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.