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Solved: Will an old 802.11 wireless device slow the whole newer network its connecte


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Sharker's Avatar
Sharker Sharker is offline
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18-Mar-2009, 04:43 PM #1
Solved: Will an old 802.11 wireless device slow the whole newer network its connecte
If you connect an old 802.11 wireless device to a newer one will it slow the whole network or just that one connection?

For instance if you connect an 802.11g network adapter to an 802.11n network will the entire 802.11n network slow to 802.11g speed? Or will only that one connection go slowly.

Reading on the net some people say it will, others say is wont. Any idea which is true?

Thanks in advance.
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dlsayremn   (David) dlsayremn is offline
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18-Mar-2009, 05:02 PM #2
No. An 802.11b adapter will only effect the speed for computer to which it is connected. A good wireless router negotiates each connection individually and does not lower all connections to lowest common denominator.

Last edited by dlsayremn; 18-Mar-2009 at 05:08 PM..
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18-Mar-2009, 09:02 PM #3
Are you sure? Because everything I've read also tells me that using a single older 802.11x device on an all 802.11N network slows everything down because the router switches from N to whatever works for EVERYBODY. If the 802.11x device isn't currently transmitting, then I guess perhaps the router will switch back to N or G or whatever. But not while it's transmitting. At least, that's what I've read.
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18-Mar-2009, 09:27 PM #4
And the score is .... one to one. Does that settle the issue for you?

I believe this statement, "in an 802.11g network, however, activity by a 802.11b participant will reduce the data rate of the overall 802.11g network" from this source.

And also, "large discrepancies can exist between the throughput an 802.11n device can achieve in a greenfield network, compared to a mixed-mode network, when legacy devices are present" from here. (A greenfield 'N' network is one that has eliminated support for a/b/g devices.)

I think that puts me somewhere between the above two answers. If your router is set to b/g/n mode a 'N' device will not attain the bandwidth it can when the router is in n only mode. Likewise, if a 'g' and 'n' client are sharing a b/g/n network the overall network bandwidth will be less than with two 'n' clients; but during the 'n' device's "turn" it will operate just as fast as if the 'g' were not present.
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dlsayremn   (David) dlsayremn is offline
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18-Mar-2009, 10:29 PM #5
TerryNet,
I stand corrected. For some reason brain was thinking broadcasting both N and G at same time instead of the way routing actually works. DUH!
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19-Mar-2009, 09:15 AM #6
Hi and thanks.

So it looks like older network devises will reduce the entire network to the lowest specification device but just to clarify:

Quote:
Likewise, if a 'g' and 'n' client are sharing a b/g/n network the overall network bandwidth will be less than with two 'n' clients; but during the 'n' device's "turn" it will operate just as fast as if the 'g' were not present.
I wasnt sure what you meant by turn. If I understand you, a g can slow the n network but when the g is not currently transferring data, the n network will be unaffected.

I dont know the technical details of how the wireless systems work but I have noticed that in general, network devices can chatter to each other, even when there is no data to transfer. Does this mean that the newer network will be slowed whenever the older network device is switched on?
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19-Mar-2009, 12:27 PM #7
You mean "turn" isn't a well known carefully defined technical term. Let me try to confuse the issue even more.

Wi-Fi is half duplex, one device talking at a time. If n devices transmit at once at least n-1 of them get sent away to wait and then retransmit. I think the following is a reasonable depiction.

Assume a high powered storage device connected by gigabit ethernet to a 'N' router. Two computers connected by Wi-Fi, C1 by 'N' and C2 by either 'N' or 'G.' C1 is copying a large file from the storage device and C2 is doing something. My picture is ...

Repeat until EOF
1. router sends data packet to C1
2. C1 acknowledges receipt
3. router sends data packet to C2
4. C2 acknowledges receipt
5. chatter and other overhead
End Repeat

Each (1) and (2) together constitutes what I meant by C1's "turn."

If you're still reading let's say C1 is copying a large file that when it is alone on the wireless takes 6 minutes and represents 66 Mbps. C2 is using a 'N' adapter. If C2 is idle and (5) is minimal then C1 should still get its file copy in 6 minutes (66 Mbps).

If C2 has a 'N' adapter and copies an identical file, and the storage device/router perfectly alternates as my small bit of code represents, both files should get copied in 12 minutes. This is still a network bandwidth of 66 Mbps, although if you are sitting at C1 you are experiencing 33 Mbps because the file copy takes 12 minutes. But the sum of C1's turns is only 6 minutes, so it is still operating at 66 Mpbs.

Want more punishment? Let's do the same as above but give C2 a 'G' adapter, and figure it can copy the same file in 18 minutes (22 Mbps). We'll still assume (5) is minimal.

Now the two copies take a total of 24 minutes. The network bandwidth has been reduced to 33 Mbps. C1 is still operating at 66 Mbps during its turns, but you now see that your file copy takes 24 minutes, or effectively 16.5 Mbps.

In a similar manner "chatter" will take longer with non-'N' devices and, hence, slow the overall network more than the same "chatter" with 'N' device.
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19-Mar-2009, 07:36 PM #8
Hi TerryNet, thanks for the in depth explanation of what happens. It answers my question very well. Your effort is appreciated.

Sharker.
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