2 Basic Concepts: data and computer networking Line Configuration Topology Transmission Mode Categories of Networks Internetworks 11/12/2018 Paul Lin Lecture2.ppt

2.1 LINE CONFIGURATION Defines the attachment of communication devices to a link Two categories: Point-to-Point Multipoint 11/12/2018 Paul Lin Lecture2.ppt

Point-to-Point Line Configuration Dedicated link with entire capacity of the channel reserved for communication Examples: PC to PC (workstation) Mainframe to PC (Workstation) Satellite links 11/12/2018 Paul Lin Lecture2.ppt

Multipoint Line Configuration Multidrop Sharing a single link: Spatially Time sharing 11/12/2018 Paul Lin Lecture2.ppt

2.2 TOPOLOGY Logical or physical layout of a network Two or more links form a topology Five Basic Topologies: Mesh, Star, Tree, Bus, Ring 11/12/2018 Paul Lin Lecture2.ppt

2.2 TOPOLOGY (continue) Relationships among devices: Peer-to-Peer Share communication link equally Primary-Secondary Master traffic controller Ethernet Hub 11/12/2018 Paul Lin Lecture2.ppt

Mesh Topology Every device has a dedicated point-to-point link to other device A fully connected mesh network: n(n-1)/2 physical channels to link to n devices n-1 I/O ports 11/12/2018 Paul Lin Lecture2.ppt

Mesh Topology (continue) Example 1: three nodes or computers Number of links: n(n-1)/2 = 3 Number of ports: n-1 = 2 11/12/2018 Paul Lin Lecture2.ppt

Mesh Topology (continue) Example 2: Four nodes or computers Number of links: n(n-1)/2 = 6 Number of ports: n-1 = 3 11/12/2018 Paul Lin Lecture2.ppt

Mesh Topology (continue) Implementation: usually implemented in a limited fashion -- a backbone connecting the main computers of a hybrid network Example: ARPARNET 11/12/2018 Paul Lin Lecture2.ppt

Mesh Technology Advantages: Dedicated point-to-point links (eliminating traffic problems) Robust (high reliability, traffic can be routed) Privacy or security (communications only between sender and receiver) Easy fault identification and fault isolation 11/12/2018 Paul Lin Lecture2.ppt

Mesh Technology Disadvantages: High cost (amount of cabling and number I/O ports) Difficult to install and reconfigure 11/12/2018 Paul Lin Lecture2.ppt

Example 3: 8 devices Mesh topology I/O port and links calculation Answer: Number of links = n(n-1)/2 = 8(8-1)/2 = 28 Number of ports per device = n-1 = 8-1 = 7 11/12/2018 Paul Lin Lecture2.ppt

Star Topology Hub (central controller) acts as a exchange controller which relays the data to other connected devices Each device has a dedicated point-to-point link only to a central controller 11/12/2018 Paul Lin Lecture2.ppt

Star Topology Advantages: Disadvantages Less expensive than a mesh topology Robust (high reliability): if one link fails, all other links remain active Easy fault identification and fault isolation through central hub Disadvantages Require more cabling than in tree, ring or bus topology (far less cable than a mesh) 11/12/2018 Paul Lin Lecture2.ppt

Tree Topology A variation of star Nodes in a tree are linked to a central hub that controls the traffic to the network 11/12/2018 Paul Lin Lecture2.ppt

Tree Topology Secondary hubs: Central hub: For connecting devices Active or passive Central hub: An active hub Repeater (enhance signals for transmitting over a longer distance) 11/12/2018 Paul Lin Lecture2.ppt

Tree Topology (continue) Advantages (same as star topology): Same advantages as star topology Allow more devices to be attached to a single central hub Allow the network to isolate and prioritize communications from different computers Disadvantages (same as star topology) Require more cabling than bus or ring topology 11/12/2018 Paul Lin Lecture2.ppt

Bus Topology Multipoint configuration: one long cable acts as a backbone to link all the devices in the network Computers are connected to the bus cable by drop lines and taps 11/12/2018 Paul Lin Lecture2.ppt

Bus Topology (continue) Advantages Ease of installation Less cabling than mesh, star, or tree topologies Disadvantages Difficult reconfiguration and fault isolation Less Robust (a fault or break in the bus cable stops all transmission) 11/12/2018 Paul Lin Lecture2.ppt

Ring Topology Dedicated point-to-point line configuration only with the two devices on either side of it Repeaters A signal is passed along the ring in one direction from device to device, until it reaches its destination 11/12/2018 Paul Lin Lecture2.ppt

Ring Topology (continue) Advantages Relatively easy to install and reconfigure (maximum ring length and number of devices) Easy fault isolation Disadvantages Unidirectional traffic A break in the ring can disable the entire network (use dual ring or a switch) 11/12/2018 Paul Lin Lecture2.ppt

Hybrid Topologies A Combination of various topologies: Star (hub) Ring Bus 11/12/2018 Paul Lin Lecture2.ppt

2.3 Transmission Mode Three modes: Simplex: one direction, either as transmitter or receiver Half-duplex: both direction; can transmit or receive, but one at a time Full-duplex: can transmit and receive simultaneously 11/12/2018 Paul Lin Lecture2.ppt

Transmission Media Coaxial cable: CATV, cable modem Shield twisted pair Un-shield twisted pair (UTP): category 5 -- up to 100 MHz Optical fiber Wireless: microwave, satellite, radio, infrared 11/12/2018 Paul Lin Lecture2.ppt

2.4 Categories of networks Local Area Network (LAN) Metropolitan Area Network (MAN): Wide Area Network (WAN): Long distance transmission of data, voice, image, and video information Enterprise network (owned by a single company) 11/12/2018 Paul Lin Lecture2.ppt

Local Area Network (LAN) Privately owned links and computers in a single office, building, or campus Bus, Ring, and Star topologies Topologies: bus, ring, star, wireless, infrared Data rates: 2 Mbps, …, 10 Mbps, 100 Mbps, Gigabits 11/12/2018 Paul Lin Lecture2.ppt

Metropolitan Area Network (MAN) City wide coverage LAN-to-LAN LAN-to-other larger network 11/12/2018 Paul Lin Lecture2.ppt

Wide Area Network (WAN) Long distance transmission of data, voice, image, and video information Enterprise network (owned by a single company) Technologies: ATM (Asynchronous Transfer Mode) Frame Relaying X.25 (Packet switching network) Circuit switching 11/12/2018 Paul Lin Lecture2.ppt

2.5 Internetworks IBM Dictionary of Computing defines internetworking as “communications between two or more networks” Two or more connected dissimilar networks: Ethernet, Token Ring Dial-up lines to ISDN (Integrated Services Digital Network) ATM 11/12/2018 Paul Lin Lecture2.ppt

2.5 Internetworks (continue) Internet (World Wide Web Router Gateways 11/12/2018 Paul Lin Lecture2.ppt