The MPLS WG Archive

[Enke Chen <enke@redback.com>]

Hi, Vijay:
Playing hello/keepvalive timers is not adequate for graceful restart.
Remember the primary goal of the graceful restart is to try to forward
packets along the right path during restart, which is not possible
by pure local action.  At the minimum you need to know if a LDP
neighbor has the ability to perserve forwarding state across restart.

-- Enke

> Message-ID: <D11B30C7348BD511A40700010283497B4F8A1B@GAYATRI>
> From: "Vijayanand C - CTD, Chennai." <vijayc@ctd.hcltech.com>
> To: mpls@UU.NET
> Cc: basila@future.futsoft.com, mani.balaram@wipro.com
> Subject: RE: I-D ACTION:draft-ietf-mpls-ldp-restart-00.txt
> Date: Fri, 22 Feb 2002 17:22:52 +0530
> 
> Hello all,
> I have an alternate suggestion for gracefully restarting LDP.I will just
> briefly outline it below. I don't know if this approach has any flaws.
> 
> This method involves modifying the existing Hello and Keep alive
> negotiations. Instead of negotiating them and maintaining same keep alive
> value for a session and the same hello value on both sides we need to
> maintain different timer values on both sides. This is not a major change to
> the existing protocol. If this is done then either side can dynamically
> change their Hello and keepalive values even after session initialization.
> Hence if LDP is going down gracefully it can increase its Hello and Keep
> alive values and advertise them before going down. Also the LDP going down
> can store its TCP-UDP socket info and its session/adjacency info instead of
> closing them. So the restart will be transparent to the peers. LDP may also
> override TCP keep alive information. This works fine when LDP alone is going
> down.  However in addition to LDP if TCP/UDP are also going down then they
> should store their state info. and go down without releasing the resources,
> so that peer TCP/UDPs dont' close the sessions.
> 
> This is only a brief outline and a few more things need to be done to
> overcome other problems.
> 
> I am not sure if this approach is worthwhile.Please correct me if I am wrong
> with your valuable feedbacks.
> 
> Regards,
> Vijay 
> 
> 
>