DECNET how to change adjacent node

[Juan M. Lazaro]

Hi to all,

There is any way to change the adjacent node in a decnet network?

My executor configuration is:

NCP>sho exec char


Node Volatile Characteristics as of 16-AUG-2022 09:55:50

Executor node = 30.107 (NODO1)

Identification = HP DECnet for OpenVMS Alpha
Management version = V4.0.0
Incoming timer = 45
Outgoing timer = 60
Incoming Proxy = Enabled
Outgoing Proxy = Enabled
NSP version = V4.1.0
Maximum links = 256
Delay factor = 80
Delay weight = 5
Inactivity timer = 60
Retransmit factor = 10
Routing version = V2.0.0
Type = routing IV
Routing timer = 600
Broadcast routing timer = 180
Maximum address = 1023
Maximum circuits = 16
Maximum cost = 1022
Maximum hops = 30
Maximum visits = 63
Maximum area = 63
Max broadcast nonrouters = 64
Max broadcast routers = 32
Maximum path splits = 1
Area maximum cost = 1022
Area maximum hops = 30
Maximum buffers = 100
Segment buffer size = 1498
Buffer size = 1498
Default access = incoming and outgoing
Pipeline quota = 14980
Alias maximum links = 32
Path split policy = Normal
Maximum Declared Objects = 31

And the circuit information is :

NCP>sho k circ char


Known Circuit Volatile Characteristics as of 16-AUG-2022 09:50:36

Circuit = EIA-0

State = on
Service = enabled
Designated router = 30.107 (NODO1)
Cost = 8
Maximum routers allowed = 33
Router priority = 64
Hello timer = 15
Type = Ethernet
Adjacent node = 30.10 (NODO3)
Listen timer = 45

I want to change the adjacent node from 30.10 (NODO3) to 30.20 (NODO4), I am looking for information on how to do that, but I don't see the way, anyone can help me?

Many thanks in advance.

Juan

[Robert Gezelter]

Juan,

I may not be understanding your question, but DECnet routing works dynamically, there is no need to declare a node in advance.

In DECnet, node names are essentially conventions (with the exception of how various applications use them, or their doppelgangers, eg. SCSNODE).

That said, there are very few situations where you would need to declare a node number in advance, most network related functionality is dynamic.

What is the precise reason for wanting to change the node name? What exactly is being done?

- Bob Gezelter, http://www.rlgsc.com

[Juan M. Lazaro]

Hi Robert,

The problem is that we hav 6 Open VMS hosts, 3 of them are in place A, and other 3 in place B, we hav an application running on them, and the communication is via decnet, the problem is that one of the nodes in place A, have an adjacent node of place B, and the application has some timeout errors, for those I want try to put an adjacent noce prom place A.

Excuse my english, hope you understand it.

Many thanks.
Juan

[Volker Halle]

Juan,

the MC NCP SHOW KNOWN CIRC CHAR command you issued on a DECnet phase IV routing node should show ALL adjacent DECnet nodes in the LAN segment associated with the circuit, from which the local node has received DECnet hello messages.

There is also a designated router shown on your LAN (with address 30.107), make sure that it can see the desired nodes (mc ncp tell 30.107 show known nodes).

You're running DECnet IV on an OpenVMS Alpha system configured as a routing node. As far as I remember, DECnet IV on OpenVMS Alpha only supports to be run as END node.

Volker.

[Robert Gezelter]

Juan,

First, a small note. The time of year setting is clearly incorrect. Look at the year.

What is your actual network topology? To be specific, what is visible on the ethernet segment that EIA-0 is connected to.

- Bob Gezelter, http://www.rlgsc.com

[Juan M. Lazaro]

Hi Volker, the output I print is from the TEST environment, Robert, for those we have a different year, because I haven't direct connection with the production environment, I must go to another place to type the commands, get the output in a flash memory and copy/paste here, anyway I attached a file with the production outputs.

The configuration is:

PLACE A
SYS11A
SYS11B
SYS11D

PLACE B
SYS11C
SYS11E

I have OpenVMS 8.2

Thanks in advance...

Juan

[Volker Halle]

Juan,

this looks straightforward: 5 DECnet nodes on the LAN(s) connected via EIA-0 and EIA-2. All visible from the local node and reachable from the designated router. This is the test environment. Are EIA-0 and EIA-2 connected to the SAME network segment or different/parallel LAN segments ?

Do you expect your production environment to look the same ?

How are the nodes located (at which sites) in your production environment ? From your initial output, it looks like only NOD01 and NOD03 can see each other via the LAN. Are those 2 nodes at the same site ? Are the other 3 nodes at the 'other' site ? Can they see NOD01 and NOD03 - I assume no.

Volker.

[Volker Halle]

JUan,

after re-reading your posts, I realize that I might have mixed up the test and production environment.

SYS11x = production - everything o.k.
NOD0x = test - problem between sites

Please confirm.

Volker.

[Juan M. Lazaro]

Hi Volker, EIA-0 and EIA-2 are diferent LAN segments.

Forgot the first information I post, that was the test environment, the last is the correct environment, I have the problem in production mode and the configuration is how I post before:

PLACE A
SYS11A
SYS11B
SYS11D

PLACE B
SYS11C
SYS11E

Thanks...

Juan

[Juan M. Lazaro]

Yes Volker, SYS11X is the production mode and where I have the problem.

Thanks again.

Juan

[Robert Gezelter]

Juan,

I concur with Volker on the NOD* vs SYS*. The information from the network having the problem is needed (e.g., NOD*).

Also, what does the Ethernet configuration look like beyond the OpenVMS systems? Has the backbone configuration been changed?

