[HECnet] Is MIM running?

[Paul Koning]

> On Oct 21, 2021, at 5:40 AM, Tomas Prybil <tomas at prybil.se> wrote:
> 
> Here is a small tcpdump with the ping from A34RTR (34.1023) and FORGER (34.101) for anyone to dig into.
> Full pcap file added as attachment.
> 
> 10:29:02.072710 34.1023 > 34.101 100 link-service 35839>34917 seg 0 dat seg count 0
> 10:29:02.082747 34.101 > 34.1023 28 disconn-confirm 34917>35839 no link terminate ...

Thanks, that's what I thought I saw at some point in the past.  So that's a type of "ping" that requires only NSP layer behavior; it sends a message to a connection number that doesn't match a currently open connection, so the other end rejects it with a "no link terminate" message.  That answer is treated as the ping response.

"traceroute" was mentioned.  That could be done, at least a rough approximation, in a similar way using defined routing and NSP layer mechanisms.  It would involve sending that message with "request return to sender" set in the routing header, and a visit count that counts down from the limit.  That's not a precise solution because the message will be returned to sender by a router whose "max visits" is less than what's in the message header.  That value can vary, so some of the routers on the path might be missed.  IP avoids this by counting down "time to live" to zero, rather than counting up "visits" to a node-dependent limit.

I'll put it on the PyDECnet wish list.

	paul