The Packet Exchange Protocol (PXP) Configuration screen (#93)
in Figure 4-5 “Packet Exchange Protocol (PXP) Configuration
Screen” is displayed when
you press the [Go To PXP] function key at the General
Protocol Configuration screen (Figure 4-4 “General Protocol Configuration Screen”). It is also displayed when you type the
path name:
@NETXPORT.GPROT.PXP
in the command window of any screen and press the [Enter]
key.
Figure 4-5 Packet Exchange Protocol (PXP) Configuration
Screen
This screen contains the information necessary to configure
packet exchange protocol (PXP) for the node. The information configured
falls into two categories:
Reliability (checksum field).
Performance parameters (retransmission fields).
Press the [Save Data] function key to transfer
the data displayed on the screen to the configuration file you are
creating or modifying. Verify that the data record has been created
by checking that the Data flag is set to Y.
Fields
- Checksum enabled (Y/N)
Checksumming is a method of error checking. Enter
a Y (yes) to enable checksumming
for all sockets for this protocol. Enter an N
(no) to allow individual sockets to choose checksumming for themselves.
PXP checksumming causes significant overhead, and is not normally
needed for this protocol. Also, error checking is provided for at
the link level. For these reasons, HP recommends the default value
(N) for this field unless communication
to a non-HP machine is desired.
Default value: N
- Retransmission interval (secs)
The time in seconds to wait for a reply from a remote
node before retransmitting a request. In general, the value to configure
should reflect the load on the local system, the remote system,
and the networks through which the request and the reply must travel.
If the value is set too low, needless retransmissions may occur,
or IPCLOOKUP calls may fail. If
the value is set too high, an unnecessarily long delay will occur
when a packet is lost, and a retransmission will be necessary. Frequent
log messages indicating that retransmissions are taking place or
that requests are failing indicate that the value needs to be increased.
Default value: 10
Range: 1-600
- Maximum retransmissions per request
This is the number of times that PXP will retransmit
a request when a reply has not been received within the retransmission
interval (explained above).
As in the discussion of retransmission interval above, this
field is a tuning parameter. The two values work together to determine
the maximum time that a PXP user will wait for a reply. This maximum
reply time is calculated as follows:
RTXinterval + (RTXinterval * MAXRTX)
where RTXinterval is the
configured retransmission interval and MAXRTX
is the configured maximum retransmissions per packet. Note that
excessive values would cause unacceptably long delays before IPCLookup
would fail under normal conditions such as the remote node failing.
Default value: 4
Range: 1-100