Expand Configuration and Management Manual (G06.24+)
Planning a Network Design
Expand Configuration and Management Manual—523347-008
3-11
When to Use a Multi-CPU Path
•
Maximum throughput is significantly increased, especially for Expand-over-IP
connections. An Expand-over-IP line-handler process and its associated NonStop
TCP/IP process must be configured in the same processor pair, placing the burden
of processing the entire communications protocol stack for each Expand-over-IP
line on one processor. A multi-line path consisting of Expand-over-IP lines cannot
achieve the throughput of a multi-CPU path because the NonStop TCP/IP
processes associated with the additional lines also must reside in the same
processor.
For more information about configuring Expand-over-IP line-handler processes,
refer to Section 7, Configuring Direct-Connect and Satellite-Connect Lines.
•
Bandwidth is increased. Traffic between neighbor nodes is distributed over all the
paths in a multi-CPU path, thus increasing overall bandwidth.
•
Multiple communications methods can be mixed in a multi-CPU path. Direct-
connect lines, satellite-connect lines, Expand-over-X.25 connections, Expand-over-
SNA connections, Expand-over-IP connections, and multi-line paths can be
members of a multi-CPU path. Expand-over-ServerNet and Expand-over-FOX
connections cannot be part of a multi-CPU path.
The major disadvantage of configuring a multi-CPU path is increased overhead. $NCP
periodically runs a rebalancing algorithm that reconsiders the pairings of Expand line
handlers on each multi-CPU path. If the load is unbalanced, $NCP selects different
pairs of line handlers. This algorithm requires additional processing time, which is not
required by Expand line-handler processes that manage multiple lines, and can be
slightly disruptive.
Figure 3-3 shows a multi-CPU path that consists of three paths between nodes \A and
\B. Each Expand line-handler process that is a member of the multi-CPU path is
configured in a separate processor.
Figure 3-3. Multi-CPU Path With Three Paths
054CDT .CDD
CPU 0
CPU 1
CPU 2
CPU 4
CPU 3
LH
LH
LH
Node \A
CPU 0
CPU 1
CPU 2
CPU 3
LH
LH
LH
Node \B
CPU 4