From: Evan Martin (martine_at_danga.com)
Date: Mon Mar 01 2004 - 01:06:49 PST
Some students made the simplifying assumption that connections can be
identified by three values: the remote address, the local port, and the
remote port. "The local address is always the same," the reasoning
went, "so why store it?"
This is fine for fishnet, but I want to remind you that there is a
reason it's taught as a four-tuple. Consider the situation of a group
of people who pay to run computers on addresses 1,2,3,4 to host their
websites. But they don't get much traffic, so they realize they can pool
their resources and share one computer. They set this one computer up
to respond as addresses 1 through 4, so if, for example, a customer at
address A connects to all four of their websites, the incoming syns will
look different: A to 1:80, A to 2:80, etc. and each can result in
producing the appropriate company's website.
Similarly, the whole point of routers between subnets is that the
routers simultaneously sit on two separate networks and forward packets
between the two. (In the router's case, they would likely have separate
hardware to plug into each network, so it might be implemented
differently internally. But if all packets are processed by the same
receiveTransport() function, it's important to distinguish packets from
one side from packets from the other.)
Anyway, Fishnet assumes each node has one address, so it's not really an
issue for your assignments.
-- Evan Martin martine_at_danga.com http://neugierig.org _______________________________________________ Cse461 mailing list Cse461_at_cs.washington.edu http://mailman.cs.washington.edu/mailman/listinfo/cse461
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