Re: [mpls] Alia Atlas' Discuss on draft-ietf-mpls-residence-time-14: (with DISCUSS and COMMENT)

Greg Mirsky <gregimirsky@gmail.com> Thu, 02 March 2017 16:37 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Thu, 2 Mar 2017 08:37:33 -0800
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To: Alia Atlas <akatlas@gmail.com>
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Cc: mpls-chairs@ietf.org, draft-ietf-mpls-residence-time@ietf.org, "mpls@ietf.org" <mpls@ietf.org>, The IESG <iesg@ietf.org>
Subject: Re: [mpls] Alia Atlas' Discuss on draft-ietf-mpls-residence-time-14: (with DISCUSS and COMMENT)
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Hi Alia,
thank you for the proposed text. Accepted. Please see the updated text
below.

Regards,
Greg

On Thu, Mar 2, 2017 at 6:48 AM, Alia Atlas <akatlas@gmail.com>; wrote:

> Hi Greg,
>
>
>
> On Thu, Mar 2, 2017 at 2:01 AM, Greg Mirsky <gregimirsky@gmail.com>; wrote:
>
>> Hi Alia,
>> thank you for your thorough review and the comments. Please find my
>> responses in-line tagged GIM>>.
>>
>> Regards,
>> Greg
>>
>> On Wed, Mar 1, 2017 at 3:05 PM, Alia Atlas <akatlas@gmail.com>; wrote:
>>
>>> Alia Atlas has entered the following ballot position for
>>> draft-ietf-mpls-residence-time-14: Discuss
>>>
>>> When responding, please keep the subject line intact and reply to all
>>> email addresses included in the To and CC lines. (Feel free to cut this
>>> introductory paragraph, however.)
>>>
>>>
>>> Please refer to https://www.ietf.org/iesg/stat
>>> ement/discuss-criteria.html
>>> for more information about IESG DISCUSS and COMMENT positions.
>>>
>>>
>>> The document, along with other ballot positions, can be found here:
>>> https://datatracker.ietf.org/doc/draft-ietf-mpls-residence-time/
>>>
>>>
>>>
>>> ----------------------------------------------------------------------
>>> DISCUSS:
>>> ----------------------------------------------------------------------
>>>
>>> Thank you for a clear document.  I think that this should be a
>>> straightforward Discuss to better clarify.
>>>
>>> In Section 4.8.1, it says "The RTM Set sub-object contains an ordered
>>> list, from egress node to
>>>    ingress node, of the RTM capable nodes along the LSP's path." but the
>>> sub-TLVs (as most clearly
>>> indicated by "4.8.1.3.  Unnumbered Interface Sub-TLV" are actually meant
>>> to be a list of interfaces.
>>>
>> GIM>> I think that the text, e.g. by stating "The Length is always 12" and
>> the Figure 10 are clear that only one interface can be listed in the
>> sub-TLV.
>> And the same is true for other sub-TLVs.
>>
>
> The draft says"Only a single RTM_SET  sub-TLV with the given Value field
> MUST be present in the RTM_SET   TLV.  If more than one sub-TLV is found
> the LSP setup MUST fail"
>
> There is nothing there that clearly states that only one of the 3 sub-TLVs
> should be place in the RTM_SET TLV for a particular node.  There is also
> the inaccuracy between putting in interface addresses versus the claim that
> it contains nodes.
>
> For instance, text could be added/changed to indicate:
>
> "The RTM_SET TLV is intended to include the subset of the RRO Object that
> represents those egress interfaces on the LSP that are RTM-capable.  After
> a node chooses an egress interface to use in the RRO sub-TLV, that same
> egress interface, if RTM-capable,  SHOULD be placed into the RTM_SET TLV
> using one of the IPv4 sub-TLV, IPv6 sub-TLV, or Unnumbered Interface
> sub-TLV.  The address family chosen SHOULD match that of the RESV message
> and that used in the RRO; the unnumbered interface sub-TLV is used when the
> egress interface has no assigned IP address.  A node MUST NOT place more
> sub-TLVs in the RTM_SET TLV than the number of RTM-capable egress
> interfaces the LSP traverses that are under that node's control."
>
> OLD TEXT:

   Sub-TLVs are organized as a last-in-first-out stack.  The first -out
   sub-TLV relative to the beginning of RTM_SET TLV is considered the
   top.  The last-out sub-TLV is considered the bottom.  When a new sub-
   TLV is added, it is always added to the top.  Only a single RTM_SET
   sub-TLV with the given Value field MUST be present in the RTM_SET
   TLV.  If more than one sub-TLV is found the LSP setup MUST fail with
   the generation of a PathErr message with the Error Code "Duplicate
   sub-TLV" Section 8.9
<https://tools.ietf.org/html/draft-ietf-mpls-residence-time-05#section-8.9>
and Error Value contains 16-bit value composed
   of (Type of TLV, Type of sub-TLV).


