pxp.intro Definition/System Architecture


Command pxp.intro Definition/System Architecture
Applicable release versions: AP/Unix
Category System Architecture (8)
Description consists of an account which allows communications to another Advanced Pick System, using either Unix communication tools, such as TCP/IP, X25, serial lines, pipes, or Advanced Pick send and get features.

Basic functions are:

- Item transfers. A TCL utility 'ppcp' (for Pick to Pick CoPy) allows copying items to another Pick virtual machine, either locally or across a network.

- Message facility. Sending Pick messages to a user logged on a distant system.

- Remote execution. Possibility of submitting a command to be executed asynchronously on a distant system.

- File mirroring. Executing all file updates and optionally deletes to a remote 'mirror' file over the network.

All function are available through the "pxpcmd" TCL command. System administration is done by logging to the account "pxp".

Fundamental Notions:

"Local System"
The local system is the virtual machine on which the user is currently logged on. On a given hardware system, there may be several Pick virtual machines, and, therefore, several "local" systems.

A host is an entity known to the local system as a potential destination. Care must be taken when defining a host over a network, since the name of the Pick host may be different from the name of the Unix host (as defined by the network).

"Service Access Point" or "SAP"
A service access point is an entity providing a communication service, such as a serial line, an Ethernet controller, or a Unix pipe. It is assumed that the SAP provides, at least, a transport level service (TSAP). This should be, at minimum, a network level like X.25-3 or a transport level like TCP/IP communication level. Each host defined on the local system has an output access point associated with it, so that the PXP subsystem can determine how to get the message on the network.

The PXP subsystem will do routing, i.e., re-direct on ch messages to the appropriate destination host, inside a multiple node network. Note this routing should not be confused with the routing provided by the Service Access Point (SAP) which simply make sure a message gets to the appropriate node on the network.
Related pxp.sap