spx_tune.h -- SPX configuration file


/etc/conf/pack.d/spx/spx_tune.h contains parameters that configure the Sequenced Packet Exchange (SPX) protocol.

Some parameters use clock ticks as the unit of measure. The kernel variable HZ represents the number of clock ticks per second. HZ is currently set to 100 in accordance with Intel Binary Compatibility Standard 2 (iBCS2).

The following parameter controls the number of connections:

Specifies the maximum number of open local SPX endpoints. It should be set to a value less than that of SPX_MAX_SOCKETS in the /etc/conf/pack.d/ipx/ipx_tune.h file, since each connection needs more than one socket.

The default is 30.

The following parameters are for flow control:

Specifies the upper limit of the number of characters contained on the message queue. When the high water mark is reached, no more messages will be received until the queue drops to the low water mark.

The default is 12000.

Specifies the number of characters which cause the queue to become accessible again.

The default is 2000.

The following parameters control data transmission:

Specifies the number of times that SPX should try to deliver a data packet. If a transmission to the remote transport endpoint fails, SPX tries this number of times before labeling the connection as broken. This is also the number of times that a connection request is sent before failing.

The default is 5.

Specifies the absolute minimum value that is used for the round-trip time.

While sending packets to and receiving packets from an endpoint, SPX calculates the total round-trip time to the remote transport endpoint. If a packet is not acknowledged, a retransmission occurs. The length of time to wait for this acknowledgment is dependent on the calculated round-trip time. If the remote transport endpoint is close, the round-trip time is small, making the connection timeout short.

The default is (HZ >> 1), which is .5 seconds.

Specifies a maximum value for the round-trip time. Each time SPX has to retransmit a packet, it multiplies its last retry interval by 1.5. If the remote transport endpoint is far away, the retry time could become very large, making it take too long for the connection to fail.

The default is (HZ * 5), which is 5 seconds.

WatchEmu is the SPX watchdog which ensures that the kernel resources allocated to SPX are kept to a minimum and that all dead connections are closed.

The following parameters control WatchEmu:

Specifies the interval in minutes that WatchEmu runs.

The default is 1.

Specifies how many minutes WatchEmu should allow a connection to remain intact without a ping acknowledgment. It should be set to some multiple of SPX_WATCHEMU_INTERVAL.

The default is (SPX_WATCHEMU_INTERVAL * 2).

Specifies the maximum number of times that SPX will try to allocate a streams message block for outbound data before giving up and closing the connection.

The default is 4294967294. It is set to this large number so that SPX will essentially always succeed.

After changing any parameters, you must rebuild the kernel and relink the system. Select Relink Kernel in the Hardware/Kernel Manager. You must then reboot your system before the changes to the kernel take effect.



See also

© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 02 June 2005