flooding LB Length, LN
        >      > Length, Fun. Length, and Arg. Length to all ISIS speakers and the
        >      > problems with the currently proposed encodings for doing that, I
        >     think
        >      > that the SRv6 SID Structure Sub-Sub-TLV should be removed from
        >      > draft-ietf-lsr-isis-srv6-extensions. A mechanism for flooding LB
        >     Length,
        >      > LN Length, Fun. Length, and Arg. Length to all ISIS speakers can be
        >      > defined in a future document.
        > 
        >     The security use case has already been pointed out earlier in this
        >     thread:
        > 
        >     https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5
        > 
        >     Given the arguments I mentioned above, I respectfully disagree with the
        >     removal of the SID Structure Sub-Sub-TLV from the ISIS SRv6 draft.
        > 
        >     thanks,
        >     Peter
        > 
        > 
        >      >
        >      > Thanks,
        >      > Chris
        >      >
        >      > On Fri, Mar 13, 2020 at 5:02 AM Peter Psenak <ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>
        >      > <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>> wrote:
        >      >
        >      >     Hi Chris,
        >      >
        >      >     On 12/03/2020 15:58, Chris Bowers wrote:
        >      >      > Peter,
        >      >      >
        >      >      > I think that the SRv6 SID Structure Sub-Sub-TLV should be
        >     removed
        >      >     from
        >      >      > draft-ietf-lsr-isis-srv6-extensions.  I think that we should
        >      >     leave the
        >      >      > ability to include sub-sub-TLVs in the SRv6 End SID Sub-TLV,
        >      >     End.X SID
        >      >      > Sub-TLV, and LAN End.X SID Sub-TLV in the encodings for those
        >      >     sub-TLVs.
        >      >      >
        >      >      > I don't think that the current text describing the SRv6 SID
        >      >     Structure
        >      >      > Sub-Sub-TLV would result in interoperable
        >     implementations.  Based
        >      >     on the
        >      >
        >      >     SRv6 base spec defines SID B, L, A, F.
        >      >
        >      >     SRv6 protocol specs are advertising these values with the
        >     SRv6 SID,
        >      >     they
        >      >     don't use them. The usage is outside of the scope of the protocol
        >      >     drafts. What exactly is the problem?
        >      >
        >      >     thanks,
        >      >     Peter
        >      >
        >      >
        >      >      > discussion with Ketan below, it appears that use cases for
        >     ISIS
        >      >     speakers
        >      >      > receiving advertised values of LB Length, LN Length, Fun.
        >     Length,
        >      >     and
        >      >      > Arg. Length are not currently well-defined.    So I think it
        >      >     makes sense
        >      >      > to defer the definition of the SRv6 SID Structure
        >     Sub-Sub-TLV to a
        >      >      > future document.
        >      >      >
        >      >      > Thanks,
        >      >      > Chris
        >      >      >
        >      >      > On Thu, Mar 12, 2020 at 6:02 AM Ketan Talaulikar (ketant)
        >      >      > <ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>>> wrote:
        >      >      >
        >      >      >     Hi Chris,____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     Dropping the
        >     draft-ietf-spring-srv6-network-programming authors
        >      >      >     since we are now back to discussing the ISIS
        >     extensions.____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     Please check inline below.____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     *From:*Chris Bowers <chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>
        >      >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>>>
        >      >      >     *Sent:* 05 March 2020 21:53
        >      >      >     *To:* Ketan Talaulikar (ketant) <ketant@cisco.com
        >     <mailto:ketant@cisco.com>
        >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>>>
        >      >      >     *Cc:* Ketan Talaulikar (ketant) <ketant@cisco.com
        >     <mailto:ketant@cisco.com>
        >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>>>;
        >      > lsr@ietf.org <mailto:lsr@ietf.org> <mailto:lsr@ietf.org
        >     <mailto:lsr@ietf.org>> <mailto:lsr@ietf.org <mailto:lsr@ietf.org>
        >      >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>>;
        >      >      >     SPRING WG List <spring@ietf.org
        >     <mailto:spring@ietf.org> <mailto:spring@ietf.org
        >     <mailto:spring@ietf.org>>
        >      >     <mailto:spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>>>;
        >      >      >     draft-ietf-spring-srv6-network-programming
        >      >      >     <draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>
        >      >      >   
        >       <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>>>; Peter
        >      >      >     Psenak (ppsenak) <ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
        >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>>>;
        >      >      >     Bruno Decraene <bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>
        >      >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>>>
        >      >      >     *Subject:* Re: [Lsr] clarification of locator block and
        >      >     locator node
        >      >      >     in draft-ietf-spring-srv6-network-programming and
        >      >      >     draft-ietf-lsr-isis-srv6-extensions____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     Ketan,____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     See inline [CB].____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >     On Wed, Mar 4, 2020 at 12:36 AM Ketan Talaulikar (ketant)
        >      >      >     <ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>>> wrote:____
        >      >      >
        >      >      >         Hi Chris,____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         You are right in that there is no assumption that
        >     all SRv6
        >      >      >         locators in a domain are allocated from the same
        >     block.
