DSL Router - internet speed allocation if more devices

Message boards : Number crunching : DSL Router - internet speed allocation if more devices
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Profile Sutaru Tsureku
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Message 1634864 - Posted: 30 Jan 2015, 4:40:20 UTC

Example ...

I have DSL2000. :-(

4 devices (PC, Smart TV, internet radio) connected to the DSL router:
At the DSL router are 2 LAN cables connected.
At each LAN cable end is a switch, 2 devices connected to one switch.

If all devices need simultaneously something from the internet, how will be the internet speed distributed?

Each devices get 1/4 (25%) of the available internet speed?
Or one devices get more as other devices (preferential treatment)?
Or successively the devices been processed, devices after devices ...?

Thanks.
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Message 1634873 - Posted: 30 Jan 2015, 5:13:38 UTC - in response to Message 1634864.  

Basically, it's first come first serve. Not by device, but the amount of traffic required per device. Your internet radio won't need much, so your PC and TV can use most of what's there. it' just depends how much traffic you need and when you use them at the same time.
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Message 1634922 - Posted: 30 Jan 2015, 8:25:57 UTC

Some routers have QOS (quality of service) settings that allow you to set a priority level for certain ports when total demand exceeds the total bandwidth available. You would have to check the documentation for your router to see if it has such settings and how to use them.
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Dena Wiltsie
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Message 1635001 - Posted: 30 Jan 2015, 13:37:54 UTC

Something that can mess up calculations is the internet most of the time uses 2K byte packets. A device will only ask for as many packets as it wants at a time. A device asking for a large amount of data may get more data because of the delay between request for data by the device requesting small amounts of data at a time. All data will be serviced as the servers deliver the data.
Some popular servers may be slow to deliver data because of the demand placed on them by other users. The answer to your question is clear in hindsight but exact balance is hard to predict.
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Richard Haselgrove Project Donor
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Message 1635008 - Posted: 30 Jan 2015, 13:57:06 UTC - in response to Message 1635001.  

Something that can mess up calculations is the internet most of the time uses 2K byte packets. A device will only ask for as many packets as it wants at a time. A device asking for a large amount of data may get more data because of the delay between request for data by the device requesting small amounts of data at a time. All data will be serviced as the servers deliver the data.
Some popular servers may be slow to deliver data because of the demand placed on them by other users. The answer to your question is clear in hindsight but exact balance is hard to predict.

We were pointed to some very useful advice with regard to RFC 1323 in the last days of the late lamented server closet at SSL, before the move to the co-lo.

At the time, the SETI (download) servers fell squarely into the category of "popular servers [may be] slow to deliver data because of the demand placed on them by other users". RFC 1323 is very helpful in evening out the flow of packets and data from that type of slow server, and might help in levelling the flow to and from different different devices sharing the same DSL router.

To refresh your memories, the thread is Windows TCP Settings - Follow up - Help with server communication.
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Message 1635009 - Posted: 30 Jan 2015, 13:57:54 UTC

Your router may have bandwidth throttling functions. So you could limit the bandwidth per MAC or IP address on your internet network if that is what you are wanting to do.
If there are no bandwidth limits & each of the 4 devices were try to use as much bandwidth as possible. Then the switches would basically give all 4 devices ~1/4 of the available bandwidth. Otherwise if devices are using less bandwidth then each one will get to use however much it needs until you reach your provider limit. At that point how the traffic is split comes down to how the software in the router/switches functions.
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Message 1635233 - Posted: 30 Jan 2015, 20:27:50 UTC

I forgot to mention something else. IP packets are not delivered in order. Because packets may not be delivered over the same path, they can be delivered in any order and it's up to the next level of the protocol to restore order if it is important. Most of the time thats TCP but TCP while the most common level isn't the only one.

We received a hard lesson in this when we noticed we were encountering retries far to often. It turned out the people who wrote our TCP layer forgot that the packets could be out of order and instead of waiting to see if the correct packet was delivered latter, the code issued a retry and discarded the remaining data. Once we knew what the problem was, it wasn't a huge task to correct it.
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Message boards : Number crunching : DSL Router - internet speed allocation if more devices


 
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