26 Nov
2022
26 Nov
'22
12:47 a.m.
There is, as far as I know, no equivalent to push, since in DECnet,
connections are never handled as a stream of bytes, but as packets, and
delivery is always immediate, and the sending side is directly informed
about the receiver actually receiving the packet. It's essentially much
more synchronous than TCP/IP. DECnet don't even necessarily buffer on
the sending side. At least with RSX, transmits goes directly from the
task out on the wire. And the send is only flagged complete when the
receiving side have received it. But on receiving side it might be in an
internal buffer and not actually delivered to the recipient task.
But I'm sure Paul remember more details.
However, one thing you do have in DECnet, which TCP/IP don't really do
well, is that you can send out of bounds, urgent data in DECnet.
Johnny
On 2022-11-26 00:05, Thomas DeBellis wrote:
In TCP, something called the 'push flag' can
be set to cause accumulated
data in the monitor (which may be one or more packets) to be sent over
the network. It is often abbreviated as "PSH".
The Tops-20 FTP client and server both set PSH on the last packet of
data from a file to send it on its way. This is done with a SOUTR% JSYS,
which stands for *S*tring *OUT* *R*ecord. This is an overloading of the
hardware record concept which is more commonly associated with
nine-track magnetic tape.
PSH can also be detected on input by doing a SINR%, which stops the
network read early, instead of waiting for a full buffer of data (which
might, in fact, never come).
I believe DECnet transport implements the same semantics, but I would
like to double check that. Where would I go in which part of what
specification? Or does anybody know?
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