Tham khảo tài liệu 'krone - white paper - utp - improving your network bit-by-bit', công nghệ thông tin, quản trị mạng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Improving Bit by Bit. many installers and customers To move signals of that frequency around efficiently within AS DATA are finding that physical my transmitting station needed what can only be described networks designed, installed as plumbing transmission lines made out of thin copper RATESand tested to the current Cat 5e pipes and ceramic insulators—the alternative being or proposed Cat 6 standards expensive, specially constructed, but very high loss, coaxial RISE, simply won’t work properly cable. Yet here we are twenty years later happily shoving at 100 Megabit Fast Ethernet, similar frequencies down twisted pairs without really let alone at Gigabit speeds. Independent Management thinking about the physics involved! Consultant Philip Turtle explains some of the reasons why this is happening and how one manufacturer seems Three factors about radio frequency signals are very to have come up with the solution. important in understanding our problem: 1. They become attenuated very rapidly in a transmission There have been numerous reports during the latter half of line system such as our twisted pair, and the power loss 1999 about Cat 5e and “proposed” Cat 6 systems being increases with both frequency and line length. So the installed and passing category testing. Yet when presented signal you get at the receiving end is much, much less with real network traffic they have failed to pass data than you started with, a mere watts out for every sensibly at all, even though the link lights on the network one-watt you put in at Cat 5 limits. interface cards (NICs) are “on,” both on the PC and the hub 2. They treat every wire as an antenna radiating energy or switch. into other conductors and receiving energy from them, too. Just think, you are trying to receive a signal which The practical solution in many cases has been to switch the is only five thousandths of the high power signal in an 100 Mb/s NICs from Full Duplex to Half Duplex, effectively adjacent wire, a
