2Tall4U Posted February 7, 2009 Author Share Posted February 7, 2009 whooh... where do i start... at the lowest level you have to look at an ethernet packet and the general reason why ethernet works. Ethernet IS the heart of the internet/web/any form of networking. Ethernet does not just specify wired connections. Ethernet IS a generalized spec of networking. It is first essential to know the process of networking from the system level to the signal level, which is defined by the 7 layer osi model. Ill just type it and you read it. 7.Application -- data--------software (i.e. email/irc/etc) 6.Presentation - data-------software (browser/xml/etc) 5.Session ------data--------protocols/os/etc (connects software layers [or layers 7 and 6] to the lower layers) 4.Transport ----- segment--ports -------------routers (if configured this way), or something like a firewall 3.Network ------ packet-----ip addresses-----routers/switches(some) 2.Datalink ------- frame-----mac--------------nic cards *all nics have a mac*/hubs/etc, 1.Physical ------- bit ---------signal on copper/glass/atmosphere--cat5, fiber optic cable, and wifi/sat. etc. go here for a better picture/reference: everytime you do something on the web through any interface, data goes from the top to the bottom of the osi model in a process called Encapsulation - which is simply wrapping the data to be compatible with the next lower layer, and when it is sent to the physical layer, it is changed modulated into whatever the physical layer is utilizing for a connection (i.e. power pulses for copper/cat5/etc, light pulses for glass/fiber, or frequencies for atmosphere/wifi/sat. etc.) When it is picked up by a router (which it's inevitable it will. My data hits my linksys before even going out on the network, and chances are if your using any kind of high speed i-net, you at least have some kind of routing device built into your modem) it goes up the osi model decapsulating the data to find out where to send the data. If you ever hear of someone talking about a layer 3 device it usually means a router of some sort, or like a layer 4 which could be a router or a firewall depending on how it is configured. Now we'll stop here in the process to explain a major reason why this would not work. You have to have to have tcp for making sure that the data that is getting sent is good. TCP- Transport control protocol. You have to have this if you want the data to arrive in the proper peices and an exact copy of what you had before. The ethernet network believe it or not is a very chaotic place. At any given time you can have what is called a collision. Any connection from one ethernet device to another could be an example of whats called a "collision domain" and it's called such because that is exactly what happens sometimes when you have a full-duplex network where two things are communicating on the same line at the same time. Now if you were just going from computer to computer or router to router you really couldnt quite define it as such, but in a reg. networking scenario this is how it is. So how does tcp make sure everything is as it should? If you looked at a data packet that uses a "connection oriented" protocol (i.e. tcp) ex: , then you would find that there is an ecc (error checking)[here shown as the part that says "checksum" bit that basicly matches the data to the bit at the end through an equation that finds if it matches or not. If it does, then it keeps going and everything is smooth. If it does not, the router/computer/firewall/server/etc. drops the packet completely and pronounces a nak (negative aknowledgement) back to the sending host computer to tell it that the data didnt send right and it needs to resend that one packet. If the router/server/etc. cannot read the raw data on the packet and match it to the ecc, then it will always drop the packet. wheww... you should have paid me money for typing all this :P wanna know more? read up and go to college. (btw, im in CCNA2 right now (cisco certified network administrator class #2) if you wanna know how i learned all this.. i got ccna3 and ccna4 to go...) I work construction part time, and I want to go to technical school, the truth is that does inspire me to go to tech school, I really do mean that Thank you for taking the time Quote Link to comment Share on other sites More sharing options...
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