        >      >      >         Therefore knowing the blocks used in the domain is
        >      >     useful.____
        >      >      >
        >      >      >     ____
        >      >      >
        >      >      >     [CB] Since you refer to "blocks" (plural) in this
        >     sentence,
        >      >     are you
        >      >      >     saying that in the scenario where all SRv6 locators in a
        >      >     domain are
        >      >      >     not allocated from the same block, you would expect
        >     different
        >      >      >     routers in the same domain to advertise different
        >     values of B
        >      >     and N?
        >      >      >     ____
        >      >      >
        >      >      >     */[KT] While personally I believe it would not be the
        >     usual
        >      >     case, it
        >      >      >     is left to the operator.____/*
        >      >      >
        >      >      >     */__ __/*
        >      >      >
        >      >      >     For example, assume we have a network where all SRv6
        >     locators
        >      >     in a
        >      >      >     domain are not allocated from the same block.  Router A
        >      >     advertises
        >      >      >     an SRv6 Locator TLV with locator = 2000::/64, and an
        >     SRv6 End SID
        >      >      >     sub-TLV with some endpoint behavior. Router B
        >     advertises an SRv6
        >      >      >     Locator TLV with locator = 3000::/64, and an SRv6 End
        >     SID sub-TLV
        >      >      >     with some endpoint behavior. What should routers A and B
        >      >     advertise
        >      >      >     as the values of B and N in their SRv6 SID Structure
        >      >     Sub-Sub-TLVs ?____
        >      >      >
        >      >      >     */[KT] It is difficult for me to figure out what the block
        >      >     and node
        >      >      >     parts are with such an addressing./*____
        >      >      >
        >      >      >     ____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         The IGP drafts covers the advertisement of the B and N
        >      >     parts of
        >      >      >         the locally configured locator on the node via
        >     IGPs. On the
        >      >      >         receiver side, the IGP may not really do much with
        >     this
        >      >      >         information, however it enables propagation of this
        >      >     information
        >      >      >         from all nodes in the network to be advertised out
        >     via BGP-LS
        >      >      >         (or other mechanisms) as part of the topology
        >     feed. Once
        >      >     this is
        >      >      >         part of the topology feed, it enables use-cases on
        >      >     controllers
        >      >      >         to perform network wide validation of the SRv6 SID
        >     block
        >      >      >         provisioning and can also help in automation of
        >     the security
        >      >      >         aspects described in
        >      >      >
        >      >
        >     https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >     [CB] If an ISIS speaker is not expected to do anything
        >     with B
        >      >     and N,
        >      >      >     then I think the text in
        >     draft-ietf-lsr-isis-srv6-extensions
        >      >     needs
        >      >      >     to clarify this.  I have a similar observation about Fun.
        >      >     Length and
        >      >      >     Arg. Length in the SRv6 SID Structure Sub-Sub-TLV . 
