Expand Configuration and Management Manual (G06.24+)

Planning a Network Design
Expand Configuration and Management Manual—523347-008
3-7
FOX Connections
FOX Connections
The Expand-over-FOX line-handler process provides connectivity in a limited
geographical area by accessing the network access method (NAM) interface of the
FOX monitor process, $ZZFOX. The major benefits of FOX connections are
•
Fault-tolerance. The FOX ring actually consists of two separate, bidirectional, fiber-
optic rings. Because the rings are bidirectional, four paths are available between
systems. The FOX ring continues to operate even if three of the four paths fail.
•
Very high throughput. The FOX fiber-optic cable consists of four fibers working in
parallel (sending and receiving in both directions).
•
Low host processor impact. Because data packet switching and forwarding are
performed by the ServerNet/Fiber eXtension (ServerNet/FX) adapters, and not by
software processes, processor utilization is more efficient.
•
Connectivity to existing FOX rings. The Expand-over-FOX line-handler process
provides connectivity to an existing FOX ring that consists of Cyclone and NonStop
K- and S-series servers.
The major disadvantages of FOX connections are that FOX networks are limited in
size (14 systems maximum) and the cost of FOX hardware is relatively high compared
to the hardware used by other connection methods. Also, FOX links can only be used
by the Expand subsystem. FOX links cannot be used in multi-line paths.
A NonStop S-series server can only exchange data directly over a FOX connection
with D-series systems that are running the D30 or later versions of the NonStop Kernel
operating system.
Refer to Time Factors and Pathchange Messages on page 18-24 for information on
adjusting settings so that routing is optimal.
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