CSCI-235 Micro-Computer in Science The Network

© Prentice-Hall, Inc Communications  Communication is the process of sending and receiving messages  Communication channels are the paths through which messages are passed  Communication devices transform electronic signals

1.3 Five components of data communication

1.4 Data flow (simplex, half-duplex, and full-duplex)

Networks  A network is a set of devices (often referred to as nodes) connected by communication links.  A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

1.6 Types of connections: point-to-point and multipoint

1.7 Categories of topology

1.8 A fully connected mesh topology (five devices)

1.9 Figure 1.6 A star topology connecting four stations

1.10 A bus topology connecting three stations

1.11 A ring topology connecting six stations

1.12 A hybrid topology: a star backbone with three bus networks

1.13 An isolated LAN connecting 12 computers to a hub in a closet

1.14 A heterogeneous network made of four WANs and two LANs

© Prentice-Hall, Inc Data Rate and Bandwidth  Any transmission system has a limited band of frequencies  This limits the data rate that can be carried

Bandwidth  Bandwidth is usually used to refer to the data rate (i.e., the amount of data that can be transmitted through a communications channel)  Digital bandwidth is measured in bits per second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps)  Low bandwidth is 56 Kbps and high bandwidth is 622 Mbps

Protocol  Protocols are fixed, formalized standards that specify how computers can communicate over a network  Set of conventions between two entities involved in a communication  Elements syntax : data format and signal levels syntax : data format and signal levels concerns the format of the data blocks concerns the format of the data blocks semantics : include control information for semantics : include control information for coordination and error handling coordination and error handling timing : speed matching and sequencing timing : speed matching and sequencing

Protocol Architecture  Software structure that implements the communication function  Consists of a layered set of protocols  Separate layers or protocols implemented in separate modules  Different applications have different requirements at each layer

2.19 Tasks involved in sending a letter

2.20 Seven layers of the OSI model

2.21 The interaction between layers in the OSI model

2.22 An exchange using the OSI model

2.23 Physical layer

© Prentice-Hall, Inc Modulation Digital Analog Digital Demodulation Modems: From Digital to Analog and Back  Modems are devices that transform signals when sending and receiving transmissions Modulation – Transforming digital signals to analog Modulation – Transforming digital signals to analog Demodulation – Transforming analog signals to digital Demodulation – Transforming analog signals to digital

© Prentice-Hall, Inc Circuit switching  Networks create an end- to-end circuit between the sending and receiving computers  Electronic switches establish and maintain the connection Switching and Routing Techniques Packet switching  Outgoing messages are divided into fixed-size data units called packets  Packets are numbered and addressed to the receiving computer  Routers examine the packets and send them to their destination

CIRCUIT SWITCHING IN OUT IN OUT Telephone Node

© Prentice-Hall, Inc AdvantagesDisadvantages Circuit switching Voice and real-time transmission No delivery delays Costly A direct electrical connection between the computers is required Packet switching Efficient, less expensive, and reliable Will function if part of the network is down Delays in receiving packets Not ideal for real- time voice communication Advantages and Disadvantages of Circuit and Packet Switching

2.28 Data link layer

2.29 Hop-to-hop delivery

2.30 Network layer

2.31 Source-to-destination delivery

2.32 Transport layer

2.33 Reliable process-to-process delivery of a message

2.34 Session layer

2.35 Presentation layer

2.36 Application layer

2.37 Summary of layers

2.38 TCP/IP and OSI model

© Prentice-Hall, Inc Local Area Network (LAN)  Links computers within a building or group of buildings  Uses direct cables, radio, or infrared signals Types of Computer Networks Wide Area Network (WAN)  Links computers separated by a few miles or thousands of miles  Uses long-distance transmission media

© Prentice-Hall, Inc Local Area Networks (LANs)  Network access is controlled by a network administrator  Users can access software, data, and peripherals  LANs require special hardware and software  Computers connected to a LAN are called workstations or nodes

© Prentice-Hall, Inc LAN Hardware and Software Networking Hardware  Network interface card (NIC) – Provides the connection between the computer and the network  Inserted into a computer’s expansion slot Networking Software  Operating system that supports networking (Unix, Linux, Windows, Mac OS)  Additional system software NIC

© Prentice-Hall, Inc Client-Server Networks  Typical corporate networks are client-server  Clients send requests to servers for programs and data, and to access peripherals

© Prentice-Hall, Inc Peer-to-Peer Networks  All computers on the network are treated as equal  Users decide which files and peripherals to share  Peer-to peer is not suited for networks with many computers  Peer-to-peer is easy to set up. Example: home networks

© Prentice-Hall, Inc Wide Area Networks (WANs)  WANs are similar to long-distance telephone systems

© Prentice-Hall, Inc WAN Applications LAN-to-LAN  WANs are used to connect LANs at two or more geographic locations  Companies use WANs to connect their branches to one network system  The largest WAN is the Internet