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Download speed: 64K FR PVC vs 56K Modem

By tech_know ·
I currently have a user that downloads data from a vendor via a modem dial-up connection to Compuserve. This download is about 50MB and takes several hours to complete. The modem usually connects at a speed of 50k. (Per the vendor, this data is notavailable to be downloaded via the Internet yet). The vendor wants to put a 64K frame relay pvc into our site and is saying that the download time will be 10 times as fast. Is that possible? If you are connecting at 50K and they want to put a 64K circuit in, I can see some improvement but not the kind that they are talking about. I want to challenge their claim without going to the expense of installing it and proving them wrong. But I don't know enough about all the factors involved to feel comfortable doing that. So, any help is appreciated!

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Download speed: 64K FR PVC vs 56K Modem

by MBatty In reply to Download speed: 64K FR PV ...

At your current dial up speed if you are getting 100% line utilisation on your dial line I estimate the download will be taking around 2.5 to 3 hours, this is without taking into account any data compression you get. But you mentioned serveral hours, so something is not at full speed.

Putting a 64k Frame Relay PVC in may improve things, but by how much will depend on a number of things;

1. Where the bottleneck on the dial up link is. It may not be the dial up line. The conection server atthier site may not be able to cope with the speed. So increasing the link speed will not improve the download time.

2. The access speed of the link into your site. The 64k PVC is a virtual speed not the link speed. PVC stands for Perminent Virtual Circuit, this is a logical circuit over a physical link. If the link speed is higher than the PVC you can burst above the PVC speed to the link speed. Thus it is possible to improve throughput. This will only provide 10 times the throughput if the link is 10 times the speed (ie around 500k).

3. The size of the access link at their site and its utilisation. Its no good having a faster pipe at your end if their end is running at 100%, as you will get no better throughput.

You are right to questions their claim of 10 times improvement. Ask then to back this up will a full refund if not delivered or a guarentee with penalties of not delivering download speeds of less than 20 minutes.

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Download speed: 64K FR PVC vs 56K Modem

by tech_know In reply to Download speed: 64K FR PV ...

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Download speed: 64K FR PVC vs 56K Modem

by NetTek In reply to Download speed: 64K FR PV ...

I, too, question their claim of 10x faster. First, when they speak of a 64k PVC, they are talking about bursts up to 64k. You also need to look at the CIR for the circuit. CIR is the Committed Information Rate, or bandwidth the carrier guarantees.It is most likely 32k.

Frame Relay is indeed more efficient than using a modem, as each frame packet only carries an information header of 2-5 bytes. But 10x faster? No way. We have frame circuits of 56k, 256k, 512k, and 768k. Our 56k circuit is not much faster than a modem.

All in all, your cheapest solution may be to have the vendor burn the data on a CD, and have it overnighted via FedEx.

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Download speed: 64K FR PVC vs 56K Modem

by tech_know In reply to Download speed: 64K FR PV ...

Thanks to all who responded. Both answers were dead on and when I showed my calculations to the vendor they agreed that this was not possible!

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Download speed: 64K FR PVC vs 56K Modem

by tech_know In reply to Download speed: 64K FR PV ...

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