Re: [Bier] WGLC : draft-ietf-bier-isis-extensions-07.txt

Eric C Rosen <[email protected]> Fri, 16 Feb 2018 09:44:42 -0500
Newsgroups gmane.ietf.isis
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Perhaps the following would be a good compromise (or perhaps not).

Have an eight-bit field whose values are taken from the "IGP Algorithms" 
Registry.

Have another eight-bit field whose values are taken from a new 
BIER-specific registry.  I don't know, maybe call it the "BIER Underlay 
Algorithm Modifier" registry.  The way the underlay paths are computed 
for a given BIER sub-domain is determined by the pair of codepoints: 
<IGP Algorithms codepoint, BIER Underlay Algorithm Modifier codepoint>.

The default value for the "BIER Underlay Algorithm Modifier" field would 
be zero.   The value zero in this field would mean "just use the IGP 
Algorithms field to figure out how the underlay paths are computed."  
Non-zero values could be used to add additional nuance. Existing drafts 
can say "the use of non-zero values in this field is outside the scope 
of this document".

The registration policy for the new registry could save about  half the 
values for "standards action", and about half for FCFS.  And a few for 
Experimental.  (This would be a good policy for the IGP Algorithms 
registry as well, imho.)

This seems to have minimal impact on existing implementations, and 
leaves room for further development of BIER while avoiding entanglements 
(or peceived entanglements) with other technologies that might be 
considered controversial.

Now perhaps the WG can proceed to the really important issues, such as 
how to best design the T-shirts.  (Though frankly I'd rather get a few 
more home-brewed beers than a T-shirt.)



