So what happens when you build networks using layer 1 equipment well suppose you want to connect uh two pcs together and uh you could just link them together with let's say with a copper cable and ethernet so you're probably familiar that with cat5e cable the maximum length is 100 meters that's 90 meters for the actual cabling and then five millimeters each each end for the patch cables um and beyond that it's not guaranteed to work because the signal will degrade too much over at longer distances so you might say well okay suppose i put some better cable in suppose i buy more expensive cat6a cable does that help well actually cat6a cable also has the 100 meter limitation what's different is that cat6a will let you do 10 gigabits over 100 meters whereas cat5e will only let you do one gigabit over 100 meters you don't actually gain any distance by using the more expensive cable but you do gain the ability to run at higher speed all right well then what about if you want to go longer than that then you might have to look at some other kind of medium so fiber would be another option now again depending on what speed you want to send out and what distance you want to go at there are a number of different options and so in the general rule is that multi-mode fiber is the worse it runs at the slowest speeds and the shortest distances and if you have single mode fiber then that runs at high speeds and over very long distances so you could build your link using fiber but you're still going to reach some limitations so with your single mode fiber depending on the lasers in whatever you have you might have a limit of 20 kilometers or it might be 40 kilometers or even sometimes 80 but you've still got that limitation there another thing you might decide to build your network with is media converters so you take a copper ethernet you convert it to fiber and then convert it back to copper again at the other end now this works fine but it's not an ideal way to build your network and the reason is that media converters are dumb unmanaged devices so you've added extra active devices in here which are things that could fail but you haven't got any way to manage them or monitor them so they can't tell you for example what bit error rate they're seeing they can't tell you what the strength of the light signals they're receiving is and so you've got no way of knowing in advance when they're going to fail so ideally you would try and avoid media converters in your network if you can and put sfps for example into sfp ports on switches because they are manageable and even though there are only layer one devices they will still give you this information that allows you to track the quality of the link and be able to detect failures you

© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.

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