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jacatone

Hello With A Question

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Hello, I'm happy to be a new member of this forum. I did have a question as well. I'm running a 1 megabit wireless connection, so my normal download speed is around 112 kilobytes on my main machine, but my wireless connected machine seems to fluctuate between the 112kBs to as low as 8 kilobytes. Win 7 Home Premium says I've got a %100 wireless connection. Anyone have any ideas? Thanks.

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Hello, I'm happy to be a new member of this forum. I did have a question as well. I'm running a 1 megabit wireless connection, so my normal download speed is around 112 kilobytes on my main machine, but my wireless connected machine seems to fluctuate between the 112kBs to as low as 8 kilobytes. Win 7 Home Premium says I've got a %100 wireless connection. Anyone have any ideas? Thanks.

Welcome jacatone. :)

Wireless Bandwidth will be much slower than wired.

What I recommend:

-Ensure you don't have to many devices connected to your adapter. Bandwidth is cut in half for each additional device. So one device on a 54 Mbit Network is actually 27 Mbit. Two would be 13.5 Mbit, etc.

-Ensure that neither the router, nor the adapter are near sources of interference. Fluorescent lights, radios, TV's, CRT Monitors, Computers, etc.

-Encryption will also slow your wireless down. Albeit not by a hugely extraordinary amount, but still. Keep that in mind.

Those are my tips.

Thanks,

EBrown

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-Ensure you don't have to many devices connected to your adapter. Bandwidth is cut in half for each additional device. So one device on a 54 Mbit Network is actually 27 Mbit. Two would be 13.5 Mbit, etc.

It does not work like that at all. It doesn't matter if you have 1 or 10 devices connected its bandwidth will not cut in half for each additional device.

-Encryption will also slow your wireless down. Albeit not by a hugely extraordinary amount, but still. Keep that in mind.

This also is not really true, WPA and WPA2 will not really slow down anything you will ever notice. You will lose potential bandwidth by moving 10 inches away from your router then you will by turn on encryption.

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It does not work like that at all. It doesn't matter if you have 1 or 10 devices connected its bandwidth will not cut in half for each additional device.

This article explains more. Although it is lacking some.

http://www.hackorama.com/wifi/

...This is the reson why eventhough the wireless network has bandwidth of say 54Mbps for 802.11.g, half of it will be used by the network for storing these extra data of the protocol and only the rest will be available for actual data....

Wi-Fi uses CSMA/CA, Carrier Sense Multiple Access Collision Avoidance. This takes up half of the bandwidth immediately because it has to check whether or not the network is available. Once it determines network availability, it can then send it's data. This is because Wi-Fi is a Shared Medium. This leads to the bandwidth being shared by every device connected to that particular Access Point. Thus you end up with half the bandwidth you would have originally gotten, under best circumstances.

Thanks,

EBrown

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This article explains more. Although it is lacking some.

http://www.hackorama.com/wifi/

I wouldn't take anything seriously you read there.

802.11g has 54Mbps theoretical bandwidth, but like mentioned earlier I get only 18Mbps through my wireless connection, and only 24Mbps when copying the same large files using my 10/100 LAN which has a theoretical 100Mbps bandwidth. So I guess it could be the power saving 4200 RPM Hard Disk on the laptop that is slowing down the network transfer. So 802.11b with its 11Mbps, might only provide an actual 6Mbps.

He can only figure out how to get 24 Mbps when coping a file over a wired 10/100 LAN but then basically blames it on his 4200 RPM notebook drive that can write at about 25 MB/s which is 200 Mbps. A 100 Mbps Lan will transfer at about 98 Mbps in the real world.

Wi-Fi uses CSMA/CA, Carrier Sense Multiple Access Collision Avoidance. This takes up half of the bandwidth immediately because it has to check whether or not the network is available. Once it determines network availability, it can then send it's data. This is because Wi-Fi is a Shared Medium. This leads to the bandwidth being shared by every device connected to that particular Access Point. Thus you end up with half the bandwidth you would have originally gotten, under best circumstances.

Thanks,

EBrown

Just because something uses "half the bandwidth immediately" doesn't mean it slows down the network to any degree you will notice. Remember once it does it "check" its all done and now full bandwidth is available.

