Avaya 3616 Series Installation Manual - Page 17

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Installation Guide

Avaya wireless telephones can be deployed across multiple subnets when used with an IP telephony

server interface if the performance requirements outlined below are met. One of two deployment

scenarios described below can be used, depending on needs and infrastructure capabilities, keeping

in mind that the Avaya wireless telephones will never actively roam across a subnet boundary without

power-cycling the handsets unless a VIEW Certified layer-3 roaming infrastructure is used in

accordance with the VIEW deployment guidelines.

In one deployment scenario for accommodating multiple subnets, each subnet is treated

independently with respect to the AVPPs and wireless network, but each subnet can still provide

service to a single IP telephony server. One or more AVPP(s) can be deployed on each subnet just as

with a single subnet system, including identifying each Registration AVPP IP address via DHCP or

static configuration. In the second scenario, a single AVPP (or set of AVPPs) is deployed, generally

on the same subnet as the IP telephony server. The Registration AVPP is identified to all phones via

DHCP or static configuration, regardless of what subnet the phone is operating in. This scenario

requires less AVPPs to be installed, but requires higher performance from the router (see performance

requirements below).

The ability to cross a subnet boundary exists in either scenario, but the Avaya handsets will need to be

power cycled to obtain new IP address within the new subnet. In addition, other configuration

considerations must be addressed. Because users will not want to re-administer the wireless

telephones to a separate subnet, Extended Service Set Identifications (ESSIDs) should be the same

or the handsets should be set to the "Learn Always" mode, the security mode and associated key

should be the same or turned off, and DHCP should be used.

6.2 Network Performance Requirements

Ethernet packets containing voice as their payload have short, useful lifetimes, making the timely

delivery of voice packets essential. Routers can introduce latency and delay between the AVPP and

the APs, resulting in poor voice quality.

Ethernet connectivity from the IP telephony server or other voice endpoint to the AVPP should never

exceed 100 milliseconds of network delay (one way), 30 milliseconds of network jitter, and 2 percent

packet loss end to end regardless of the physical properties of the link. The link from the AVPP to the

APs should be under 100 milliseconds of network delay, one millisecond of jitter and under two

percent packet loss. In both cases, the jitter requirements are for wired network jitter and do not

include the RF link.

One feature of the AVPP is to control the timing of packets through the AP. The delay between the

AVPP and the AP does not need to be strictly controlled as long as it is consistent. The jitter

requirement between the IP telephony server and the AVPP is a function of how the audio is

packetized for encapsulation and the packet queuing in the AVPP.

Jitter between the AVPP and the AP should be measured at the wired Ethernet connection to the AP.

If the AP is an AP switch attached to lightweight APs and products are VIEW Certified the system,

jitter can be measured at the entry to the AP switch. For this measurement, assume the AVPP is

delivering packets at 30 millisecond intervals with no jitter. The time is measured from the arrival of

one packet from the AVPP directed to a single wireless telephone to the next packet from the AVPP to

the same wireless telephone. The jitter measurement is the time difference from the ideal 30

millisecond arrival of packets at the AP.

Octiober 2008