Date   : Sun, 01 Nov 2009 22:14:09 -0000
From   : mu.list@... (Mark Usher)
Subject: Econet packet size

Also reading through the "File server protocol interface" document, I found
the following.

It is certainly the case that it is left to the software to determine the
packet sizes, as mentioned in numerous places and the only physical
limitation is that of the network clock and timeout being reached as per my
previous post.

Bridges certainly have a fixed buffer size for forwarding packets, so could
possibly prevent some software from working as intended.

Acorn did seem to go for 500bytes as the maximum in several pieces of
software and mention it as a standard in one document, only for another such
as the excerpt below to implement a 4k buffer.

-Mark


Load file

This is the actual load operation. This protocol is used after the command
line has
been decoded, either by the file server or the local operating system.

The client initiates the exchange by sending to the file server's command
port:

Byte    Meaning

1       reply port
2       2 (function code)
3       data port
4       CSD handle
5       Lib handle
6
      file name, terminated by CR - may be wildcarded

The file server's reply is sent to the client's reply port, as specified in
the client's
initial packet (see above):

Byte    Meaning

1 - 2   standard Rx header (command code = 14 if leaf name       is
resolved,
                otherwise = 0)
3 - 6   file load address
7 - 10  file execute address
11 - 13 file size
14      file access
15 - 16 file creation date
17
     leaf name, terminated by CR, with wild-cards resolved (if returned)

The client and file server now enter the `data transfer' phase of the
protocol. If the
file is of zero length then this phase is omitted. If the file server
detects an error (eg
a disc error) then the required amount of data will be sent, but its data
content is
undefined.

The file server sends each block of data to the client's data port, as
specified in the
client's initial packet:

Byte    Meaning

1
      data blocks of undefined size repeated until `file size' data has been
                sent (maximum data block size is currently 4k)

The client does not acknowledge these packets.