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Oracle® Solaris 11.4 Tunable Parameters Reference Manual

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Updated: January 2019
 
 

SCTP Tunable Parameters

This section describes parameters related to the stream control transmission protocol.

_addip_enabled Parameter

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

_cookie_life Parameter

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 Parameter.

Commitment Level

Unstable

_deferred_ack_interval Parameter

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

_heartbeat_interval Parameter

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

_ignore_path_mtu Parameter

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

_initial_mtu Parameter

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

_initial_out_streams Parameter

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

_initial_ssthresh Parameter

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

_ipv4_ttl Parameter

Description

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 Parameter (IPv4).

Default

64 bytes

Range

1 to 255

Dynamic?

Yes

When to Change

Do not change this value in a normal network environment.

Commitment Level

Unstable

_ipv6_hoplimit Parameter

Description

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 Parameter (IPv6).

Default

60

Range

1 to 255

Dynamic?

Yes

When to Change

Do not change this value in a normal network environment.

Commitment Level

Unstable

_maxburst Parameter

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

_max_in_streams Parameter

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

_max_init_retr Parameter

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 Parameter. Ideally, _max_init_retr should be less than or equal to _pa_max_retr.

Commitment Level

Unstable

_new_secret_interval Parameter

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

_pa_max_retr Parameter

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 Parameter 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

_pp_max_retr Parameter

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

_prsctp_enabled Parameter

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

_rto_initial Parameter

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

_rto_max Parameter

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

_rto_min Parameter

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

_shutack_wait_bound Parameter

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 Parameter.

Commitment Level

Unstable

_xmit_lowat Parameter

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.

Commitment Level

Unstable

cwnd-max Parameter

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

This parameter does not need to be changed in normal circumstances. If the system needs to communicate with peers far away (round trip time in the order of hundreds of milliseconds) using very fast network (in the order of Gbps), increase the default value to match the bandwidth-delay product to those peers. Note that max-buf parameter should also be increased at the same time.

Commitment Level

Stable

largest_anon_port Parameter

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 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.

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

Stable

max-buf Parameter

Description

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().

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

able

recv-buf Parameter

Description

Defines the default receive buffer size in bytes. See also max-buf Parameter.

Default

102,400

Range

8,192 to the current value of max-buf

Dynamic?

Yes

When to Change

An application can use setsockopt (SO_RCVBUF) to change the individual connection's receive buffer. See the setsockopt(3C) man page for information.

Commitment Level

able

send-buf Parameter

Description

Defines the default send buffer size in bytes. See also max-buf Parameter.

Default

102,400

Range

8,192 to the current value of max-buf

Dynamic?

Yes

When to Change

An application can use setsockopt (SO_SNDBUF) to change the individual connection's send buffer.

Commitment Level

Stable

smallest-anon-port Parameter

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 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.

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

table