IP Telephony network engineering overview
278 Avaya Application Solutions IP Telephony Deployment Guide
In general, these concerns dictate a hierarchical network that consists of at most three layers
(
Table 65: Layers in a hierarchical network
on page 278):
●
Core
●
Distribution
●
Access
Some smaller networks can collapse the functions of several layers into one device.
For IP Telephony to work well, WAN links must be properly sized with sufficient bandwidth for
voice and data traffic. Each voice call uses between 6.3 Kbps and 80 Kbps, depending on the
desired codec, quality, and header compression used. G.729, which uses 24 Kbps of
bandwidth, is one of the most promising standards today. Traditional telephone metrics, such as
average call volume, peak volume, and average call length, can be used to size interoffice
bandwidth demands. See
Traffic engineering
for more information.
Quality of Service (QoS) also becomes increasingly important with WAN circuits. In this case,
QoS means the classification and the prioritization of voice traffic. Voice traffic must be given
absolute priority through the WAN. If links are not properly sized or queuing strategies are not
properly implemented, the quality and the timeliness of voice and data traffic will be less than
optimal.
Table 65: Layers in a hierarchical network
Layer
Description
Core
The core layer is the heart of the network. The purpose of the core
layer is to forward packets as quickly as possible. The core layer
must be designed with high availability in mind. Generally, these
high-availability features include redundant devices, redundant power
supplies, redundant processors, and redundant links. Today, core
interconnections increasingly use Gigabit Ethernet.
Distribution
The distribution layer links the access layer with the core. The
distribution layer is where QoS feature and access lists are applied.
Generally, Gigabit Ethernet connects to the core, and either Gigabit
Ethernet or 100base-TX/FX links connect the access layer.
Redundancy is important at this layer, but not as important as in the
core.
Access
The access layer connects servers and workstations. Switches at this
layer are smaller, usually 24 to 48 ports. Desktop computers and
workstations are usually connected at 10 Mbps (or 10 Mbps), and
servers are connected at 100 Mbps (or 1 Gbps). Limited redundancy
is used. Some QoS and security features can be implemented in the
access layer.
Содержание Application Solutions
Страница 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Страница 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Страница 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 74: ...Avaya Application Solutions platforms 74 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Страница 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 214: ...Voice quality network requirements 214 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 239: ...Reliability Issue 3 4 1 June 2005 239 Figure 69 S8700 Media Server in a high reliability configuration ...
Страница 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Страница 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 350: ...Implementing Communication Manager on a data network 350 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Страница 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...