[e2e] bytes vs. packets

Dave Crocker dhc2 at dcrocker.net
Sat Aug 9 07:46:26 PDT 2003


VS> contributor has for years bemoaned the great mistake made in TCP of
VS> counting bytes instead of records as in x.25 and as far as I can tell
VS> never did understand the TCP window.

I'd like to get a bit of discussion on this choice.  Not debate about
TCP, but clarification about the trade-off in the choice between
datagram-counting and byte-counting.

The DCCP spec uses packets, not bytes, and it is being produced by
knowledgeable folk.  So it's worth being clear when each choice makes

Also the absence of a record-marker in TCP has often been a pain. Now, I
can understand separating application-level constructs, like "record"
from network-level transfer constructs, like datagram. However the need
for record markers is considerable.

As I recall, the compelling argument for byte-counting, in TCP, was that
TCP was permitted to re-frame the data, as it saw fit.  So there was no
guarantee that the datagram boundaries would be preserved.

 Dave Crocker <mailto:dcrocker at brandenburg.com>
 Brandenburg InternetWorking <http://www.brandenburg.com>
 Sunnyvale, CA  USA <tel:+1.408.246.8253>, <fax:+1.866.358.5301>

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