[nsp] High delay of modem connection over VoIP

Luis E lucho1111 at hotmail.com
Wed Jul 9 15:13:02 EDT 2003


Sirs:

We have a CISCO VoIP Network to provide IP telephony to our customers.   The 
CISCO VoIP Network is interconnected to PSTN over E1 lines using 5850 
gateways.
We want to provide dial-up Internet access to our customers. Most customer 
are on the PSTN side with standard phone lines and they dial using a modem 
to a Access Server (TNT MAX box) which is located at other side the VoIP 
network. We deliver the link to TNT box over an E1 R2 using a 2600.
Basically the scenario is as follow:

Remote PC--phone_line----PSTN---CISCO5850---VoIP Network----2600----E1 
line---TNT Access Server

We have made several test calls and the modem are interconnecting well but 
we noted a higher delay when doing a ping from the Remote PC to TNT box.   
Typically delays over a dialup connection is 110 ms over PSTN lines but in 
our scenario VoIP the average delay starts at 280 ms and sometimes the 
average goes up to 480 ms. The modems remain connected but this delay 
affects the browsing.

Why is a higher delay over a modem connection through a VoIP network?
We need to decrease this delay to acceptable values similar as a modem 
connection over PSTN Network.

Regards,
Luis

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