TCP/IP (Parallel Library) Configuration and Management Manual

Configuring Parallel Library TCP/IP for Complex and
Heavy-Use Environments
HP NonStop TCP/IP (Parallel Library) Configuration and Management Manual—522271-006
3-6
Distributor Listening Model
hop required in the conventional TCP/IP environment and also because TCP/IP often
runs in a different processor than the listening process for load distribution.
In the Parallel Library TCP/IP environment, with round-robin filtering enabled, you can
have multiple copies of the monolithic listener running in different processors, all
sharing the same port (shown in Figure 3-2 on page 3-5). Because round-robin filtering
is enabled, the adapter distributes the incoming connections to the different listening
processes, and the listening processes, in a sense, distribute those connections within
its own process by creating sockets for each connection. An example of how this kind
of dual-layer distribution could work is described in the following steps:
1. The first incoming connection request goes to the listening process in the first
processor and the listening process creates a socket for the connection.
2. The second connection request goes to the listening process in the second
processor and the listening process creates a socket for the connection.
3. The third connection request goes to the listening process in the third processor
and the listening process creates a socket for the connection.
4. The fourth connection request goes to the listening process in the first processor
and the listening process creates a second socket for that connection.
5. The fifth connection request goes to the listening process in the second processor
and the listening process creates a second socket for that connection.
In summary, you can use the Parallel Library TCP/IP feature of all processors having
access to one adapter to scale your monolithic listener server process (by adding more
processes in different processors and distributing the work load among them), and
eliminate an IPC hop between the server process and the TCP/IP process (which
increases transmission speed).
Configuration Example for the Monolithic Listening Model on page 3-15 tells you how
to configure this listener model.
Distributor Listening Model
This method uses an interface process which serves as a distributor by using NonStop
inter-process communication (IPC) to talk to multiple back-end server instances. In this
method, the distributor binds to a well-known port and then accepts multiple
connections by creating a socket for each connection. The distributor listener then
performs the accepts, sends, receives, and so on, on those sockets, on behalf of the
back-end servers. The distributor handles all data flow and control, and forwards the
received data using NSK inter-process communication to back-end server processes.
A good example of this method is a TCP/IP application developed for the Pathway
environment.
The Pathway environment provides a rich set of server process-management facilities
and load-balancing facilities. A front-end distributor process using a set of verbs
collectively referred to as PATHSEND, communicates with the back-end servers.