On 2/16/2018 12:51 AM, Les Ginsberg (ginsberg) wrote:
>
> Andrew –
>
> There is no change being considered to the size of the algorithm field 
> for Segment Routing.  That is 8 bits – there are mature SR documents 
> and multiple implementations that use that encoding. There is also the 
> IGP registry defined in an SR document (though not necessarily 
> exclusively for SR use) which defines 8 bit values.
>
> The only thing which is being discussed here is whether BIER should 
> use an 8 bit or 16 bit algorithm field. Also, even if it is decided 
> BIER should use a 16 bit algorithm, it is conceivable that the values 
> defined in the IGP algorithm registry may still be of use to BIER.
>
> Les
>
> *From:*BIER [mailto:[email protected]] *On Behalf Of *Dolganow, 
> Andrew (Nokia - SG/Singapore)
> *Sent:* Thursday, February 15, 2018 7:39 PM
> *To:* IJsbrand Wijnands <[email protected]>
> *Cc:* Greg Shepherd <[email protected]>; [email protected]; 
> [email protected]; Xiejingrong <[email protected]>; 
> [email protected]; Eric C Rosen <[email protected]>
> *Subject:* Re: [Bier] [Isis-wg] WGLC : 
> draft-ietf-bier-isis-extensions-07.txt
>
> Well,
>
> Now, there are multiple treads being discussed here under one topic:
>
> - how big should the the field be?
>
> - should there be common registry for all technologies?
>
> - where should it be defined and which WG should standardize it?
>
> To me the first question is totally dependent on the answer to the 
> last two, since the use case pointed out suggests a common registry.
>
> Now there may be different opinions (I believe there are from this 
> exchange) whether we should or should not have a common registry, how 
> complicated would it be and whether it would tax all groups trying to 
> use that. But even before we go there, the basic question has to be 
> answered:
>
> - which WG would own that registry. It is not in a charter of BIER to 
> own it nor it is in a charter of SR nor it is in a charter of ISIS. Do 
> none of them should own and mandate use. We are chartering LSR now - 
> should we add registry for all IGP algorithms, we have routing WG, 
> others?  Would like to hear AD’s opinion. Note that although LSR 
> appears obvious, the algorithms to compute BIER may be 
> controller-based that do bot require LSR (same applies to SR).
>
> - if we do agree to have a common registry, I would assume we all then 
> tax everyone to signal that the same way. That would mean changes to 
> SR and changes to BIER.
>
> This seems a lot. We have implementations of both technologies, so are 
> changes to those warranted or is it too late and we should pursue 
> independent  alg definition and registry as it has been set-up in the 
> existing drafts. And we are talking only of those two but more WG will 
> come and want to define things for them as well.
>
> Andrew
>
> Sent from my iPhone
>
>
> On Feb 16, 2018, at 2:51 AM, IJsbrand Wijnands <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     I think its clear from the discussion there are different opinions
>     on the matter on how to make BIER use the BAR field. The reason
>     for me to support 16 bits is that everybody seemed ok go move
>     forward with an 8bits BAR without a registry, a 16bits BAR does
>     not change anything, its just a bigger field. But at least with
>     16bits, we can split in Type, Value, and support different
>     use-cases. IMO, pointing to whatever the Unicast underlay is
>     providing is the main use-case, but it allows other ways to do things.
>
>     One thing is clear, with just 8bits, it will be very hard to reach
>     an agreement what the registry would look like. If we make it
>     16bits, we know we can solve multiple use-cases. The main question
>     (I think) is whether we document how a 16bit BAR is carved up now,
>     or we defer that to later. And as I said, since everybody seemed
>     ok with 8bit BAR without a registry, I don’t see why its now
>     different for 16bits. It gives us time to workout exactly how to
>     use it and get input from the WGs.
>
>     And, of course, the goal is to create a registry for the 16 bits
>     through a new draft!
>
>     Thx,
>
>     Ice.
>
>
>
>         On 15 Feb 2018, at 18:28, Tony Przygienda <[email protected]
>         <mailto:[email protected]>> wrote:
>
>
>
>         On Thu, Feb 15, 2018 at 9:20 AM, Greg
>         Shepherd <[email protected] <mailto:[email protected]>> wrote:
>         On Thu, Feb 15, 2018 at 8:53 AM, Tony
>         Przygienda <[email protected]
>         <mailto:[email protected]>> wrote:
>
>
>         On Thu, Feb 15, 2018 at 8:38 AM, Greg
>         Shepherd <[email protected] <mailto:[email protected]>> wrote:
>         For the record, there is no SR Registry. There is only an IGP
>         Algo Type Registry as defined in
>         draft-ietf-ospr-segment-routing-extensions-24 section 8.5
>
>         So is that a good idea, having multiple drafts in flight with
>         fields expecting to have magic couplings to each other while
>         leaving e'thing "unspecified" to "publish RFCs" while we
>         "decide things later"?
>
>         That was a pivot, but still; there is no reference, there is
>         no coupling.
>
>         Tangental: draft-ietf-ospr-segment-routing-extensions-24 has
>         been around for a while, and the IGP Algo registry will
>         be tied to this draft and it's fate. If anyone is expecting to
>         use this registry outside of the scope of this draft, it
>         would be in their best interest to pull the registry
>         description out into a separate draft.
>
>
>         OK, and I agree that if such a registry is pulled and under a
>         clear charter of mandating multiple technologies within
>         an independent body then a discussion starts to make sense and
>         what the size of that should be given that mandates
>         algorithms over multiple technologies (SR, unicast, mcast,
>         whatever) and implies a "God's eye view" of all the elements
>         of all the technologies (and if a computation touches elements
>         from two technologies they become [optionally] coupled).  We
>         are not talking IGP registry or multicast computation registry
>         or SR registry then but a "wider scope registry". Yes, that is
>         an intriguing thought with its own validity but outside the
>         scope of charter we're under as BIER.  Personally, I
>         consider multiple, if needed loosely coupled registries for
>         each technology a less centralized and hence "more Internet
>         like" solution but I see how opinions on such a thing can
>         diverge ...
>
>         thanks
>
>         --- tony
>
>
>
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    Perhaps the following would be a good compromise (or perhaps not).<br>
    <br>
    Have an eight-bit field whose values are taken from the "IGP
    Algorithms" Registry.<br>
    <br>
    Have another eight-bit field whose values are taken from a new
    BIER-specific registry.  I don't know, maybe call it the "BIER
    Underlay Algorithm Modifier" registry.  The way the underlay paths
    are computed for a given BIER sub-domain is determined by the pair
