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Chapter 4 (1)
- 2. Ethernet History Developed to replace “Sneakernet" Originally developed in 1973 by Xerox Corp. for internal computer networks Stayed an internal technology until 1979 IEEE 802.3 Coaxial 10Mbps
- 3. Ethernet Basic Concept Ethernet quirks due to early design decisions: “Shared Cable” concept Data frames with MAC address CSMA/CD
- 4. The Ethernet Topology Early Ethernet based on bus topology
- 5. The Ethernet Topology Ethernet still operates in a logical bus topology regardless of physical topology In the early 1990s the bus gave way to the hub Hub is multi-port repeater “Bus in a box”
- 6. Ethernet Frames Recall from chapter 2 that frames are packages of data defined in the datalink layer of the OSI model Ethernet frame:
- 7. CSMA/CD Carrier Sense Multiple Access (with) Collision Detection Carrier Sense Multiple Access Collision Detection Collision Domain
- 8. Early Ethernet Networks: A History Lesson IEEE 802.3 “Ethernet” standard: 10baseT 10Mbps baseband Twisted pair
- 9. Physical vs. Logical Topology Physical: How the cables are connected Logical: How the data flows Ethernet is now a Logical bus and a physical star Was it always like this? How was it different?
- 10. Physical components of Ethernet UTP (Unshielded Twisted Pair) Ethernet requires CAT3 or higher & RJ-45 Connector Cabling made up of 4 pairs Each Pair has a color & color with white stripe Orange, Green, Blue, Brown Wrapped in an outer sheath that has NO shielding (unshielded)
- 11. Cable Termination 4 Pairs, but what order? Where the cable meets the connector is explicitly defined by: TIA/EIA 568A & 568B
- 12. Transmission Modes Half Duplex NIC can only transmit OR receive at one time Think of a walkie talkie Full Duplex NIC can transmit AND receive at the same time Think of a telephone
- 14. Fiber vs. Copper Comparison 10BaseT 10BaseFL Speed 10Mbps 10Mbps Signal Type Baseband Baseband Max. Distance 100 Meters 2000 Meters Node Limit 1024 Nodes 1024 Nodes Topology Star-Bus Star-Bus Cable Type CAT3 UTP Multimode Fiber
- 15. Fiber vs. Copper Comparison 10BaseT 10BaseFL Speed 10Mbps 10Mbps Signal Type Baseband Baseband Max. Distance 100 Meters 2000 Meters Node Limit 1024 Nodes 1024 Nodes Topology Star-Bus Star-Bus Cable Type CAT3 UTP Multimode Fiber
- 16. Connecting Ethernet Segments Hubs replace the bus cable very early on Hubs have limited port counts That’s a good thing 2 types of ports on a hub Regular Uplink(usually only one)
- 17. Crossing Over TIA 568B specifies how to terminate both ends of a cable to make a “straight-through” cable TIA 568B on one end and 568A on the other makes a “crossover” cable Reverses the send/receive pairs to allow direct connection between to devices Can take the place of the uplink port on hubs
- 18. The Path to Switching Repeaters Extend the range of the network Hubs Think of them as “multi-port repeaters” Bridges Think of them as “filtering repeaters” Switches A whole other level of networking
- 19. Switches The problem with hubs They have no intelligence Shared bandwidth 10Mbps / 10 clients = 1Mbps Switches offer intelligence and thus more bandwidth
- 20. Switches Switches look like hubs but that’s where the similarities end. Hub: repeats all traffic to all ports Switch: only sends traffic to the port connecting to the recipient’s NIC SAT (Source Address Table) Directory of who is connected to what port
- 21. Switches Problems with SAT and connecting switches Network “Loops” can bring down the network Spanning tree was developed to solve this
- 22. Spanning Tree Protocol Spanning tree directs switch to shut down (block) the duplicate path