Scott, You raise a very valid point, Half Duplex can have a penalty regarding throughput and/or collisions, in some cases. As well it can break bandwdith mangement routines to some extent, because its not static how much bandwidth will be available at a given time in a direction to share between all the flows in that direction. The question that arises is... which loses more bandwidth/spectrum? Half Duplex or Full Duplex with asymemtrical usage mismatch? Depends, but definately a factor to consider.
Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Scott Reed" <[email protected]> To: "WISPA General List" <[email protected]> Sent: Thursday, May 20, 2010 12:25 PM Subject: Re: [WISPA] Bandwidth > To point one, it depends on the device and the settings. If set to full > duplex, there should not be collisions in a ptp configuration, but some > inexpensive equipment will still show collisions. In half duplex, there > may be, since only one side can talk at a time. I agree, this is only > for CDMA networks. > > Tom's discussion in his earlier post is excellent. > > Tom DeReggi wrote: >> For Ethernet colision detection type networks, you are correct. >> That is what many WISPs forget when deploying PtMP. They incorrectly >> think a >> CDMA 25mb link will double their 10mb TDD link as they scale. They learn >> that as customer get added, the capacity is not nearly as much as they >> thought.. >> >> But with Ethernet backbones it does not always work the same, for two >> reasons.... >> >> 1) There is only one end device, so its not possible for collisions, and >> collision avoidance algorythms aren't really needed. >> 2) If using TDD Ethernet, transmits are scheduled, without the typical >> overhead of Ethernet. >> >> I can run successfully run a bandwidth test of 95mb over a 100mb Cogent >> fiber circuti, and with a Tlink-45 set 36mbps mod, tested to pass 30mbps >> with radio tests, I can count on passing 30mbps through it. >> So again, it comes down to the design and technology of the backbone. >> >> Tom DeReggi >> RapidDSL & Wireless, Inc >> IntAirNet- Fixed Wireless Broadband >> >> >> ----- Original Message ----- >> From: "Scott Reed" <[email protected]> >> To: "WISPA General List" <[email protected]> >> Sent: Thursday, May 20, 2010 11:08 AM >> Subject: Re: [WISPA] Bandwidth >> >> >> >>> Old rule of thumb for Ethernet, because it is based on collision >>> detection, is 70-75% is the max you want. Above this and collisions >>> often become an issue. I assume the same is true for the faster links >>> as well. >>> >>> Jeremie Chism wrote: >>> >>>> At what percentage of your backbone usage do you look at adding more >>>> capacity. At peak times I run at 65-70 percent of capacity. Just >>>> looking for suggestions. >>>> >>>> Sent from my iPhone >>>> >>>> >>>> -------------------------------------------------------------------------------- >>>> WISPA Wants You! Join today! >>>> http://signup.wispa.org/ >>>> -------------------------------------------------------------------------------- >>>> >>>> WISPA Wireless List: [email protected] >>>> >>>> Subscribe/Unsubscribe: >>>> http://lists.wispa.org/mailman/listinfo/wireless >>>> >>>> Archives: http://lists.wispa.org/pipermail/wireless/ >>>> >>>> >>>> >>>> >>> -- >>> Scott Reed >>> Sr. Systems Engineer >>> GAB Midwest >>> 1-800-363-1544 x2241 >>> 1-260-827-2241 >>> Cell: 260-273-7239 >>> >>> >>> >>> -------------------------------------------------------------------------------- >>> WISPA Wants You! Join today! >>> http://signup.wispa.org/ >>> -------------------------------------------------------------------------------- >>> >>> WISPA Wireless List: [email protected] >>> >>> Subscribe/Unsubscribe: >>> http://lists.wispa.org/mailman/listinfo/wireless >>> >>> Archives: http://lists.wispa.org/pipermail/wireless/ >>> >> >> >> >> -------------------------------------------------------------------------------- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> -------------------------------------------------------------------------------- >> >> WISPA Wireless List: [email protected] >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ >> >> >> > > -- > Scott Reed > Sr. Systems Engineer > GAB Midwest > 1-800-363-1544 x2241 > 1-260-827-2241 > Cell: 260-273-7239 > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
