Nortel Networks NN43001-563 Flexible Numbering Plan, Electronic Switched Network (ESN5) network signaling, Echo cancellation, Echo canceller tail delay

Dialing plans 67

Flexible Numbering Plan

A Flexible Numbering Plan (FNP) allows the length of Location Codes

(LOCs) to vary from node to node. As well, the total number of digits dialed

to reach a station can vary from station to station. It also allows ﬂexibility for

the length of the location codes from node to node. An FNP can be used

to support country-speciﬁc dialing plans. FNP also allows users to dial

numbers of varying lengths to terminate at a destination. Flexibility of the

number of digits which can be dialed is achieved using Special Numbers

(SPNs).

Electronic Switched Network (ESN5) network signaling

IP Trunk3.01 (and later) and ITG Trunk 2.x support a mixed network of

remote nodes with ESN5 and standard (that is, non-network) signaling.

ESN5 is an extension of MCDN signaling which can be used by IPTrunk

3.01 (and later), ITG Trunk2.x, and IP Peer( CS 1000M).

ESN5 inserts the Network Class of Service (NCOS) preﬁx ahead of the

dialed numbers. Make sure that, if ESN5 is to be used, it is provisioned on

both the IP trunk cards and the Route Data Block (RDB) for that node. If

ESN5 is provisioned for an IP Trunk3.01 (and later) node, all remote ITG

2.x and IP Trunk3.01 (and later) node must have that node provisioned as

"SL1ESN5" in the dialing plan. If this is not done, a default NCOS is inserted

by the ESN5 node receiving the call from the non-ESN5 VoIPgateway. Fore

more information, see "ESN5 network signaling" (page 231).

Echo cancellation

All telephony voice services now in use reﬂect some level of echo back

to the user. The term "echo" refers to the return of a signal’s reﬂection

to the originator.

Packetvoice networks introduce sufﬁcient latency to cause what a caller

would consider an audible echo. The echo path is round-trip. Any speech

coding, packetization, and buffering delaysaccumulate in both directions of

transmission, increasing the likelihood of audibility.

Echo cancellation reduces feedback sounds and background noise for

clearer voice quality. Some less advanced IP telephony products do not

include echo cancellation circuitry, resulting in voice quality of a level below

business communications standards. Without echo cancellation, the talking

parties can hear varying levels of echo as they speak.

Echo canceller tail delay

Early versions of ITG TrunkDSPs and DSP ﬁrmware had a maximum echo

canceller (ECAN) tail delay of 32 ms. More recent cards and ﬁrmware

support higher tail delays, with the ITG-P and the Media Card 32-port card

supporting up to 128 ms. However, when the capability was added, the

Nortel Communication Server 1000

IP TrunkFundamentals

NN43001-563 02.01 Standard

Release 5.5 21December 2007