HP-UX 11i Release Notes (December 2000)

Internet and Networking Services
Network Transport (new)
Chapter 10 195
To disallow subnet fields with all ones or all zeroes, set the ndd
parameter ip_check_subnet_addr to 1 in the nddconf file.
ndd
ndd is a networking configuration tool used to customize the networking
kernel. To make an 11i system more Internet friendly and easier to run
“out of the box”, some of the ndd tunable parameters defaults changed.
Some unsupportable tunable parameters are now “supported”. Also,
some new tunable parameters have been added. Some of the changes
reflect changes to the networking industry standards.
Specific Changes
1) All 1’s or all 0’s now allowed in masked bits of subnet address:
ip_check_subnet_addr shows whether or not that RFC1122 or
RFC1878 enforces the network subnet mask. If it is a 0 (zero), then the
RFC1122 behavior is seen. If it is a 1 (one), then RFC1812 is seen. The
default is now RFC1812 behavior. See ifconfig for more information.
This new behavior makes available up to twice as many IP addresses
than a similarly configured RFC1122 machine. This new feature is an
enhancement.
2) Selective acknowledgement for TCP supported tcp_sack_enable
enables selective acknowledgement. This enhancement could improve
performance in networks with large transmission windows by allowing
TCP recipients to indicate lost segments within large transmission
blocks. The TCP sender can then retransmit only the lost segments.
Supported parameter values are:
2 Local system enables SACK if remote system first
sends SACK (Default).
1 Local system requests the SACK option during a
connect() request.
0 Local system never uses SACK.
3) Send and receive buffers now limited to hiwater_max:
tcp_hiwater_max and udp_recv_hiwater_max (default 2GB) set the
maximum receive buffer size that setsockopt or t_optmgmt can set for a
socket. tcp_xmit_hiwater_max sets the maximum send buffer size