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Oracle Solaris Tunable Parameters Reference Manual     Oracle Solaris 11 Express 11/10
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Document Information

Preface

1.  Overview of Oracle Solaris System Tuning

2.  Oracle Solaris Kernel Tunable Parameters

3.  NFS Tunable Parameters

4.  Internet Protocol Suite Tunable Parameters

Where to Find Tunable Parameter Information

Overview of Tuning IP Suite Parameters

IP Suite Parameter Validation

Internet Request for Comments (RFCs)

IP Tunable Parameters

_icmp_err_interval and _icmp_err_burst

_respond_to_echo_broadcast

_addrs_per_if

ip_squeue_fanout

TCP Tunable Parameters

_deferred_ack_interval

_local_dack_interval

_deferred_acks_max

_local_dacks_max

_wscale_always

_tstamp_always

send_maxbuf

recv_maxbuf

_max_buf

_cwnd_max

_slow_start_initial

_slow_start_after_idle

sack

_rev_src_routes

_time_wait_interval

ecn

_conn_req_max_q

_conn_req_max_q0

_conn_req_min

_rst_sent_rate_enabled

_rst_sent_rate

TCP/IP Parameters Set in the /etc/system File

ipcl_conn_hash_size

ip_squeue_worker_wait

TCP Parameters With Additional Cautions

_keepalive_interval

_ip_abort_interval

_rexmit_interval_initial

_rexmit_interval_max

_rexmit_interval_min

_rexmit_interval_extra

_tstamp_if_wscale

_recv_hiwat_minmss

UDP Tunable Parameters

send_maxbuf

recv_maxbuf

IPQoS Tunable Parameter

_policy_mask

SCTP Tunable Parameters

_max_init_retr

_pa_max_retr

_pp_max_retr

_cwnd_max

_ipv4_ttl

_heartbeat_interval

_new_secret_interval

_initial_mtu

_deferred_ack_interval

_ignore_path_mtu

_initial_ssthresh

_max_buf

_ipv6_hoplimit

_rto_min

_rto_max

_rto_initial

_cookie_life

_max_in_streams

_initial_out_streams

_shutack_wait_bound

_maxburst

_addip_enabled

_prsctp_enabled

Per-Route Metrics

5.  Network Cache and Accelerator Tunable Parameters

6.  System Facility Parameters

A.  Tunable Parameters Change History

B.  Revision History for This Manual

Index

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

_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

_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

_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

_ipv4_ttl

Description

Controls the time to live (TTL) value in the IP version 4 header for the outbound IP version 4 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. Consider increasing this parameter if the path to the destination is likely to span more than 64 hops.

Commitment Level

Unstable

_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

_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

_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

_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

_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

_initial_ssthresh

Description

Sets the initial slow start threshold for a destination address of the peer.

Default

102,400

Range

1024 to 4,294,967,295

Dynamic?

Yes

When to Change

Refer to RFC 2960, section 7.2.1.

Commitment Level

Unstable

_max_buf

Description

Controls the maximum 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

8,192 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

_ipv6_hoplimit

Description

Sets the value of the hop limit in the IP version 6 header for the outbound IP version 6 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. Consider increasing this parameter if the path to the destination is likely to span more than 60 hops.

Commitment Level

Unstable

_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

_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

_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

_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

_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

_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

_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

_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

_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

_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