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From: barmar@THINK.COM (Barry Margolin)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: problem with ftp
Message-ID: <19910211212243.8.BARMAR@OCCAM.THINK.COM>
Date: 11 Feb 91 21:22:00 GMT
References: <9102111926.AA09697@jessica.stanford.edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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    Date: Mon, 11 Feb 91 11:26:29 -0800
    From: "Philip Almquist" <almquist@jessica.stanford.edu>

    IP networks are required to support 68 octet packets without network
    layer (IP) fragmentation (RFC 791 page 25).  The Internet folklore that
    says that this number is 576 is erroneous.

Thanks for the correction.  However, it's reasonably safe to assume that
most media have an MTU of at least 512.  I can't think of any that
don't, and I would be surprised if anyone invented a new medium with a
smaller MTU (the current direction is generally towards larger packet
sizes).

    Finally, a minor nit: the standards talk about octets rather than bytes.
    Octets are eight bit quantities.  Bytes are also eight bit quantities on
    most most modern computers, but computer architecture is beyond the
    scope of the TCP/IP standards.

I know that, and I debated using "octet" in my message.  I chose to use
terminology consistent with the question.  It's rarely necessary to make
this fine distinction outside standards documents (people on systems
with non-8-bit-bytes generally know how to translate to their own frame
of reference).

                                                barmar