Issue 3.4.1 June 2005
311
Quality of Service guidelines
This chapter contains guidelines for deploying Quality of Service (QoS) for an IP Telephony
network. This chapter begins with an overview of Class of Service (CoS) versus QoS.
Class of Service refers to mechanisms that tags traffic in such a way that the traffic can be
differentiated and segregated into various classes. Quality of Service refers to what the network
does to the tagged traffic to give higher priority to specific classes. If an endpoint tags its traffic
with Layer 2 802.1p priority 6 and Layer 3 Differentiated Services Code Point (DSCP) 46, for
example, the Ethernet switch must be configured to give priority to value 6, and the router must
be configured to give priority to DSCP 46. The fact that certain traffic is tagged with the intent to
give it higher priority does not necessarily mean it will receive higher priority. CoS tagging does
no good without the supporting QoS mechanisms in the network devices.
Topics covered in this section include:
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CoS
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Layer 2 QoS
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Layer 3 QoS
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IEEE 802.1 p/Q
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DiffServ
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RSVP
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Queuing methods
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Traffic shaping and policing
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Fragmentation
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RTP
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Examples of QoS implementation
CoS
IEEE 802.1p/Q at the Ethernet layer (Layer 2) and DSCP at the IP layer (Layer 3) are two
standards-based CoS mechanisms that are used by Avaya products. These mechanisms are
supported by the IP Telephone, the S8300 Media Server, and the C-LAN and MedPro circuit
packs. Although TCP/UDP source and destination ports are not CoS mechanisms, they can be
used to identify specific traffic, and can be used much like CoS tags. Other non-CoS methods to
identify specific traffic are to key in on source and destination IP addresses and specific
protocols, such as RTP. The MedPro circuit pack and IP Telephones use RTP to encapsulate
audio.
Summary of Contents for Application Solutions
Page 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Page 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Page 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Page 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Page 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Page 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...