Just because bandwidth is shared, that doesn't give you less of anything till one of those users starts to use something.

USB is shared, but that doesn't mean if you have 10 devices plugged in each device only has 1/10 of the bandwidth. It all depends on who/what is using how much of the available bandwidth. The reason why you get about 1/2 the actual speed of a B or G network is not because of anything being shared its because of the environment around the router. Walls and other Electronic devices/signals impede the WIFI signal thus slowing it down. If you take your computer and put it right next to the router you will get much closer to the 54 Mbps G max.

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He can only figure out how to get 24 Mbps when coping a file over a wired 10/100 LAN but then basically blames it on his 4200 RPM notebook drive that can write at about 25 MB/s which is 200 Mbps. A 100 Mbps Lan will transfer at about 98 Mbps in the real world.

100Mbps LAN will give you 200Mbps on a full duplex switched network.

Dlewis, you know what Hub's are?

A hub is an intermediary device, such as a switch or router, but it doesn't work very efficiently. Just like wireless.

In a hub, when a packet arrives to a port, it is repeated to ALL other ports. This forces a hub network to work at half duplex, meaning data can only go one way with one packet at a time. Bandwidth is shared in an ALMOST identical way to wireless networks, but you don't lose bandwidth when you use a single computer on a hub.

Hub's, and ALL other Wired Ethernet Media, use CSMA/CD, Carrier Sense Multiple Access Collision Detection. This means it will look out on the network, JUST like wireless, and see if it is available. If it is, it sends it's packet. The only difference is, Wireless keeps collisions to a bare minimum, CSMA/CD allows collisions on a 10/100 Hub network. This means that if two devices send at the same time, and they see the collision BEFORE they finish transmitting the packet (which is why it doesn't work on Gigabit) they will send a 32-bit signal to inform ALL devices on the network of the collision, and every device in that collision domain will back off of sending for a certain amount of time, which is randomly generated by the NIC card.

Now, when you think about it, all that 100Mbit bandwidth is actually split in half for every connected device. As NO TWO can send at once. Same thing with wireless, if Device A and Device B send at once, they will be alternating for each packet, therefore only getting 13.5 of the available 27 Megabits of bandwidth. CSMA/CA is still working, so it requires that half of the bandwidth. You end up with A sending a packet and then B then back to A, etc. They can't both do that at full speed.

And even if I am wrong about the CSMA/CA keeping that half of the bandwidth for the full time, you still have the devices transmitting together. Leaving you half bandwidth. Sure if you stopped using every other wireless device you would get the most bandwidth you could, but that's a hypothetical situation.

You can also use 802.11a which will have MUCH less interference than 802.11b/g/n, because 802.11a works on the 5Ghz frequency, whereas 802.11b/g/n work at 2.4Ghz, just like your cell phones.

Thanks,

EBrown

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100Mbps LAN will give you 200Mbps on a full duplex switched network.

Dlewis, you know what Hub's are?

A hub is an intermediary device, such as a switch or router, but it doesn't work very efficiently. Just like wireless.

In a hub, when a packet arrives to a port, it is repeated to ALL other ports. This forces a hub network to work at half duplex, meaning data can only go one way with one packet at a time. Bandwidth is shared in an ALMOST identical way to wireless networks, but you don't lose bandwidth when you use a single computer on a hub.

Hub's, and ALL other Wired Ethernet Media, use CSMA/CD, Carrier Sense Multiple Access Collision Detection. This means it will look out on the network, JUST like wireless, and see if it is available. If it is, it sends it's packet. The only difference is, Wireless keeps collisions to a bare minimum, CSMA/CD allows collisions on a 10/100 Hub network. This means that if two devices send at the same time, and they see the collision BEFORE they finish transmitting the packet (which is why it doesn't work on Gigabit) they will send a 32-bit signal to inform ALL devices on the network of the collision, and every device in that collision domain will back off of sending for a certain amount of time, which is randomly generated by the NIC card.

Now, when you think about it, all that 100Mbit bandwidth is actually split in half for every connected device. As NO TWO can send at once. Same thing with wireless, if Device A and Device B send at once, they will be alternating for each packet, therefore only getting 13.5 of the available 27 Megabits of bandwidth. CSMA/CA is still working, so it requires that half of the bandwidth. You end up with A sending a packet and then B then back to A, etc. They can't both do that at full speed.

