tcp_tstamp_always
| Description | If set to 1, TCP always
sends SYN segment with the timestamp option. Note that if TCP receives a SYN
segment with the timestamp option, TCP responds with a SYN segment with the
timestamp option even if the parameter is set to 0.
| | Default | 0 (disabled)
| | Range | 0 (disabled), 1 (enabled)
| | Dynamic? | Yes
| | When to Change | In summary, if an
accurate measurement of round trip time (RTT) and TCP sequence number wraparound
is a problem, enable it.
Refer to RFC 1323 for more reasons to enable this option.
| | Commitment Level | Unstable
|
tcp_xmit_hiwat
| Description | The default send window
size in bytes. Refer to the following discussion of per-route metrics for
setting a different value on a per route basis. See tcp_max_buf
also.
| | Default | 49,152
| | Range | 4096 to 1,073,741,824
| | Dynamic? | Yes
| | When to Change | Note that this is
the default value. An application can use setsockopt(3XNET) SO_SNDBUF to change
the individual connection's send buffer.
| | Commitment Level | Unstable
|
tcp_recv_hiwat
| Description | The default receive
window size in bytes. Refer to the following discussion of per-route metrics
for setting a different value on a per-route basis. See tcp_recv_hiwat_minmss
and tcp_max_buf also.
| | Default | 49,152
| | Range | 2048 to 1,073,741,824
| | Dynamic? | Yes
| | When to Change | Note that this is
the default value. An application can use setsockopt(3XNET) SO_RCVBUF to change
the individual connection's receive buffer.
| | Commitment Level | Unstable
|
tcp_max_buf
| Description | The maximum buffer size
in bytes. It controls how large the send and receive buffers are set to by
an application using setsockopt(3XNET).
| | Default | 1,048,576
| | Range | 8192 to 1,073,741,824
| | Dynamic? | Yes
| | When to Change | If TCP connections
are being made in a high-speed network environment, increase the value to
match the network link speed.
| | Commitment Level | Unstable
|
tcp_cwnd_max
| Description | The maximum value of
TCP congestion window (cwnd) in bytes.
For more information on TCP congestion window, refer to RFC 1122 and
RFC 2581.
| | Default | 1,048,576
| | Range | 128 to 1,073,741,824
| | Dynamic? | Yes
| | When to Change | This is the maximum
value a TCP cwnd can grow to. Note that even if an application uses setsockopt(3XNET)
to change the window size to a value higher than tcp_cwnd_max,
the actual window used can never grow beyond tcp_cwnd_max.
Thus, tcp_max_buf should be greater than tcp_cwnd_max in general.
| | Commitment Level | Unstable
|
tcp_slow_start_initial
| Description | The maximum initial
congestion window (cwnd) size in MSS of a TCP connection.
Refer to RFC 2414 on how initial congestion window size is calculated.
| | Default | 4
| | Range | 1 to 4
| | Dynamic? | Yes
| | When to Change | Do not change the
value.
If the initial cwnd size causes network congestion under special circumstances,
decrease the value.
| | Commitment Level | Unstable
|
tcp_slow_start_after_idle
| Description | The congestion window
size in MSS of a TCP connection after it has been idled (no segment received)
for a period of one retransmission timeout (RTO).
Refer to RFC 2414 for the calculation.
| | Default | 4
| | Range | 1 to 16,384
| | Dynamic? | Yes
| | When to Change | For more information,
see tcp_slow_start_initial.
| | Commitment Level | Unstable
|
|
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