Retry is when the radio is required to resend a packet or fragment multiple times for the client (be it the AP or the CPE) to receive it. High retry rates often occur if the signal is low or has other high interference in the area which causing the degredation. Certain models of AP provide statistics on the number of 'Long' or 'Short' (depending on preamble setting I believe) that have occured in the client <-> AP link. I've noticed that many manufacturers fail to show the retry rates (i.e. if a packet gets through that's okay) - however, some (cisco, alvarion) show the number of retries (and max retries - i.e. I've sent the packet 10 times and still not received an ACK therefore it's exceeded its max retries and is dropped) across a link. Typically, even if you are within the dB rating of a link (e.g. -85dB for 11Mbps) a high number of retries can occur, reducing effective throughput.
----- Original Message ----- From: "Peter Cartwright" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, October 28, 2003 6:44 PM Subject: RE: [smartBridges] Slow download speed > Colin, > > What is it that causes a "retry"? > > Peter > > Loop Scorpio Ltd > providers of Ledbury Broadband and Highnam Broadband > www.ledburybroadband.co.uk > www.highnambroadband.co.uk > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Colin Watson > Sent: 28 October 2003 18:40 > To: [EMAIL PROTECTED] > Subject: Re: [smartBridges] Slow download speed > > > 1200Kbit/s? or 1200 Kilobyte/s? - We get about 400 Kilobyte/s (400Kb/sec) > throughput to our backlink. It'd be worth checking the smartbridge > statistics, see if their is a high number of errors on the ethernet side. > Also (I don't know if you can do this on SmartBridge AP's) you may have a > statistic to show the number of retries the customer is experiencing - High > retries will equate to low throughput. If they have got a high number of > retries, check their signal strength they get back to the AP client-->AP, > and finally, check for local 2.4 interference. > > ----- Original Message ----- > From: "Roger Howard" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Tuesday, October 28, 2003 6:06 PM > Subject: [smartBridges] Slow download speed > > > > I just installed an APPO on Sunday, with 3' of LMR400 going to a Pac > > Wireless 16dbi 90 degree horizontally polarized sector antenna. It's 100' > > high on the side of a water tower. > > > > I'm seeing significantly improved signal strengths at customer sites than > I > > was getting with the old 14.5dbi Maxrad on my first access point, but > > download speeds are terrible. I'm seeing around 1200k upload speed fairly > > consistantly (figure my T1 is the bottleneck there) but the download speed > > is very variable. Anything from the test failing, or maybe 90k or > sometimes > > several hundred k. When I switch back to the original access point (rotate > > the antenna for correct polarity) the performance improves. > > > > Does anyone have any idea what may be causing this? I'm going to try an > 18v > > power supply since there is about 150' of CAT5. Any other ideas what might > > be causing it? I'll confirm soon whether the 18v helped. > > > > Thanks, > > Roger > > > > ----------ANNOUNCEMENT---------- > > Don't forget to register for WISPCON IV > > http://www.wispcon.info/us/wispcon-iv/wispcon-iv.htm > > > > 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://archives.part-15.org > > > > > > > > ----------ANNOUNCEMENT---------- > Don't forget to register for WISPCON IV > http://www.wispcon.info/us/wispcon-iv/wispcon-iv.htm > > 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://archives.part-15.org > > > ----------ANNOUNCEMENT---------- > Don't forget to register for WISPCON IV > http://www.wispcon.info/us/wispcon-iv/wispcon-iv.htm > > 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://archives.part-15.org > > ----------ANNOUNCEMENT---------- Don't forget to register for WISPCON IV http://www.wispcon.info/us/wispcon-iv/wispcon-iv.htm 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://archives.part-15.org
