[137480] in North American Network Operators' Group
Re: Packet over SONET failback
daemon@ATHENA.MIT.EDU (Rob Evans)
Mon Feb 14 06:47:35 2011
In-Reply-To: <301B4391-D67C-4106-8DF8-FC4021DCCB3F@lixfeld.ca>
Date: Mon, 14 Feb 2011 11:47:29 +0000
From: Rob Evans <internetplumber@gmail.com>
To: Jason Lixfeld <jason@lixfeld.ca>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> PoS failure detection happens in under 50ms, but what about the failback?=
=A0Same deal? =A0I ask because I've got two routers connected to opposite =
ends of a spare PoS link that I've been playing with and I'm noticing that =
the failback on the far side seems to be about 15 seconds (assuming the nea=
r side failover was initiated with an interface shutdown command and thusly=
no shut'd to re-enable the link).
I think there are a couple of issues at play here. First of all,
SONET/SDH restoration happens at layer 1, whereas it looks like you're
waiting for a router to reroute. Your reroute times will be tied to
recalculation of IGPs.
Secondly, is this with a Cisco? Try setting "pos ais-shut" on both
sides. Unless you do that, the router won't generate and AIS, and it
will take the encapsulation timeout (HDLC, PPP) for the interface on
the other side to go down and signal that to the routing protocols on
top.
Rob
