For Geeks @nd the not so Geeky

What is Data Communication

Data Communication and Networking

Physical Topology Logical Topology
Bus Ethernet –> Broadcast
Ring Token Ring –> Token
(Extended) Star

Two examples of data communications networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI).
A variation of Token Ring and FDDI is Arcnet. Arcnet is data segment token passing on a bus topology.

Network Systems and Data Communication Include

  • How the physical network is built Data Communication Security
  • How computers connect to the network
  • How the data is formatted for transmission
  • How that data is sent
  • How to deal with errors

Data Communication Systems and WANs

  • Operate over a large and geographically separated area
  • Allow users to have real-time communication capabilities with other users
  • Provide full-time remote resources connected to local services
  • Provide e-mail, Internet, file transfer, and e-commerce services

Some Common WAN Technologies

  • Modems
  • Integrated Services Digital Network (ISDN)
  • Digital subscriber line (DSL)
  • Frame Relay
  • T1, E1, T3, and E3
  • Synchronous Optical Network (SONET)

SANs Offer the Following Features

  • Performance – SANs allow concurrent access of disk or tape arrays by two or more servers at high speeds. This provides enhanced system performance.
  • Availability – SANs have built-in disaster tolerance. Data can be duplicated on a SAN up to 10 km (6.2 miles) away.
  • Scalability – A SAN can use a variety of technologies. This allows easy relocation of backup data, operations, file migration, and data replication between systems.

Secure Data Communication – VPN’s

  • Access VPN – links small office and home (SOHO) users to the corporate network using a dedicated session over DSL, cable, ISDN or analog dial-up
  • Intranet VPN – links regional and remote offices to the the internal company network using dedicated connections
  • Extranet – link external business partners to the company’s internal network over a dedicated connection

Data Communication Protocol and Bandwith

  • Limited by physics and technology
  • Not Free
  • Requirements growing at a rapid rate
  • Critical to network performance
  • Bandwidth is the measure of how many bits of information can flow from one place to another in a given amount of time

The actual bandwidth of a network is determined by a combination of the physical media and the technologies chosen for signaling and detecting network signals.

Thisl bandwidth is determined by the signaling methods, NICs, and other network equipment that is chosen.
Therefore, the bandwidth is not determined solely by the limitations of the medium.

Throughput refers to actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network.

Unfortunately, for many reasons, throughput is often far less than the maximum possible digital bandwidth of the medium that is being used.

Factors that Determine Throughput in Data Communication

  • Internetworking devices
  • type of data being transferred
  • Network topology
  • Number of users on the network
  • User computer
  • Server computer
  • Power conditions

Analog bandwidth is measured by how much of the electromagnetic spectrum is occupied by each signal.
The analog video signal that requires a wide frequency range for transmission cannot be squeezed into a smaller band.

Therefore, if the necessary analog bandwidth is not available, the signal cannot be sent.
In digital signaling all information is sent as bits, regardless of the kind of information it is.

Unlimited amounts of information can be sent over the smallest or lowest bandwidth digital channel.

Open Systems Interconnection Model


OSI Model PDU TCP/IP Model
Application Data Application
Transport TCP/UDP Segment Transport
Network IP Packet Internet
Data Data Frame Network Access
Physical Data Bits

Dividing the Network into Seven Layers Provides the Following Advantages

  • It breaks network communication into smaller, more manageable parts.
  • It standardizes network components to allow multiple vendor development and support.
  • It allows different types of network hardware and software to communicate with each other.
  • It prevents changes in one layer from affecting other layers.
  • It divides network communication into smaller parts to make learning it easier to understand.

Networks Layers in Data Communication perform These 5 Conversion Steps to Encapsulate and Transmit Data

  • Images and text are converted to data.
  • The data is packaged into segments.
  • The data segment is encapsulated in a packet with the source and destination addresses.
  • The packet is encapsulated in a frame with the MAC address of the next directly connected device.
  • The frame is converted to a pattern of ones and zeros (bits) for transmission on the media.

TCP/IP and OSI Model –


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