Installing and Administering LAN/9000 Software

Note that the infrastructure of the network (routers, switches) must

allow IP packets with the address 17.1.1.1 to be properly routed to this

system's interfaces on the 15.n.n.n and 16.n.n.n networks for this

conﬁguration to be useful.

/etc/rc.conﬁg.d/netconf ﬁle statements for the above VIP:

INTERFACE_NAME[2]=lo0:1

IP_ADDRESS[2]=15.1.1.1

ifconﬁg command for the above VIP:

ifconfig lo0:1 inet 15.1.1.1

Note that you cannot assign VIPs to the primary loopback interface,

lo0:0, or lo0.

TCP Performance Enhancements

• TCP Selective Acknowledgment (SACK, RFC 2018)

TCP selective acknowledgment (SACK) deﬁnes a new TCP option

that allows recipients to selectively acknowledge out-of-sequence

data. The TCP sender can then retransmit only the lost segments and

adjust its send window to reﬂect the actual amount of received data.

The use of TCP SACK is controlled by the ndd parameter

tcp_sack_enable.

Supported parameter values are:

0: Local system never uses SACK.

1: Local system sends the SACK option in SYN packet

2: Local system enables SACK if remote system negotiates the use of

SACK in SYN packet (default)

Negotiation of the use of SACK is done by sending TCP SYN packets

with an Option Kind value of 4 to indicate that the system can receive

(and process) SACKs.

TCP packets with SACK information will have an Option Kind value

of 5.

• Scaled Windows and Timestamps (RFC 1323)