| 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 timestamps 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.
|