[HECnet] "Dropped by adjacent node" ....

[Paul_Koning at Dell.com]

On May 28, 2014, at 12:17 AM, Peter Lothberg <roll at Stupi.SE> wrote:


On May 27, 2014, at 3:17 PM, Bob Armstrong <bob at jfcl.com> wrote:

in Phase IV the hello timer value is sent in the hello message
and that value times 3 (or 2) is used for the listen timer
=20
That would explain why having LEGATO send hello messages more often
doesn't make any difference=85

If you send hellos more often, you time out sooner; either way, you time ou=
t if you lose 3 hellos in a row (or, probably just barely, if you lose two =
in a row).   The assumption is that no LAN is that badly broken.

The way to run DECnet over a flaky long distance network is to use point to=
point mode with a data link layer that deals with packet loss.   DDCMP is a=
n example of such a data link layer; X.25 is also (after a fashion).   That=
=92s what the DECnet design intended.
	paul


Putting a PTP DECnet link in TCP would do the same as DDCMP/X.25/Lapb

-P

The earlier DMC emulation in SIMH 3.9 (payload only, not DDCMP) was essentially point to point over TCP.   Yes, that gives you what DDCMP does.   It   s better than X.25/LAPB because those suffer from having a two way rather than three way handshake.

	paul