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

Alia Atlas <akatlas@gmail.com> Thu, 02 March 2017 14:48 UTC

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From: Alia Atlas <akatlas@gmail.com>
Date: Thu, 2 Mar 2017 09:48:46 -0500
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To: Greg Mirsky <gregimirsky@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 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/statement/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."

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.
>

Thanks.

Regards,
Alia