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Bandwidth - Promises and expectations

Answered Question
Nov 21st, 2006
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Hello. I am curious about the internetworking industry. When a company tells you they can drop fiber into your shop and give you 10Mbps speed, what does this mean? 5Mb up and 5Mb down? 10MB at any given time including up and down?

How do you know you are getting the speeds promised? Bandwidth testers are reliable and unreliable. The support techs seem to just want to get close to what was promised and quit.

What about the promise of instant bandwidth increases by "turning the knob"? If you have equipment that can support it, can ISPs provide that type of instant access?


Finally, why do I have to tune my Windows PC (RFC 1323) to get speeds higher than 6Mbps?


I could really use some answer. Our ISP is feeding me too many lines and we are not even near what was promised.

Correct Answer by nikolasgeyer about 10 years 9 months ago

In Australia (and I dare say most other countries) the connections unless specified otherwise, are full-duplex so it should be 10Mbps down and 10Mbps up.


As for increasing the bandwidth, it usually only requires a few commands to be entered on the router terminating your service. However alot of ISP's usually have a long turn-around time on actually getting this done (contracts etc can drag out the process).


And as for Windows, that is correct as well. By default it doesnt handle large amounts of bandwidth very well, its TCP windowing by default is very small/limited etc.

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Correct Answer
nikolasgeyer Tue, 11/21/2006 - 15:22
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In Australia (and I dare say most other countries) the connections unless specified otherwise, are full-duplex so it should be 10Mbps down and 10Mbps up.


As for increasing the bandwidth, it usually only requires a few commands to be entered on the router terminating your service. However alot of ISP's usually have a long turn-around time on actually getting this done (contracts etc can drag out the process).


And as for Windows, that is correct as well. By default it doesnt handle large amounts of bandwidth very well, its TCP windowing by default is very small/limited etc.

scottmac Tue, 11/21/2006 - 15:29
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Unless otherwise specified, if someone is delivering "10Mbps," that implies full duplex (i.e., 10Mbps in each direction concurrently). Check your contract for the specific terms; I'm sure it will vary from ISP / provider to ISP / Provider.


* How do you know you're getting what you pay for?


Well, many ISP/Providers offer a website that will show you what our traffic levels are (both directions, usually).


For those that don't, you are frequently provided the option of contacting the support group and requesting stats for a given period. Please note that you should request the stats *ahead* of time, becasue not all organizations keep much historical data.


It is also possible for youto monitor yourself, using utilities like MRTG (or in some cases, the GUI on the router / firewall) to see what your bandwidth utilization is.


* Why do you have to modify your PC?


You don't, unless it's the only client on the network ... and maybe not then. Much will depend on your applications and how they interface to the network stack.


Many PCs (running common applications) cannot generate enough traffic to consistently fill a 10 meg pipe to the WAN or Internet. The bandwidth provided to the Internet/WAN generally assumes that multiple clients will need concurrent access.


The bandwidth becomes available as aggregate bandwidth (i.e., the collection of clients *can* usually fill the pipe).


*AS far as the techs wanting to get "as close as possible and leave" remember that the bandwidth provided is raw bandwidth.


TCP/IP and associated routing protocols and other maintenance traffic all have a certain amount of overhead. Some percentage of your total bandwidth will be lost to the framing, packet headers, route updates, etc ... so "close" frequently *is* the max once you consider the overhead.


Unless your monitoring utility provides stats related to RAW bandwidth, remember to knock down the max to accommodate the overhead.


There is no reason for the ISP to try to screw you out of the contracted service. ISP / bandwidth provision is a very competitive industry, customer satisfaction (and SLA) is frequently the only thing keeping a customer on the provider's network.


If you're not happy, contact your account team / representitive and let them know what you are not happy about, and what they can do to "make it right." Be prepared to negotiate; some of the service you want may be available for an extra charge ... like routine bandwidth utilization reports.


Good Luck


Scott


iwadm Wed, 11/22/2006 - 09:53
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THANKS! This makes much more sense than anything I have been told thus far.


The techs suggested we move our people over to the new line and I have put it off because I did not wish to have them testing on our production line.


Now, it sounds like I need to get people on this line to get better statistical data.


I will review the contract and move from there.


This is great information. Thank you SO MUCH for taking the time out to provide this.

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