HP-UX 11i June 2001 Release Notes

Internet and Networking Services
Network Transport (new at 11i original release)
Chapter 10206
T_OPTMGMT
Kernel parameters tcp_recv_hiwater_max (for TCP sockets, default
2GB) and udp_recv_hiwater_max (for UDP sockets, default 2GB) now
limit the XTI_RCVBUF parameter maximum buffer size. Kernel
parameter tcp_xmit_hiwater_max (default 2GB) now limits the
XTI_SNDBUF parameter’s maximum buffer size.
A t_optmgmt() call with a tdsu or etsdu option that exceeds the
corresponding kernel parameter value will fail with TBADOPT.
If you determine that certain applications always ask for the largest
buffer or transport service data unit (tsdu) allowed, then the
administrator may want to set these variables and limit the amount of
memory used by such applications.
When an application opens enough of these large sockets and the system
does not contain a lot of memory, then the system may starve for memory
if the application quits reading from the endpoint.
Applications that request sockets with buffers or tsdus larger than
high-water marks set by you will fail. The t_optmgmt() function
returns the t_errno value TBADOPT.