Traffic engineering
182 Avaya Application Solutions IP Telephony Deployment Guide
Example 7: LAN bandwidth
In
Example 6: IP bandwidth considerations
, the total IP LAN bandwidth usage for each site was
calculated, and expressed in Erlangs at the bottom of
Table 34: IP LAN bandwidth usages
(Erlangs) for Example 6: IP bandwidth considerations
on page 179. Specifically, the total LAN
bandwidth usage in Site 1 is 123.5 Erlangs, in Site 2 is 56.6 Erlangs, and in Site 3 is 29.2
Erlangs. This implies that the average number of bidirectional media streams that are
simultaneously in use at any given time in Site 1 is 123.5. Analogous statements can also be
made regarding Sites 2 and 3.
Every media stream across the IP LAN in any of the three sites is assumed to use the
uncompressed G.711 codec, since bandwidth is relatively inexpensive within a private LAN, as
opposed to a public WAN. Assume, for the sake of this example, a standard IP packet size of 20
ms. So for the G.711 codec,
Table 37: Bandwidth requirements for media streams
on page 181
indicates that each media stream consumes 87.2 kbps of IP LAN bandwidth. It may be tempting
at this point to simply multiply 87.2 kbps by 123.5 simultaneous bidirectional media streams, to
arrive at the estimate for the overall LAN bandwidth needed for Site 1. However, 123.5 is merely
the average number of simultaneous media streams, and approximately half of the time, there
are at least 124 simultaneous media streams in use.
In this example, suppose that the goal is to supply enough bandwidth to adequately support the
media streams at least 99.9% of the time. The standard infinite-server queueing model implies
that less than 0.1% of the time there are at least 159 simultaneous media streams in the Site 1
LAN. So, it is sufficient to engineer the LAN bandwidth to support 158 simultaneous media
streams. Therefore, the Site 1 LAN requires at least (158 simultaneous media streams) x (87.2
kbps per media stream) = 13.8 Mbps of bandwidth, in each direction. This result, along with the
analogous results for Sites 2 and 3, are provided in
Table 38: IP LAN bandwidth requirements
in each direction, for Example 7: LAN bandwidth
.
In
Table 38
, the number of simultaneous media streams for “P001” represents the 99.9th
percentile for the number of simultaneous unidirectional streams, as determined by applying the
standard infinite-server queueing model.
A slight variation of the procedure that was used to determine LAN bandwidth in
Example 7:
LAN bandwidth
can be used to determine WAN bandwidth. Using compressed RTP (cRTP) is a
means to conserve bandwidth. Specifically, the use of cRTP reduces the overhead due to IP,
UDP, and RTP from 40 bytes to between 2 and 4 bytes (4 bytes are assumed for this example).
Using the PPP overhead of 7 bytes (which would vary if ATM, HDLC, or Frame Relay were
Table 38: IP LAN bandwidth requirements in each direction, for
Example 7: LAN
bandwidth
Resource
Site 1
(Atlanta)
Site 2
(Boston)
Site 3
(Cleveland)
Simultaneous media streams for
“P001”
158
81
47
LAN bandwidth (Mbps)
13.8
7.1
4.1
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 ...