optimizenet command

Purpose

Manages network tuning parameters.

Syntax

optimizenet [ -reboot | -perm ] { -set Tunable[=NewValue] | -default Tunable }

optimizenet -list [ Tunable ]

optimizenet -h [ Tunable ]

Description

The optimizenet command is used to configure network tuning parameters. The optimizenet command sets or displays current or next boot values for network tuning parameters. This command can also make permanent changes or defer changes until the next reboot. Whether the command sets or displays a parameter is determined by the accompanying flag. The -set flag performs both actions. It can either display the value of a parameter or set a new value for a parameter.

If the -list flag is specified without any Tunables, only Tunables modifiable by this command will be displayed.

Flags

Flag name	Description
-default Tunable	Resets Tunable to its default value. If the Tunable needs to be changed (not currently set to its default value) and it is of type `Reboot`, it will not be changed; a warning displays instead.
-h Tunable	Displays help about Tunable parameter if one is specified.
-list [Tunable]	Lists the characteristics of one or all Tunables, one per line, using the following format: NAME CUR DEF BOOT MIN MAX UNIT TYPE DEPENDENCIES ------------------------------------------------------------------ General Network Parameters ----------------------------------------------------------------- sockthresh 85 85 85 0 100 %_of_thewall D ----------------------------------------------------------------- fasttimo 200 200 200 50 200 millisecond D ----------------------------------------------------------------- inet_stack_size 16 16 16 1 kbyte R ----------------------------------------------------------------- where CUR current value DEF default value BOOT reboot value MIN minimal value MAX maximum value UNIT tunable unit of measure TYPE Parameter type: D (Dynamic), S (Static), R (Reboot), B (Bosboot), M (Mount), I (Incremental), and C (Connect) DEPENDENCIES List of dependent tunable parameters, one per line
-perm	Makes changes apply to both current and reboot values when used in combination with -set or -default. These combinations cannot be used on Reboot type parameters because their current value can't be changed. When used with -set without specifying a new value, values displays only if the current and next boot values for a parameter are the same. Otherwise NONE displays as the value.
-reboot	Makes changes apply to reboot values when used in combination with -set or -default. When used with -set without specifying a new value, next boot values for tunables display instead of the current values.
-set Tunable [=NewValue ]	Displays the value or sets the Tunable to NewValue. If a tunable needs to be changed (the specified value is different than current value), and is of type Reboot it will not be changed but a warning displays instead. When -reboot is used in combination without a new value, the nextboot value for Tunable is displayed. When -perm is used in combination without a new value, a value displays only if the current and next boot values for tunable are the same Otherwise NONE displays as the value.

