Subject: Hello Extension - destination IP address

From: "KHARE,MADHUKAR (A-NewEngland,ex1)" <[email-masked]>
Date: Tue, 13 Nov 2001 07:48:21 -0700

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?

---

From: David Charlap <[email-masked]>
Date: Tue, 13 Nov 2001 12:34:51 -0500

"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".
> 

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.

-- David