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