High delay of modem connection over VoIP

Discussion in 'Cisco' started by Luis, Jul 9, 2003.

  1. Luis

    Luis Guest

    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
     
    Luis, Jul 9, 2003
    #1
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  2. Luis

    Luis Guest

    Aaron:

    I understand a higher delay than 110 ms is expected because the
    packetization.

    However, I like to know what is the typical round trip time expected
    for a modem connection over IP.

    Thanks,
    Luis




    Aaron Leonard <> wrote in message news:<>...
    > The quick answer is that you CAN'T have a 110ms ping
    > round trip time on a modem over VoIP call. The packetization
    > delay inherent in VoIP prevents that.
    >
    > Here are some guidelines on using modem passthrough over VoIP:
    >
    > http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00800b3568.html
    >
    > see especially
    >
    > http://www.cisco.com/en/US/products...s_feature_guide09186a00800b3568.html#xtocid17
    >
    > Aaron
    >
    > ---
    >
    > ~ 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
     
    Luis, Jul 11, 2003
    #2
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