[Cse461] Re: hw2 q1

From: Janet Davis (jlnd_at_cs.washington.edu)
Date: Mon Feb 09 2004 - 10:58:56 PST

  • Next message: Janet Davis: "[Cse461] Re: hw2 #5"

    A clarification and a questions on hw2 q1:

    Clarification: Where it says "when forwarding a packet, each node sends it
    to the last neighbor that forwarded a packet from that source address",
    read, "last neighbor that forwarded a _previously unseen_ packet from
    that source address." That is, you don't update the forwarding table when
    you get a duplicate packet.

    On Sun, 8 Feb 2004, Tsz (Oscar) Ng wrote:

    > For 1a, do we assume that the network topology doesn't change while the
    > packet is transmitting (i.e. a node is added or removed)?

    Yes, please assume that the topology doesn't change for part (a).

    However, you may assume that if two paths have the same propagation delay
    to a particular node, two copies of the packet delivered along both paths
    will arrive in random order. For instance, consider this topology with
    all propagation delays equal:

      B
     / \
    A D
     \ /
      C

    If A floods a packet to the broadcast address, it's random whether the
    first copy to arrive at D will come from B or C.

    Cheers,
    Janet

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