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Re: Rapidly-variable routing on the time scale of seconds to minutes?

  • From: James
  • Date: Mon Jan 31 22:09:42 2005

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?

-J

-- 
James Jun                                            TowardEX Technologies, Inc.
Technical Lead                      Boston IPv4/IPv6 Web Hosting, Colocation and
james@towardex.com            Network design/consulting & configuration services
cell: 1(978)-394-2867           web: http://www.towardex.com , noc: www.twdx.net




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