Hi Shraddha, If this is truly TE, why would you use the OSPF prefix/link attribute instead of the actual TE metric specified in RFC 3630? Thanks, Acee
On 9/29/15, 1:05 PM, "Shraddha Hegde" <[email protected]> wrote: >Acee, > >I am not sure if I am able to convey what I mean by the "controller use >case" in the previous mail thread. Here is another attempt to explain the >use case. > >With metric change there is no guarantee that LSP will move to a >different path. If the current path satisfies all constraints of the LSP >and there is no better path >Satisfying the constraints then the LSP would remain up and very much on >the link that is going to be replaced. I mentioned in another mail >thread, the high metric is >Usable metric and does not mean "link down". > >Link maintenance is a special scenario. The LSP MUST move out of the >link. Controller can take special actions if it knows the link is in >overload state >For Ex: Relax certain constraints of the LSP for the duration of >maintenance and move the LSP on a different path. >All these activities should happen in a non- disruptive fashion for the >service and that’s the reason the link metric cannot be changed to >max-metric (0xffffffff) > >If the "link overload" information remains at the link level, controller >needs to take action based on metric alone. >It might work for most cases assuming there are better alternate paths >satisfying same constraints but we cannot guarantee >LSPs will move from the link in all cases. If we consider a case when >multiple links in the network go for maintenance/replacement >simultaneously >then there is higher probability that alternate paths satisfying the >constraints can't be found and controller needs to perform special >actions to >move the LSPs around. > >IMHO, "link overload" is a characteristic of the link just like color, >bandwidth etc and it makes sense to flood it area wide just like other >attributes of the link. > >Rgds >Shraddha > >-----Original Message----- >From: Pushpasis Sarkar >Sent: Tuesday, September 29, 2015 8:27 PM >To: Acee Lindem (acee) <[email protected]> >Cc: Shraddha Hegde <[email protected]>; OSPF WG List <[email protected]>; >Hannes Gredler <[email protected]>; Mohan Nanduri ><[email protected]>; Jalil, Luay <[email protected]> >Subject: Re: OSPF Link Overload - draft-hegde-ospf-link-overload-01 > >Hi Acee, > > > > >On 9/29/15, 8:15 PM, "Acee Lindem (acee)" <[email protected]> wrote: > > >>I apologize if I offended you. I just wanted to avoid the circular >>discussions and repetition of information having no bearing on the >>issues raised. >[Pushpasis] No no. You have not offended me in any ways. So we are good >then. I was worried that I might have offended you instead. :) >> >> >>> [Pushpasis] Like mentioned already, and again in my opinion, this will >>>help the controller deal with scenarios where it needs to distinguish >>>between situations in which a link has been administratively put into >>>‘out-of-order’ from situations where the link has degraded to a >>>‘malfunctioning’ state and needs attention. Unfortunately I cannot come >>>up with a use-cases how this distinction can be used (other than >>>diverting service traffics away from the links). Perhaps some of the >>>operators may throw more light. >> >>I’d like to hear from the operators (especially the authors Luay and >>Mohan). >[Pushpasis] Me too :) >> >> >>> >>> >>> Hoping I have not failed to communicate once more. If you still feel >>>so, please let me know. And I will refrain myself from answering on >>>this thread further. >> >>I think we are communicating now - the main question is what does this >>link-maintenance condition needs to be flooded throughout the OSPF >>routing domain when it seems that link-local signaling would offer a >>much more straight-forward solution. The response so far has been, “For >>the controller use-case” without any explanation of why increasing the >>forward and reverse metrics isn’t enough (especially since you are doing >>this anyway for backward compatibility). Les Ginsberg raised the same >>point. >[Pushpasis] I will not further exaggerate my already-expressed reasoning >as I do not have a definite use case in hand. Hoping some operators in >the working group may have more solid use-cases for this. > >Thanks and Regards, >-Pushpasis > >> >>Thanks, >>Acee _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
