Riverstone Networks WICT1-12 - Manual (Page 707)

Riverstone Networks RS Switch Router User Guide Release 8.0 31-3
Service Configuration Creating a Service
31.2 CREATING A SERVICE
31.2.1 Aggregate Rate Limiting Service
An aggregate rate limiting policy can not be applied to an interface that spans ports on more than one channel. For
example, an aggregate rate limiting policy can not be applied to the interface ip2 if it interfaces with a VLAN that
consists of ports et.1.(1-4) and et.2.(1-4). The aggregate rate limiting mode will need to be enabled on the line card to
be able to configure aggregate rate limiting.
To create an aggregate rate limiting service, use the following command:
Here is an example:
Hardware Credit Buckets
Aggregate rate limiting uses a hardware credit bucket scheme to perform rate limiting. It is essentially allocated space
in memory and is built into all rate-enabled line cards. Hardware credit bucket works by limiting how much traffic is
allowed to pass through a physical port. As traffic passes through the port, credits are deducted from the credit bucket.
Service providers control the amount of credit in the bucket, depending on the amount of bandwidth allocated; the
more bandwidth, the more credit for that type of traffic. When traffic passes through a physical port or matches a
predefined profile while passing through an interface, credit is deducted from the bucket. When all the credits have
been used and traffic has exhausted all allocated bandwidth, action is taken on the excess traffic. Packets are either
dropped, dropped to a lower priority, or ToS precedence is rewritten.
The credit bucket scheme consists of two major components, credit count and replenish rate:
Credit count – The amount of credits in each bucket. Credit count defines how much credit is available for a physical
port or a specific type of traffic. It determines when traffic is considered to be excessive, based on the availability of
credit.
Replenish rate – Determines when or how often credit buckets are refilled. If the replenish rate is too low, there will
not be a sufficient amount of credits when traffic arrives. If the replenish rate is too high, it will reduce the effectiveness
of the rate-limiting policy.
Create an aggregate
rate limiting service.
service
<name>
create rate-limit aggregate rate
<rate> [
no-action
|
drop-packets
|
lower-priority
|
lower-priority-except-control
|
tos-precedence-rewrite
<num> |
tos-precedence-rewrite-lower-priority
<num> |
tos-rewrite
<num> |
tos-rewrite-lower-priority
<num>]
|
time-select
<num>]
! Create an aggregate service, limiting an aggregate flow to 2 million bps and drops packets if the rate is exceeded
rs(config)# service mktaggregate create rate-limit aggregate rate 2000000 drop-packets