25 Feb
2020
25 Feb
'20
3:43 p.m.
On Tuesday, February 25, 2020 at 6:31 AM, Paul Koning wrote:
It is not merely TCP:
PDP-11 simulator V4.0-0 Current git commit id: 146f05d1
sim> help dmc attach
Device DMC is currently disabled
DMC device attach commands:
DMC help. Type <CR> to exit, HELP for navigation help
Attach
The device must be attached to a receive port, use the ATTACH command
specifying the receive port number.
sim> ATTACH DMC0 port
The Peer host:port value must be specified before the attach command.
The default connection uses TCP transport between the local system and
the peer. Alternatively, UDP can be used by specifying UDP on the
ATTACH command:
sim> ATTACH DMC0 port,UDP
DMC Configuration?
The commits that added this help (and the related functionality) were in late 2013.
- Mark
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.