The MPLS WG Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] New Internet Draft on ERO
1. You need to specify both ingress and egress identifiers for two reasons: a) On broadcast media (think GigE, 10 GigE) when a router has multiple interfaces attached to the same switch, you want the RSVP packet and MPLS LSPs to use the correct adjacency. And the only way to get that is to specify a pair. This scenario is commonly used in POP architectures where there are two GigE switches in the middle and each router has one link to each GigE switch and the GigE switches are interconnected. b) Specifying both ingress and egress is more explicit and leaves no guesswork. 2. I just asked a simple question with respect to fast reroute: How do you do it when you have unnumbered interfaces. At first thought, I thought it would be very hard to do, after thinking about it for a few minutes I think if you make certain assumptions and make extensive use of the IGP-TE database, you can possibly get by. But why? Why are we arguing over 4 more bytes in the signaling message. We don't have 56K leased line links any more. OC192c has become the standard and 768c is right around the corner. I don't see any point it haggling on four bytes. Hence we defined the EERO. I hope I cleared the "mystery" for you and Jonathan ;-) Bora At 9:24 AM -0500 2/27/01, Bala Rajagopalan wrote: >Hi, > >This is all rather mysterious. Following up >on Jonathan Lang's and Yakov's earlier questions, >could you please describe what the problem is >w.r.t fast reroute? > >Also, in your draft, what's the need to specify >both ingress and egress interface identifiers >for EERO hops? isn't one of them enough? > >Regards, > > > >Bala Rajagopalan >Tellium, Inc. >2 Crescent Place >P.O. Box 901 >Oceanport, NJ 07757-0901 >Tel: (732) 923-4237 >Fax: (732) 923-9804 >Email: braja@tellium.com > >> -----Original Message----- >> From: Bora Akyol [mailto:akyol@pluris.com] >> Sent: Monday, February 26, 2001 6:49 PM >> To: Yakov Rekhter >> Cc: Bora Akyol; mpls@UU.NET >> Subject: Re: New Internet Draft on ERO >> >> >> At 3:14 PM -0800 2/26/01, Yakov Rekhter wrote: >> >Bora, >> > >> >> My question is as follows: >> >> >> >> How do you do fast reroute when you have unnumbered >> interfaces in the >> >> ERO as in the unnumbered draft? What out of band >> information is added >> >> to what's in the ERO when we do CSPF? Is everyone doing >> it the same >> >> way? >> >> >> >> If we use the (newly defined) EERO then fast reroute is >> the same for >> >> both numbered and unnumbered interfaces and it actually >> becomes quite >> >> easy. >> > >> >Could you point me to the MPLS WG document(s) that specifies >> >how to perform fast re-route ? >> > >> >Yakov. >> >> Well, there was the ID from George Swallow that we discussed in San >> Diego. And then there were some discussions on the list that I >> participated in 1998. Vishal Sharma et al, produced IDs on that >> subject as well. >> >> >> Maybe it is time that we write a BCP on that topic. Would this fall >> into CCAMP or MPLS? In the last IETF, **all** of the fast >> reroute/recovery schemes were sent to CCAMP AFAIK. >> >> I know how we implemented fast reroute and I am sure you know of at >> least two implementations. >> >> So if there is interest on the WG, I can volunteer to put together a >> group of people to write such a BCP. >> >> But my original question still stands, >> >> how do you do fast reroute when you have unnumbered interfaces? It is >> possible to do, but becomes much easier if you have the router ID as >> part of the ERO subobject as we did in our EERO specification. Please > > see draft-akyol-mpls-exp-ero-00.txt > > > > > > Regards > > > > Bora > >
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