Eric,
Fast reroute or local protection may be used only be a temporary or
short-term mechanism while a long term solution is to use path
protection because the head node is the best router to decide end-to-end
constraints (Please correct me if iam wrong).
So i thought there should be some mechanism for fast notification to the
head node instead of using the slow PathERR messages.Another aspect is
reliability with which the PathErr message is dispatched to the ingress
or head-node.Since rsvp messages may get lost,
does cisco IOS provide the ack mechanism as given in the
draft-ietf-rsvp-refresh-reduct.txt?
Thanks a lot,
Krishna
Eric Osborne wrote:
>
> On Thu, Jun 21, 2001 at 07:46:47AM -0700, Krishna Doddapaneni wrote:
> > Hi Eric,
> > Thanks for your reply.
> > If i configure path protection the way suggested by you.How would the
> > ingress router or the head node be notified when a failure occurs in the
> > path? Does it use PathERR message or uses special notifiaction message
> > as specified by draft-chang-mpls-path-protection(A path/Restoration
> > Mechanism for MPLS Networks)?
>
> There's no special mechanisms just because you changed the autoroute
> metric. The headend finds out via a PathERR (or IGP flood change, the
> two race) that its path is no longer valid. What pre-establishing the
> backup tunnel does for you is to save the time it would take to
> re-calculate a new path if necessary (milliseconds, trivial) and
> re-signal that path (RSVP, milliseconds to seconds, can be longer than
> you'd like).
>
> eric
>
> > Thanks a lot,
> > Krishna
> >
> > Eric Osborne wrote:
> > >
> > > On Tue, Jun 19, 2001 at 03:43:36PM -0400, Krishna Doddapaneni wrote:
> > > > Hi Guys,
> > > > Does cisco supports path protection in MPLS ?In the cisco website i saw
> > > > the support for only link protection.Is Cisco thinking of supporting
> > > > node protection in the near future?
> > >
> > > Are you asking about node protection, or path protection?
> > >
> > > Both are at varying stages of work - have your favorite cisco sales
> > > folks get in touch with me if you want more info.
> > >
> > > You can do a limited path-protection-like thing now by
> > >
> > > - configuring 2 tunnels to the same destination
> > > - making sure they don't take the same physical path (this can be
> > > tricky to do large-scale or with any dynamicity (is that a word?))
> > > - configure the "primary path" with
> > > tunnel mpls traffic-eng autoroute metric relative -2
> > > - and the backup path with
> > > tunnel mpls traffic-eng autoroute metric relative -1
> > >
> > > <obCisco>
> > > path protection is nifty, but IMHO doesn't scale that well. Link and
> > > node protection are far more scalable. There are a few cases where
> > > path protection is useful, but not as many as people seem to think...:)
> > > </obCisco>
> > >
> > > eric
> > >
> > > > Thanks in advance,
> > > > Krishna
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