        >     As far
        >      >     as I can
        >      >      >     tell, none of the endpoint behaviors that are currently
        >      >     specified to
        >      >      >     be carried in ISIS End, End.X, and LAN End.X SIDs sub-TLVs
        >      >     uses an
        >      >      >     Argument, so there is never a case where an SRv6 SID
        >     Structure
        >      >      >     Sub-Sub-TLV should have a non-zero value for Arg.
        >     Length. What
        >      >      >     should an ISIS speaker do if it receives a non-zero
        >     value of the
        >      >      >     Arg. Length for an endpoint behavior that doesn't use an
        >      >     argument?
        >      >      >     Are there any use cases envisioned where an ISIS
        >     speaker needs to
        >      >      >     know the Arg. Length ? ____
        >      >      >
        >      >      >     */[KT] The behaviors currently listed in the draft do
        >     not have an
        >      >      >     argument nor is the use of B and N required for them.
        >     We cannot
        >      >      >     preclude a future use-case or extension where such
        >     behaviors
        >      >      >     introduced are also applicable to ISIS. So IMHO ruling
        >     such
        >      >     aspects
        >      >      >     out might not be the right thing to do from a protocol
        >      >     extensibility
        >      >      >     perspective.____/*
        >      >      >
        >      >      >     */__ __/*
        >      >      >
        >      >      >     */Thanks,____/*
        >      >      >
        >      >      >     */Ketan/*____
        >      >      >
        >      >      >     __ __
        >      >      >
        >      >      >         Thanks,____
        >      >      >
        >      >      >         Ketan____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         *From:*Chris Bowers <chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>
        >      >      >         <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>>>
        >      >      >         *Sent:* 02 March 2020 23:39
        >      >      >         *To:* Ketan Talaulikar (ketant) <ketant@cisco.com
        >     <mailto:ketant@cisco.com>
        >      >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >      >         <mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>>>
        >      >      >         *Cc:* Ketan Talaulikar (ketant)
        >      >      >         <ketant=40cisco.com@dmarc.ietf.org
        >     <mailto:40cisco.com@dmarc.ietf.org>
        >      >     <mailto:40cisco.com@dmarc.ietf.org
        >     <mailto:40cisco.com@dmarc.ietf.org>>
        >      >      >         <mailto:40cisco..com@dmarc.ietf.org
        >     <mailto:40cisco..com@dmarc.ietf.org>
        >      >     <mailto:40cisco..com@dmarc.ietf.org
        >     <mailto:40cisco..com@dmarc.ietf.org>>>>; lsr@ietf.org
        >     <mailto:lsr@ietf.org>
        >      >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>
        >      >      >         <mailto:lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>>; SPRING WG
        >      >     List <spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>
        >      >      >         <mailto:spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>>>;
        >      >      >         draft-ietf-spring-srv6-network-programming
        >      >      >       
        >       <draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>
        >      >      >
        >      >       <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>>>;
        >      >      >         Peter Psenak (ppsenak) <ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
        >      >      >         <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com> <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>>>>;
        >      >     Bruno Decraene
        >      >      >         <bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>
        >     <mailto:bruno.decraene@orange.com <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>>>
        >      >      >         *Subject:* Re: [Lsr] clarification of locator
        >     block and
        >      >     locator
        >      >      >         node in draft-ietf-spring-srv6-network-programming and
        >      >      >         draft-ietf-lsr-isis-srv6-extensions____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         Ketan,____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         Based on current documents, allocating all SRv6
        >     locators
        >      >     used in
        >      >      >         a domain from a single block is optional.____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         However, assuming for the moment that a network
        >     operator has
        >      >      >         chosen to allocate all SRv6 locators used in a
        >     domain from a
        >      >      >         single block, so that there is a well-defined
        >     value of B
        >      >     and N
        >      >      >         across a domain, what is the use of having a
        >     router advertise
        >      >      >         its own understanding of these two values?  And
        >     what is a
        >      >      >         receiver supposed to do with this information?____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         Thanks,____
        >      >      >
        >      >      >         Chris____
        >      >      >
        >      >      >         ____
        >      >      >
