| 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.
|
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