Comparing modem and other technologies

Internetwork Processors Switch – makes connections between telecommunications circuits in a network Router – intelligent communications processor that interconnects networks based on different protocols Hub – a port switching communications processor Gateway – connects networks using different communications architectures

Communications Processors Corporate LAN in upper left hand corner uses a hub to connect its multiple workstations to the network switch. The switch sends the signals to a series of switches and routers to get the data to its destination.

Telecommunications Processors Multiplexer Allows a single communications channel to carry simultaneous data transmissions from many terminals

Telecommunications Software Used by servers and other computers to manage network performance Network Operating Systems Middleware

Network management functions Traffic Management – manage network resources and traffic to avoid congestion and optimize service levels to users Security – provide authentication, encryption, firewall, auditing and enforcement Network Monitoring – troubleshoot and watch over the network, informing network administrators of potential problems before they occur Capacity Planning – survey network resources and traffic patterns and users’ needs to determine how best to accommodate the needs of the network as it grows and changes

Network Topologies Topology: structure of a network Star: ties end user computers to a central computer Ring: ties local computer processors together in a ring on a relatively equal basis Bus: local processors share the same communications channel

Network Topologies

Network Architectures & Protocols Protocol: standard set of rules and procedures for the control of communications in a network Network Architecture: Master plan of standard protocols, hardware, software and interfaces between end users and computer systems Goal of promoting an open, simple, flexible, and efficient telecommunications environment

OSI & TCP/IP Models Open Systems Interconnection (OSI) Model A seven-layer model that serves as a standard model for network architectures Model for how messages should be transmitted between two points in a network Each layer adds functions Transmission Control Protocol / Internet Protocol (TCP/IP) A five layer telecommunications protocol used by the Internet

OSI & TCP/IP Models Two groups of layers. Upper four layers are used whenever a message passes from or to a user. Lower three layers are used when message passes through the host computer. If message is being sent to another host, it skips these layers. TCP/IP analogous to postal system. TCP: analogous to postal system and processes and protocols to use the mail. IP: analogous to zip code and address.

Internet Telephony Using an Internet connection to pass voice data using IP Voice over IP (VoIP) Skips standard long-distance phone charges

Bandwidth Bandwidth Transmission Rates: Frequency range of a telecommunications channel Determines transmission rate Classified in bits per second (bps) Transmission Rates: Narrow-band – low-speed Broadband – high-speed Bandwidth is sometimes called baud rate. Think of channel as a pipe with water in it. The wider the pipe, the more water that can flow through it. Narrow-band – unshielded twisted-pair Broadband – microwave, fiber optic or satellite

Transmission Speeds

Switching Alternatives Circuit Switching Switch opens a circuit to establish a link between a sender and receiver it remains open until the communication session is completed Packet Switching Break messages into groups called packets Transmit packets separately Circuit switching: telephone service Packet switching: Internet, x.25 protocols, ATM

Network Interoperability Ensure that anyone anywhere on one network Can communicate With anyone anywhere on another network Telecommunications as discussed in this chapter wouldn’t be possible without interoperability

Case 3: Voice Over IP is the Real Thing VoIP works by Digitizing a voice signal, Chopping it into packets, and Sending them over a company’s network or the Internet Packets are reassembled at the destination Minnesota Department of Labor has cut its monthly phone bill in half

Case Study Questions What are the main benefits that can be gained by companies that switch to VoIP systems? What are some of the major cost factors that may limit a positive rate of return from investments in VoIP projects? Should more companies switch to VoIP systems? Visit the websites of Avaya and Cisco Systems to view their VoIP news, products, and services to help you answer.

Real World Internet Activity VoIP is becoming a highly competitive marketplace for the delivery of services and the development of software to support the process. Using the Internet, See if you can identify who the major players are in this market. Where do you see the next significant development for VoIP? Do you think the concept will eventually replace conventional telephone technologies? Why or why not?

Real World Group Activity The original concept for the Internet never included many of the uses we have found for it and consider commonplace today. While Internet2 is on the horizon, we need to think about what uses we may want from the Internet in the future. In small groups, Brainstorm how we might use the Internet in the future. Do we run the risk of overloading the Internet or relying on it too much?