Re: [Cse461] Re: Question 5

From: Janet Davis (jlnd_at_cs.washington.edu)
Date: Tue Feb 10 2004 - 13:11:01 PST

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    On Tue, 10 Feb 2004, Dung Nguyen wrote:

    > Could you please define loop? does it mean that a node see a packet twice?
    > or a node processes a packet twice?

    A routing loop means that, for some destination, the next-hops in the
    nodes' routing tables form a loop. Temporary loops can form while routing
    tables are being updated after a failure.

    In the case of Fishnet, this would mean a node sees the same packet twice.

    In the case of the Internet, there is no sequence number to stop a router
    from processing a packet twice. (Why would you not want to keep track of
    per-source packet sequence numbers in Internet routers?) This means the
    packet could actually go around in a loop and be forwarded more than once
    by the same routers.

    Cheers,
    Janet 

    -- 
Janet Davis
jlnd_at_cs.washington.edu
http://www.cs.washington.edu/homes/jlnd/
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