IP networks must provide a number of services to adequately support voice transmission using VoIP. These services include security, predictability, measurability, and some level of delivery guarantee. Network administrators and architects achieve this service level by managing delay, delay variation (jitter), bandwidth provisioning, and packet loss parameters with quality of service (QoS) techniques. This course introduces the concept of a converged network, identifies four problems that could lead to poor quality of service, and describes solutions to those problems. It also explains and evaluates the three generic models of implementing QoS.
Differentiated services (DiffServ) is a multiple-service model for implementing quality of service (QoS) in the network. With DiffServ, the network tries to deliver a particular kind of service that is based on the QoS specified by each packet. This specification can occur in different ways, such as using the differentiated services code point (DSCP) in IP packets or source and destination addresses. The network uses the QoS specification of each packet to classify, shape, and police traffic and to perform intelligent queuing. This course focuses on the DiffServ model and explains the mechanisms that are used to implement DiffServ.
The Modular quality of service (QoS) command-line interface (CLI), or MQC, provides a modular approach to the configuration of QoS mechanisms. MQC allows network administrators to introduce new QoS mechanisms and reuse available classification options.
This course outlines how to implement QoS policies using MQC, and introduces the concepts of classification and marking. It explains the different markers that are available at the data-link and network layers, and identifies where classification and marking should be used in a network. The lesson also describes different approaches for improving the efficiency of WAN links.Learning Objectives
- Identify how the four key quality issues for voice traffic impact voice quality
- Identify QoS goals for voice traffic
- Match the four methods for implementing and managing a QoS policy – CLI, MQC, Cisco AutoQoS, and QPM – with their characteristics
- Describe three models of QoS implementation
- Identify the purpose and function of DiffServ
- Match the different per-hop behaviors that are used in DSCP with their descriptions
- Recognize the mechanisms that are implemented when deploying a DiffServ model
- Identify the components of the Cisco QoS baseline model and its variants
- Recognize how to implement QoS by using MQC
- Recognize how to configure classification with MQC, input interface and RTP ports, and marking
- Identify the Cisco IOS commands that are used to configure class-based marking and trust boundaries
- Recognize how to configure mapping between the data link layer CoS and network layer QoS
- Match link efficiency mechanisms to their functions
- Describe VoIP susceptibility to increased latency when large packets traverse slow WAN links
- Recognize how LFI operates and how it reduces the delay and jitter of VoIP packets
- Distinguish between the commands used to configure MLP, FRF.12, and cRFP