Nortel Networks NN43001-563

68 System description

default in TM 3.1 remained unchanged at 32 ms, even though the ECAN

performance was signiﬁcantly better with 128 ms. This problem has been

resolved in TM 3.1, butITG Trunk and IP Trunk nodes deﬁned by customers

with the original TM 3.1 software still use the incorrect default value.

Recent releases of TM 3.1 that are properly conﬁgured, with all applicable

patches and the ﬁx integrated, have the defaultfor new systems set to 128

ms. This results in all new nodes being given the correct default value.

However,it will not change the value on systems that are already conﬁgured

unless the user deliberately changes the value.

IP Trunk3.01 includes an enhancement to accommodate this issue. Since

a 32-ms ECAN tail delay is usually only provisioned "by default" and not

by deliberate user programming, the IP Trunk3.01 application maps an

ECAN tail delay of 32 seconds to the corrected defaultof 128 ms. This

addresses the vast majority of users who want the optimum availableECAN

performance. However, a small number of users, for various reasons, may

want the 32-ms tail delay.

Users that can accept poorer echo performance and really want a 32 ms

delay can use a value of 8 ms, which the IP Trunkapplication maps to 32

ms. A delay of 8 ms is completely unacceptable to end users, so this does

not result in any loss of user capabilities. In addition, a value of 16 ms,

which is also unsatisfactory,is mapped to a delay of 64 ms, maintaining the

same two-to-one ratio with the next lowervalue in both the TM 3.1 and IP

Trunkenvironment. (In this case, the 8 ms value is half the 16 ms, and the

32 ms value is half the 64 ms value.)

Table8 "Echo canceller tail delay mapping from TM 3.1 to IP Trunk3.01"

(page 68) shows the mapping between the delayvalue conﬁgured in TM

3.1 and the actual delay value used in IP Trunk3.01. The actual conﬁgured

delay value can be displayedusing the CLI command itgCardShow.If

the TM 3.1 value is mapped, "Default - xxx" is displayed,where "xxx" is

the mapped value. If the TM 3.1 value is 64, 96, or 128 ms, "Value from

TM 3.1 - xxx" is displayed.

Table 8

Echo canceller tail delay mapping from TM 3.1 to IP Trunk3.01

Provisioned in TM 3.1 (in ms) Value used by IP Trunk 3.01

832

16 64

32 (default value in IP Trunk 3.01 and

earlier) 128 (default value in IP Trunk 3.01)

64 64

Nortel Communication Server 1000

IP TrunkFundamentals

NN43001-563 02.01 Standard

Release 5.5 21 December 2007