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

"Acee Lindem (acee)" <acee@cisco.com> Thu, 27 July 2017 21:49 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: Thu, 27 Jul 2017 21:49:07 +0000
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Subject: Re: [OSPF] I-D Action: draft-ietf-ospf-link-overload-07.txt
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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.

  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>et>; Peter Psenak (ppsenak)
><ppsenak@cisco.com>o.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>om>; Ketan Talaulikar
>>(ketant) <ketant@cisco.com>om>; 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/
>>>>
>>>> _______________________________________________
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>>>> .
>>>>
>>>
>>>_______________________________________________
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>>
>