WB 15.15

4 OpenFlow per-flow rate limiting

OpenFlow supports per-flow rate-limiters for OpenFlow 1.0 as HP vendor extensions.

A rate-limiter controls the rate of packets passing through a switch. Per-flow rate-limiters associate

an arbitrary number of flows with a rate-limiter. Using OpenFlow with per flow rate-limiters, any

number of flows can be flexibly mapped to a rate-limiter, regardless of their source and destination

ports. The use of rate-limiters requires a version of ovs-ofctl which includes HP QoS extension.

Rate-limiters are addressed by a limiter_id, an arbitrary 32 bit number. Configuration of rate-limiters

is done through a simple message from the OpenFlow controller which can add, modify or remove

a rate-limiter. Flows are directed to rate-limiters through an action. Multiple flows can be associated

with the same rate-limiter. Statistics can be read from the OpenFlow controller for each rate-limiter.

NOTE: Per-flow rate-limiters are used only if the hardware rate-limiter for the instance is disabled.

QoS extensions

HP QoS extension to the OpenFlow protocol provides support for rate-limiters. A rate-limiter controls

the rate of packets passed through it. Per-flow rate-limiters associate an arbitrary number of flows

with a rate-limiter. The HP QoS vendor extensions support per-flow rate-limiters with only drop rate

flag and not mark rate or other flags.

Maintain limiter in rule

The rule structure maintains the limiter identification and a flag to indicate if the rule has a limiter

ID associated with it.

Create a limiter

A per-flow rate-limiter is added/created from the OpenFlow controller using the add-limiter

command. Note that this requires the controller to have the HP QoS extensions.

On receiving a vendor request from the OpenFlow controller, the vendor ID is checked for

HPX_VENDOR_ID and then passed on to “ofputil_decode_hpx” to be decoded. On receiving a

message of type OFPUTIL_HPX_ADD_LIMITER, a new meter is created with the parameters received

in the message. The meters are created, updated and deleted by calls to platform independent

functions, which in turn call the platform dependent functions.

Get limiter details

The details on the limiters configured can be retrieved by issuing a dump-limiters command

from the OpenFlow controller. These details can also be checked on the switch using show

openflow <inst_name> limiters.

Support flow with a limiter

A flow can be associated with a per-flow rate-limiter by giving the limiter ID in actions. For example,

assume that a per flow rate-limiter with ID 100 is created with an add-limiter command from

the OpenFlow controller. From an ovs controller with HP QoS extensions, a flow can be associated

with this rate-limiter using the rate_limit key word in the actions as indicated below.

ovs-ofctl add-flow tcp:192.168.1.2:6633

idle_timeout=0,ip,nw_src=20.20.20.41,

action=output:57,rate_limit:100

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