25 Feb
2020
25 Feb
'20
3:31 p.m.
On Feb 24, 2020, at 9:44 PM, Peter Lothberg <roll
at Stupi.SE> wrote:
I would not recomend DDCMP over TCP, as you have no idea what the
TCP implementaion does for timers etc and TCP is streams, you need
to identify the packet boundaries.
DDCMP over TCP has been part of SIMH for quite some time.
The stream nature is not an issue, of course. DDCMP over wires also has a stream physical
layer and knows how to do packet framing perfectly well. The answer is the same in both
places: header CRC framing.
DDCMP over UDP gives DDCMP full control over
retransmit timers etc
for making the connection reliable and what the actual netwrk is doing
is visible to the DDCMP layer.
That's true. Then again, DDCMP does not have any congestion control or timer
adjustment or other things that are useful when sending frames over IP network as opposed
to fixed delay wires that don't congest.
As I mentioned, if you have PyDECnet at both ends, you can use DDCMP over UDP. If
you're using SIMH, you're limited to what it implements, which is DDCMP over TCP.
paul