- Bob Gezelter, http://www.rlgsc.com

[Hoff]

DECnet is not IP, and DECnet routing does not work like IP gateway routing.

There is typically no error and no issue and no need to mess with DECnet (level one) routing on an Ethernet, save for cases where there's a woefully underpowered or overloaded server acting as a DECnet designated router, and that's not common these days, and would be unexpected with a half-dozen hosts on an Ethernet.

If you want to force this configuration (and constrain the options DECnet has here) (and there can be reasons to implement this), then the usual approach is to migrate to DECnet area routing (level two routing), and separate the functional or geographic differences into unique DECnet areas.

If your network is geographically dispersed (as is implied by that flaky network segment), then the usual solution is enabling the hosts on either end of the point-to-point connection link as DECnet area routers. (If this is a VLAN connection involving switches or such, then those DECnet area routers might not be directly connected to the point-to-point links.)

Irrespective of routing, DECnet end-node hosts can and do spot adjacencies on an Ethernet, and no DECnet routers are required when all hosts involved are on the same (logical or physical) Ethernet; end-nodes can communicate directly.

(I don't remember off-hand if the DECnet end-nodes can spot each other across areas. That configuration isn't particularly common, in my experience; by the time folks are rolling out area routing, there are usually several routers active on each network segment and one or more area routers will be active, so the end-nodes will have connectivity.)

[Hoff]

ps: Try to fix that flaky or overloaded network segment.

Flaky networks play havoc with DECnet and with IP. Back-offs and retransmits can cause cascading (and nasty) communications failure modes.

And they expose application bugs.

And FWIW, many applications aren't particularly good at recognizing and recovering from flaky networks and from network disconnections, meaning that modern (mobile) network communications can cause some serious disruptions within these applications.

[Volker Halle]

Juan,

if the SYS11x nodes are the production environment and you 'have problems' in the production environment, then what are these problems ?

The 5 SYS11x nodes seem to see each other on the LAN as shown by your attached .TXT file. Can you do SET HOST between all of them ?

Volker.

[Juan M. Lazaro]

Hi and thanks to all!

Yes I have switches between the hosts, the problem is in SYS11X configuration, forgot NODXX.

I can acces via SET HOST between all nodes in the area, the problem is than between SYS11D and SYS11B, I have frecuent connection timeouts in the EIA-0 circuit, and I supose it is because first it goes to SYS11C machine (adjacent SYS11D node, and in PLACE B), and then it returns to SYS11B, in PLACE A, I'm not sure how DECNET routing works, for those I want to put like adjacent node in SYS11D the node SYS11B.

Many thanks to all.

Juan

[Robert Gezelter]

Juan,

Ok. I strongly suggest doing a NCP SHOW CIR EIA-0 COUNT on the nodes that are having a problem. I would also be strongly inclined to use WireShark to look at precisely what is transiting the actual backbone.

As Hoff noted, LAN problems can have all manner of strange side effects. The error counters are extremely useful, as is the trace of what is actually happening on the network segment.

- Bob Gezelter, http://www.rlgsc.com

[Juan M. Lazaro]

Hi Robert,

I must put SYS11D out of production mode and now is in other network (TEST), I was doing some tests changing the executor type to nonrouting IV, but the only test I can do is in production with the application running on it...

But when I have the problem, with the command

SHOW COUNT NODE SYS11B

I have 14 response timeouts, but I don't have the counters from the circuit, and the client don't let me put the machine in production mode.

Thanks

Juan

[Volker Halle · Accepted solution]

Juan,

let's start with some basics on how DECnet routing works:

- each end node sends an Endnode Hello multicast message to all routers every Hello Timer seconds

- each routing node sends an Ethernet Router Hello multicast messages to all DECnet nodes every Hello Timer seconds

That's how the routers learn about the end node and the end nodes learn about the routers and the routers learn about each other.

If an application on a node wants to connect to another application on another node, it sends the first packet to the designated router (typically the router with the highest DECnet address on the local LAN), who then forwards the packet to the destination node. If the destination node is on the SAME LAN, it sets the 'intra ethernet bit' and future packet exchange happens directly between the 2 nodes on the same LAN.

Reponse timeouts are NODE counters and count how often a packet sent via a logical link to another node is not being acknowledged in time. This is typically an indication of DECnet packets getting 'lost' in the network path between the communicating nodes.

You should first look at the DECnet LINE counters and at all physical and datalink layer counters of all network components between the 2 systems involved.

If the node has now been removed from the production network, you can still at least test it's ability to communicate with other nodes in the test network. Using the DTSEND utility, you can test DECnet packet exchange between any 2 DECnet nodes and generate a lot of traffic to test the network components.

Volker.

[Juan M. Lazaro]

Hi Volker,

Many thanks to your time expent in that, and about the explanation on how DECnet runs, it is more clear to me now...

I'm going to look DTSEND utility and try to reproduce the error in test and let you know the results.

Thanks to all the people who help me in that.

Cheers,

Juan

[Juan M. Lazaro]

Perfect!!! great utility DTSEND... I was testing the DECNET network, at the end, I saw than have an elevate number of Response timeouts, I have decide to change the network card, and pass the tests again, and it works correctly, I haven´t hade more response timeouts, while running the test, in the other node I have a

MONITOR DECNET /ALL/INTER=1

running and I can see how some times there is no traffic while the DTSEND is running, and after that, looking the counters of the node I'm sending the traffic can see one respones timeout plus than before...

Thanks a lot to all for your help, I couldn't understand DECNET network without your explanations.

Have a great day,

Juan

[Juan M. Lazaro]

I was having response timeouts that were solved when I replace the network card.