Product specifications

Chapter 4: System Management Efficient Networks
®
Router family
Technical Reference Guide
Page 4-48 Efficient Networks
®
QoS Deployment Example
To understand how priority and weight can be used to decide service levels for your
applications, consider the following example:
A company decides to use QoS between a branch office and headquarters. There are
several network applications to be supported, each with different latency tolerance
levels and mission criticality:
IP telephony - This application requires a substantial amount of bandwidth
with minimal network latency. It is a mission-critical business application.
Videoconferencing - This application also requires a substantial amount of
bandwidth with minimal network latency. It is also a mission-critical business
application.
File Transfer Protocol - This application requires a minimum amount of
bandwidth and is latency-tolerant. The files may or may not be mission-
critical.
HyperText Transfer Protocol - This application requires modest "bursts" of
bandwidth intermittently. It can tolerate network latency, but not excessively.
The web content may or may not be mission-critical.
Simple Mail Transfer Protocol - As a store-and-forward application, email is
very tolerant of network latency and requires bandwidth only intermittently.
The importance of email messages is extremely variable from the most
mission-critical to useless spam.
To support IP telephony and videoconferencing, the network administrator chooses to
set the High priority weight to 50%. The administrator assigns a priority of High to IP
telephony and videoconferencing in the QoS policies.
The Network Administrator decides to set the Medium priority weight at 25%. File
Transfer Protocol is assigned Medium priority in the QoS settings.
Normal priority traffic is assigned a weight of 15%. The network administrator decides
that HTTP is a normal priority application and implements the QoS policy accordingly.
The remaining 10% of bandwidth is set as the weight for Low priority applications.
Email is given this priority in the QoS policy settings.
NOTE:
By default, all traffic that is not associated with a QoS policy is handled as Low
priority.
As a result of the QoS policies implemented in our example, IP telephony and
videoconferencing data packets will receive high priority queuing, and a minimum of
50% of the total capacity bandwidth at any one time. This minimum bandwidth will
always be available to these applications regardless of other traffic on the network at
any given time. Because of their high priority, IP telephony and videoconferencing
packets will be the last to be dropped during periods of saturation. Additional