The Ultimate simple broadcast: Aloha mechanism - blindly blast it to a satellite which comes back down to radio towers
	-No avoidance due to travel latency to satellite
	-Graph of Offered Load vs. Throughput looks like a hill shaped curve - 1/2e utilization
	-Slotted Aloha - all messages must start at certain slot times. This makes it so that either messages overlap 100% or don't overlap at all - 1/e utilization
	
Ethrenet - physical coax cable - has CSMA/CD (carrier sense multiple access with collision detection)
	-Carrier Sense - listening before broadcast
	-Collision Detection - Listen while broadcasting as well (simultaneous start time collision)
		-Random backoff in this case
	-Ethernet Frame: destination address, source address, type, data, frame check sequence (error detection and correction)
	-Problems with original Ethernet
		-Reliability - A broken device jamming network
		-Fairness - not enforced
		-Bandwidth limited to cable
		-Limited to cable length - 4000 ft
			-Switches and Hubs are used here
		-Security - Everyone can see everything
	-Recent Ethernet designs
		-mostly just trancievers changing
		-Wireless - a,b,g,n
		-Speeds - 10M, 100M, 1G, 10G
		

Ring Network - a type of broadcast network	
	Token Packet- special packet circulates around the ring of stations
	
		if a station needs to send something, wait for token
			recieve token
			send data packet
			send token
		if a station recieves a packet
			if the sender was this station, do nothing
			else read data
				resend packet out
		if a station recieves a token without needing to send a packet
			send token back out

	Problems:
		-Station dies and token cannot circulate
		-Token goes missing
		-Starvation is possible
		-More than 1 token = chaos

Methods for linking two machines:
	-Circuit switching - a line between two machines (think telephones and switch operators)
	-Packet switching - break communications into packets and send those one at a time
	-Message switching - circuit is set up for a message then dropped

Different networks connected through gateways

Names vs Address vs Routes
	Name: Symbolic name
	Address: Much like a house address - stacking increasingly specific locations
	Route: The path a packet takes - the sender has to provide the route. Very clumsy

	Internet takes care of most of this. Gateways take care of routing. 

Communications Problems
	-Lost Packets
		-Transmission error - Corrupted addresses or content
		-A node has limited buffering, is overloaded and drops the packet
		-Reciever is down
	-Out of order Packets - 2 packets take different routes
	
Datagram Protocol - sends packets but does not guarantee anything about their arrival

Transport Protocol 
	-Senders and recievers have to deal with acknowledgements and other such state
	-Deals with duplicates and out of order packets
	-Flow control - How far ahead the sender can send

TCP/IP - a bunch of network protocols that make up the internet protocol suite - Represents levels 3 and 4 in the ISO
ISO Levels - 
	3 - Network
		-IP - Addresses 
		-ICMP - Internet Control Message Protocol - Used by gateways and hosts
		-ARP - Address resolution protocol
		-RARP - Reverse ARP
	4 - Transport Layer
		-TCP - Transmission Control Protocol - Dealing with timouts, floodcontrol, etc.
		-UDP - more performance, less reliability
	5-7 -  Session, Presentation, Application layers - just software that sits on the internet
		-SMTP, DNS, FTP, Telnet