Network congestion typically occurs in the form of router buffer overflows, when nodes send more packets than the network can accommodate. Various algorithms prevent traffic congestion through establishing controls on the sending systems. These algorithms are supported in Oracle Solaris and can be easily added or directly plugged into the OS, as shown in the following table that describes the supported built-in algorithms.
Congestion control is enabled by setting the following control-related TCP properties. Although these properties are listed for TCP, the control mechanism that is enabled by these properties also applies to SCTP traffic.
Contains a list of algorithms, separated by commas, that are currently operational on the system. You can add or remove algorithms to enable only those algorithms that you want to use. This property can have multiple values. Therefore you must use either the += qualifier or the -= qualifier, depending on the change that you want to make.
Used by default when applications do not specify the algorithms explicitly in socket options. The value of the cong_default property applies to both global and non-global zones.
The following example shows how you would add an algorithm for congestion control to the protocol:
# ipadm set-prop -p cong_enabled+=algorithm tcp
Remove an algorithm as follows:
# ipadm set-prop -p cong_enabled-=algorithm tcp
Replace the default algorithm as follows:
# ipadm set-prop -p cong_default=algorithm tcp
The following example shows how you might implement congestion control. In this example, the default algorithm for the TCP protocol is changed from newreno to cubic Then, the vegas algorithm is removed from the list of enabled algorithms.
# ipadm show-prop -p extra_priv_ports tcp PROTO PROPERTY PERM CURRENT PERSISTENT DEFAULT POSSIBLE tcp extra_priv_ports rw 2049,4045 -- 2049,4045 1-65535 # ipadm show-prop -p cong_default,cong_enabled tcp PROTO PROPERTY PERM CURRENT PERSISTENT DEFAULT POSSIBLE tcp cong_default rw newreno -- newreno newreno,cubic, highspeed,vegas tcp cong_enabled rw newreno,cubic, newreno,cubic, newreno newreno,cubic, highspeed, highspeed, highspeed,vegas vegas vegas # ipadm set-prop -p cong_enabled-=vegas tcp # ipadm set-prop -p cong_default=cubic tcp # ipadm show-prop -p cong_default,cong_enabled tcp PROTO PROPERTY PERM CURRENT PERSISTENT DEFAULT POSSIBLE tcp cong_default rw cubic cubic newreno newreno,cubic, highspeed tcp cong_enabled rw newreno,cubic, newreno,cubic, newreno newreno,cubic, highspeed highspeed highspeed,vegas