Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-05.txt

"Ketan Talaulikar Talaulikar (ketant)" <> Thu, 20 April 2017 04:36 UTC

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From: "Ketan Talaulikar Talaulikar (ketant)" <>
To: "Acee Lindem (acee)" <>, Acee Lindem <>, Shraddha Hegde <>
CC: "" <>
Thread-Topic: [OSPF] I-D Action: draft-ietf-ospf-link-overload-05.txt
Date: Thu, 20 Apr 2017 04:36:23 +0000
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Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-05.txt
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Hi Shraddha/Authors,

I would like to share the following comments and feedback on this draft.

1) I did not understand the motivation for the use of link-local scoped RI LSA for the link-overload signalling when we have the ability to do so via the TLV in the area-scoped Extended Link Attribute LSA. I think it may be a good idea (an optimization) to use the TLV in an area-scoped RI LSA to indicate link overload for all the router links instead of signalling individually for all its links in the Extended Link Attribute LSA - but this is not what the draft proposes. So could you explain the reason for the link-local scoped RI LSA TLV usage?

2) The Link Overload TLV is defined with a remote IP address field now. This does not seem like a good idea. We have had traditionally certain TLVs in OSPF LSAs that describe links i.e. Remote Interface IP address and Link Local/Remote Identifiers and cover both numbered and unnumbered links. The draft-ppsenak-ospf-te-link-attr-reuse proposed to specifically re-use these TLVs so that links may be described correctly in the new extended link attribute LSA for generic use-cases such as the Link Overload TLV here. It seems rather odd that we are now introducing these fields like remote address in individual TLVs and proposing *hacky* encoding of link-ids in the remote IP address field for unnumbered links instead of re-using existing well defined generic TLVs.

3) I am not sure why the reference to use of OSPFv3 extended LSAs for link level area-scoped signalling was removed from this version of the draft.

4) I also have an objection to the reference of RFC4203 for the procedures for obtaining the remote interface-id since that mechanism is outside the scope of what this draft is trying to standardize. Specifically, I have a problem since it gives an impression that the mechanism described in RFC4203 is *the* procedure for obtaining the remote interface-id since that specification is very specific to the GMPLS/TE use-cases and it is not a generic/based OSPF protocol mechanism. We have proposed an alternate mechanism for doing this in a manner consistent with OSPFv3 and ISIS in draft-ppsenak-ospf-lls-interface-id. We can debate the need for this mechanism in a separate thread, but the reference to RFC4203 does not seem necessary here to me.


-----Original Message-----
From: OSPF [] On Behalf Of Acee Lindem (acee)
Sent: 20 April 2017 04:02
To: Acee Lindem <>; Shraddha Hegde <>
Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-05.txt

Hi Shraddha, 

The only non-editorial comment that I have is that the draft references
RFC 4203 as the way to learn the remote interface ID on an unnumbered link
( As
you know, this is a very controversial topic with some of us wanting this
to be in the hello packets consistent with OSPFv3 and IS-IS as opposed to
using a link-scoped TE Opaque LSA as suggested in the OSPF GMPLS
Extensions RFC ( I would
suggest removing the reference.


On 4/19/17, 9:11 AM, "Acee Lindem" <> wrote:

>Hi Shraddha, 
>I think this version addresses all my comments. I will do a detailed
>review this week and, most likely, start the WG last call. I encourage
>other WG members to do the same.
>> On Apr 19, 2017, at 9:08 AM, Shraddha Hegde <>
>> Hi Acee,
>> New version draft-ietf-ospf-link-overload-06 is posted where the
>>remote-ipv4 addr is moved to a new sub-TLV.
>> Pls review.
>> The authors of the draft believe that draft has undergone multiple
>>revisions/reviews and is ready for WG last call.
>> Rgds
>> Shraddha
>> -----Original Message-----
>> From: OSPF [] On Behalf Of Acee Lindem
>> Sent: Saturday, March 18, 2017 2:28 AM
>> Cc:
>> Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-05.txt
>> Hi Shraddha, et al,
>> With respect to section 4.1, I agree that matching link endpoints in
>> OSPFv2 requires more information. However, this is a general problem
>>and the remote address should be a separate OSPFv2 Link Attribute LSA
>>TLV rather than overloading the link overload TLV ;^)
>> Thanks,
>> Acee
>> On 2/23/17, 11:18 AM, "OSPF on behalf of"
>> < on behalf of> wrote:
>>> A New Internet-Draft is available from the on-line Internet-Drafts
>>> directories.
>>> This draft is a work item of the Open Shortest Path First IGP of the
>>>       Title           : OSPF Link Overload
>>>       Authors         : Shraddha Hegde
>>>                         Pushpasis Sarkar
>>>                         Hannes Gredler
>>>                         Mohan Nanduri
>>>                         Luay Jalil
>>> 	Filename        : draft-ietf-ospf-link-overload-05.txt
>>> 	Pages           : 13
>>> 	Date            : 2017-02-23
>>> Abstract:
>>>  When a link is being prepared to be taken out of service, the traffic
>>>  needs to be diverted from both ends of the link.  Increasing the
>>>  metric to the highest metric on one side of the link is not
>>>  sufficient to divert the traffic flowing in the other direction.
>>>  It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be
>>>  able to advertise a link being in an overload state to indicate
>>>  impending maintenance activity on the link.  This information can be
>>>  used by the network devices to re-route the traffic effectively.
>>>  This document describes the protocol extensions to disseminate link-
>>>  overload information in OSPFv2 and OSPFv3.
>>> The IETF datatracker status page for this draft is:
>>> There's also a htmlized version available at:
>>> A diff from the previous version is available at:
>>> Please note that it may take a couple of minutes from the time of
>>> submission until the htmlized version and diff are available at
>>> Internet-Drafts are also available by anonymous FTP at:
>>> _______________________________________________
>>> OSPF mailing list
>> _______________________________________________
>> OSPF mailing list
>> _______________________________________________
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