SCTP Tunable Parameters

`_max_init_retr`

Description: 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.
Default: 8

Range: 0 to 128
Dynamic?: Yes
When to Change: The number of INIT retransmissions depend on _pa_max_retr. Ideally, _max_init_retr should be less than or equal to _pa_max_retr.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_pa_max_retr`

Description: Controls the maximum number of retransmissions (over all paths) for an SCTP association. The SCTP association is aborted when this number is exceeded.
Default: 10

Range: 1 to 128
Dynamic?: Yes
When to Change: The maximum number of retransmissions over all paths depend on the number of paths and the maximum number of retransmission over each path. Ideally, sctp_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.)
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_pp_max_retr`

Description: Controls the maximum number of retransmissions over a specific path. When this number is exceeded for a path, the path (destination) is considered unreachable.
Default: 5

Range: 1 to 128
Dynamic?: Yes
When to Change: Do not change this value to less than 5.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_cwnd_max`

Description: Controls the maximum value of the congestion window for an SCTP association.
Default: 1,048,576
Range: 128 to 1,073,741,824
Dynamic?: Yes
When to Change: Even if an application uses setsockopt(3XNET) 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.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_ipv4_ttl`

Description: Controls the time to live (TTL) value in the IP version 4 header for the outbound IPv4 packets on an SCTP association.
Default: 64
Range: 1 to 255
Dynamic?: Yes
When to Change: Generally, you do not need to change this value.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_ipv6_hoplimit`

Description: Sets the value of the hop limit in the IPv6 header for the outbound IPv6 packets on an SCTP association.
Default: 60

Range: 0 to 255
Dynamic?: Yes
When to Change: Generally, you do not need to change this value.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_heartbeat_interval`

Description

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.

Default

30 seconds

Range

0 to 86,400 seconds

Dynamic?

Yes

When to Change

Refer to RFC 2960, section 8.3.

Commitment Level

Unstable

Change History

For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_new_secret_interval`

Description: Determines when a new secret needs to be generated. The generated secret is used to compute the MAC for a cookie.
Default: 2 minutes

Range: 0 to 1,440 minutes
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 5.1.3.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_initial_mtu`

Description: Determines the initial maximum send size for an SCTP packet including the length of the IP header.
Default: 1500 bytes

Range: 68 to 65,535
Dynamic?: Yes
When to Change: Increase this parameter if the underlying link supports frame sizes that are greater than 1500 bytes.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_deferred_ack_interval`

Description: Sets the time-out value for SCTP delayed acknowledgment (ACK) timer in milliseconds.
Default: 100 milliseconds

Range: 1 to 60,000 milliseconds
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 6.2.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_ignore_path_mtu`

Description: Enables or disables path MTU discovery.
Default: 0 (disabled)

Range: 0 (disabled) or 1 (enabled)
Dynamic?: Yes
When to Change: 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.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_initial_ssthresh`

Description: Sets the initial slow start threshold for a destination address of the peer.
Default: 1,048,576

Range: 1,024 to 4,294,967,295
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 7.2.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`send_buf`

Description: Defines the default send buffer size in bytes. See also max_buf.
Default: 102,400
Range: 8,192 to the current value of max_buf
Dynamic?: Yes
When to Change: An application can use setsockopt(3XNET) SO_SNDBUF to change the individual connection's send buffer.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_xmit_lowat`

Description: Controls the lower limit on the send window size.
Default: 8,192

Range: 8,192 to 1,073,741,824
Dynamic?: Yes
When to Change: 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. If required, consider changing this parameter in accordance with send_buf.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`recv_buf`

Description: Defines the default receive buffer size in bytes. See also max_buf.
Default: 102,400
Range: 8,192 to the current value of max_buf
Dynamic?: Yes
When to Change: An application can use setsockopt(3XNET) SO_RCVBUF to change the individual connection's receive buffer.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`max_buf`

Description: Controls the maximum send and receive buffer size in bytes. It controls how large the send and receive buffers are set to by an application that uses getsockopt(3SOCKET).
Default: 1,048,576

Range: 102,400 to 1,073,741,824
Dynamic?: Yes
When to Change: Increase the value of this parameter to match the network link speed if associations are being made in a high-speed network environment.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_rto_min`

Description: Sets the lower bound for the retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
Default: 1,000

Range: 500 to 60,000
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 6.3.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_rto_max`

Description: Controls the upper bound for the retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
Default: 60,000

Range: 1,000 to 60,000,000
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 6.3.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_rto_initial`

Description: Controls the initial retransmission timeout (RTO) in milliseconds for all the destination addresses of the peer.
Default: 3,000

Range: 1,000 to 60,000,000
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 6.3.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_cookie_life`

Description: Sets the lifespan of a cookie in milliseconds.
Default: 60,000

Range: 10 to 60,000,000
Dynamic?: Yes
When to Change: Generally, you do not need to change this value. This parameter might be changed in accordance with _rto_max.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_max_in_streams`

Description: Controls the maximum number of inbound streams permitted for an SCTP association.
Default: 32

Range: 1 to 65,535
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 5.1.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_initial_out_streams`

Description: Controls the maximum number of outbound streams permitted for an SCTP association.
Default: 32

Range: 1 to 65,535
Dynamic?: Yes
When to Change: Refer to RFC 2960, section 5.1.1.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_shutack_wait_bound`

Description: Controls the maximum time, in milliseconds, to wait for a SHUTDOWN ACK after having sent a SHUTDOWN chunk.
Default: 60,000

Range: 0 to 300,000
Dynamic?: Yes
When to Change: Generally, you do not need to change this value. This parameter might be changed in accordance with _rto_max.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_maxburst`

Description: Sets the limit on the number of segments to be sent in a burst.
Default: 4

Range: 2 to 8
Dynamic?: Yes
When to Change: You do not need to change this parameter. You might change it for testing purposes.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_addip_enabled`

Description: Enables or disables SCTP dynamic address reconfiguration.
Default: 0 (disabled)

Range: 0 (disabled) or 1 (enabled)
Dynamic?: Yes
When to Change: The parameter can be enabled if dynamic address reconfiguration is needed. Due to security implications, enable this parameter only for testing purposes.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`_prsctp_enabled`

Description: Enables or disables the partial reliability extension (RFC 3758) to SCTP.
Default: 1 (enabled)

Range: 0 (disabled) or 1 (enabled)
Dynamic?: Yes
When to Change: Disable this parameter if partial reliability is not supported in your SCTP environment.
Commitment Level: Unstable
Change History: For information, see SCTP Parameter Name Changes (Oracle Solaris 11).

`smallest_anon_port`

Description: 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 and it does not specify 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.
Unit: Port number
Default: 32,768
Range: 1,024 to 65,535
Dynamic?: Yes
When to Change: When a larger ephemeral port range is required.
Commitment Level: Unstable
Change History: For information, see [tcp,sctp,udp]_smallest_anon_port and [tcp,sctp,udp]_largest_anon_port.

`largest_anon_port`

Description: 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 and it does not specify 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.
Unit: Port number
Default: 65,535
Range: 32,768 to 65,535
Dynamic?: Yes
When to Change: When a larger ephemeral port range is required.
Commitment Level: Unstable
Change History: For information, see [tcp,sctp,udp]_smallest_anon_port and [tcp,sctp,udp]_largest_anon_port.

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