[105809] in North American Network Operators' Group
Re: Possible explanations for a large hop in latency
daemon@ATHENA.MIT.EDU (Sam Stickland)
Tue Jul 1 20:07:58 2008
Date: Wed, 02 Jul 2008 01:07:23 +0100
From: Sam Stickland <sam_mailinglists@spacething.org>
To: Robert Richardson <bobrmr@gmail.com>
In-Reply-To: <4aebc7330806261819o6e5eda7aqd16faabfefdc5f1d@mail.gmail.com>
Cc: nanog list <nanog@merit.edu>
Errors-To: nanog-bounces@nanog.org
Even if they are decrementing TTL inside of their MPLS core, the TTL
expired message still has to traverse the entire MPLS LSP (tunnel), so
the latency reported for each "hop" is in fact the latency of the last
hop in the MPLS network. Always.
Sam
Robert Richardson wrote:
> They probably don't propagate TTL w/in their MPLS core. Depending on how
> they have MPLS implemented, you may only see 2 hops on the network; the
> ingress and egress routers. If the ingress router was in NYC and the egress
> in Seattle, you could understandably expect a large jump in RTT.
>
> Not an ATT customer but do know other providers run their MPLS core's this
> way...
>
> -Robert
>
> On Thu, Jun 26, 2008 at 6:09 PM, John T. Yocum <john@fluidhosting.com>
> wrote:
>
>