    of codepoints: &lt;IGP Algorithms codepoint, BIER Underlay Algorithm
    Modifier codepoint&gt;.<br>
    <br>
    The default value for the "BIER Underlay Algorithm Modifier" field
    would be zero.   The value zero in this field would mean "just use
    the IGP Algorithms field to figure out how the underlay paths are
    computed."  Non-zero values could be used to add additional nuance. 
    Existing drafts can say "the use of non-zero values in this field is
    outside the scope of this document". <br>
    <br>
    The registration policy for the new registry could save about  half
    the values for "standards action", and about half for FCFS.  And a
    few for Experimental.  (This would be a good policy for the IGP
    Algorithms registry as well, imho.)<br>
    <br>
    This seems to have minimal impact on existing implementations, and
    leaves room for further development of BIER while avoiding
    entanglements (or peceived entanglements) with other technologies
    that might be considered controversial.<br>
    <br>
    Now perhaps the WG can proceed to the really important issues, such
    as how to best design the T-shirts.  (Though frankly I'd rather get
    a few more home-brewed beers than a T-shirt.)<br>
    <br>
    <br>
    <br>
    <div class="moz-cite-prefix">On 2/16/2018 12:51 AM, Les Ginsberg
      (ginsberg) wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:[email protected]">
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      <div class="WordSection1">
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D">Andrew
            –<o:p></o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D">There
            is no change being considered to the size of the algorithm
            field for Segment Routing.  That is 8 bits – there are
            mature SR documents and multiple implementations that use
            that encoding. There is also the IGP registry defined in an
            SR document (though not necessarily exclusively for SR use)
            which defines 8 bit values.<o:p></o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D">The
            only thing which is being discussed here is whether BIER
            should use an 8 bit or 16 bit algorithm field. Also, even if
            it is decided BIER should use a 16 bit algorithm, it is
            conceivable that the values defined in the IGP algorithm
            registry may still be of use to BIER.<o:p></o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D"><o:p> </o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D">  
            Les<o:p></o:p></span></p>
        <p class="MsoNormal"><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif;color:#1F497D"><o:p> </o:p></span></p>
        <div style="border:none;border-left:solid blue 1.5pt;padding:0in
          0in 0in 4.0pt">
          <div>
            <div style="border:none;border-top:solid #E1E1E1
              1.0pt;padding:3.0pt 0in 0in 0in">
              <p class="MsoNormal"><b><span
                    style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif">From:</span></b><span
style="font-size:11.0pt;font-family:&quot;Calibri&quot;,sans-serif">
                  BIER [<a class="moz-txt-link-freetext" href="mailto:[email protected]">mailto:[email protected]</a>]
                  <b>On Behalf Of </b>Dolganow, Andrew (Nokia -
                  SG/Singapore)<br>
                  <b>Sent:</b> Thursday, February 15, 2018 7:39 PM<br>
                  <b>To:</b> IJsbrand Wijnands <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]">&lt;[email protected]&gt;</a><br>
                  <b>Cc:</b> Greg Shepherd <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]">&lt;[email protected]&gt;</a>;
                  <a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>; <a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>; Xiejingrong
                  <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]">&lt;[email protected]&gt;</a>;
                  <a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>; Eric C Rosen
                  <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]">&lt;[email protected]&gt;</a><br>
                  <b>Subject:</b> Re: [Bier] [Isis-wg] WGLC :
                  draft-ietf-bier-isis-extensions-07.txt<o:p></o:p></span></p>
            </div>
          </div>
          <p class="MsoNormal"><o:p> </o:p></p>
          <p class="MsoNormal">Well, <o:p></o:p></p>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">Now, there are multiple treads being
              discussed here under one topic:<o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">- how big should the the field be?<o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal">- should there be common registry for
              all technologies?<o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal">- where should it be defined and which
              WG should standardize it?<o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">To me the first question is totally
              dependent on the answer to the last two, since the use
              case pointed out suggests a common registry. <o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">Now there may be different opinions (I
              believe there are from this exchange) whether we should or
              should not have a common registry, how complicated would
              it be and whether it would tax all groups trying to use
              that. But even before we go there, the basic question has
              to be answered: <o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal">- which WG would own that registry. It
              is not in a charter of BIER to own it nor it is in a
              charter of SR nor it is in a charter of ISIS. Do none of
              them should own and mandate use. We are chartering LSR now
              - should we add registry for all IGP algorithms, we have
              routing WG, others?  Would like to hear AD’s opinion. Note
              that although LSR appears obvious, the algorithms to
              compute BIER may be controller-based that do bot require
              LSR (same applies to SR). <o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">- if we do agree to have a common
              registry, I would assume we all then tax everyone to
              signal that the same way. That would mean changes to SR
              and changes to BIER. <o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal"><o:p> </o:p></p>
          </div>
          <div>
            <p class="MsoNormal">This seems a lot. We have
              implementations of both technologies, so are changes to
              those warranted or is it too late and we should pursue
              independent  alg definition and registry as it has been
              set-up in the existing drafts. And we are talking only of
              those two but more WG will come and want to define things
              for them as well. <o:p></o:p></p>
          </div>
          <div>
            <p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
            <div id="AppleMailSignature">