And even if I am wrong about the CSMA/CA keeping that half of the bandwidth for the full time, you still have the devices transmitting together. Leaving you half bandwidth. Sure if you stopped using every other wireless device you would get the most bandwidth you could, but that's a hypothetical situation.

Dude. Stop. Go back and read what I said again because your digging your self a very big hole.

100Mbps LAN will give you 200Mbps on a full duplex switched network.

I have no clue why you brought that up. I never mentioned anything about full/half duplex anything.

You can also use 802.11a which will have MUCH less interference than 802.11b/g/n, because 802.11a works on the 5Ghz frequency, whereas 802.11b/g/n work at 2.4Ghz, just like your cell phones.

Cell phones don't use 2.4 Ghz. Thats a cordless phone in your house. And no one uses 802.11 A networks anymore, for various reason but mainly because they just suck and the range is much shorter.

Edited by dlewis23

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Now, when you think about it, all that 100Mbit bandwidth is actually split in half for every connected device. As NO TWO can send at once. Same thing with wireless, if Device A and Device B send at once, they will be alternating for each packet, therefore only getting 13.5 of the available 27 Megabits of bandwidth. CSMA/CA is still working, so it requires that half of the bandwidth. You end up with A sending a packet and then B then back to A, etc. They can't both do that at full speed.

Stop saying split in half because its not true or correct. Just because you have 2 devices connected to a hub/switch/router/whatever doesn't mean they split the bandwidth in half at all. The bandwidth is just shared among them.

Here is an example.

I have 2 COLO servers connected to a switch and the switch has 100 Mbps of bandwidth. That doesn't mean that each server has 50 Mbps just by them being connected. It all has to do with what each server is doing.

I can have one serving files at ~90 Mbps and the other can be serving files at ~10 Mbps. Nothing is ever split in half.

Here is a bandwidth graph for both servers for the exact same time. And they are connected to the same switch.

graph1.png

graph2.png

They don't just get 50 Mbps of bandwidth. Ever hear of QOS?

Also STOP, saying 27 Mbps of bandwidth for a 54G network. Because that also is not correct. CSMA/CA doesn't take the 54 and cut it in half. The reason you don't get 54 Mbps is as I said before because of the environment around you and distance from the router as well as a few other small things. But the number is just not cut in half. It can be lower or higher then 27 Mbps.

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I have 2 COLO servers connected to a switch and the switch has 100 Mbps of bandwidth. That doesn't mean that each server has 50 Mbps just by them being connected. It all has to do with what each server is doing.

LMAO Switched networks work at Full Duplex with 200Mbps Bandwidth. Neither will have 50 unless they are forced to serve at that rate. I said Hubs, which is the exact same as wireless. (Alright, not the exact same, but mostly. They use different, albeit similar, protocols to take care of collisions.)

Stop saying split in half because its not true or correct. Just because you have 2 devices connected to a hub/switch/router/whatever doesn't mean they split the bandwidth in half at all. The bandwidth is just shared among them.

That's like comparing apples to tangerines. Yeah, they're both fruits, but they work ENTIRELY differently. Switches/Routers would have been correct, but hubs share the media among all connected devices. Therefore the Bandwidth will be MUCH less. Switches and routers work at full duplex, therefore they will end up at 2000Mbps/200Mbps/20Mbps depending on the LAN speed you choose.

They don't just get 50 Mbps of bandwidth. Ever hear of QOS?

QOS simple allows certain packets to take priority over others. Most people use it to allow Audio priority over Video priority over Data. I have no idea why you would use it for data servers, but that's entirely your choice.

I can have one serving files at ~90 Mbps and the other can be serving files at ~10 Mbps. Nothing is ever split in half.

Or you can have both serving at 100Mbps and not worry about it. Unless you use a hub.

Here is a bandwidth graph for both servers for the exact same time. And they are connected to the same switch.

graph1.png

graph2.png

You must be doing something wrong because those graphs don't correlate to each other at all. One of them dips down extremely while the other is chugging along. All that proves is that one of them worked slower for several hours.