        >      >      >         On Fri, Feb 28, 2020 at 8:23 AM
        >      >     <bruno.decraene@orange.com <mailto:bruno.decraene@orange.com>
        >     <mailto:bruno.decraene@orange.com <mailto:bruno.decraene@orange.com>>
        >      >      >         <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>>> wrote:____
        >      >      >
        >      >      >             Hi Ketan,____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Thanks fort the follow up.____
        >      >      >
        >      >      >             Clarification inline [Bruno]____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             *From**:*Ketan Talaulikar (ketant)
        >      >     [mailto:ketant@cisco.com <mailto:ketant@cisco.com>
        >     <mailto:ketant@cisco.com <mailto:ketant@cisco.com>>
        >      >      >             <mailto:ketant@cisco.com
        >     <mailto:ketant@cisco.com> <mailto:ketant@cisco.com
        >     <mailto:ketant@cisco.com>>>]
        >      >      >             *Sent:* Friday, February 28, 2020 11:11 AM
        >      >      >             *To:* DECRAENE Bruno TGI/OLN; Ketan Talaulikar
        >     (ketant);
        >      >      >             Chris Bowers
        >      >      >             *Cc:* lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>
        >      >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>>; SPRING WG List;
        >      >      >             draft-ietf-spring-srv6-network-programming;
        >     Peter Psenak
        >      >      >             (ppsenak)
        >      >      >             *Subject:* RE: [Lsr] clarification of locator
        >     block and
        >      >      >             locator node in
        >      >     draft-ietf-spring-srv6-network-programming
        >      >      >             and draft-ietf-lsr-isis-srv6-extensions____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Hi Bruno,____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             I believe the description and usage of Locator is
        >      >     very well
        >      >      >             described and covered in the net-pgm draft as
        >     also the
        >      >      >             corresponding IGP extensions. Is the question
        >     is more
        >      >     about
        >      >      >             the “block” part of it (what is not in the
        >     block part
        >      >     is in
        >      >      >             the node part as per the text in the net-pgm
        >     draft)?____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             The “block” is again not a new thing. Please
        >     check the
        >      >      >             following:____
        >      >      >
        >      >      >             Under
        >      >      >
        >      >
        >     https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5
        >      >      >             … look for “block”____
        >      >      >
        >      >      > https://tools.ietf.org/html/rfc8402#section-2 … look under
        >      >      >             SRGB for SRv6____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             [Bruno]____
        >      >      >
        >      >      >             To clarify, my question was not specific to
        >     “block” but
        >      >      >             related to the usage, by the receiver, of the
        >     following
        >      >      >             piece of information:____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >                    LB Length: SRv6 SID Locator Block
        >     length____
        >      >      >
        >      >      >                    LN Length: SRv6 SID Locator Node length____
        >      >      >
        >      >      >                    Fun. Length: SRv6 SID Function length____
        >      >      >
        >      >      >                    Arg. Length: SRv6 SID Arguments length____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             So perhaps I don’t get Chris’s point and would
        >     wait
        >      >     for him
        >      >      >             to clarify.____
        >      >      >
        >      >      >             [Bruno] I’ll leave this to Chris.____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Thanks,____
        >      >      >
        >      >      >             Ketan____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             *From:*Lsr <lsr-bounces@ietf.org
        >     <mailto:lsr-bounces@ietf.org>
        >      >     <mailto:lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>>
        >      >      >             <mailto:lsr-bounces@ietf.org
        >     <mailto:lsr-bounces@ietf.org>
        >      >     <mailto:lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>>>>
        >     *On Behalf Of
        >      >      >             *bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>
        >     <mailto:bruno.decraene@orange.com <mailto:bruno.decraene@orange.com>
        >      >     <mailto:bruno.decraene@orange.com
        >     <mailto:bruno.decraene@orange.com>>>
        >      >      >             *Sent:* 28 February 2020 14:34
        >      >      >             *To:* Ketan Talaulikar (ketant)
        >      >      >             <ketant=40cisco.com@dmarc.ietf.org
        >     <mailto:40cisco.com@dmarc.ietf.org>
        >      >     <mailto:40cisco.com@dmarc.ietf.org
        >     <mailto:40cisco.com@dmarc.ietf.org>>
        >      >      >             <mailto:40cisco..com@dmarc.ietf.org
        >     <mailto:40cisco..com@dmarc.ietf.org>
        >      >     <mailto:40cisco..com@dmarc.ietf.org
