Some basics about networking that my friend Joao helped me with prior to my Cisco interview.

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Physical layer.

	Network layer. IP (every machine that you talk to has an IP number via network sockets). 
		Transport layered protocols. 

			TCP is what makes the handshake with the server. 

			UDP is not reliable, no handshaking, just gets puts on the wire . This is faster than TCP. Does have checksum, but if the checksum fails then there’s 			no way to get it back. 

				HTTP is building on top of these.  SMTP. FTP. all build on above. 

Port number for certain types of connections. 

Client creates a local TCP socket, which specifies host 

Server could have multiple sockets. One socket for each client it is connected to. 

Process writes to a socket