Switching to VoIP

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Key Issues: Quality of Service

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Key Issues: Quality of Service

• Quality of Service is decreased when packet loss, jitter, and latency increase.

• There are two styles of Quality-of-Service mechanisms to deal with the problem:

CoS and QoS.

• CoS solutions are coarsely grained, best-effort approaches the rely on packet pri-

oritization.

• CoS solutions are best in situations in which voice traffic represents 30% or less

of the total traffic, such as enterprise networks.

• 802.1p and DiffServ are the two most common CoS solutions for Voice over IP.

• QoS solutions are finely grained, guaranteed-delivery approaches that reserve

bandwidth across the network.

• QoS solutions are best when there is limited bandwidth, or in carrier-grade net-

works.

• COPS is a system for centrally storing and maintaining QoS and CoS policies.

• RSVP is the most common QoS solution for enterprise-grade voice services over

IP.

• Some ISPs offer QoS services to facilitate the use of the Internet and/or VPN for

voice applications.

• Many small-office and residential broadband routers support 802.1p, and a few

even support DiffServ.

• Linux’s kernel-based firewall, Netfilter, can be used as a DiffServ edge router if

the Linux Traffic Control components are compiled into the Linux kernel.

• In Windows NT, 2000, and ...