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V.90 Throughput

Hi, Please can someone settle an argument between myself and a colleague.

As I understand it, V.90 allows download speeds up to 56K and upload of 33.6K. Therefore if dialing from an analogue V.90 modem to a V.90 modem attached to an ISDN line, the maximum throughput I will get is 33.6k because the upload will be 33.6 from the ISDN side.

My colleauge states that because the modem is attached to the ISDN there is one less A/D conversion and so the throughput will be 56K. I disagree.

Also, if I am correct, how do I achieve greater throughput when I dial my ISP with my V.90 modem, or is it just my connect speed is higher but the actual throughput is still 33.6k

Hope this makes sense, please settle this argument so that we can once again have peace in the office.

Regards

Lee

1 REPLY
Cisco Employee

Re: V.90 Throughput

You are correct it will only be 33.6 (if you are lucky and have a good connection) Also, modems retrain all the time during a call in an attempt to adapt to changing line conditions and provide highest speed, so the speed can vary somewhat. And you will only get 56k on the downlink if you are connected to the same CO as the terminating router.

Peace

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