[137481] in North American Network Operators' Group
Re: Packet over SONET failback
daemon@ATHENA.MIT.EDU (Jason Lixfeld)
Mon Feb 14 07:53:54 2011
From: Jason Lixfeld <jason@lixfeld.ca>
In-Reply-To: <AANLkTinMLYkf40eU8GxcFQi254CGNDgNBi3L_JpoaYCc@mail.gmail.com>
Date: Mon, 14 Feb 2011 07:53:38 -0500
To: Rob Evans <internetplumber@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 2011-02-14, at 6:47 AM, Rob Evans wrote:
>> PoS failure detection happens in under 50ms, but what about the =
failback? Same deal? I 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 near side failover was initiated with an interface =
shutdown command and thusly no shut'd to re-enable the link).
>=20
> 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.
>=20
> 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.
It's becoming clear from the responses that my initial post was lacking =
a bit of info.
It's not actually SONET all the way through. It's GigE from the router =
to the SONET node, an unprotected OC192 wave to another node, out GigE =
to the far end router.
I didn't mention that because I didn't think it mattered; I assumed the =
speed in which the GigE on the other side came up was protocol agnostic. =
I assumed that as soon as the far end of the SONET node saw the near =
end go back up, it would turn the laser back on on the far side bringing =
the interface back up. I assumed also that since it took a whole 15 =
seconds that it had something to do with the SONET side of things.
I'm not necessarily talking about forwarding of packets here, I'm =
talking simply about the time it takes the far side interface to come =
back up over a SONET node; layer 1. Maybe this has nothing at all to do =
with SONET, I dunno :) It was gleaned that the next step might be to =
look at the SONET node and see if it's waiting 15 seconds to turn the =
laser back on or something.=
