Cluster I/O Protocols (CIP) Configuration and Management Manual (H06.16+, J06.05+)

TCP-MAX-REXMIT-COUNT
This NonStop TCP/IPv6 Monitor attribute, which set the maximum number of continuous
retransmissions allowed before a TCP connection was dropped, can be set by issuing the CLIMCMD
{clim–name | ip–address} climconfig sysctl command. See “TCP_RXMTCNT” (page 191).
TCPPATHMTU
This NonStop TCP/IPv6 Monitor attribute is used to turn on Path MTU discovery. Path MTU discovery
is on by default in CIP; if you want Path MTU discovery turned off, use the CLIMCMD {clim–name
| ip–address} climconfig sysctl -update net.ipv4.ip_no_pmtu_disc command.
TCPRECVSPACE
This NonStop TCP/IPv6 MON attribute, which sets the size of the window for receiving data for
the TCP protocol, can be set globally with the CLIMCMD {clim–name | ip–address} climconfig
sysctl -update net.ipv4.tcp_rmem "value value value" command.
This attribute, if changed, must be the same on all CLIMs in a Provider.
The value variables affect kernel behavior for different conditions:
• The first value sets the minimum TCP receive send buffer space available for a single TCP
socket.
• The second value sets the default buffer space allowed for a single TCP socket.
• The third value sets the maximum TCP receive buffer space.
You can also set the maximum and default sizes for socket buffers for all connections by using the
climconfig sysctl -update net.core.rmem_max value and
net.core.rmem_default value sysctl commands.
NOTE: The net.ipv4.tcp_rmem parameter overrides the net.core.rmem_max and
net.core.rmem_default sysctl commands for TCP connections. Changes to this sysctl parameter
must be made on all CLIMs that share the same Provider.
To change the sysctl parameters on the CLIM:
1. Stop the CLIMs and the Provider.
2. Alter the sysctl parameters.
3. Start the CLIMs and the Provider.
If the CLIM is an Open type, reboot it.
Background
CIP supports the RFC1323 TCP high performance extensions. This includes large TCP windows to
support links with high latency or bandwidth. To make use of them, you must increase the send
and receive buffer sizes.
Programmatic Alternative
The TCP send window size can also be set on individual sockets by setting the SO_RCVBUF option.
TCPSACKON
This NonStop TCP/IPv6 Monitor attribute, which specifies whether or not all TCP connections use
TCP selective acknowledgements (unless specifically disabled by an application) can be set by
using the CLIMCMD {clim–name | ip–address}climconfig sysctl -update
net.ipv4.tcp_sack command.
TCPSENDSPACE
This NonStop TCP/IPv6 MON attribute, which sets the size of the window for sending data for
the TCP protocol, can be set globally by using the CLIMCMD {clim–name |
TCP/IP Attributes in CIP 197