Avaya IP Telephony Konfigurationsanleitung PDF herunterladen (Seite 108)

108 Efficient Networking

P0937663 03.1

Other intranet resource considerations

Bottlenecks caused by non-WAN resources do not occur often. For a more complete evaluation

consider the impact of incremental IP telephony traffic on routers and LAN resources in the

intranet. The IP telephony traffic moves across LAN segments that are saturated, or routers whose

central processing unit (CPU) utilization is high.

Implementing the network, LAN engineering

To minimize the number of router hops between the systems, connect the gateways to the intranet.

Ensure that there is enough bandwidth on the WAN links shorter routes. Place the gateway and the

LAN router near the WAN backbone. This prevents division of the constant bit-rate IP telephony

traffic from bursty LAN traffic, and makes easier the end-to-end Quality of Service engineering

for packet delay, jitter and packet loss.

Further network analysis

This section describes how to examine the sources of delay and error in the intranet. This section

discusses several methods for reducing one-way delay and packet loss. The key methods are:

• “Reduce link delay” on page 109

• “Reducing hop count” on page 109

• “Adjust the jitter buffer size” on page 110

Components of delay

End-to-end delay is the result of many delay components. The major components of delay are as

follows:

• Propagation delay: Propagation delay is the result of the distance and the medium of links

moved across. Within a country, the one-way propagation delay over terrestrial lines is under

18 ms. Within the U.S., the propagation delay from coast-to-coast is under 40 ms. To estimate

the propagation delay of long-haul and trans-oceanic circuits, use the rule of thumb of 1 ms per

100 terrestrial miles.

If a circuit goes through a satellite system, estimate each hop between earth stations adds 260

ms to the propagation delay.

• Serialization delay: The serialization delay is the time it takes to transmit the voice packet one

bit at a time over a WAN link. The serialization delay depends on the voice packet size and the

link bandwidth, and is the result of the following formula:

serialization delay in ms 8

IP packet size in bytes

link bandwidth in kbit/s

---------------------------------------------------------





1 2 ... 103 104 105 106 107 108 109 110 111 112 113 ... 145 146

Keine Kommentare

Avaya IP Telephony Konfigurationsanleitung Seite 108