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Sahithyan's S3
Sahithyan's S3 — Data Communication Networking

Layered Architecture

Functionality of communication through the network is split into separate layers.

Advantages

  • Simplified Design
    Each layer handles specific functions, making the system easier to design and manage.
  • Modularity
    Layers are independent; changes in one layer don’t affect others.
  • Interoperability
    Standardized interfaces allow different systems and vendors to work together.
  • Ease of Troubleshooting
    Problems can be isolated to specific layers.
  • Flexibility
    New technologies can be implemented in one layer without redesigning the whole system.
  • Scalability
    Easier to scale or upgrade systems layer by layer.

OSI Model

Short for Open Systems Interconnection Model. A conceptual framework used to describe how data is transmitted over a network. Consists of 7 layers, each responsible for a specific function in the communication process.

Application Layer

Provide network-based services to applications. Protocols used by the applications come under the application layer.

Examples:

  • File transfer (FTP)
  • Email (SMTP)
  • Web browsing (HTTP)
  • Voice over IP (VoIP)
  • Real-time communication (WebRTC)

Presentation Layer

Prepares data for transmission, and the application layer. Translates the data from and to a standard format.

Handles:

  • Formatting
  • Encryption
  • Compression

Usually in real systems, not implemented as a separate layer:

  • Data formatting, encryption and compression are usually handled, and required at the application layer.
  • Integrated protocols handle presentation tasks without requiring a separate layer.

Examples:

  • JPEG (Joint Photographic Experts Group)
  • MPEG (Moving Picture Experts Group)
  • ASCII (American Standard Code for Information Interchange)

Session Layer

Provide a means of controlling the dialogue between two users (applications).

Handles:

  • Session management: starts and ends communication sessions
  • Dialog control (full vs half duplex): who can send data and when. prevents data collisions. ensures proper ordering of data packets.
  • Token management
  • Synchronization: manages the timing of data transmission to ensure that data is transmitted at the right time.
  • Recovery management

Not often implemented separately in real systems, because it is usually integrated into the transport layer or application layer. Modern applications handle sessions by their own standards.

Examples:

  • HTTP (Hypertext Transfer Protocol)
  • FTP (File Transfer Protocol)

Transport Layer

Transmits semgents between 2 hosts. A host is a device that is running applications and using transport protocols to send or receive data over a network.

Handles:

  • Connection establishment and termination
  • Multiplexing and demultiplexing
    Allows multiple applications to share a single connection using different ports.
  • Segmentation and reassembly
    Breaks larger data into smaller segments, and reassembles them at the destination
  • Error detection and correction
    Detects errors in data transmission and corrects them.
  • Flow control
    Manages the data transfer rate to prevent congestion and ensure reliable delivery.
  • Congestion control

Examples:

  • TCP (Transmission Control Protocol)
  • UDP (User Datagram Protocol)

Network Layer

Transmits packets (aka. datagrams) across different networks from source to destination.

Handles:

  • Logical addressing: which machine to send the packet to
  • Routing: how to reach the destination efficiently
  • Datagram encapsulation

Examples:

  • IPv4 (Internet Protocol version 4)
  • IPv6 (Internet Protocol version 6)
  • ICMP (Internet Control Message Protocol)
  • MPLS (Multiprotocol Label Switching)

Transmits frames with headers, control and addres information. Provides reliable, error-free transmission across a single link (single medium), in the same network.

Handles:

  • data framing: dividing a data stream into manageable chunks
  • error detection and correction
  • flow control
    Manages frame flow rate to prevent overflow
  • addressing and routing

Media Access Control (MAC)

A unique hardware identifier to a network interface card (NIC). Usually a 48-bit identifier. Used for uniquely identifying devices on a network. Can be spoofed in the software level for security purposes.

A method used to control how devices share and access the communication medium. Each device in a local network has a unique MAC address.

Physical Layer

Transmits a raw string of bits over a physical medium. Can either be wired or wireless.

Handles:

  • Bit rate: how fast the bits are sent
  • Encoding
  • Signaling