NETWORKING TECHNOLOGIES

Telecommunications Systems Purpose – to transmit data from one location to another Voice data Computer data Video data Any data Major components Transmission media Network topology Data communications hardware Protocols used in system Network software Telecommunications services

Data Format for Network Transmission Data inside computers is in digital form Networks transmit two forms of data Analog – voice over telephone Digital – data over ISDN telephone line Analog network cannot carry digital data Most of existing telephone system is an analog network Conversion of digital data to analog format (when necessary) Modulation Amplitude modulation Frequency modulation Convert on one end of transmission; de-convert on other end Modulation–demodulation, or modem for short

How Modems Work

Bandwidth The measure of capacity of transmission media Bits per second (bps) Kilobits per second Modem communications over telephone lines Megabits per second Most existing local area networks Gigabits per second High speed data networks Internet backbone

Network Media Physical media Electrical signal Optical signal Wire Twisted pair Phone System LAN Coaxial Signal interference Optical signal Fiber optic cable Thin glass fibers surrounded by coating Uses lasers for light source Very fast Physical media require installation of cable Expensive Time consuming

Network Media Wireless media Radio frequency Terrestrial microwave Low power radio waves Affected by electromagnetic interference Highly vulnerable to snooping Conflicting standards IEEE 802.11a, b, and G Limited distance Terrestrial microwave Tower Satellite Geosynchronous – GEO Medium earth orbit – MEO Low earth orbit – LEO Infrared Close proximity and “line of sight” location required

Media Types and Speed

Computer Networks Two or more computers that are connected for the purpose of sharing data File sharing (e.g. MP3s) E-mail Database sharing Computer must be connected to the network media Network interface card (NIC) Each NIC has its own unique address Once connected to the network, the computer (or other device) becomes a network node

Transmitting Data in a Network Circuit switched network Entire circuit from end to end must be open and available Guarantees message goes through Any one segment along the way goes down, the circuit is disabled Packet switched network Message data divided into small pieces called packets, each with destination address and packet id Special network hardware routes packets to destination where message is reassembled More fault tolerant than circuit switched networks

Network Topologies The configurations of network components Widely used network topologies Bus Star Ring Mesh Tree Hybrid

Bus Network Topology Most simple network topology All devices connected to a common central cable Inexpensive Easily expanded If cable fails, the entire network will shut down Bus is topology used most widely in businesses

Bus Network Topology (Continued)

Star Network Topology Star topology is centered around central routing device called a hub All network nodes connect to the hub Easy to install and update If hub fails, network fails Hub can also be a bottleneck

Ring Network Topology Each node connected to two other nodes in a ring Similar to the buss, but with the ends of the buss connected together More reliable than buss or star If one node fails, data rerouted around failed node Expensive and difficult to install Usually used by larger organizations who can afford the expense and to whom the reliability is very important

Ring Network Topology (Continued)

Mesh Network Topology Every node connected to every other node Fast Reliable No hub or bus to fail If one device goes down, it is the only node affected Expensive Every node must be wired to every other node Difficult to add nodes If there are 32 nodes in a mesh network and you wish to add a new node, how many new cables must you add? 32 nodes Add new 33rd node New node must connect to all 32 existing nodes, therefore 32 cables to add

Tree Network Topology Combination of bus and star Two or more star networks connected using a bus for the backbone

Hybrid Topologies Combine two or more of the other topologies Bus used for LANs and ring used for campus backbone linking LANs together

Network Architecture Defines how network functions at a logical level Two primary types Client-server Peer-to-peer (P2P)

Client-server Network Architecture Nodes are either clients or servers Clients use services Servers provide services Access to shared data E-mail Printing FAX Client software on client node cooperates with server software on server node WWW is largest client server application

Peer-to-Peer Network Architecture All nodes on the network are equal. Any node can be both a client and a server. Napster was an example of a P2P network used to share MP3 files. Windows printer and file sharing use P2P.

Local Area Networks (LANs) Computer network where the nodes are all in close proximity Department Floor in office building Small business building Provides access to shared resources Servers Printers Databases Internet access

Larger Networks Campus area network (CAN) Connects LANs within a limited geographic area School Corporate campus Military installation Metropolitan area network (MAN) Within a town or city Wide area network (WAN) Two or more LANs that are geographically separate but linked through a public telephone network

Data Communications Hardware Hub Modem Router – special hardware in packet switched networks that determines optimal routing path for packets Gateway – converts data from one standard to another; allows connections of disparate networks

Protocols An agreed upon set of rules that govern communications in a network TCP/IP The protocol suite for the Internet Transmission Control Protocol (TCP) Provides a reliable byte-stream transfer service between two endpoints on an internet Internet Protocol (IP) Defines a delivery mechanism for packets of data sent between all systems on an Internet Widely used by business, even for internal networks

Protocols (Continued) Ethernet A set of rules for constructing message in a local network Most widely used protocol for transmitting data over LANs Listen before talk Simple Inexpensive Flexible Collisions High message volume greatly reduces transmission speed

Protocols (Continued) Token Ring Also a set of rules for constructing message in a local network Only one node “talks” at a time Complex Expensive More fault tolerant than Ethernet No collisions Transmission speed unaffected by message volume

Network Software Network operating system Network management software Novell NetWare Microsoft Windows Server 2003 Network management software Helps ensure security of network Monitors performance Helps administrators reconfigure network Remote administration via push technology Network monitoring software Packet sniffers – see data as it moves over network Keystroke monitors – see what users are doing

Telecommunications Services Value Added Networks (VANs) Proprietary networks built using common carriers Provide enhanced services Video conferencing Electronic data interchange (EDI) Virtual Private Networks (VPNs) Use encryption to provide a secure end-to-end connection over common carriers or the Internet Remote access to internal networks w/o dialup Leased lines High speed, long distance data transfer

Leased Line Comparisons