HP-UX TCP/IP Performance White Paper, March 2008

datagrams fragments being dropped, you might consider increasing this

value. Before you do, check the frequency of such drops so you can

compare it to after you make the change. If the frequency remains the

same after you have increased the value, it implies that the IPv6

fragment drops were the result of perceived duplicates and not because

there was not enough space.

If you see a large number of IPv6 datagram fragment drops in the output

of "netstat -p ipv6" you might also want to check the frequency of

UDP and TCP checksum failures with "netstat -p udp" and "netstat -p tcp"

respectively. This can mean that two otherwise unrelated, fragmented IPv6

datagrams could be reassembled into one packet which will only be detected

by the upper-layer checksum.

The best course of action should this be happening would be to try to

eliminate the fragmentation. The next best course of action would be

to try to further restrict the amount of time the system will "hang-on"

to an IPv6 datagram fragment. For more on that, refer to the discussion

of "ip6_fragment_timeout". [-,-] Default: 2000000 bytes

This tunable is very similar to ip_reass_mem_limit For IPv6. Please refer ip_reass_mem_limit to

for more description.

ip6_send_redirects:

Set to 1 to allow IPv6 send ICMPv6 "Redirect" packets; set to 0 to

disable.

If the system is forwarding IPv6 datagrams, and it is asked to forward

a datagram when it knows there is a "better" route, it will send an ICMPv6

"Redirect" message to the source of the datagram to tell it the better

route. The system will still forward the datagram.

If the value of ip6_send_redirects is set to zero, the system will still

forward the wayward datagram, but it will not tell the source that there

is a better way for it to send its datagrams. [0,1] Default: 1 (enable)

Only IPv6 routers send ICMPv6 redirect message. An ICMPv6 redirect message is used by the routers to

inform hosts of a better first hop for a destination.

ip6_tcp_status:

Obtains a complete report similar to "netstat -an" on all IPv6 TCP

connections.

ip6_udp_status:

Obtains a complete report similar to "netstat -an" on all IPv6 UDP

connections.

ip6_ire_reachable_interval:

The Neighbor Discovery constant REACHABLE_TIME, Section 10 of

RFC 2461. This is the base value for computing the random Reachable

value. Used with "ip6_min_random_factor" and "ip6_max_random_factor"