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From: acliu@skat.usc.edu (Alex C. Liu)
Newsgroups: comp.sys.cbm
Subject: Re: kermit vs. xmodem - was Re: kermit problem
Summary: Punter Faster than Xmodem?
Keywords: Punter vs. Xmodem
Message-ID: <24010@usc.edu>
Date: 10 Apr 90 01:27:51 GMT
References: <14836@s.ms.uky.edu> <1424@ac.dal.ca>
Sender: news@usc.edu
Organization: Maze Inc.
Lines: 32

In article <1424@ac.dal.ca> mike@ac.dal.ca writes:
>Sorry, only Punter Protocol transfers 256 bytes... Standard Xmodem does 128
>bytes, and Xmodem1-K does 1024 at a time.. and xmodem is very much
>faster than kermit... and punter is faster still...

Actually, Punter and Xmodem have around the same software overhead.

Let's see,
Xmodem uses a 4 byte header per 128 bytes or 5 bytes in the case of
Xmodem CRC.  So in average Xmodem blocks are 132 bytes long.

punter needs a 7 byte header per 255 bytes.  (Note, Punter uses 255
byte blocks, not 256 bytes!)  That is 263 bytes per block.

For HandShacking, Xmodem sends single byte codes i.e. <ACK> and <NAK>s
Punter uses a more Complex protocol that instead of sending a single
Byte Code would seend a 3 byte code plus another 2 3 byte codes for
control.  In other words, it would transfer 9 bytes in between blocks.

Now, in order to send 128 bytes, Xmodem will add 5 (or 6 in the case
of CRC mode) extra bytes.  Punter for every 255 bytes, would send 16
extra bytes.  So in average Punter is sending about 8 extra bytes per
each 128 bytes.

From this, I would say that Punter has a LOT more overhead than
Xmodem.  But, Punter DO have some advantages over Xmodem, in the sense
that Punter is a lot more robust than Xmodem, and it will not increase
the file size.
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Alex C. Liu                   | INTERNET: acliu%skat@usc.edu
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