Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt

"Acee Lindem (acee)" <acee@cisco.com> Thu, 06 July 2017 09:24 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: "Peter Psenak (ppsenak)" <ppsenak@cisco.com>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>, Shraddha Hegde <shraddha@juniper.net>
CC: "ospf@ietf.org" <ospf@ietf.org>
Thread-Topic: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
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Date: Thu, 6 Jul 2017 09:24:47 +0000
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Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
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Hi Peter, Shradha, 

On 7/6/17, 3:30 AM, "OSPF on behalf of Peter Psenak (ppsenak)"
<ospf-bounces@ietf.org on behalf of ppsenak@cisco.com> wrote:

>On 06/07/17 05:50 , Ketan Talaulikar (ketant) wrote:
>> Hi Shraddha,
>>
>> Thanks for taking care of some of the comments shared previously.
>>Please find below some more that were probably missed or not taken care
>>of.
>>
>> 1) I see that the use of link-local scope RI LSA has still been
>>retained in this version and not sure why. RI LSA is for node attributes
>>and it's use for signalling of link is not right IMO. Why not use the
>>link-local scope Extended Link LSA instead?
>
>an alternative would be to always flood area scope Extended Link LSA. It
>should not harm anything and could be used by other routers in area as a
>"heads-up" that remote link is becoming overloaded.

I think this would be a good way forward as the OSPF Extended Attribute
LSA will most likely be advertised for SR in OSPF Service Provider domains
anyway. So, just advertising the area-scope for all use cases would seem
to be the simplify this approach and get us past this discussion. In fact,
the -00 version of the draft had area-scope alone and I, regretfully, had
suggested the OSPF RI as possible way to get support either scope.

Thanks,
Acee 

>
>
>>
>> 2) Sec 5.1, why is advertising of MAX-METRIC for the link to be
>>overloaded a SHOULD and not a MUST? Isn't this mandatory to ensure
>>backward compatibility? What if the router on which overload is
>>signalled does not do MAX-METRIC but the implementation on the remote
>>side end up doing MAX-METRIC. Would it not result in asymmetric metric
>>in a un-intended manner? Please consider changing all SHOULD here to
>>MUST to ensure backward compatibility.
>>
>> 3) Sec 5.4, can you please make similar change in language related to
>>the RFC4203 reference as you've done in other parts in this version?
>>
>> Also I don't agree with the rationale you've given for not using LLS
>>for the link-local signalling. Even if the hello processing were
>>delegated to the LC, there are already a lot of protocol events which
>>can happen via hello packets (which includes LLS) that require
>>signalling update to the control plane OSPF main process. An
>>implementation aspect such as this should hardly be a good reason to not
>>use LLS for link-local signalling such as overload.
>
>+1 on the above.
>
>thanks,
>Peter
>
>>
>> Thanks,
>> Ketan
>>
>> -----Original Message-----
>> From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of Shraddha Hegde
>> Sent: 03 July 2017 11:11
>> To: internet-drafts@ietf.org; i-d-announce@ietf.org
>> Cc: ospf@ietf.org
>> Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
>>
>> OSPF WG,
>>
>> New version of the ospf-link-overload draft is posted.
>> Editorial comments received so far have been addressed in this version.
>>
>> There was one comments to move the link-overload sub-TLV to LLS in
>>hello messages.
>> Many implementations delegate the Hello processing to
>>linecards/different deamons
>> Once adjacency is established. Hello messages are not sent to control
>>plane
>> post adjacency establishment. The link-overload information typically
>>needs to be processed
>> after adjacency establishment, it introduces unnecessary complexity in
>>hello processing.
>> We had a discussion among authors on this and feel advertising
>>link-overload sub-TLV
>> in the LSAs is the most appropriate mechanism.
>>
>>
>>
>> Rgds
>> Shraddha
>>
>> -----Original Message-----
>> From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of
>>internet-drafts@ietf.org
>> Sent: Monday, July 3, 2017 11:01 AM
>> To: i-d-announce@ietf.org
>> Cc: ospf@ietf.org
>> Subject: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
>>
>>
>> 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
>>IETF.
>>
>>          Title           : OSPF Link Overload
>>          Authors         : Shraddha Hegde
>>                            Pushpasis Sarkar
>>                            Hannes Gredler
>>                            Mohan Nanduri
>>                            Luay Jalil
>> 	Filename        : draft-ietf-ospf-link-overload-07.txt
>> 	Pages           : 14
>> 	Date            : 2017-07-02
>>
>> 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:
>> https://datatracker.ietf.org/doc/draft-ietf-ospf-link-overload/
>>
>> There are also htmlized versions available at:
>> https://tools.ietf.org/html/draft-ietf-ospf-link-overload-07
>> https://datatracker.ietf.org/doc/html/draft-ietf-ospf-link-overload-07
>>
>> A diff from the previous version is available at:
>> https://www.ietf.org/rfcdiff?url2=draft-ietf-ospf-link-overload-07
>>
>>
>> Please note that it may take a couple of minutes from the time of
>>submission until the htmlized version and diff are available at
>>tools.ietf.org.
>>
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>>
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>
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