1 LANs are Subnet Standards Only Physical and Data Link Layer standards Implemented by the NICs:NICs Application Transport Internet LAN Subnet (NIC) Application Transport Internet LAN Subnet (NIC)

2 Subnets

3CharacteristicsCharacteristicsDescriptionDescription Access Method CSMA/CD Transfer Speed Standard Ethernet – 10 Mbps Fast Ethernet – 100 Mbps Gigabit Ethernet – 1 Gbps (1000 Mbps) Standard Ethernet – 10 Mbps Fast Ethernet – 100 Mbps Gigabit Ethernet – 1 Gbps (1000 Mbps) Collision DetectionCarrier Sense Multiple Access Detects signalTransmits signalCollision detected Ethernet (802.3)

4 Ethernet: CSMA/CD CSMA/CD process

5 Sample Ethernet Frame

6 Ethernet Ethernet frame

7 Logical Topology Bus logical topology: signals travel from one network device to all other devices on network –Broadcast –Required by bus, star, star-wired physical topologies

8 Bus Single cable connects all network nodes without intervening connectivity devices Devices share responsibility for getting data from one point to another Terminators stop signals after reaching end of wire –Prevent signal bounce Inexpensive, not very scalable Difficult to troubleshoot, not fault-tolerant

9 Bus

10 Star A typical star topology network

11 Star Any single cable connects only two devices –Cabling problems affect two nodes at most Requires more cabling than ring or bus networks –More fault-tolerant Easily moved, isolated, or interconnected with other networks –Scalable Supports max of 1024 addressable nodes on logical network

12 Hybrid: Star-Wired Ring A star-wired ring topology network

13 Star-Wired Bus A star-wired bus topology network

14 Network Cables Coaxial ThinNet ThickNet 10Base2, 10Base5 Fiber-Optic Twisted-Pair Unshielded (UTP) Shielded (STP) 10BaseT

15 10Base2 /Thinnet

16 The Rule A thinnet network can combine as many as five cable segments connected by four repeaters; but only three segments can have stations attache –" This is known as the rule. repeaters can be used to join Ethernet segments and extend the network

17 ThinNet Rule

18 10Base2 Standard Coaxial cable, or thinnet, which has a maximum segment length of 185 meters. Thinnet cabling components include: BNC barrel connectors. BNC T connectors. BNC terminators

19 10Base-5 / Thicknet

20 Thicknet rule

21 10BaseT Standard In 1990, the IEEE committee published the specification for running Ethernet over twisted-pair wiring. –UTP Most networks of this type are configured in a star pattern, but internally they use a bus signalling system like other Ethernet configurations

22 10BaseT Specifications Summary

23 10BaseFL Standard is an Ethernet network that typically uses fiber-optic cable to connect computers and repeaters. The maximum distance 2000 meters (about 6500 feet).