The MPLS WG Archive

["Feng, Mark" <m_feng@trillium.com>]

That's not the point I am trying to make. If it is so desired that, when
there is no active sessions, the Hello exchange is stopped, this should be
done even when the neighbours are configured, instead of discovered.

As to whether to maintain the Hello exchange when there is no active
sessions, my only concern is that, by stopping the exchange, the RSVP
neighbour might think that the communication has been lost. Whether this is
OK as to the original intent of the RFC, I am not sure.

- Mark

> -----Original Message-----
> From: Hariom P [mailto:hmp123@hotmail.com]
> Sent: Tuesday, November 13, 2001 2:28 PM
> To: m_feng@trillium.com; David.Charlap@marconi.com; mpls@UU.NET
> Subject: RE: Hello Extension - destination IP address
> 
> 
> I totally agree with David. RSVP hellos are designed for "faster node 
> failure detection" and there is no point in doing this 
> detection when no 
> RSVP sessions are active between two peers..
> 
> 
> with regards,
> hmp
> 
> 
> >From: "Feng, Mark" <m_feng@trillium.com>
> >To: "'David Charlap'" <David.Charlap@marconi.com>,        
> "'mpls@uu.net'" 
> ><mpls@UU.NET>
> >Subject: RE: Hello Extension - destination IP address
> >Date: Tue, 13 Nov 2001 13:26:32 -0800
> >
> >I agree with most of the comments; but I have one doubt. Please see 
> >comments
> >below.
> >
> >- Mark
> >
> > > -----Original Message-----
> > > From: David Charlap [mailto:David.Charlap@marconi.com]
> > > Sent: Tuesday, November 13, 2001 9:35 AM
> > > To: 'mpls@uu.net'
> > > Subject: Re: Hello Extension - destination IP address
> > >
> > >
> > > "KHARE,MADHUKAR (A-NewEngland,ex1)" wrote:
> > > >
> > > > This is regarding the Hello extension for RSVP.  We are 
> unsure what
> > > > to use for the destination IP address for a Hello 
> Request message.
> > > >
> > > > The draft just says "The IP destination address is the 
> IP address
> > > > of the neighbor node".  When the first Hello Req is sent out, we
> > > > don't know the address of the neighbor node".
> > > >
> > > > Are we supposed to use a broadcast IP address first time around?
> > >
> > > No.  Hellos are not sent to broadcast addresses.  They are
> > > not used for
> > > discovering neighbors.
> > >
> > > If your router doesn't have neighbor addresses 
> configured, then you
> > > won't know your neighbor addresses until after you receive
> > > other packets
> > > from them - like Path and Resv messages.  Once you know the
> > > address, you
> > > can begin sending Hellos.
> > >
> > > If you do this (discovering neighbors for Hellos by snooping
> > > other RSVP
> > > packets), then you may want to stop sending Hellos when 
> the all of the
> > > neighbor's RSVP state is torn, since you won't be able to 
> tell whether
> > > the neighbor went offline, changed address, or simply doesn't have
> > > state.
> > >
> >
> >Why is it necessary to stop sending the Hello in this case? 
> IMO, the way 
> >the
> >Hello state machine works is independant of the means to discover the
> >neighbour. Even if the neighbour's RSVP states are gone, the 
> neighbour
> >should still respond to the Hello messages. This should be 
> applicable in 
> >the
> >case when the neighbour is configured.
> >
> >By stopping the Hello exchange, the neighbour might 
> incorrectly think that
> >there is a problem communicating with the current node.
> >
> > > -- David
> > >
> 
> 
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