[HECnet] Booting VMS 5.5.2 cluster satellite node [SIMH 4.0] over slow link

[Vladimir Machulsky]

Hi, guys!

I'm trying to boot latest SIMH (4.0-current) as LAVC satellite node over
link with latency about 100ms.
Boot node is VAX/VMS 5.5.2 with latest PEDRIVER ECO.
Result: MOP part of boot sequence is work without a hitch, but SCS part is
failing miserably. 

The most frequent result:
SIMH console filled with 10 x " %VAXcluster-W-NOCONN, No connection to disk
server " messages, halting with 
"%VAXcluster-F-CTRLERR, boot driver virtual circuit to SCSSYSTEM 0000
Failed"
Sometime it goes little further:
...
%VAXcluster-W-RETRY, Attempting to reconnect to a disk server
%VAXcluster-W-NOCONN, No connection to disk server
%VAXcluster-W-RETRY, Attempting to reconnect to a disk server
%VAXcluster-W-NOCONN, No connection to disk server VULCAN
%VAXcluster-W-RETRY, Attempting to reconnect to a disk server
%VAXcluster-W-NOCONN, No connection to disk server
%VAXcluster-W-RETRY, Attempting to reconnect to a disk server
%VAXcluster-I-CONN, Connected to disk server VULCAN
%VAXcluster-W-NOCONN, No connection to disk server VULCAN
%VAXcluster-W-RETRY, Attempting to reconnect to a disk server
...
And halting after minute or so of filling console with those messages.

Whenever I setup throttling in SIMH to 2500K ops/s, the node boots
successfully, 
joins cluster successfully and work flawlessly, but slow. 
Boot process takes about half hour. After boot, changing throttle value to
3500K ops/s still works. 
Increasing throttle value further broke system, with the same messages about
disk server.
Throttled SIMH performance is about 5VUPS. 

The only information about maximum channel latency restrictions found in 
"Guidelines for OpenVMS Cluster Configurations" manual is that:
"When an FDDI is used for OpenVMS Cluster communications, the ring latency
when the FDDI ring is idle should not exceed 400 ms."
So I suppose that 100ms latency link should be good enough for booting
satellite nodes over it. 

My understanding of situation is that combination of PEDRIVER/[PEBTDRIVER
within NISCS_LOAD] with fast hardware 
and slow links is a primary reason of such behavior. Please correct me if
I'm wrong. 

Do anyone have experience with booting VMS clusters over slow links? OS
version recommendations? 
Probably some VMS tunable variables are exists for making PEDRIVER happy on
fast hardware? 
Having PEDRIVER listings can shed lights for such PEDRIVER's buggy behavior.

Link details:

Two Cisco 1861 routers connected with Internet via ADSL on one side and 3G
HSDPA on other side. 
TCP/IP between sites is routed over IPSec site-to-site VPN. Ping between
sites is about 100ms.
Over that VPN built DECnet family (eth.type = 0x6000..0x600F) bridge with
L2TPv3 VPN.

--
BR, Vladimir Machulsky