Chapter 1 - Introduction to Computer Networks and Data Communications Flashcards
Computer network
An interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas
Local Area Network
networks that are small in geographic size spanning a room, floor, building, or campus
Metropolitan area netowork
networks that serve an area of 1 to 30 miles, approximately the size of a typical city
Wide area network
a large network that encompasses parts of states, multiple states, countries, and similar devices
Personal area network
a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices
Voice network
a network that transmits only telephone signals (almost extinct)
Data network
a network that transmits voice and computer data (replacing voice networks)
Data communications
the transfer of digital or analog data using digital or analog signals
Telecommunications
the study of telephones and the systems that transmit telephone signals (becoming simply data communications)
Network management
the design, installation, and support of a network, including its hardware and software
Network cloud
a network (local or remote) that contains software, applications, and/or data
Advantages of networking
• Provide a means to share software, data, equipment and communications quickly, easily and inexpensively.
• Saves time and money
-Provides quick access to files and resources
• Provides a means to secure data.
-Protects information from being stolen or destroyed
Disadvantages of networking
- Additional personnel are often needed to maintain and modify the network
- Losing access to files when the network is down
- Vulnerability to hackers, viruses and dissatisfied workers.
Microcomputer-to-Local Area Network Layout
- This network Highly common throughout business and academic environments, and homes
- Medium-to high-speed connection
- Computers(devices) requires a NIC (network interface card) connects to a hub-like device(switch)
Microcomputer-to-Internet Layout
- Popular with home users and small businesses
- For some, a dial-up modem is used to connect user’s microcomputer to an Internet service provider
- Technologies such as DSL and cable modems are replacing modems
Local Area Network-to-Local Area Network Layout
- Found in systems that hava two or more LANs and a need for them to intercommunicate
- A bridge-like device(such as a switch) is typically used to interconnect LANs
Local Area Network-to-Wide Area Network Layout
- One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network)
- A router is the typical device that performs LAN to WAN connections
- Routers are more complex devices than switches
Local Area Network-to-Metropolitan Area Network Layout
- Used to interconnect companies (usually their local area networks) to networks that encompass a city
- High-speed networks with redundant circuits
- Metro Ethernet is latest form of metropolitan LAN
Cell Phone Layout
- Constant expanding market across the U.S. and world
- Third generation services available in many areas and under many types of plans with fourth generation services starting to appear
- Latest generation includes higher speed data transfers (100s to 1000s of kilobits per second)
What is the two most common architectures known today?
OSI (Open Systems Interconnection) and TCP/IP Protocol
The layers of TCP/IP
- Application layer
- Transport layer
- Internet layer
- Network interface layer (Physical)
Application layer
- The application layer works with specific networking application.
- Common network application include web browsing, e-mail, file transfers and remote logins
Transport layer
• To ensure reliable data by sequencing packets and reassembling them into their correct order.
-Packets are transmitted over many miles and may use different routes. The packets may not arrive in the same sequence they were transmitted and may require reassembly into their correct order. Reassembly into the correct order is especially important in transmitting digital images.
Internet layer
• Sending packets across potentially multiple networks. Internet-working requires data from the source network to the destination network. This process is called routing.
In the internet protocol suite, the Internet Protocol performs two basic functions:
Host addressing and identification
Packet routing
This is the basic task of sending packets of data (data-gram) from source to destination by forwarding them to the next network router closer to the final destination.
The Open System Interconnection (OSI) Model
- Application layer
- Presentation layer
- Session layer
- Transport layer
- Network layer
- Data-link layer
- Physical layer
Presentation layer
• Responsible for “final presentation” of data (code conservation, compression, encryption). It is responsible for converting character codes into a code that is recognizable by a computer.
Session layer
• The session layer establishes a connection between two different computers and provides security based on computer and user name recognition. The two computers may not normally by compatible for data exchange, such as PC and a Macintosh. The session layer and transport layers are sometimes combined. When you think of the session layer, think of a handshake at the introduction and at the end of the meeting.
Network interface layer (Physical)
• Network Access Layer is the first layer of the four layer TCP/IP model.
• Network Access layer defines details of how data is physically sent through the network, including how bits are electrically or optically signaled by hardware devices that interface directly with a network medium.
-Coaxial cable, optical fiber, or twisted pair copper wire.
As packets are transmitted from one network to another, several different routes may be used.
Network layer
• First layer of the TCP/IP model
• Defines details:
-How data is physically sent through the network
-How bits (0,1) are electrically or optically signaled by hardware devices
• Interface directly with a network medium:
-Coaxial cable
-Optical fiber
-Twisted pair copper wire
• Several different routes may be used
Data link layer
• The data link layer describes how the raw data is packed for transfer from one network interface card to another. The data link layer also contains information such as the address of the source and destination and the size of the packet, and it provides for error checking.
Physical layer
- Is the lowest layer of the model. It consists of the cable and connectors used for constructing the network. This layer is only concerned with how digital signals, the binary 1s and 0s, are carried electrically from one networked device to another.
- Handles the transmission of bits over a communications channel
- Includes voltage levels, connectors, media choice, modulation techniques
Data transmission
The movement of information using some standard methods: • Electrical signals -A conductor • Optical signals: -Optical fibers -Electromagnetic areas
Types of Network Subnets
- Circuit Switched Network
* Packet Switched Network
Circuit Switched Network
• A dedicated circuit is established between:
-Sender
-Receiver
~All data passes over this circuit
• Example:
-Telephone system
• Network must establish a connection before the sender and the receiver
• Connection is dedicated until:
-One party or another
~Terminates the connection
Packet Switched Network
• All data messages are transmitted using:
-Fixed-sized packages
~Called packets
• More efficient use of telecommunications
• Datagram:
-Each packet:
~On its own
~May follow its own path
• The source breaks long messages
-Into smaller chunks of data
~Known as packets
Network based transmission technology
- Broadcast Network
* Point-to-Point Networks
Broadcast Network
• Have a single communication channel
-Shared
~By all machines on the network
• Allow the possibility of:
-Addressing a packet to all destinations
~By using a special code in the address field
• Called broadcasting
• Some broadcast systems:
-Support transmission to a subset of the machines
~Known as multicasting
Point-to-Point Networks
• Consists of many connections between: -Individual pairs of machines • First visit: -One or more intermediate machines • Routing algorithms: -Plays an important role • General rule: -Smaller, geographically localized networks ~Use broadcasting -Larger networks ~Use point-to-point
