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

Planning a Network Design
Expand Configuration and Management Manual — 529522-013
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Defining Paths Between Systems
Defining Paths Between Systems
Each system in an Expand network can have up to 255 Expand line-handler
processes. An Expand line-handler process can be configured to handle a single line
or a path consisting of up to eight parallel lines. You can also associate up to 16
Expand line-handler processes in separate processors with one another to form a
multi-CPU path.
This subsection provides information to help you determine when to:
•
Configure a single-line Expand line-handler process
•
Configure a multi-line path between neighbor nodes
•
Configure a multi-CPU path
•
Enable the multipacket frame feature
•
Enable the variable packet size feature
•
Enable the congestion control feature
When to Use a Single-Line Expand Line-Handler Process
Single-line Expand line-handler processes are less expensive and require somewhat
less processing time than multi-line paths. However, they lack the fault-tolerance that
multi-line paths and multi-CPU paths provide.
When to Use a Multi-Line Path
A path that consists of more than one line is called a multi-line path. A multi-line path
can consist of up to eight parallel lines. The major benefits of configuring a multi-line
path are:
•
Fault-tolerance is increased. If one or more lines in a multi-line path fail, the
Expand subsystem automatically reroutes data over the remaining lines in the
path. You can also attach lines in the path to different hardware communications
devices for an additional level of fault-tolerance.
•
Bandwidth is increased. The Expand subsystem simultaneously transmits data
over all the lines in a multi-line path, thus increasing overall bandwidth.
•
Multiple communications methods can be mixed in a multi-line path. You can mix
direct-connect lines, X.25 connections, and SNAX connections in the same multi-
line path. You cannot mix satellite-connect and Expand-over-IP lines with other line
types. Expand-over-ServerNet connections cannot be part of a multi-line path.
The major disadvantages of configuring a multi-line p
ath are:
•
Overhead is increased. The Expand subsystem uses a packet-queueing algorithm
to select the best line in a multi-line path on which to queue the next packet. This
algorithm requires additional processing time, which is not required by Expand
line-handler processes that manage a single line.
•
Out-of-sequence (OOS) packet buffering is increased. The frequency of OOS
packets increases when packets are sent over a path that consists of lines of