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Oracle® Solaris 11.4 Tunable Parameters Reference Manual

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Updated: January 2019
 
 

UDP Tunable Parameters

This section describes parameters specific to the UDP protocol.

_ipv4_ttl Parameter

Description

Controls the time to live (TTL) value in the IPv4 header for outbound UDP 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 UDP 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

largest-anon-port Parameter

Description

This parameter controls the largest port number UDP 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

Defines the maximum send and receive buffer size for a UDP socket. It controls how large the send and receive buffers might be set to by an application that uses setsockopt().

Default

2,097,152

Range

65,536 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

Stable

recv-buf Parameter

Description

Defines the default receive buffer size for a UDP socket. For more information, see max-buf Parameter.

Default

57,344 bytes

Range

128 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 for a UDP socket. For more information, see max-buf Parameter.

Default

57,344 bytes

Range

1,024 to the current value of max-buf

Dynamic?

Yes

When to Change

An application can use setsockopt (SO_SNDBUF) to change the size for an individual socket. In general, you do not need to change the default value.

Commitment Level

Stable

smallest-anon-port Parameter

Description

This parameter controls the smallest port number UDP 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

Stable