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Oracle Solaris Tunable Parameters Reference Manual     Oracle Solaris 11 Information Library
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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 and _respond_to_echo_multicast (ipv4 or ipv6)

_send_redirects (ipv4 or ipv6)

forwarding (ipv4 or ipv6)

ttl

hoplimit (ipv6)

_addrs_per_if

hostmodel (ipv4 or ipv6)

ip_squeue_fanout

IP Tunable Parameters With Additional Cautions

_pathmtu_interval

_icmp_return_data_bytes (ipv4 or ipv6)

TCP Tunable Parameters

_deferred_ack_interval

_local_dack_interval

_deferred_acks_max

_local_dacks_max

_wscale_always

_tstamp_always

send_buf

recv_buf

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

smallest_anon_port

largest_anon_port

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_buf

recv_buf

max_buf

smallest_anon_port

largest_anon_port

IPQoS Tunable Parameter

_policy_mask

SCTP Tunable Parameters

_max_init_retr

_pa_max_retr

_pp_max_retr

_cwnd_max

_ipv4_ttl

_ipv6_hoplimit

_heartbeat_interval

_new_secret_interval

_initial_mtu

_deferred_ack_interval

_ignore_path_mtu

_initial_ssthresh

send_buf

_xmit_lowat

recv_buf

max_buf

_rto_min

_rto_max

_rto_initial

_cookie_life

_max_in_streams

_initial_out_streams

_shutack_wait_bound

_maxburst

_addip_enabled

_prsctp_enabled

smallest_anon_port

largest_anon_port

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

IP Tunable Parameters

_icmp_err_interval and _icmp_err_burst

Description

Controls the rate of IP in generating ICMP error messages. IP generates only up to _icmp_err_burst IP error messages in any _icmp_err_interval.

The _icmp_err_interval parameter protects IP from denial of service attacks. Setting this parameter to 0 disables rate limiting. It does not disable the generation of error messages.

Default

100 milliseconds for _icmp_err_interval

10 error messages for _icmp_err_burst

Range

0 – 99,999 milliseconds for _icmp_err_interval

1 – 99,999 error messages for _icmp_err_burst

Dynamic?

Yes

When to Change

If you need a higher error message generation rate for diagnostic purposes.

Commitment Level

Unstable

Change History

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

_respond_to_echo_broadcast and _respond_to_echo_multicast (ipv4 or ipv6)

Description

Controls whether IP responds to a broadcast ICMPv4 echo request or a IPv6 multicast ICMPv6 echo request.

Default

1 (enabled)

Range

0 (disabled) or 1 (enabled)

Dynamic?

Yes

When to Change

If you do not want this behavior for security reasons, disable it.

Commitment Level

Unstable

Change History

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

_send_redirects (ipv4 or ipv6)

Description

Controls whether IPv4 or IPv6 sends out ICMPv4 or ICMPv6 redirect messages.

Default

1 (enabled)

Range

0 (disabled) or 1 (enabled)

Dynamic?

Yes

When to Change

If you do not want this behavior for security reasons, disable it.

Commitment Level

Unstable

Change History

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

forwarding (ipv4 or ipv6)

Description

Controls whether IPv4 or IPv6 forwards packets with source IPv4 routing options or IPv6 routing headers.

Default

0 (disabled)

Range

0 (disabled) or 1 (enabled)

Dynamic?

Yes

When to Change

Keep this parameter disabled to prevent denial of service attacks.

Commitment Level

Unstable

Change History

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

ttl

Description

Controls the time to live (TTL) value in the IPv4 header for the outbound IPv4 packets on an IP association.

Default

255

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 IP Parameter Name Changes (Oracle Solaris 11).

hoplimit (ipv6)

Description

Sets the value of the hop limit in the IPv6 header for the outbound IPv6 packets on an IP association.

Default

255

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 IP Parameter Name Changes (Oracle Solaris 11).

_addrs_per_if

Description

Defines the maximum number of logical IP interfaces associated with a real interface.

Default

256

Range

1 to 8192

Dynamic?

Yes

When to Change

Do not change the value. If more logical interfaces are required, you might consider increasing the value. However, recognize that this change might have a negative impact on IP's performance.

Commitment Level

Unstable

Change History

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

hostmodel (ipv4 or ipv6)

Description

Controls send and receive behavior for IPv4 or IPv6 packets on a multi-homed system. This property can have the following values: weak, strong, and src-priority. The default value is weak.

Default

weak

Range

weak, strong, or src-priority

  • weak

    • Outgoing packets - The source address of the packet going out need not match the address configured on the outgoing interface.

    • Incoming packets - The destination address of the incoming packet need not match the address configured on the incoming interface.

    • strong

      • Outgoing packets - The source address of the packet going out must match the address configured on the outgoing interface.

      • Incoming packets - The destination address of the incoming packet must match the address configured on the incoming interface.

    • src-priority

      • Outgoing packets - If multiple routes for the IP destination in the packet are available, the system prefers routes where the IP source address in the packet is configured on the outgoing interface.

        If no such route is available, the system falls back to selecting the best route, as with the weak ES case.

      • Incoming packets - The destination address of the incoming packet must be configured on any one of the host's interface.

Dynamic?

Yes

When to Change

If a machine has interfaces that cross strict networking domains (for example, a firewall or a VPN node), set this parameter to strong.

Commitment Level

Unstable

Change History

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

ip_squeue_fanout

Description

Determines the mode of associating TCP/IP connections with squeues.

A value of 0 associates a new TCP/IP connection with the CPU that creates the connection. A value of 1 associates the connection with multiple squeues that belong to different CPUs.

Default

0

Range

0 or 1

Dynamic?

Yes

When to Change

Consider setting this parameter to 1 to spread the load across all CPUs in certain situations. For example, when the number of CPUs exceed the number of NICs, and one CPU is not capable of handling the network load of a single NIC, change this parameter to 1.

This property can only be set in the /etc/system file.

Zone Configuration

This parameter can only be set in the global zone.

Commitment Level

Unstable

IP Tunable Parameters With Additional Cautions

Changing the following parameters is not recommended.

_pathmtu_interval

Description

Specifies the interval in milliseconds when IP flushes the path maximum transfer unit (PMTU) discovery information, and tries to rediscover PMTU.

Refer to RFC 1191 on PMTU discovery.

Default

10 minutes

Range

5 seconds to 277 hours

Dynamic?

Yes

When to Change

Do not change this value.

Commitment Level

Unstable

Change History

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

_icmp_return_data_bytes (ipv4 or ipv6)

Description

When IPv4 or IPv6 sends an ICMPv4 or ICMPv6 error message, it includes the IP header of the packet that caused the error message. This parameter controls how many extra bytes of the packet beyond the IPv4 or IPv6 header are included in the ICMPv4 or ICMPv6 error message.

Default

64 for IPv4

1280 for IPv6

Range

8–6636 for IPv4

8-1280 for IPv6

Dynamic?

Yes

When to Change

Do not change the value. Including more information in an ICMP error message might help in diagnosing network problems. If this feature is needed, increase the value.

Commitment Level

Unstable

Change History

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