[Simh] Ultrix network issues

[Mark Pizzolato]

Hi Douglas,

On Thursday, November 15, 2018 at 8:50 AM, Douglas Hall wrote:
> I've been successfully running Ultrix 4.5 on a Microvax3900 sim , but I've had
> problems with networking since migrating the sim to a Xen DomU host.
> 
> TCP network performance for file transfers is painfully slow. I've reproduced
> the problem with ftp and rcp. After an initial flurry of traffic Ultrix only
> responds to incoming tcp packets after, in some cases, as much as 2 minutes
> later.  Interactive sessions seem to have no problems.
> 
> The only thing that has changed has been the migration to Xen (it was
> previously running on a Vmware ESxi host) and a change from tap to raw
> ethernet interfaces.  The underlying OS (Debian Stretch) and the Ultrix install is
> identical between systems.
> 
> I've got other OSs working fine with no network issues, various VMS versions.
> 
> Anyone got any pointers, or have also seen similar issues with Ultrix?
> 
> Running latest simh code from GitHub.

From what you've said here, not being a Xen user myself, it is not 100% clear 
exactly what's running where.

Is it: Ultrix on simh running on Debian Stretch running under Xen?
OR:  Ultrix on simh running on Xen running under Debian Stretch?
OR: Something else...?

Without regard to that, if you:
1) Stop the VMS instance running under your configuration
2) Stop the Ultrix instance running under your configuration
3) Change the Ultrix's configuration file to attach the VMS instance's boot disk image
4) Start simh with the otherwise unchanged Ultrix configuration 
5) Confirm that networking with the VMS OS running in the simh Ultrix simulator is absolutely normal or if it exhibits issues similar to the Ultrix OS's behavior.

Let us/me know what happens.

Good Luck.

- Mark