              <p class="MsoNormal">Andrew <o:p></o:p></p>
              <div>
                <p class="MsoNormal"><o:p> </o:p></p>
              </div>
              <div>
                <p class="MsoNormal">Sent from my iPhone<o:p></o:p></p>
              </div>
            </div>
            <div>
              <p class="MsoNormal" style="margin-bottom:12.0pt"><br>
                On Feb 16, 2018, at 2:51 AM, IJsbrand Wijnands &lt;<a
                  href="mailto:[email protected]" moz-do-not-send="true">[email protected]</a>&gt;
                wrote:<o:p></o:p></p>
            </div>
            <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
              <div>
                <div>
                  <p class="MsoNormal">I think its clear from the
                    discussion there are different opinions on the
                    matter on how to make BIER use the BAR field. The
                    reason for me to support 16 bits is that everybody
                    seemed ok go move forward with an 8bits BAR without
                    a registry, a 16bits BAR does not change anything,
                    its just a bigger field. But at least with 16bits,
                    we can split in Type, Value, and support different
                    use-cases. IMO, pointing to whatever the Unicast
                    underlay is providing is the main use-case, but it
                    allows other ways to do things.<o:p></o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><o:p> </o:p></p>
                </div>
                <div>
                  <p class="MsoNormal">One thing is clear, with just
                    8bits, it will be very hard to reach an agreement
                    what the registry would look like. If we make it
                    16bits, we know we can solve multiple use-cases. The
                    main question (I think) is whether we document how a
                    16bit BAR is carved up now, or we defer that to
                    later. And as I said, since everybody seemed ok with
                    8bit BAR without a registry, I don’t see why its now
                    different for 16bits. It gives us time to workout
                    exactly how to use it and get input from the WGs.<o:p></o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><o:p> </o:p></p>
                </div>
                <div>
                  <p class="MsoNormal">And, of course, the goal is to
                    create a registry for the 16 bits through a new
                    draft!<o:p></o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><o:p> </o:p></p>
                </div>
                <div>
                  <p class="MsoNormal">Thx,<o:p></o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><o:p> </o:p></p>
                </div>
                <div>
                  <p class="MsoNormal">Ice.<o:p></o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><o:p> </o:p></p>
                </div>
                <div>
                  <p class="MsoNormal"><br>
                    <br>
                    <o:p></o:p></p>
                  <blockquote
                    style="margin-top:5.0pt;margin-bottom:5.0pt">
                    <p class="MsoNormal">On 15 Feb 2018, at 18:28, Tony
                      Przygienda &lt;<a
                        href="mailto:[email protected]"
                        moz-do-not-send="true">[email protected]</a>&gt;
                      wrote:<br>
                      <br>
                      <br>
                      <br>
                      On Thu, Feb 15, 2018 at 9:20 AM, Greg
                      Shepherd &lt;<a href="mailto:[email protected]"
                        moz-do-not-send="true">[email protected]</a>&gt; wrote:<br>
                      On Thu, Feb 15, 2018 at 8:53 AM, Tony
                      Przygienda &lt;<a
                        href="mailto:[email protected]"
                        moz-do-not-send="true">[email protected]</a>&gt; wrote:<br>
                      <br>
                      <br>
                      On Thu, Feb 15, 2018 at 8:38 AM, Greg
                      Shepherd &lt;<a href="mailto:[email protected]"
                        moz-do-not-send="true">[email protected]</a>&gt; wrote:<br>
                      For the record, there is no SR Registry. There is
                      only an IGP Algo Type Registry as defined in
                      draft-ietf-ospr-segment-routing-extensions-24
                      section 8.5<br>
                      <br>
                      So is that a good idea, having multiple drafts in
                      flight with fields expecting to have magic
                      couplings to each other while leaving e'thing
                      "unspecified" to "publish RFCs" while we "decide
                      things later"? <br>
                      <br>
                      That was a pivot, but still; there is no
                      reference, there is no coupling. <br>
                      <br>
                      Tangental:
                      draft-ietf-ospr-segment-routing-extensions-24 has
                      been around for a while, and the IGP Algo registry
                      will be tied to this draft and it's fate. If
                      anyone is expecting to use this registry outside
                      of the scope of this draft, it would be in their
                      best interest to pull the registry description out
                      into a separate draft.<br>
                      <br>
                      <br>
                      OK, and I agree that if such a registry is pulled
                      and under a clear charter of mandating multiple
                      technologies within an independent body then a
                      discussion starts to make sense and what the size
                      of that should be given that mandates
                      algorithms over multiple technologies (SR,
                      unicast, mcast, whatever) and implies a "God's eye
                      view" of all the elements of all the technologies
                      (and if a computation touches elements from two
                      technologies they become [optionally] coupled).
                       We are not talking IGP registry or multicast
                      computation registry or SR registry then but a
                      "wider scope registry". Yes, that is an intriguing
                      thought with its own validity but outside the
                      scope of charter we're under as BIER.  Personally,
                      I consider multiple, if needed loosely coupled
                      registries for each technology a less centralized
                      and hence "more Internet like" solution but I see
                      how opinions on such a thing can diverge ... <br>
                      <br>
                      thanks<br>
                      <br>
                      --- tony <br>
                       <br>
                      <br>
                      <br>
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