Re: A network you can trust

Paul Tsuchiya (
Fri, 25 Mar 88 08:08:29 EST

There are really two issues with regards to this VC/datagram discussion.
One is what the network does, and the other is what the host does.
It seems to me obvious that the host wants to protect itself and provide
itself good service regardless of what the network claims to provide,
and so should run a strong transport like TCP. It is silly to argue
that one of the virtues of VCs is that it requires less work on the
part of the host.

Ignoring hosts, however, and just considering the network layer,
the discussion is still interesting. I like datagram in the sense
that the network isn't obligated to do sequence and guarenteed
delivery and so on, and can squash packets if it has to. However,
I like some of the "set up" notions of VC. These days, there are
many things that one might want to "set up" (or more appropriately,
cache) in the gateways along the path. These include routing
information, address information (like a Landmark Address, for instance),
VISA information. All of these things can be done without destroying
the "datagram" aspect of the network.

Some people are thinking of more sophisticated network "setup", like
rate request and assignment. This is not datagram in the sense that
the network tells you roughly how fast you can go, but it is not
VC in that the network is happy to squash packets if it needs to.

Paul F. Tsuchiya The MITRE Corp. 7525 Colshire Dr.

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