TCP/IP (Parallel Library) Migration Guide

Migration Considerations
HP NonStop TCP/IP (Parallel Library) Migration Guide—522272-003
3-5
Firewall Considerations
Failure Data System (TFDS). However, if the failure is detected in the TCP/IP
library within the application context, the TCP/IP library cannot call TFDS to notify
to GCSC.
•
Upon failure of any Parallel Library TCP/IP processor or TCPMON process,
applications connected to Guardian TCP sockets which were on that failed
processor or process do not have their TCP connection reset. This behavior is
unlike conventional TCP/IP.
•
For fault-tolerant socket applications, if the application primary process fails, the
backup application receives an ECONNRESET error upon its first socket request
after takeover.
Firewall Considerations
When considering migration to Parallel Library TCP/IP, ensure that your firewall
products support gratuitous ARP packets.
Guardian Socket Migration
If an application passes the ACCEPT_NW2 request to another application in a different
processor, the Parallel Library TCP/IP environment must move that socket, and any
data queued on that socket, to the processor where ACCEPT_NW2 is running. This
move of the socket and data is referred to as “socket migration.”
You can improve performance and save processor time across the system if you set up
your applications to pass untouched the sa_data portion of the sockaddr_in
structure that is returned when the ACCEPT_NW request completed.
The library does not know where the listening socket is when an application issues an
accept_nw2 call. Hence, under normal circumstances, before the library can migrate
the socket to the right processor, the library broadcasts a message to all processors to
ask the Parallel Library TCP/IP environment which processor has this connection. After
the library finds the processor that has the connection, the library will migrate the
socket to that processor and data transfer will begin.
To eliminate the need to broadcast to all other processors, the listening socket’s
application should include the sa_data portion of the sockaddr_in structure
untouched, and the server handling the new connection should also include the
sa_data portion of the sockaddr_in structure that it is using in the accept_nw2
call.
By programming applications that use the accept_nw2 call in this manner (to include
the sa_data portion of the sockaddr_in structure), the library will know where the
listening socket is and only has to send the message to one processor instead of to all
processors to find the listening socket.