        >     <mailto:40cisco..com@dmarc.ietf.org>>>>; Chris Bowers
        >      >      >             <chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>
        >      >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>
        >     <mailto:chrisbowers.ietf@gmail.com
        >     <mailto:chrisbowers.ietf@gmail.com>>>>
        >      >      >             *Cc:* lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>
        >      >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>>; SPRING WG List
        >      >      >             <spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>
        >      >     <mailto:spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>>>;
        >      >      >             draft-ietf-spring-srv6-network-programming
        >      >      >           
        >       <draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>
        >      >      >
        >      >       <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>
        >      >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org
        >     <mailto:draft-ietf-spring-srv6-network-programming@ietf.org>>>>;
        >      >      >             Peter Psenak (ppsenak) <ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
        >      >      >             <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com> <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>>>>
        >      >      >             *Subject:* Re: [Lsr] clarification of locator
        >     block and
        >      >      >             locator node in
        >      >     draft-ietf-spring-srv6-network-programming
        >      >      >             and draft-ietf-lsr-isis-srv6-extensions____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Hi Ketan,____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             *From:*Lsr [mailto:lsr-bounces@ietf.org
        >     <mailto:lsr-bounces@ietf.org>
        >      >     <mailto:lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>>]
        >     *On Behalf Of
        >      >      >             *Ketan Talaulikar (ketant)
        >      >      >             *Sent:* Friday, February 28, 2020 6:30 AM____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Hi Chris,____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             I agree with Peter and I would suggest to drop
        >     LSR since
        >      >      >             this is not a protocol specific thing.____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             I believe the text in
        >      >      >             draft-ietf-spring-srv6-network-programming clears
        >      >     says what
        >      >      >             locator block and locator node are. What more
        >     details
        >      >     do you
        >      >      >             think are required?____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             [Bruno] Speaking as an individual, the draft could
        >      >     possibly
        >      >      >             clarify the usage of these information/fields
        >     by the
        >      >      >             receiver. Possibly using the same name/term (e.g.
        >      >     SRv6 SID
        >      >      >             Locator Block length) to ease the references
        >     between both
        >      >      >             drafts.____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Thanks,____
        >      >      >
        >      >      >             --Bruno____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Thanks,____
        >      >      >
        >      >      >             Ketan____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             *From:*Lsr <lsr-bounces@ietf.org
        >     <mailto:lsr-bounces@ietf.org>
        >      >     <mailto:lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>>
        >      >      >             <mailto:lsr-bounces@ietf.org
        >     <mailto:lsr-bounces@ietf.org>
        >      >     <mailto:lsr-bounces@ietf.org <mailto:lsr-bounces@ietf.org>>>>
        >     *On Behalf Of *Chris Bowers
        >      >      >             *Sent:* 27 February 2020 22:46
        >      >      >             *To:* lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>
        >      >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>
        >     <mailto:lsr@ietf.org <mailto:lsr@ietf.org>>>; SPRING WG List
        >      >      >             <spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>
        >      >     <mailto:spring@ietf.org <mailto:spring@ietf.org>
        >     <mailto:spring@ietf.org <mailto:spring@ietf.org>>>>
        >      >      >             *Cc:* Peter Psenak (ppsenak)
        >     <ppsenak@cisco.com <mailto:ppsenak@cisco.com>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
        >      >      >             <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com> <mailto:ppsenak@cisco.com
        >     <mailto:ppsenak@cisco.com>>>>
        >      >      >             *Subject:* [Lsr] clarification of locator
        >     block and
        >      >     locator
        >      >      >             node in
        >     draft-ietf-spring-srv6-network-programming and
        >      >      >             draft-ietf-lsr-isis-srv6-extensions____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             SPRING and LSR WGs,____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             I think that we need a much more detailed
        >     description
        >      >     of the
        >      >      >             locator block and locator node in either
