12-07-2008, 08:41 AM
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Intellectual
Join Date: Mar 2008
Posts: 202
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Some questions about wireless networking
I have some general questions about wireless networking. Here at my college, there are a bunch of Xbox 360's and we like to play Halo 3. I have two routers on my network, neither of them are DHCP servers, my ICS server takes care of that. One router is my D-Link WR-1310 (802.11G), and the second is my brand new old Linksys BEFW11S4v4 (802.11B). The Linksys router is my "Open" access point, meaning that it is unsecured, I just open it up every now and then for Halo 3 or StarCraft.
Here is my problem. With my Xbox 360 connected via ethernet, and then 3 other Xbox 360s connected wirelessly, Halo 3 works but sometimes gets laggy. The whole game doesn't lag, usually only one or two 'boxes start to have minor issues. This is an old 802.11B router, so it either 11mbps isn't fast enough, or the router just doesn't have enough processing power.
I'd swap its' place with my D-Link 802.11G router, but the B router only has WEP security, and I want WPA for my secured AP.
So now, I'm kicking myself for buying an old 802.11B router, I wish i would have paid the extra $25 for the G router, but it's what I have so I need to make it work or just put up with the problems.
Is there any way I can make it handle the workload? What do all these settings like "Short Preamble", "DTIM Interval", "RTS Threshold", and "Beacon Interval" mean? I've always wondered what all of this means anyway, so not only would I like to try to fix the problem but I want to learn the technical things about WiFi.
I'd also like to figure out why some clients (Such as my Axim) refuse to connect to my secured, 802.11G D-Link AP.
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Joel Crane
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12-08-2008, 07:59 AM
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Pontificator
Join Date: Mar 2007
Posts: 1,466
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Quote:
Originally Posted by Joel Crane
I have some general questions about wireless networking. Here at my college, there are a bunch of Xbox 360's and we like to play Halo 3. I have two routers on my network, neither of them are DHCP servers, my ICS server takes care of that. One router is my D-Link WR-1310 (802.11G), and the second is my brand new old Linksys BEFW11S4v4 (802.11B). The Linksys router is my "Open" access point, meaning that it is unsecured, I just open it up every now and then for Halo 3 or StarCraft.
Here is my problem. With my Xbox 360 connected via ethernet, and then 3 other Xbox 360s connected wirelessly, Halo 3 works but sometimes gets laggy. The whole game doesn't lag, usually only one or two 'boxes start to have minor issues. This is an old 802.11B router, so it either 11mbps isn't fast enough, or the router just doesn't have enough processing power.
I'd swap its' place with my D-Link 802.11G router, but the B router only has WEP security, and I want WPA for my secured AP.
So now, I'm kicking myself for buying an old 802.11B router, I wish i would have paid the extra $25 for the G router, but it's what I have so I need to make it work or just put up with the problems.
Is there any way I can make it handle the workload? What do all these settings like "Short Preamble", "DTIM Interval", "RTS Threshold", and "Beacon Interval" mean? I've always wondered what all of this means anyway, so not only would I like to try to fix the problem but I want to learn the technical things about WiFi.
I'd also like to figure out why some clients (Such as my Axim) refuse to connect to my secured, 802.11G D-Link AP.
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- Is it only the wirelessly connected Xboxes that are having the problem? Perhaps a wired test to check it out?
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Short and Long Radio Preambles:
The radio preamble is a section of data at the head of the Physical Layer Convergence Protocol that contains information that the device and client devices need when sending and receiving packets.
The 18 byte ("long preamble") preamble is used to signal "here is a train of data coming" to the receiver. The 802.11b standard gives an option of reducing the size of the PLCP preamble to 9 bytes ("short preamble"), this significantly increases the throughput performance at higher data rates.source
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Just a "envelope address "...where is this data going?
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An access point buffers all multicast frames and sends them immediately following the next DTIM (delivery traffic indication message) if any one client associated with the access point enables power saving mode. When all stations have power saving off, then the access point transmits a multicast frame as soon as possible and doesnt wait for the next DTIM.
The DTIM interval, which you configure in the access point, indicates when the DTIM occurs. A DTIM interval is a count of the number of beacon frames that must occur before the access point sends the buffered multicast frames. For example, a DTIM interval equal to one means that the multicast frames are sent after each beacon frame. A DTIM interval of two indicates that multicast frames are sent after every two beacon frames, and so on. Because each beacon frame includes a field that identifies the DTIM interval, all stations know when to wake up and receive multicast frames if theyre implementing power saving.
Keep in mind that the optimum DTIM interval setting is a tradeoff between throughput and power savings. A low DTIM interval will result in better throughput, but battery life will decrease for stations implementing power save mode.
Source
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This is a "synchcronize your watches and meet back here at 5pm" type of setting. This way a device doesn't have to be perpetually listening to get the data...it can sleep/powersave in between. setting it low is bad for powersaving but faster throughput. Since the XBoxes are plugged in...set it to 1?
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Imagine there are two 802.11 end users (Station A and Station B) and one access point. Station A and Station B can't hear each other because of high attenuation (e.g., substantial range), but they can both communicate with the same access point. Because of this situation, Station A may begin sending a frame without noticing that Station B is currently transmitting (or vice versa). This will very likely cause a collision between Station A and Station B to occur at the access point. As a result, both Station A and Station B would need to retransmit their respective packets, which results in higher overhead and lower throughput.
If either Station A or Station B activates RTS/CTS, however, the collision will not happen. Before transmitting, Station B would send a RTS and receive a CTS from the access point. The timing value in the CTS (which Station A also receives) will cause Station A to hold off long enough for Station B to transmit the frame. Thus, the use of RTS/CTS reduces collisions and increases the performance of the network if hidden stations are present.
Keep in mind, though, that an increase in performance using RTS/CTS is the net result of introducing overhead (i.e., RTS/CTS frames) and reducing overhead (i.e., fewer retransmissions). If you don't have any hidden nodes, then the use of RTS/CTS will only increase the amount of overhead, which reduces throughput. A slight hidden node problem may also result in performance degradation if you implement RTS/CTS. In this case, the additional RTS/CTS frames cost more in terms of overhead than what you gain by reducing retransmissions. Thus, be careful when implementing RTS/CTS. source
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This is going to require experimentation. It seems that by reducing it you introduce overhead. More data sent with less actual gain. It is supposed to be a "All of you, Stop talking all at once! First you, then you, then you" . If you've ever seen Senatorial/ Congress proposal debates then you know it could also be beneficial if only one person speaks at a time.
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Beacon interval. This represents the amount of time between beacon transmissions. Before a station enters power save mode, the station needs the beacon interval to know when to wake up to receive the beacon (and learn whether there are buffered frames at the access point).Source
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Set to lowest setting?
This is all a big google and conjecture. Overall I think just a quick test ethernet vs wifi will tell you for sure that 802.11b is probably too slow for gaming.
Another cheat would be to use the encrypted AP as your gaming router. Just password change temporarily and then change it back...
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12-08-2008, 08:06 AM
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Intellectual
Join Date: Mar 2008
Posts: 202
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As always, thanks Cybrid! One Xbox is connected via ethernet, the other 3 are connected via WiFi and have to be.
As to temporarily changing the encryption, I was doing that before but got tired of it, hence the second AP.
Another thing I have noticed about the Linksys 802.11b router is that clients connect much faster and more reliably. It generally takes my laptop 2-3 tries to get it to connect to my D-Link 802.11g router, and my Axim won't connect at all. It is very strange.
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Joel Crane
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