2 Mar
2026
2 Mar
'26
5:35 p.m.
Greetings!
Mentioning pyDECnet might be a red herring, but that's what I'm using to
connect to HECnet so I'm mentioning it. I'm trying to connect to Mark
Matlock's RSX11M.COM (Static IP:216.177.191.101) and we are getting some weird
errors.
My pyDECnet circuit line looks like this - modeled after Supratim's circuit config
that he sent me last year.:
circuit DDCMP-30-1 DDCMP tcp:60001:rsx11m.com:7728 --t3=15 --cost=9
On Mark's side he has an RSX11M host as the area router and the connection for me
is set up thusly:
MNC SET CIR IP-0-5 MODE DDCMP
MNC SET CIR IP-0-5 TCP HOST 0.0.0.0:0 PORT 7728
NCP SET CIR IP-0-5 STA ON
The connection isn't working. Mark is seeing errors like this:
02:53:40 MLTNET - IP-0-5 Incoming packet size error (1541) from
76.213.76.105:51354. Abort.
02:53:42 MLTNET - IP-0-5 Incoming packet size error (1541) from
76.213.76.105:34404. Abort.
02:53:44 MLTNET - IP-0-5 Incoming packet size error (1541) from
76.213.76.105:34412. Abort.
The A17RTR node has what look to be the normal settings. the Segment buffer size is
normal for DDCMP.
NCP>tell a17rtr show exe char
Node Volatile Characteristics as of 2-MAR-2026 09:35:20
Executor node = 17.1023 (A17RTR)
Identification = THEMIS2 - A17RTR - DECnet/Python Area-17 Router at Saginaw,
TX (DFW)
Management version = V4.0.0
Software identification = DECnet/Python V1.1.0
Incoming timer = 30
Outgoing timer = 30
NSP version = V4.0.0
Maximum links = 4095
Delay factor = 32
Delay weight = 3
Inactivity timer = 300
Retransmit factor = 5
Routing version = V2.0.0
Type = area
Maximum area = 63
Area maximum cost = 128
Area maximum hops = 16
Segment buffer size = 576
Does anyone know what causes the packet size to be bigger than normal? The ethernet
interface on the pyDECnet host is set to 1500MTU as is my firewall/router.
Where else can I look? I don't see anything in the pyDECnet documentation that
talks about DDCMP packet size. Where else can I look?
Regards,
John H. Reinhardt