Network tunable parameters

Parameter	Description
arptab_bsiz	Purpose: Specifies Address Resolution Protocol (ARP) table bucket size. Values: Default: 7 Range: 1 to MAXSHORT Type: Reboot Diagnosis netstat -protocol arp will show the number of ARP packets sent and the number of ARP entries purged from the ARP table. If large number of entries are being purged, the ARP table size should be increased.
arptab_nb	Purpose: Specifies the number of ARP table buckets. Values: Default: 73 Range: 1 to MAXSHORT Type: Reboot Diagnosis: netstat -protocol arp will show the number of ARP packets sent and the number of ARP entries purged from the ARP table. If large number of entries are being purged, the ARP table size should be increased. Increase this value for systems that have a large number of clients or servers. The default provides for 73 x 7 = 511 ARP entries, but assumes an even hash distribution.
clean_partial_conns	Purpose: Specifies whether or not SYN (synchronizes the sequence number) attacks are being avoided. Values: Default: 0 (off) Range: 0 or 1 Type: Dynamic Tuning: This option should be turned on for servers that need to protect against network attacks. If on, randomly removes partial connections to make room for new non-attack connections.
net_malloc_police	Purpose: Specifies the size of the net_malloc and net_free trace buffers. Values: Default: 0 Range: 0 to MAXINT Type: Dynamic Tuning: If the value of this variable is non-zero, all net_malloc and net_free buffers will be traced in a kernel buffer and by system trace hook HKWD_NET_MALLOC. Additional error-checking will also be enabled. This includes checks for freeing a free buffer, alignment, and buffer overwrite. Enable this parameter only when investigating some network problem, because performance is affected negatively when turned on. The default value is zero (policing off). Values of net_malloc_police larger than 1024 will allocate that many items in the kernel buffer for tracing.
rfc1323	Purpose: Enables window scaling and time stamps as specified by RFC 1323 (TCP Extensions for High Performance). Window scaling allows the TCP window sizes (tcp_recvspace and tcp_sendspace) to be larger than 64KB (65536) and is typically used for large MTU networks. Values: Default: 0 (off) Range: 0 or 1 Type: Connect Tuning: The default value of 0 disables the RFC enhancements on a systemwide scale. A value of 1 specifies that all TCP connections will attempt to negotiate the RFC enhancements. Make changes before attempting to set tcp_sendspace and tcp_recvspace to more than 64 KB.
route_expire	Purpose: Specifies whether unused routes created by cloning, or created and modified by redirects expire. Values: Default: 1 (on) Range: 0 or 1 Type: Dynamic Tuning: A value of 1 allows route expiration, which is the default. Negative values are not allowed for this option.
tcp_pmtu_discover	Purpose: Enables or disables path MTU discovery for TCP applications. Values: Default: 1 Range: 0 or 1 Type: Dynamic Tuning: A value of 0 disables path MTU discovery for TCP applications, while a value of 1 enables it.
tcp_recvspace	Purpose: Specifies the system default socket buffer size for receiving data. This affects the window size used by TCP. Values: Default: 16384 bytes Range: 4096 to 1048576 Type: Connect Diagnosis: Setting the socket buffer size to 16 KB (16,384) improves performance over standard Ethernet and Token-Ring networks. Lower bandwidth networks, such as Serial Line Internet Protocol (SLIP), or higher bandwidth networks, such as Serial Optical Link, should have different optimum buffer sizes. The optimum buffer size is the product of the media bandwidth and the average round-trip time of a packet. For high-speed networks, like gigabit Ethernet or ATM 622, a value of 65536 should be used for the minimum size for best performance. For values larger than 65536, you must enable rfc1323 (rfc1323=1) to enable TCP window scaling.
tcp_sendspace	Purpose: Specifies the system default socket buffer size for sending data. Values: Default: 16384 bytes Range: 4096 to 1048576 Type: Connect Tuning: This affects the window size used by TCP. Setting the socket buffer size to 16 KB (16,384) improves performance over standard Ethernet networks. Lower bandwidth networks, such as Serial Line Internet Protocol (SLIP), or higher bandwidth networks, such as Serial Optical Link, should have different optimum buffer sizes. The optimum buffer size is the product of the media bandwidth and the average round-trip time of a packet: (optimum_window=bandwidth * average_round_trip_time) For high-speed networks, like gigabit Ethernet or ATM 622, a value of 65536 should be used for the minimum size for best performance. For values larger than 65536, you must enable rfc1323 (rfc1323=1) to enable TCP window scaling.
udp_recvspace	Purpose: Specifies the system default socket-buffer size for receiving UDP data. Values: Default: 42080 bytes Range: 4096 to 1048576 Type: Connect Diagnosis: Nonzero n in netstat -stats report of udp: n socket buffer overflows Tuning: Increase size, preferably to multiple of 4096.
udp_sendspace	Purpose: Specifies the system default socket-buffer size for sending UDP data. Values: Default: 9216 bytes Range: 4096 to 1048576 Type: Connect Diagnosis: Increase size, preferably to multiple of 4096.

Exit Status

See Exit status for Virtual I/O Server commands.

Examples

To display the maximum size of the mbuf pool, type:
```
optimizenet -set thewall
```
To change the default socket buffer sizes on your system, type:
```
optimizenet -reboot -set tcp_sendspace=32768
```
To use a machine as an internet work router over TCP/IP networks, type:
```
optimizenet -set ipforwarding=1
```
To list the current and reboot value, range, unit, type and dependencies of the arptab_bsiz parameter, type:
```
optimizenet -list arptab_bsiz
```
To display help information on arptab_bsiz, type:
```
 optimizenet -h arptab_bsiz 
```

Related Information

The entstat command, the lsnetsvc command, the mktcpip command, the netstat command, and the traceroute command.

Last updated: Wed, November 18, 2020