[Info-vax] SMTP chunk sizes

[JF Mezei]

On 15-03-24 06:42, Jan-Erik Soderholm wrote:

> How does a simple plain FTP perform over the same NIC?

I have found that FTP on VMS underperforms by large amount, even when
you adjust various FTP logical names. However, the idea is good. But
unlikely the user will be allowed to test FTP to that SMTP server.

> I have seen weird results from miss-configured full/hald duplex

I agree.

The DATA phase of plain old SMTP should really be sent at line speed and
received at line speed by receiving SMTP server. There is no
*application* interaction during the transfer, only TCP level ACks to
indicate the remote end has received the data.

What is the OP's upload speed ? The timeouts do happen for large files
at slow upload speeds (think dialup).

Again, Wireshark is yoru friend here. Find out what happens at the
packet level. How long does it take for an ACK to come back ? Do ACKs
start off fast and then stop ? This could be indication of the
application at other end not reading the data from the link, so that
machine's TCP stack will reaslise buffers are full and stop ACKing packets.

If there is a problem with the link, using chunking would not solve the
problem.