CPSC 3600 - DAY 16
MARCH 29, 2017

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				WIRED LAN TECHNOLOGY
				--------------------

Backwards compatability
Hardware, wiring, media have changed dramatically

Frame Format

	Way information packet is organized including field size and meaning
	Remained consistant since '70s, ensuring backwards compatability.

	6-byte destination address
	6-byte source address
	2-byte type
	46-1500 bytes of payload
	4-byte CRC

	Type field provides multiplexing/demultiplexing.
		Allows multiple processes to run simultaneously

IEEE Standard (802.3)

	Original type header now read as payload length
	Added LLC/SNAP header (Logical Link Control/ Sub-network attachment pt)
	Not very widely used.

LAN Connections/Network Interface Cards

	Computer perceives LAN as I/O device
	Network Interface Card plugs into computer bus
		handles address recognition, CRC computation, frame recognition
	NIC physically is circuit board with plug for computer bus and socket
	accepting LAN plug

Thicknet Wiring

	Original wiring scheme was thicknet
	Heavy coax cable (10base5)
	Hardware for thicknet was divided into two parts
	Network Interface Card -> handled the digital aspects of communication
	Transceiver -> handled carrier detection, conversion to voltages, etc.

Thinnet 
	
	Second generation uses a thinner coaxial cable that was more flexilble
	Formally named 10Base2
	Rather than using AUI connections between a computer and tranciever
	Thinnet integrates a reciever directly on the NIC and runs a coax
	cable from one computer to another

Thinnet Ethernet Wiring

	Lower overall cost
	Ease of Installation
	No External Tranceivers
	Can be installed in a convenient path

Twisted Pair Ethernet Wiring and Hubs

	Third generation of Ethernet wiring known as Twisted pair
	And it made a dramatic shift in two ways in comparison to previous
	generations.
		In place of coax cables, Twisted Pair Ethernet uses a central
		electroic device, known as a hub, seperate from the computers
		attached to the network

		Instead of heavy, shielded cabling, uses twisted pair

	The electrical components in the hub emulate a physical cable making
	the entire system operate like a conventional ethernet

	For example a computer attached to a hub and uses CSMA/CD to access the
	network, recieves a copy of each frame, and uses the address in a frame
	to determine whether to process or ignore the frame

	Logically, Twisted pair Ethernet employs a bus topology, but physically
	it forms a star-shaped topology.

Wiring in Office Buildings

+------------+-----------------------+----------------+----------------------+
|Designation | Name		     | Data Rate      | Cable Used	     |
+------------+-----------------------+----------------+----------------------+
| 10BaseT    | Twisted Pair Ethernet | 10 Mbps	      | Category 5	     |
+------------+-----------------------+----------------+----------------------+
| 100BaseT   | Fast Ethernet	     | 100 Mbps	      | Category 5E	     |
+------------+-----------------------+----------------+----------------------+
| 1000BaseT  | Gigabit Ethernet      | 1 Gbps         | Category 6	     |
+------------+-----------------------+----------------+----------------------+

Higher speed technologies use a switch instead of a hub.  Interfaces 
automatically sense the speed at which a connection can operate
	Slows down to accommodate older devices

Twisted pair Ethernet RJ45 connectors

Straight and Crossed Ethernet

	Crossed
		conecting pin on one end to a different pin on the other
		usually used to connect two switches

	Straight
		connects each pin to its corresponding pin
		usually used to connect computers to switches

	Most hardware requires either straight or crossed