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

"Acee Lindem (acee)" <acee@cisco.com> Thu, 27 July 2017 21:59 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: "Acee Lindem (acee)" <acee@cisco.com>, 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: Thu, 27 Jul 2017 21:58:58 +0000
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Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
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On 7/27/17, 5:49 PM, "OSPF on behalf of Acee Lindem (acee)"
<ospf-bounces@ietf.org on behalf of acee@cisco.com> wrote:

>Hi Shraddha, Co-authors,
>
>I just read the draft and I there shouldn’t be any more contention.
>However, I have a couple questions on the use cases.
>
>  1. In the pseudowire use case (7.1), I don’t understand where OSPF
>link-overload is being advertised. I guess the assumption is that the
>pseudowires are running OSPF? Also, the use case references a private VLAN
>with 3 CEs. However, I see pseudowires as P2P.

I guess VPLS is also characterized as a pseudowire service.

Thanks,
Acee 

>
>  2. In the OSPF L3VPN use case, mention that the CEs are dual-homed. This
>include in my editorial comments.
>
>  3. In the Hub-and-Spoke use case (7.4), why wouldn’t one just use RFC
>6987 rather than advertising link-overload for all the links?
>
>I’ll send my editorial comments offline.
>
>Thanks,
>Acee 
>
>   
>
>On 7/27/17, 6:03 AM, "Shraddha Hegde" <shraddha@juniper.net> wrote:
>
>>Acee/OSPF WG,
>>
>>I just realized my post on updated draft for -08 version posted on 17-07
>>was stuck at confirmation stage.
>>
>>I think it's useful to have normative language to ensure
>>interoperability. I have updated the "elements of procedure"
>>Section accordingly. Please review the -08 version.
>>
>>Thanks
>>Shraddha
>>
>>-----Original Message-----
>>From: Acee Lindem (acee) [mailto:acee@cisco.com]
>>Sent: Tuesday, July 25, 2017 3:59 AM
>>To: Shraddha Hegde <shraddha@juniper.net>; Peter Psenak (ppsenak)
>><ppsenak@cisco.com>; Ketan Talaulikar (ketant) <ketant@cisco.com>
>>Cc: ospf@ietf.org
>>Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
>>
>>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>; Ketan Talaulikar
>>>(ketant) <ketant@cisco.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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>>>>OSPF@ietf.org
>>>>https://www.ietf.org/mailman/listinfo/ospf
>>>
>>
>
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