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Chapter_4_Network_and_Data_Communication

Module II: Networks and Data Communication

Chapter 4: Networks and Data Communication

Data Communications Overview

  • Data: Messages to be shared between sender and receiver.

  • Communication Channel: Capable and reliable pathway for transporting messages.

  • Protocols: Establish accurate meanings of messages for both senders and receivers.

  • Physical Connection: Independent of the messages sent.

  • Message: Information exchanged between communicating parties.

Connection between Applications

  • Sharing: Connection exists between applications on sender and receiver's ends.

  • Signaling: Represents messages transported physically.

  • Examples:

    • POTS (Plain Old Telephone Service)

    • Web Servers and Browsers.

HTTP Request and Response Example

  • HTTP Request sent:

    • GET /webapps/login/ HTTP/1.1

    • Host: blackboard.bentley.edu

    • Date: Wed, 23 Jul 2008 22:01:44 GMT

    • User-Agent and Connection information included.

  • HTTP Response received:

    • HTTP/1.1 200 OK

    • Contains various headers like Date, Server info, Set-Cookie, etc.

    • Includes body content as <HTML content>.

Messages within Communication

  • Collaboration: Involves communication between cooperating applications at each end.

  • Forms of Messages: Can include data, programs, files.

  • Limitations: Varying message lengths and multimedia representation.

    • Messages are represented as a byte stream in serial communication.

    • Longer messages may tie up channels, causing issues for others.

Packets

  • Definition: Group of related packets forming a single message.

  • Structure:

    • Encapsulated data within a packet header.

    • Header contains information about the packet.

  • Purpose: Solve channel availability issues and maximize utilization.

  • Analogy: Packets are like envelopes containing pages of data.

    • Also referred to as frame or datagram.

Packet Header

  • Also Known As: Preamble.

  • Contents:

    • Description of packet.

    • Destination address.

    • Source address.

    • Information about the data sent.

Advantages of Packets

  • Increases efficiency and simplifies operations.

  • Suitable for routing data.

  • Allows multiple packets from different sources to share a channel.

  • Each sender-receiver pair appears to have its own channel.

  • Facilitates block data processing instead of character-by-character.

  • Simplifies synchronization with clear start and stop points.

Channel Characteristics (1)

  • Definition: Path for messages between nodes.

  • Details:

    • May include intermediate nodes forwarding packets.

    • Each end’s interfaces may differ.

  • Links: Segments within a channel.

  • Bandwidth: Bit rate of the overall channel.

    • Guided Channels: Communications limited to specific paths.

    • Unguided Channels: Not limited to a specific path.

Channel Characteristics (2)

  • Data Transmission Directionality:

    • Simplex: One-direction communication.

    • Half-duplex: Two directions but only one at a time.

    • Full Duplex: Both directions simultaneously.

  • Connections: Point-to-point or multipoint.

  • Examples: Wired Ethernet, Bluetooth, WiMax.

Network Topology

  • Definition: The fundamental layout of a network.

  • Impacts: Availability, speed, and congestion.

  • Types:

    • Physical Topology: Actual wiring layout.

    • Logical Topology: Operational relationships between components.

Types of Network Topologies

  1. Mesh Network

    • Multiple paths between nodes; failure of one node doesn't stop the network.

  2. Bus Topology

    • Simplest wiring; often for wireless networks.

  3. Star Topology

    • Nodes connect to a central device; failure of the central device causes entire network failure.

  4. Ring Topology

    • Closed loop; packets travel from node to node.

Local Area Networks (LAN)

  • Definition: Connects computing devices in a small localized area.

  • Typical Size: From a single room to multiple buildings nearby.

  • Components: Mostly personal computers and workstations.

  • Connection: Routers and gateways may connect to other networks.

Ethernet Hubs and Switches

  • Ethernet Hubs:

    • Based on bus topology; passive device for connections.

    • Declining use in favor of switches.

  • Ethernet Switches:

    • Allows direct connections between any two nodes.

    • Supports multiple communications simultaneously at full bandwidth.

Wireless Ethernet Characteristics

  • Max data rates and ranges for various standards:

    • 802.11a: 54 Mbps, 60 feet.

    • 802.11b: 11 Mbps, 300 feet.

    • 802.11g: 54 Mbps, 300 feet.

    • 802.11n: 150 Mbps, 600 feet (up to 4 streams).

    • 802.11ac: 450 Mbps, under development (supports up to 8 streams).

Metropolitan Area Networks (MAN)

  • Definition: Larger than a LAN but within a geographic scope of 30 miles.

  • Features: May connect multiple interconnected buildings (Campus Area Network).

  • Role: Often required running wires or connecting facilities using service providers.

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