NEW TEXT:

   Sub-TLVs are organized as a last-in-first-out stack.  The first-out
   sub-TLV relative to the beginning of RTM_SET TLV is considered the
   top.  The last-out sub-TLV is considered the bottom.  When a new sub-
   TLV is added, it is always added to the top.

   The RTM_SET TLV is intended to include the subset of the RRO sub-TLVs
   that represents those egress interfaces on the LSP that are RTM-
   capable.  After a node chooses an egress interface to use in the RRO
   sub-TLV, that same egress interface, if RTM-capable, SHOULD be placed
   into the RTM_SET TLV using one of the IPv4 sub-TLV, IPv6 sub-TLV, or
   Unnumbered Interface sub-TLV.  The address family chosen SHOULD match
   that of the RESV message and that used in the RRO; the unnumbered
   interface sub-TLV is used when the egress interface has no assigned
   IP address.  A node MUST NOT place more sub-TLVs in the RTM_SET TLV
   than the number of RTM-capable egress interfaces the LSP traverses
   that are under that node's control.  Only a single RTM_SET sub-TLV
   with the given Value field MUST be present in the RTM_SET TLV.  If
   more than one sub-TLV is found the LSP setup MUST fail with the
   generation of a ResvErr message with the Error Code "Duplicate sub-
   TLV" Section 7.9 and Error Value contains 16-bit value composed of
   (Type of TLV, Type of sub-TLV).



> It isn't clear whether these are supposed to be the egress interface, the
>>> ingress interface, or just any
>>> interface
>>
>> GIM>> In order for the process described in section 4.8 to work RTM node
>> MUST use the same ID in RTM_SET sub-TLV as in RRO subobject.
>>
>
> Right - but I don't see the draft saying that clearly.  See my suggested
> text above.
>
>
>> - or why sending just a Router ID wouldn't be sufficient.
>>> There is no indication as to whether
>>> it is ok to include both the IPv4 and IPv6 address Sub-TLVs for the same
>>> node or how to select which one
>>> to use.
>>>
>> GIM>> Selection should follow election of ID for corresponding subobject
>> in RRO.
>>
>
> Agreed - see suggested text.
>
>>
>>> ----------------------------------------------------------------------
>>> COMMENT:
>>> ----------------------------------------------------------------------
>>>
>>> 1) I am disappointed that the sub-TLV needed for an OSPFv3 Extended LSA
>>> isn't defined.  While I understand that a normative reference isn't
>>> desirable - instead of "left for future study", it would be better to say
>>> that the sub-TLV should use the same format as in Sec 4.3 and that the
>>> type allocation and full details are left to a future document.   This is
>>> exactly how gaps are created for networks running only IPv6.   If
>>> draft-ietf-ospf-ospfv3-lsa-extend-13 were not waiting for
>>> implementations
>>> and had a clear time-frame for how and when to progress, this would also
>>> be a Discuss.
>>>
>> GIM>> I agree that your proposal narrows the gap for IPv6 extension for
>> RTM capability advertisement. Will apply the text you've suggested in the
>> next version. Hope OSPF WG agrees to this change.
>>
>
> OLD TEXT:

   The capability to support RTM on a particular link (interface) can be
   advertised in OSPFv3 using LSA extensions as described in
   [I-D.ietf-ospf-ospfv3-lsa-extend
<https://tools.ietf.org/html/draft-ietf-mpls-residence-time-14#ref-I-D.ietf-ospf-ospfv3-lsa-extend>].
Exact use of OSPFv3 LSA
   extensions is for further study.

NEW TEXT:

   The capability to support RTM on a particular link (interface) can be
   advertised in OSPFv3 using LSA extensions as described in
   [I-D.ietf-ospf-ospfv3-lsa-extend].  The sub-TLV SHOULD use the same
   format as in Section 4.3.  The type allocation and full details of
   exact use of OSPFv3 LSA extensions is for further study.



> Thanks.
>
> Regards,
> Alia
>