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Re: MIME and TCP/IP over ATM

1992-05-27 16:49:21

        From owner-ietf-822(_at_)dimacs(_dot_)rutgers(_dot_)edu Wed May 27 
13:27:29 1992
        Date: Wed, 27 May 1992 13:33:26 -0600
        To: ietf-822(_at_)dimacs(_dot_)rutgers(_dot_)edu
        Subject: MIME and TCP/IP over ATM

        I am on the brink of convincing a (very big) client that MIME/SMTP is 
the way
        to go in the immediate and shortterm future in multimedia mail.  He is
        planning to move towards ATM for local and wide area networks, but has 
a few
        questions I am having trouble answering.

        I have 2 very basic questions for those of you MIME/TCPIP experts out 

        1.  Can MIME and TCP/IP run over ATM at 100 - 622 Mbps?
            Is this being done now?

Yes, TCP is used every day over FDDI networks at 100 Mbps.  At the
upper end, Cray has reported (at IETF) ~ 800Mbps TCP operation,
although it takes a passel of buffering in the hosts.  Also, I
seriously doubt your very big client will want to spend the money to
have an entire 622 Mbps channel for a single TCP connection, so I don't
think this is a real question.

We know of no technical barrier to Gbps operation in the protocols
themselves, only a lack of fast enough host interfaces and CPUs
[RFC-1323].  There are not very many worked examples of ATM running
ANTHING at 622 Mbps, but when there are, there should be no problem in
principle in running TCP, and therefore any TCP-based application, over

        2.  At what equivalent OSI layer does SMTP run? Layer 4?
            How about MIME?

The Internet layer model does not exactly match the OSI layer model
very closely.  SMTP and MIME run in the application layer of TCP/IP,
which corresponds roughly to layers 5, 6, and 7 of the OSI model.

Bob Braden

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