        >      >      >             draft-ietf-spring-srv6-network-programming or
        >      >      >             draft-ietf-lsr-isis-srv6-extensions.  See
        >     original email
        >      >      >             below.____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Thanks,____
        >      >      >
        >      >      >             Chris____
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             On Thu, Feb 27, 2020 at 11:08 AM Peter Psenak
        >      >      >             <ppsenak@cisco.com <mailto:ppsenak@cisco.com>
        >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>
        >      >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>
        >     <mailto:ppsenak@cisco.com <mailto:ppsenak@cisco.com>>>> wrote:____
        >      >      >
        >      >      >                 Hi Chris,
        >      >      >
        >      >      >                 On 27/02/2020 17:54, Chris Bowers wrote:
        >      >      >                  > LSR WG,
        >      >      >                  >
        >      >      >                  > Section 9 of
        >      >     draft-ietf-lsr-isis-srv6-extensions-05
        >      >      >                 defines the  SRv6
        >      >      >                  > SID Structure Sub-Sub-TLV. In
        >     particular, it
        >      >     defines
        >      >      >                 encoding for the
        >      >      >                  > locator block length and the locator
        >     node length.
        >      >      >                 The text refers to
        >      >      >                  >
        >     [I-D.ietf-spring-srv6-network-programming] for the
        >      >      >                 definition of these
        >      >      >                  > concepts.
        >      >      >                  >
        >      >      >                  > As far as I can tell, the only reference to
        >      >     locator
        >      >      >                 block and locator
        >      >      >                  > node in
        >      >     draft-ietf-spring-srv6-network-programming-10
        >      >      >                 is section 3.1
        >      >      >                  > which has the following text:
        >      >      >                  >
        >      >      >                  >     A locator may be represented as B:N
        >     where B is
        >      >      >                 the SRv6 SID block
        >      >      >                  >     (IPv6 subnet allocated for SRv6
        >     SIDs by the
        >      >      >                 operator) and N is the
        >      >      >                  >     identifier of the parent node
        >      >     instantiating the
        >      >      >                 SID...
        >      >      >                  >
        >      >      >                  > I think that we need a much more detailed
        >      >     description
        >      >      >                 of the locator
        >      >      >                  > block and locator node.
        >      >      >
        >      >      >                 sure, but that would be in the
        >      >      >               
        >       draft-ietf-spring-srv6-network-programming-10, not in
        >      >      >                 draft-ietf-lsr-isis-srv6-extensions, as
        >     these are
        >      >     not a
        >      >      >                 protocol
        >      >      >                 specific constructs.
        >      >      >
        >      >      >                 thanks,
        >      >      >                 Peter
        >      >      >
        >      >      >                  >
        >      >      >                  > Thanks,
        >      >      >                  >
        >      >      >                  > Chris
        >      >      >                  > ____
        >      >      >
        >      >      >
        >      >     
        >       _____________________________________________________________________________________________________________________________
        >      >      >
        >      >      >             ____
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        >      >     jointes.
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        >      >     
        >       _____________________________________________________________________________________________________________________________
        >      >      >
        >      >      >             ____
        >      >      >
        >      >      >             Ce message et ses pieces jointes peuvent
        >     contenir des
        >      >      >             informations confidentielles ou privilegiees et ne
        >      >     doivent donc____
        >      >      >
        >      >      >             pas etre diffuses, exploites ou copies sans
        >      >     autorisation. Si
        >      >      >             vous avez recu ce message par erreur, veuillez le
        >      >     signaler____
        >      >      >
        >      >      >             a l'expediteur et le detruire ainsi que les pieces
        >      >     jointes.
        >      >      >             Les messages electroniques etant susceptibles
        >      >     d'alteration,____
        >      >      >
        >      >      >             Orange decline toute responsabilite si ce
        >     message a ete
        >      >      >             altere, deforme ou falsifie. Merci.____
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        >     by law;____
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