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Administration Guide

Switch communication modes

Two communication protocols are offered for the adapter:

  1. AIX sockets using standard IPv4 protocol.
  2. Dedicated user space access (via message passing libraries) and multiuser environments (via IP).

Both modes can be used concurrently, as if the adapter was actually two separate adapters.

IPv6 is not supported. See Appendix G, Tolerating IPv6 alias addresses for more information.

Switch communication using IP (TCP/IP and UDP/IP)

The switch adapters are configured for IP by default during the installation process. You can assign specific IP network addresses statically during installation or dynamically using ARP (Address Resolution Protocol). When you assign the IP address statically, there are restrictions on mapping of nodes to low order addresses (see the information on switch node numbering in the PSSP: Installation and Migration Guide). When you assign the IP address range dynamically using ARP, there are no restrictions.

Any application can communicate over the switch by opening a standard socket and specifying appropriate IP addresses. Additional system facilities based on IP, such as NFS, and licensed programs such as AFS, can also be configured to use the switch. With the possible exception of applications that depend on network-specific functions (LAN broadcasts, for example), most applications work over the switch without modification.


  1. The iptrace command supports both switch adapters and provides interface-level packet tracing for incoming and outgoing packets.

  2. The standard AIX commands ifconfig and arp have been modified to support the switch adapters. Refer to the PSSP: Command and Technical Reference for more information.

  3. |Static routes associated with the switch will not be automatically |reconfigured during node reboot. The routes for the switch are |associated with the interface to the SP Ethernet admin LAN upon reboot because |the switch is not available during the phase of system initialization when the |static routes are reconfigured. If you want the routes added |automatically, IBM suggests that you put them in a script and have the script |called as the last entry in /etc/inittab.

Switch communication using user space message passing

The user space message passing mode supports parallel applications requiring maximum bandwidth and minimum latency. This mode is used by Parallel Environment for AIX to provide their exported message passing interfaces.

This mode uses adapter windows which are composed of instances of parallel tasks and protocols (either the Low Level Application Programming Interface (LAPI) or the Message Passing Interface (MPI)). Each adapter window is associated with a protocol and a task. A task running two protocols (such as MPI and LAPI) has two windows associated with it. The number of adapter windows sharing the SP Switch adapter cannot exceed 4. |The SP Switch2 supports up to 32 adapter windows.

For example, four adapter windows, each containing one parallel task and one protocol can share the following switch adapter. Since this is an example using the SP Switch, the number of adapter windows and the number of protocols does not exceed four.

Figure 9. User space message passing

View figure.

Four adapter windows in the following graphic encompass three parallel tasks and four protocols. The third task uses both LAPI and MPI. Again, in this case the number of adapter windows does not exceed four.

Figure 10. User space message passing

View figure.

The tasks can be part of the same job or of separate jobs. All tasks in the same job must use the same combination of protocols.

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