[77678] in North American Network Operators' Group
RE: Rapidly-variable routing on the time scale of seconds to minutes?
daemon@ATHENA.MIT.EDU (Charles Shen)
Mon Jan 31 22:18:06 2005
From: "Charles Shen" <charles@cs.columbia.edu>
To: "'James'" <haesu@towardex.com>
Cc: "'John Fraizer'" <nanog@enterzone.net>, <nanog@merit.edu>
Date: Mon, 31 Jan 2005 22:17:20 -0500
In-Reply-To: <20050201030839.GA63085@scylla.towardex.com>
Errors-To: owner-nanog-outgoing@merit.edu
> On Mon, Jan 31, 2005 at 09:59:39PM -0500, Charles Shen wrote:
> [ snip ]
> >
> > >From the responses, the answer to "the rapidly-variable routing on
> > >the time
> > scale of seconds to minutes" seems to be:
> >
> > 1. It could be link layer load balancing, with the two interfaces
> > belonging to the same router. 2. It could be per-flow load
> balancing
> > where flows are defined via both L3 and L4 info, so
> traceroute probe
> > could not reflect the truth.
> >
> > My question is then: would it be safe to argue that the above two
> > causes explain all (or most of?) the observed "fluttering" routers?
> > (some examples listed below) What we are concerned about is
> > per-packet load balancing (packets in the same flow go through
> > different paths), which will cause trouble to protocols
> that install
> > state information in routers along the flow path.
>
> AFAIK, multiple routers showing up in a single-hop in
> traceroute response is a sign of packet-by-packet load
> balancing, not flow based.
>
> I could be wrong, though this was my past observation.
>
> P.S.: What router-interacting applications are you using?
>
I am talking about e.g. QoS reservation signaling applications.
