TCP/IPv6 Configuration and Management Manual (G06.29+, H06.03+, J06.03+)

Overview of NonStop TCP/IPv6
HP NonStop TCP/IPv6 Configuration and Management Manual—524523-012
2-6
Round-Robin Filtering
In a single-IP configuration, remote clients trying to connect to the NonStop TCP/IPv6
network only need to know a single IP address to receive the processing power of up
to 16 processors.
Round-Robin Filtering
For multiple processors to share an interface (SLSA LIF), a NonStop TCP/IPv6 feature
called round-robin filtering must be enabled. Round-robin filtering allows the adapter to
distribute incoming connections to multiple listening processes in different processors
sharing the same port.
Round-robin filtering refers to the distribution of incoming connections to the first
listening process in line, then the second, then the third, and so on, until the last
listening process is reached, at which point the distribution returns again to the first
listening process in line. For example, you could configure a Web server in each
processor and enable round-robin filtering so that the Web servers receive inbound
requests in a round-robin manner.
To use the round-robin feature you must explicitly configure it; the default configuration
is for non-round-robin. If you are using Logical-Network Partitioning (LNP), you must
also define the appropriate transport-service provider in the same TACL session in
which you define the filter key so incoming connections are distributed among
application instances within the same LNP. For application servers in an LNP
environment to use the round-robin filtering feature, they must share both the round-
robin, filter-key DEFINE and the transport-service provider (TCP6SAM process)
DEFINE.
You must set the DEFINE to enable round-robin filtering on your server processes:
ADD DEFINE =PTCPIP^FILTER^KEY, class map, file file-name
file-name is arbitrary but serves as the key or password. This key provides a
measure of security: only users who know the key can access round-robin on the port.
The key can have up to eight alphanumeric characters; however, the first character
must be a letter. The default setting is non-round-robin. If you do not specify the file-
name, round-robin filtering does not take effect. When round-robin filtering is not in
effect, whoever registers the first application has exclusive use of the port. Each
application that uses round-robin filtering on the same port must use the above ADD
DEFINE with the same key.
If you specify only the PTCPIP^FILTER^KEY, all applications that share that DEFINE
share all ports. If you are using logical-network partitioning (see Logical-Network
Partitioning (LNP) on page 2-7), all applications that share the filter-key DEFINE and
the transport-service provider (TCP6SAM process) share all ports in that LNP.
Caution. Special considerations apply for using round-robin filtering. For information about
these considerations, see Considerations for Round-Robin Filtering
on page 6-2.