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

"Acee Lindem (acee)" <acee@cisco.com> Mon, 24 July 2017 22:29 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: Shraddha Hegde <shraddha@juniper.net>, "Peter Psenak (ppsenak)" <ppsenak@cisco.com>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>
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: Mon, 24 Jul 2017 22:28:55 +0000
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Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
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Hi Shraddha, 

Great - I think we are all in sync.

What are your thoughts on using “MUST” for the setting the link metrics in
sections 5.1, 5.2, 5.3 and 5.5? I checked RFC 6987 (and RFC 3137) and they
don't use normative language since setting the link-metrics to 0xffff is
the very definition of OSPF stub router behavior.

Also, one more reference to RFC 4203.

*** 438,445 ****
     field in the Extended Link TLV carries the Local interface-id instead
     of the IP address.  The Local/Remote Interface ID sub-TLV MUST be
     originated when there are multiple parallel unnumbered interfaces
!    between two nodes.  Procedures to obtain interface-id of the remote
!    side are defined in [RFC4203].
  
  
  
--- 438,445 ----
     field in the Extended Link TLV carries the Local interface-id instead
     of the IP address.  The Local/Remote Interface ID sub-TLV MUST be
     originated when there are multiple parallel unnumbered interfaces
!    between two nodes.  One of the mechanisms to obtain remote
!    interface-id is described in [RFC4203].
  


Thanks,
Acee 


On 7/10/17, 12:52 AM, "Shraddha Hegde" <shraddha@juniper.net> wrote:

>All,
>
>Link-local flooding was added as an optimization for use-cases that do
>not need area level flooding on request from Acee.
>I agree flooding area level in all cases is a reasonable way forward as
>the overhead isn't much.
>
>If anyone has objections to removing Link-local scope advertisement, do
>let me know.
>
>Rgds
>Shraddha
>
>
>-----Original Message-----
>From: Acee Lindem (acee) [mailto:acee@cisco.com]
>Sent: Thursday, July 6, 2017 2:55 PM
>To: Peter Psenak (ppsenak) <ppsenak@cisco.com>om>; Ketan Talaulikar (ketant)
><ketant@cisco.com>o.com>; Shraddha Hegde <shraddha@juniper.net>
>Cc: ospf@ietf.org
>Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
>
>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-0
>>> 7
>>>
>>> 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/
>>>
>>> _______________________________________________
>>> OSPF mailing list
>>> OSPF@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ospf
>>>
>>> _______________________________________________
>>> OSPF mailing list
>>> OSPF@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ospf
>>>
>>> _______________________________________________
>>> OSPF mailing list
>>> OSPF@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ospf
>>> .
>>>
>>
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