Traffic Management - CCIE Routing and Switching Exam Certification Guide - page 518

be configured, providing different service policies for each flow. For more information on
CBWFQ, consult Cisco's web site at www.cisco.com/univercd/cc/td/doc/product/software/
ios120/120newft/120t/120t5/cbwfq.htm.
Other QoS and Traffic Management Mechanisms
This section covers Generic Traffic Shaping (GTS), Frame Relay Traffic Shaping (FRTS), IEEE
802.1P, and compression.
GTS
GTS uses queuing on an Asynchronous Transfer Mode (ATM), Frame Relay, or other type of
network to limit traffic bursts, which can cause congestion. GTS is a way to control the flow of
traffic on a particular interface or for specific traffic. It reduces the outbound traffic flow by
limiting traffic to a specified rate.
The idea is to shape the traffic to a specified rate to avoid congestion. It is important to under-
stand that this is not a policing scheme, just a shaping mechanism. A policing mechanism, Com-
mitted Access Rate (CAR), is discussed in the following section. Traffic shaping is supported
on all media and encapsulation types on the router. Traffic shaping can also be applied to a
specific access list on an interface.
The interface configuration command for GTS is as follows:
traffic-shape rate bit-rate [burst-size [excess-burst-size]]
The bit-rate is the specified maximum rate for traffic on the interface. The burst-size is the
sustained number of bits that can be sent per burst interval. The excess-burst-size is the number
of bits that can be sent beyond the burst size. By default, the excess-burst-size is equal to the
burst-size .
Another format of the command that uses access lists to configure traffic flow limits to specified
traffic is as follows:
traffic-shape group group-num bit-rate [burst-size [excess-burst-size]]
The group-num is the access-list number.
In Example 11-4, Ethernet 0 is configured to limit FTP traffic to 2 Mbps, and Ethernet 1 is
configured to limit all output to 7 Mbps.