HP 3000 Manuals

NS3000/iX NMMGR Screens Reference Manual

Packet Exchange Protocol (PXP) Configuration 

The Packet Exchange Protocol (PXP) Configuration screen (#93) in figure
4-5 is displayed when you press the [Go To PXP] function key at the
General Protocol Configuration screen (figure 4-4).  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) Config 

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   The time in seconds to wait for a reply from a
(secs)                    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   This is the number of times that PXP will
per request               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

MPE/iX 5.0 Documentation