Expand Configuration and Management Manual (H06.21+, J06.10+)

Troubleshooting
Expand Configuration and Management Manual — 529522-013
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Adding Low-Speed Lines to a Multi-Line Path
Adding Low-Speed Lines to a Multi-Line Path
Adding more low-speed lines to a multi-line path can increase the number of OOS
frames that a path must reassemble. The effect in this case is not on the buffer space
used but on the total time taken for the sending Expand line-handler process to receive
its ACK. As a result, the sending node might experience an increase in Layer 4
timeouts. The solution to this problem is to reconfigure the Expand line-handler
process to have larger Layer 4 timeout (L4TIMEOUT modifier) and OOS timeout
(OSTIMEOUT modifier) values.
Duplicate Node
The Expand subsystem identifies nodes primarily by their node (system) number. For
any single network, each node must have a unique number in the range 0 through 254.
It is possible to introduce a node into a network with a configured node number that is
the same as that of a node that already exists in the network. The results of such a
mistake vary depending on the network topology, but can be characterized by a few
general symptoms, as described below:
•
Applications that previously succeeded begin to fail with file-system error 201. All
failing applications are attempting to access the same destination node.
•
The number of NCPM packets increases steadily. NCPM packets can be observed
by issuing an Expand subsystem SCF STATS PATH command.
•
When an SCF INFO PROCESS $NCP, NETMAP command is issued, connections
repeatedly alternate between connected and disconnected states.
The effect of a duplicate node number on user applications depends on the network
topology and, in p
articular, on the size of the network. Those nodes closer (in terms of
the routing algorithm) to the erroneously numbered node than to the correctly
numbered node regard the invalid node as a better route and alter their routing tables
and connect to the invalid node. Applications that were communicating with the valid
node are not able to continue and might receive file-system error 201.
To resolve a duplicate node name and/or number problem, see Changing System
Names and Numbers on page 18-23.
Note. The multi-line path does not need to be attached to the sending node. In a multiple-hop
circuit, the problem can be caused by a multi-line path on the receiving node.
Note. Any one of the symptoms described above can b
e caused by factors other than a
duplicate node in the network. However, the presence of all symptoms and their persistence is
a good indication that a duplicate node number has been introduced.