This section describes parameters related to the stream control transmission protocol.
0 (disabled)
0 (disabled) or 1 (enabled)
Yes
The parameter can be enabled if dynamic address reconfiguration is needed. Due to security implications, enable this parameter only for testing purposes.
Unstable
60,000
10 to 60,000,000
Yes
Generally, you do not need to change this value. This parameter might be changed in accordance with _rto_max.
Unstable
Controls the maximum value of the congestion window for an SCTP association.
1,048,576
128 to 1,073,741,824
Yes
Even if an application uses setsockopt() to change the window size to a value higher than _cwnd_max, the actual window used can never grow beyond _cwnd_max. Thus, max_buf should be greater than _cwnd_max.
Unstable
Sets the time-out value for SCTP delayed acknowledgment (ACK) timer in milliseconds.
100 milliseconds
1 to 60,000 milliseconds
Yes
Refer to RFC 2960, section 6.2.
Unstable
Computes the interval between HEARTBEAT chunks to an idle destination, that is allowed to heartbeat.
An SCTP endpoint periodically sends an HEARTBEAT chunk to monitor the reachability of the idle destinations transport addresses of its peer.
30 seconds
0 to 86,400 seconds
Yes
Refer to RFC 2960, section 8.3.
Unstable
0 (disabled)
0 (disabled) or 1 (enabled)
Yes
Enable this parameter if you want to ignore MTU changes along the path. However, doing so might result in IP fragmentation if the path MTU decreases.
Unstable
Determines the initial maximum send size for an SCTP packet including the length of the IP header.
1500 bytes
68 to 65,535
Yes
Increase this parameter if the underlying link supports frame sizes that are greater than 1500 bytes.
Unstable
Controls the maximum number of outbound streams permitted for an SCTP association.
32
1 to 65,535
Yes
Refer to RFC 2960, section 5.1.1.
Unstable
Sets the initial slow start threshold for a destination address of the peer.
1,048,576
1,024 to 4,294,967,295
Yes
Refer to RFC 2960, section 7.2.1.
Unstable
Controls the time to live (TTL) value in the IPv4 header for outbound SCTP messages sent over IPv4. For more information, see the description for ttl (IPv4).
64 bytes
1 to 255
Yes
Do not change this value in a normal network environment.
Unstable
Sets the value of the hop limit in the IPv6 header for the outbound SCTP messages sent over IPv6. For more information, see the description for hoplimit (IPv6).
60
1 to 255
Yes
Do not change this value in a normal network environment.
Unstable
Sets the limit on the number of segments to be sent in a burst.
4
2 to 8
Yes
You do not need to change this parameter. You might change it for testing purposes.
Unstable
Controls the maximum number of inbound streams permitted for an SCTP association.
32
1 to 65,535
Yes
Refer to RFC 2960, section 5.1.1.
Unstable
Controls the maximum number of attempts an SCTP endpoint should make at resending an INIT chunk. The SCTP endpoint can use the SCTP initiation structure to override this value.
8
0 to 128
Yes
The number of INIT retransmissions depend on _pa_max_retr. Ideally, _max_init_retr should be less than or equal to _pa_max_retr.
Unstable
Determines when a new secret needs to be generated. The generated secret is used to compute the MAC for a cookie.
2 minutes
0 to 1,440 minutes
Yes
Refer to RFC 2960, section 5.1.3.
Unstable
Controls the maximum number of retransmissions (over all paths) for an SCTP association. The SCTP association is aborted when this number is exceeded.
10
1 to 128
Yes
The maximum number of retransmissions over all paths depend on the number of paths and the maximum number of retransmission over each path. Ideally, _pa_max_retr should be set to the sum of _pp_max_retr over all available paths. For example, if there are 3 paths to the destination and the maximum number of retransmissions over each of the 3 paths is 5, then _pa_max_retr should be set to less than or equal to 15. (See the Note in Section 8.2, RFC 2960.)
Unstable
Controls the maximum number of retransmissions over a specific path. When this number is exceeded for a path, the path (destination) is considered unreachable.
5
1 to 128
Yes
Do not change this value to less than 5.
Unstable
Enables or disables the partial reliability extension (RFC 3758) to SCTP.
1 (enabled)
0 (disabled) or 1 (enabled)
Yes
Disable this parameter if partial reliability is not supported in your SCTP environment.
Unstable
Controls the initial retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
3,000
1,000 to 60,000,000
Yes
Refer to RFC 2960, section 6.3.1.
Unstable
Controls the upper bound for the retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
60,000
1,000 to 60,000,000
Yes
Refer to RFC 2960, section 6.3.1.
Unstable
Sets the lower bound for the retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
1,000
500 to 60,000
Yes
Refer to RFC 2960, section 6.3.1.
Unstable
Controls the maximum time, in milliseconds, to wait for a SHUTDOWN ACK after having sent a SHUTDOWN chunk.
60,000
0 to 300,000
Yes
Generally, you do not need to change this value. This parameter might be changed in accordance with _rto_max.
Unstable
8,192
8,192 to 1,073,741,824
Yes
Generally, you do not need to change this value. This parameter sets the minimum size required in the send buffer for the socket to be marked writable.
Unstable
Specifies the default congestion control algorithm used by the protocol when new connections are created. Applications can opt to choose a different algorithm through the TCP_CONGESTION option in the setsockopt() call. Only enabled algorithms can be set as default. See cong_enabled) and the setsockopt(3SOCKET) man page.
newreno
newreno, cubic, highspeed, vegas
Yes
This parameter does not need to be changed in normal circumstances.
Stable
Specifies the set of congestion control algorithms that are enabled on the system. The newreno algorithm can never be disabled. Disabled algorithms cannot be set as default (see cong_default) or be used by applications.
By default, all algorithms installed on the system are enabled.
newreno, cubic, highspeed, vegas
Yes
This parameter does not need to be changed in normal circumstances.
Stable
This parameter controls the largest port number SCTP can select as an ephemeral port. An application can use an ephemeral port when it creates a connection with a specified protocol but not a port number. Ephemeral ports are not associated with a specific application. When the connection is closed, the port number can be reused by a different application.
Port number
65,535
32,768 to 65,535
Yes
When a larger ephemeral port range is required.
Stable
Controls the maximum send and receive buffer size in bytes. It controls how large the send and receive buffers might be set to by an application that uses setsockopt().
1,048,576
102,400 to 1,073,741,824
Yes
Increase the value of this parameter to match the network link speed if associations are being made in a high-speed network environment.
able
Defines the default receive buffer size in bytes. See also max_buf.
102,400
8,192 to the current value of max_buf
Yes
An application can use setsockopt (SO_RCVBUF) to change the individual connection's receive buffer.
able
Defines the default send buffer size in bytes. See also max_buf.
102,400
8,192 to the current value of max_buf
Yes
An application can use setsockopt (SO_SNDBUF) to change the individual connection's send buffer.
Stable
This parameter controls the smallest port number SCTP can select as an ephemeral port. An application can use an ephemeral port when it creates a connection with a specified protocol but not a port number. Ephemeral ports are not associated with a specific application. When the connection is closed, the port number can be reused by a different application.
Port number
32,768
1,024 to 65,535
Yes
When a larger ephemeral port range is required.
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