Riverstone Networks WICT1-12 - Manual (Page 575)

Riverstone Networks RS Switch Router User Guide Release 8.0 26-13
QoS Configuration Limiting Traffic Rate
26.10 LIMITING TRAFFIC RATE
Note Some commands in this facility require updated RS hardware.
Rate limiting provides the ability to control the usage of a fundamental network resource, bandwidth. It allows you to
limit the rate of traffic that flows through the specified interfaces, thus reserving bandwidth for critical applications.
The RS supports the following types of rate limiting:
Per-flow Rate Limiting – Configure policies that limit individual flows to a specified rate. This is the default rate
limiting mode on the RS.
Aggregate Rate Limiting – Configure policies that limit an aggregation of flows (all flows that match an ACL) to a
specified rate. This type of rate limiting is performed completely in hardware and must be enabled on a per-line card
basis. If you enable aggregate rate limiting on a line card, you cannot use per-flow or flow-aggregate rate limiting with
that card.
Note Aggregate rate limiting is only supported on certain line cards. Make sure the line
card supports hardware rate limiting.
• Software-based Flow-aggregate Rate Limiting – Configure policies that limit an aggregation of
flows (all flows that match an ACL) to a specified rate. For example, limit traffic to or from a
particular subnet. This type of rate limiting is performed mostly in software. However, forwarding
of packets is done in the hardware. Flow-aggregate rate limiting is designed for use with line cards
that do not support aggregate rate limiting.
• Port-level Rate Limiting – Configure policies that limit traffic coming into a particular port. This
type of policy can be used to limit any type of traffic and is enabled on a per line card basis. If you
enable port-level rate limiting on a line card, you cannot use per-flow or flow-aggregate rate limiting
with that card.
Note You can also limit outbound traffic by using the WAN rate shaping feature
described in
Section 30.13, "WAN Rate Shaping" . Whereas rate limiting discards
packets when the traffic exceeds the the configured rate for the stream, rate
shaping buffers packets for a limited period in order to attempt successful delivery.
A traffic profile is used to define the traffic characteristics before an upper limit is assigned. The traffic profile is
created using an ACL, which can utilize any combination of the parameters supported in IP ACL. A rate limiting policy
can then be defined by using the ACL and traffic rate limitations. You define the action to be taken on the traffic that
exceeds the upper limit. For example, dropping packets. Except for port rate limiting, the rate limiting policy is then
applied to a logical IP interface.
Rate limiting policies work only in one direction. That is, only the traffic coming into the interface to which a policy
is applied will be subject to rate limiting (except for output port rate limiting policies, which are applied to egress
ports). If both incoming and outgoing traffic to a network or subnet needs to be rate limited, then you should create
separate policies to be applied to each interface.