[Info-vax] interconnect nodes

[Stephen Hoffman]

On 2020-11-24 22:38:48 +0000, Edgar Ulloa said:

> I have this scenario
> 3 ovms 8.4 nodes each in a city
> node B communicates well with A and C
> nodes a and c there is no communication between them.
> If I have no way to intercommunicate them via routers or physical gategays,
> is there any way to make them communicate with each other using node b 
> as if it were a gateway?
> the communication will be sftp ssh telnet
> this can?
> any ideas?


If you're referring to clustering and not networking...



SCS does not support nor implement SCS routing.

Each cluster member host needs a direct path to every other host within 
a cluster.

This is the so-called rule of total connectivity,

Cluster communications are available via select point-to-point or 
multi-point links (e.g. DSSI, CI), via LAN, or via bridged LAN, or via 
SCS over IP, or a mixture.

Cluster communications links must officially be a minimum of slow 
Ethernet (10Mbps) speed, but links that glacial are badly prone to 
congestion stalls.

For this cluster configuration...

If a cluster connection from "A" to "C" via "B" is unavailable, "A" and 
"C" will detect the cluster partitioning and will stall pending manual 
recovery.

You'll either need a link from "A" to "C" that does not pass through 
"B"—whether SCS via IP or otherwise—for this to work when the "B" site 
tips over.

Or you'll want to downgrade "A" or "C" to a non-clustered 
configuration, and relocate periodic backups or otherwise replicate 
data to the downgraded site.



If you're referring to IP networking and not clustering...


Your link choices are much wider than with clustering, but you'll still 
need local internet connections or dedicated links around the "B" site 
for redundancy.

But if you're not interested in link redundancy, then it is 
possible—awkward, clumsy, expensive—to set up OpenVMS as either a 
DECnet router or an IP router.

With IP and with no interest in link redundancy, it'd be fairly typical 
to have "A", "B", and "C" in separate IP subnets, and then install a 
(cheap) router at "B", and off you go.

OpenVMS—pretty much any server—makes a rotten IP router. Or DECnet 
router, for that matter.

If you're centrally asking how to set up OpenVMS as an (awkward) IP 
router, check the docs for whichever IP stack you're using.

Though far more typically, existing IP network links provide this 
configuration without using the OpenVMS host at "B" site as a router.



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Pure Personal Opinion | HoffmanLabs LLC