802.11b was designed for small networks in one building. Improvements have been made so that WISPs can use it. In a standard WISP scenario many nodes are hidden. However, just because a unit can not pass data over a givin link does not mean that it can't hear the other end. A RTS/CTS packet is, by design, very small. Even though a directional antenna is called 'directional' it can still pick up signals from every direction. I commonly use a 9db panel atnenna laid flat on my dask to warDrive. I can receive signals from an AP over 3 miles away. So don't assume that just because you would not be able to pass data directly between two clients (in adHoc mode) that they can not see SOME data or at least RTS/CTS packets.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jerry Carter Sent: Wednesday, May 28, 2003 10:55 PM To: [EMAIL PROTECTED] Subject: Re: [smartBridges] Poor Rate I dont quite understand here. Unless you use an omni on everything how could any customer see another? Wouldnt they have to be aiming at each other? So what I am asking would they not all be hidden nodes and require some sort of RTS/CTS?? ----- Original Message ----- From: "Tom Haynes" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, May 28, 2003 9:28 PM Subject: RE: [smartBridges] Poor Rate These numbers are just a qualified quess based on other manufacturers suggestions and my personal experience. RTS/CTS should be varied on a per customer basis. The lower you set the number the more badwidth is lost to overhead (IE more bandwidth used to manage the channel). The higher the numbers, the less bandwidth lost to overhead, but there is more 'confusion' on the channel. The bandwidth lost is only on the channel used and does not eat up resources beyond the AP (IE no backbone speed lost). Lets look at it this way. If you set all clients to "0" then every single packet sent will require a request. If you only have 10-20 clients associated with an AP and each client is limited to 1mb then no one will notice any slowdowns (in theory). The AP puts everyother client 'on hold' untill the transmission is complete. This would only need to be done if the clients can not 'see' eachother. Once you add more than 10-20 clients or you need more bandwidth for each client then you need to tweak the numbers to get a good balance between bandwidth overhead and reliable speed. A good rule of thumb is if a client can not 'see' more than 10-20% of all associated clients then you need adjust that clients RTS/CTS. The fewer clients any one client can see the lower you need to set RTS/CTS. Unseen clients RTS/CTS 10% max-1500 25% 800 50% 600 75% 400 90% 200 100% 100-0 These numbers are just a guideline. If ACK FAILURES or speed is unacceptably slow, raise the RTS/CTS. If ACK FAILURES fall and speed is acceptable then lower the number more. YOU SHOULD NEVER NEED TO LOWER RTS/CTS ON AN ACCESS POINT unless it is in client bridge mode (which makes it a client like a bridge) RTS/CTS is a probability game. What are the chances that a packet transmitted by client A will interupt client X's transmission? If the answer is 'likely' then RTS/CTS should be lowered so that client A will ask for permission to send. Fragmentation is used to combat the effects of interference and constant RTS/CTS packets. When you lower RTS/CTS and most clients respond well but a few clients start having problems, set the problem clients FRAGMENTATION to around 1500. If problems INCREASE change it to 2000. If problems DECREASE then try lowering FRAGMENTATION lower untill you get an acceptable failure rate. I hope this helps. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, May 28, 2003 9:40 AM To: [EMAIL PROTECTED] Subject: RE: [smartBridges] Poor Rate > Try setting the Fragmentation to around 600 and RTS/CTS to 350 on the > airBridge unit. Leave the settings the same on the AP. Make sure you are > using an 18v power supply on both ends. Turn the 'Dial-a-power' down about > 10% on both units (about 3 ticks in the GUI). Are there other clients > associated with this AP? If so, set the other clients RTS/CTS to around 500 > for the near ones and 350 for those over 1 mile. > Where did you get these numbers from? You sound like a man with a mission here, and I'll be darned if I know what/why/how these numbers should be. Any suggestions as to how to know when you've got the best settings? Ping test? RSSI/LinkQ stats? Thanks. Tim Foster www.AledoBroadBand.com Aledo's only high-speed ISP The PART-15.ORG smartBridges Discussion List To Join: mailto:[EMAIL PROTECTED] (in the body type subscribe smartBridges <yournickname> To Remove: mailto:[EMAIL PROTECTED] (in the body type unsubscribe smartBridges) Archives: http://198.63.203.6 The PART-15.ORG smartBridges Discussion List To Join: mailto:[EMAIL PROTECTED] (in the body type subscribe smartBridges <yournickname> To Remove: mailto:[EMAIL PROTECTED] (in the body type unsubscribe smartBridges) Archives: http://198.63.203.6 The PART-15.ORG smartBridges Discussion List To Join: mailto:[EMAIL PROTECTED] (in the body type subscribe smartBridges <yournickname> To Remove: mailto:[EMAIL PROTECTED] (in the body type unsubscribe smartBridges) Archives: http://198.63.203.6 The PART-15.ORG smartBridges Discussion List To Join: mailto:[EMAIL PROTECTED] (in the body type subscribe smartBridges <yournickname> To Remove: mailto:[EMAIL PROTECTED] (in the body type unsubscribe smartBridges) Archives: http://198.63.203.6