Also STOP, saying 27 Mbps of bandwidth for a 54G network. Because that also is not correct. CSMA/CA doesn't take the 54 and cut it in half. The reason you don't get 54 Mbps is as I said before because of the environment around you and distance from the router as well as a few other small things. But the number is just not cut in half. It can be lower or higher then 27 Mbps.

http://www.cs.clemson.edu/~westall/851/802.11/802_CSMA_CA.pdf

Page 18. Also page 21, which gives you 9Mbps with RTS/CTS to protect you from having two nodes in range of the Router, but NOT each other.

In total we have 428μs to transmit 1460 bytes of payload, which gives us a throughput of 27Mbit/s.

Thanks,

EBrown

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I'm with dlewis23 here. There's no explicit split in half thing about bandwidth, the only rule is that the throughoutput of both (or more) connected devices combined cannot surpass whatever limit the object they're connected to has. The bandwidth graphs he showed have one correlation, the combined bandwidth is 100 mbps or less, because that can't be surpassed. In a case where the combined bandwidth would want to go above 100 mbps, QOS decides which server/service gets priority. Makes perfect sense to use it in the case of multiple servers on a single link.

As for the 54mbps thing of wireless... that's highly theoretical.

Hubs are simple devices, they do not check for collisions at all. Unless you want the traffic to be cloned, they are to be avoided.

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I have no idea why you would use it for data servers, but that's entirely your choice.

Simple. If one of the servers was running MySQL you would want the MySQL packets to get priority over say an image.

Or you can have both serving at 100Mbps and not worry about it. Unless you use a hub.

No I couldn't. I can only have one transmitting at 100 Mbps, and the over receiving at 100 Mbps. They both can not be receiving or transmitting at 100 Mbps at the same time.

You need to lean how full duplex works, it doesn't give you 200 Mbps in one direction, it allows you to have 100 Mbps going in and out at the same time. Stop adding it up.

You must be doing something wrong because those graphs don't correlate to each other at all. One of them dips down extremely while the other is chugging along. All that proves is that one of them worked slower for several hours.

First, they do correlate to each other in that they are maxing the 100 Mbps port in the beginning of the graph. You just don't know what the servers are doing. The large dip in the first graph is just the natural dip in the traffic for the day that happens to most sites. The second server is for backup and a few other things but it can only reach a maximum of about 15 Mbps because the other server is using majority of the bandwidth. They will never have the same flow because they are both doing different things.

I will reply to the rest of your post later.

Edited by dlewis23

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I'm with dlewis23 here. There's no explicit split in half thing about bandwidth, the only rule is that the throughoutput of both (or more) connected devices combined cannot surpass whatever limit the object they're connected to has. The bandwidth graphs he showed have one correlation, the combined bandwidth is 100 mbps or less, because that can't be surpassed. In a case where the combined bandwidth would want to go above 100 mbps, QOS decides which server/service gets priority. Makes perfect sense to use it in the case of multiple servers on a single link.

As for the 54mbps thing of wireless... that's highly theoretical.

Hubs are simple devices, they do not check for collisions at all. Unless you want the traffic to be cloned, they are to be avoided.

That is what I am saying, and I have been for the past 4 posts. So he's partially right, QOS will change much of the bandwidth sharing. However, on a shared medium, it will be half of the original, should no QOS be in place.

No I couldn't. I can only have one transmitting at 100 Mbps, and the over receiving at 100 Mbps. They both can not be receiving or transmitting at 100 Mbps at the same time.

You need to lean how full duplex works, it doesn't give you 200 Mbps in one direction, it allows you to have 100 Mbps going in and out at the same time. Stop adding it up.

For 1: I never stated that Full Duplex gave you 200Mbps in one direction. Bandwidth is the total amount of data that can possibly be transmitted over the medium at any one point in time. It is 200Mbps on a 100Mbps network. That cable can handle 100Mbps going both ways at any one point in time, with no collisions.

And 2: Yes, they can BOTH be transmitting and receiving at the same time. Once can transmit out of the network while the other receives from a different server on the network. Thus you would have 200Mbps going through the network. Now if they are sending/receiving from each other, I am not sure that they can both do it at the same time. I guess it depends more on the NIC card for that. Should you use two NIC cards in each, then they can send and receive to each other at the same time.

Thanks,

EBrown

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