Voice Gateways: Handling Echo, Cross Connect, Timers and Verification

4 topics!

Echo – What, Where and How?

Usually a 2 to 4 wire conversion
Low delay <25ms (You can’t tell..)

IP Network can add delay before it hits the PSTN
Echo cancellation (ITU-T G.168) goes here (applied on VG at PSTN interface used DSP/snapshots)
Enabled by default
Can increase the coverage

Configuration…
Same commands on all PSTN ports.
echo-cancel enable (Enabled by default)
echo-cancel coverage ? (Value in milliseconds. Most deployments 64ms default)

echo-cancel erl worst-case ? 0,3,6dB (Echo Return Loss)

show voice port 1/0/0

Cross Connect Your Voice Ports

Allows you to bridge analog ports directly out a DS0 channel (CAS-ONLY)
Analog ports must be on the same module as digital port
Uo to four analog ports per digital port
DS0-Group of one timeslot used for each analog port, signaling must match

Configuration….
controller t1 1/0
ds0-group 0 timeslots 1 type fxo-loop-start

conf t
connect FXS-DS0-BRIDGE voice-port 1/0/0 to 1/0 0

Timers and Verification

IMG_3780