tcp_conn_req_min
| Description | The default minimum
value of the maximum number of pending TCP connection requests for a listener
waiting to be accepted. This is the lowest maximum value of listen(3SOCKET) an application
can use.
| | Default | 1
| | Range | 1 to 1024
| | Dynamic? | Yes
| | When to Change | This can be a solution
for applications that use listen(3SOCKET) to set the maximum number of pending
TCP connections to a value too low. Increase the value to match the incoming
connection request rate.
| | Commitment Level | Unstable
|
TCP Parameters Set in the /etc/system File
These parameters can be set only in the /etc/system
file. After the file is modified, reboot the system.
The following entry sets tcp_conn_hash_size:
set tcp:tcp_conn_hash_size=1024
|
tcp_conn_hash_size
| Description | Controls the hash table
size in the TCP module for all TCP connections.
| | Data Type | Signed integer
| | Default | 512
| | Range | 512 to 1,073,741,824
| | Implicit | The value should be a power
of 2.
| | Dynamic? | No. The parameter can only
be changed at boot time.
| | Validation | If you set the parameter
to a value that is not a power of 2, it is rounded up to the nearest power
of 2.
| | When to Change | If the system consistently
has tens of thousands of TCP connections, increase the value accordingly.
With the default value, TCP performs well up to a few thousand active connections.
Note that increasing the hash table size means more memory consumption so
set an appropriate value to avoid wasting memory unnecessarily.
| | Commitment Level | Unstable
|
ipc_tcp_conn_hash_size
| Description | Controls the hash table
size in an IP module for all active (in ESTABLISHED state) TCP connections.
| | Data Type | Unsigned integer
| | Default | 512
| | Range | 512 to 2,147,483,648
| | Implicit | It should be a power of
two.
| | Dynamic? | No. This parameter can
only be changed at boot time.
| | Validation | If you set the parameter
to a value that is not a power of 2, it is rounded up to the nearest power
of two.
| | When to Change | If the system consistently
has tens of thousands of active TCP connections, increase the value accordingly.
With the default value, the system performs well up to a few thousand active
connections. Note that increasing the hash table size means more memory consumption
so set an appropriate value to avoid wasting memory unnecessarily.
| | Commitment Level | Unstable
|
TCP Parameters With Additional Cautions
Changing the following parameters is not recommended unless there are
extenuating circumstances that are described with each parameter.
tcp_ip_abort_interval
| Description | The default total retransmission
timeout value for a TCP connection in milliseconds. For a given TCP connection,
if TCP has been retransmitting for tcp_ip_abort_interval
period of time and it has not received any acknowledgment from the other endpoint
during this period, TCP closes this connection.
For TCP retransmission timeout (RTO) calculation, refer to RFC 1122,
4.2.3. See also tcp_rexmit_interval_max.
| | Default | 8 minutes
| | Range | 500 millisecond to 1193 hours
| | Dynamic? | Yes
| | When to Change | Do not change this
value. See tcp_rexmit_interval_max for exceptions.
| | Commitment Level | Unstable
|
tcp_rexmit_interval_initial
| Description | The default initial
retransmission timeout (RTO) value for a TCP connection in milliseconds. Refer
to the following discussion of per route metrics for setting a different value
on a per-route basis.
| | Default | 3 seconds
| | Range | 1 millisecond to 20 seconds
| | Dynamic? | Yes
| | When to Change | Do not change this
value. Lowering the value can result in unnecessary retransmissions.
| | Commitment Level | Unstable
|
tcp_rexmit_interval_max
| Description | The default maximum
retransmission timeout value (RTO) in milliseconds. The calculated RTO for
all TCP connections cannot exceed this value. See also tcp_ip_abort_interval.
| | Default | 60 seconds
| | Range | 1 millisecond to 2 hours
| | Dynamic? | Yes
| | When to Change | Do not change the
value in a normal network environment.
If in some special circumstances, the round trip time (RTT) for a connection
is in the order of 10 seconds, you can change the value to a higher value.
If you change this value, you should also change the tcp_ip_abort_interval parameter to match it. Change the value of tcp_ip_abort_interval to at least four times the value of tcp_rexmit_interval_max.
| | Commitment Level | Unstable
|
|
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