Availability Guide for Application Design

Improving Availability on the Internet
Availability Guide for Application Design—525637-004
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The iTP WebServer Architecture
Conventional TCP/IP
In essence, conventional TCP/IP has one listening process on each port. The
conventional TCP/IP connections are managed by the Distributor process. The
Distributor receives all incoming requests for new connections from the TCP/IP
processes and used to previously distribute them to the iTP Secure WebServer, using
the NonStop TS/MP Pathsend facility. Beginning with iTP webServer 4.1, the Pathsend
facility were removed.
Parallel Library TCP/IP and TCP/IPv6
Parallel Library TCP/IP and TCP/IPv6 have multiple listener sockets on the same port.
Parallel Library TCP/IP and TCP/IPv6 allow the server direct access to the
communication environment from their own processors instead of having to
communicate via the processor that contains the HP TCP/IP process. This is done by
linking to a system library containing the TCP/IP procedures and allowing the server to
call the functions doing TCP/IP-related processing in its own context.
Running with the Auto-Accept feature, an iTP WebServer no longer needs its
Distributor component. The httpd servers will assume the listening as well as the
distributing functions of the Distributor. The Distributor server class will be completely
removed from the PATHWAY environment.
Running the iTP WebServer relies on the properly configured Parallel Library TCP/IP
or TCP/IPv6 environments. Every processor specified in the Server CPUS command
(in the httpd.config configuration file) needs to be enabled to run Parallel Library
TCP/IP or TCP/IPv6, as the case may be. In other words, the TCPMAN needs to be
properly configured and running. As a result, a TCPMON (the monitor process) runs on
every processor specified in the Server’s processor command.
Unlike the conventional TCP/IP subsystem, the Parallel Library TCPIP and the
TCP/IPv6 allow the iTP WebServer to create a listening socket on each of these
processors. By creating a listening socket on each of these processors, the httpd
servers provide the listening capability for themselves. Therefore, mixing the Parallel
Library TCP/IP or the TCP/IPv6 with conventional TCP/IP subsystems is not
permissible. If both TCPSAM process and conventional TCP/IP process are specified
as the transport service providers, the Auto-Accept feature will not be enabled. The iTP
WebServer will be running as a conventional TCP/IP configuration.
iTP Secure WebServer httpd
The iTP Secure WebServer httpd has two main functions:
•
A file server. The httpd process transfers and stores files, such as HTML
documents.
•
A message-switching facility. The httpd process forwards messages from web
clients to application programs.
The httpd process is implemented as a server class in NonStop TS/MP. Therefore
multiple httpd processes can execute in parallel; the number of processes fluctuates