© 2006 Cisco Systems, Inc. All rights reserved. Optimizing Converged Cisco Networks (ONT) Module 3: Introduction to IP QoS

© 2006 Cisco Systems, Inc. All rights reserved. Lesson 3.2: Implementing Cisco IOS QoS

© 2006 Cisco Systems, Inc. All rights reserved. Objectives  Describe the need for QoS as it relates to various types of network traffic.  Identify QoS mechanisms.  Describe the steps used to implement QoS.

© 2006 Cisco Systems, Inc. All rights reserved. What Is Quality of Service? Two Perspectives  The user perspective Users perceive that their applications are performing properly Voice, video, and data  The network manager perspective Need to manage bandwidth allocations to deliver the desired application performance Control delay, jitter, and packet loss

© 2006 Cisco Systems, Inc. All rights reserved. Different Types of Traffic Have Different Needs Application Examples Sensitivity to QoS Metrics DelayJitter Packet Loss Interactive Voice and Video YYY Streaming Video NYY Transactional/ Interactive YNN Bulk Data File Transfer NNN Need to manage bandwidth allocations  Real-time applications especially sensitive to QoS Interactive voice Videoconferencing  Causes of degraded performance Congestion losses Variable queuing delays  The QoS challenge Manage bandwidth allocations to deliver the desired application performance Control delay, jitter, and packet loss

© 2006 Cisco Systems, Inc. All rights reserved. Cisco IOS QoS Tools  Congestion management: PQ CQ WFQ CBWFQ  Queue management WRED  Link efficiency Link fragmentation and interleave RTP and CRTP  Traffic shaping and traffic policing QoS Toolbox

© 2006 Cisco Systems, Inc. All rights reserved. Priority Queuing PQ puts data into four levels of queues: high, medium, normal, and low.

© 2006 Cisco Systems, Inc. All rights reserved. Custom Queuing CQ handles traffic by assigning a specified amount of queue space to each class of packet and then servicing up to 17 queues in a round-robin fashion.

© 2006 Cisco Systems, Inc. All rights reserved. Weighted Fair Queuing WFQ makes the transfer rates and interarrival periods of active high-volume conversations much more predictable.

© 2006 Cisco Systems, Inc. All rights reserved. Weighted Random Early Detection WRED provides a method that stochastically discards packets if congestion begins to increase.

© 2006 Cisco Systems, Inc. All rights reserved.

Implementing QoS Step 1: Identify types of traffic and their requirements. Step 2: Divide traffic into classes. Step 3: Define QoS policies for each class.

© 2006 Cisco Systems, Inc. All rights reserved. Step 1: Identify Types of Traffic and Their Requirements  Network audit: Identify traffic on the network.  Business audit: Determine how important each type of traffic is for business.  Service levels required: Determine required response time.

© 2006 Cisco Systems, Inc. All rights reserved. Step 2: Define Traffic Classes Scavenger Class Less than Best Effort

© 2006 Cisco Systems, Inc. All rights reserved. Step 3: Define QoS Policy  A QoS policy is a network-wide definition of the specific levels of QoS that are assigned to different classes of network traffic.

© 2006 Cisco Systems, Inc. All rights reserved. Quality of Service Operations How Do QoS Tools Work? Classification and Marking Queuing and (Selective) Dropping Post-Queuing Operations

© 2006 Cisco Systems, Inc. All rights reserved. Self Check 1.What types of applications are particularly sensitive to QoS issues? 2.What is WFQ? How is it different than FIFO? 3.What are the 3 basic steps involved in implementing QoS? 4.What is Scavenger Class?

© 2006 Cisco Systems, Inc. All rights reserved. Summary  QoS is important to both the end user and the network administrator. End users experience lack of QoS as poor voice quality, dropped calls or outages.  Network traffic differs in its ability to handle delay, jitter and packet loss. Traffic sensitive to these issues requires priority treatment. QoS measures can provide priority to sensitive traffic, while still providing services to more resilient traffic.  Implementing QoS involves 3 basic steps: identify the types of traffic on your network, divide the traffic into classes, and define a QoS policy for each traffic class.

© 2006 Cisco Systems, Inc. All rights reserved. Q and A

© 2006 Cisco Systems, Inc. All rights reserved. Resources  QoS Best Practices At-A-Glance 82/cdccont_0900aecd80295aa1.pdf  QoS Tools At-A-Glance 82/cdccont_0900aecd80295abf.pdf

© 2006 Cisco Systems, Inc. All rights reserved.