The MPLS WG Archive

[Dimitrios Pendarakis <DPendarakis@tellium.com>]

David,

I agree with Lyndon's comment. If you read through the rest of
my email, you 'll see that the discussion is not about the 
ability of RSVP Hello to detect link failures:

DP> LMP hello allows you to detect 
DP> individual link (or control channel) failures; RSVP Hello allows
DP> you to detect that you 've lost contact with your signaling peer
DP> for whatever reason (failure of all redundant control channels, 
DP> failure of the RSVP daemon, etc.).

Thanks,
Dimitrios

> -----Original Message-----
> From: Lyndon Ong [mailto:lyndon_ong@eudoramail.com]
> Sent: Wednesday, May 30, 2001 12:05 PM
> To: mpls@UU.NET; David Charlap
> Subject: Re: Last call - RSVP problems
> 
> 
> Hmm, I'm confused here - I did not think the discussion was 
> about RSVP Hello's function, it's understood to be detecting
> node failure rather than link or control channel failure.
> 
> I thought the question was whether RSVP Hello was necessary if
> you have an alternative way of detecting control channel
> failure, in which case you can tell when there are no control
> channels left standing.  Detection of control channel failure
> could be through LMP Hello or if you have some alternative 
> means, like monitoring control channel error rates.
> 
> Cheers,
> 
> Lyndon
> --
> 
> On Wed, 30 May 2001 10:55:39   David Charlap wrote:
> >Dimitrios Pendarakis wrote:
> >> 
> >> Could you please clarify why you think RSVP Hello doesn't work for
> >> parallel (redundant) control channels?
> >
> >RSVP Hello messages are sent between adjacent IP addresses.  If there
> >are multiple unnumbered links between two routers, only one set of
> >Hellos are generated for all the links.  If the multiple 
> links are all
> >numbered, then Hello messages are sent for each of the links.
> >
> >As a result of this, RSVP Hello can only detect link failure when all
> >links between two routers are numbered.  If there are 
> unnumbered links
> >between two routers, Hellos will not be interrupted until all of the
> >links fail - meaning it will only detect node failure.
> >
> >-- David
> >
> 
> 
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