The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: beginner's query
On Thu, 20 May 2004 09:50:18 +0100 (BST), Puddinhead Wilson <puddinghead_wilson007@yahoo.co.uk> wrote: > I would appreciate if someone could help me understand > this: > > 4.3.5. Loops > > While the EXPLICIT_ROUTE object is of finite length, > the existence of loose nodes implies that it is > possible to construct forwarding loops > during transients in the underlying routing > protocol. This can be > detected by the originator of the explicit route > through the use of > another opaque route object called the RECORD_ROUTE > object. The > RECORD_ROUTE object is used to collect detailed > path information and > is useful for loop detection and for diagnostics. > > > #1. Does this not assume every intermediate node in > the LSP that has been setup a unique identifier? TE signalling in general always assumes that every node has a unique identifier, most commonly referred to as the Router ID. > #2. If such a scenraio does occur, ie. an LSP is > indeed setup where there is a loop, and there are no > constraints specified, is it safe to assume that there > is a loop in the original topology itself? No, I don't think that's always true. If the ERO is part stric and part loose, and the strict part sends a reservation in effect off of the shortest path tree to a destination, then an expanding node (the one that deals with the loose ERO) may well decide to send the reservation back down the shortest path tree and cross the segments it's already gone over. This seems like the sort of thing that could be easily safeguarded against in an implementation, and I've never run into this issue in the real world, so I'm kinda speculating here. You could even hit this, I suppose, with a succession of loose EROs. But certainly with *no* ERO, if there's a loop in signalling it's because there's a loop in the routing. eric > > --- Sunil Menon K <k_sunilmenon@rediffmail.com> > wrote: > >> HI Sundeep, >> >> An good starting point would be some wonderful Cisco >> presentations on Traffic Engineering by the MPLS >> Gurus ,Robert Razakus and Eric Osborne. >> >> Thanks, >> Sunil >> >> On Thu, 20 May 2004 Sundeep Singh wrote : >> >Hi, >> >I fail to understand the format of the "Path >> message" as specified in RFC >> >3209. what does the different types of brackets >> signify? >> >And say i wish to reserve 10kbps of bandwidth for a >> particular FEC, how is >> >this conveyed using a Path message? >> >Also is there some good reference other than the >> RFC, where i can look for >> >a better understanding of RSVP-TE. >> > >> >Thanks, >> >Sundeep. >> >-- >> > >> >------- >> >The MPLS-OPS Mailing List >> >Subscribe/Unsubscribe: >> http://www.mplsrc.com/mplsops.shtml >> >Archive: >> http://www.mplsrc.com/mpls-ops_archive.shtml >> > > > > > > ____________________________________________________________ > Yahoo! Messenger - Communicate instantly..."Ping" > your friends today! Download Messenger Now > http://uk.messenger.yahoo.com/download/index.html > > ------- > The MPLS-OPS Mailing List > Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml > Archive: http://www.mplsrc.com/mpls-ops_archive.shtml ------- The MPLS-OPS Mailing List Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml Archive: http://www.mplsrc.com/mpls-ops_archive.shtml
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