The MPLS WG Archive

[John Drake <jdrake@calient.net>]

Actually, Ping uses the soft state nature of RSVP to rebuild control plane
state in the case
where the data plane state exists but the control plane state doesn't.  

-----Original Message-----
From: Yangguang Xu [mailto:xuyg@lucent.com]
Sent: Wednesday, August 15, 2001 2:50 PM
To: Ping Pan
Cc: mpls@UU.NET
Subject: Re: [Fwd: I-D ACTION:draft-pan-rsvp-te-restart-01.txt]



See my reply below,

> >
> > The restart procedure you described virtually turns the RSVP from a soft
state
> > protocol to a hard state protocol.
> >
> 
> How? Please explain.
> 

>From RFC 2205 "RSVP takes a "soft state" approach to managing the
reservation
state in routers and hosts. RSVP soft state is created and periodically
refreshed by Path and Resv messages.  The state is deleted if no matching
refresh messages arrive before the expiration of a "cleanup timeout"
interval."

The "state" here is data plane state. If you separate the control and
transport
plane, you can't depend on the periodically refreshing of Path and Resv
message
to maintain the data plane state any more. Indeed, you can't even associate
the
health of control and data plane any more.

Thanks,

Yangguang