[HECnet] Re: DDCMP Connection issues via PyDECnet

Hm. The command "MNC SET CIR IP-0-5 MODE DDCMP" should have given a warning that this has been deprecated. In essence, it does nothing. All links are just multinet links, which is DDCMP, with a small header to just get whole packets when using TCP.   Johnny

On 02/03/2026 17.38, Johnny Billquist wrote: > I don't think I've ever tried that DDCMP mode. I don't even remember what it does... > > Why are you wanting to use it? > >    Johnny >

> On 02/03/2026 17.35, John H. Reinhardt wrote: >> Greetings! >> >>    Mentioning pyDECnet might be a red herring, but that's what I'musing 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 errorslike this: >> >> >>     02:53:40  MLTNET - IP-0-5 Incoming packet sizeerror (1541) from >>                76.213.76.105:51354. Abort. >>     02:53:42  MLTNET - IP-0-5 Incoming packet sizeerror (1541) from >>                76.213.76.105:34404. Abort. >>     02:53:44  MLTNET - IP-0-5 Incoming packet sizeerror (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 canI look? >> >> Regards, >>    John H. Reinhardt