Networking - 1.2 - LAN, WAN, Inter-networks

Local Area Network (LAN) - An individual network usually spans a single geographical area, providing services and applications to people within a common organizational structure, such as a single business, campus or region.
Wide Area Network (WAN) - Individual organizations usually lease connections through a telecommunications service provider network. These networks that connect LANs in geographically separated locations are referred to as Wide Area Networks.

Internetworks - A global mesh of interconnected networks for communication. Ex: Internet

The term intranet is often used to refer to a private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization’s members, employees, or others with authorization.

Rules that Govern Communications

Communication in networks is governed by pre-defined rules called protocols.

A group of inter-related protocols that are necessary to perform a communication function is called a protocol suite. These protocols are implemented in software and hardware that is loaded on each host and network device. Networking protocols suites describe processes such as:

The format or structure of the message

The process by which networking devices share information about pathways with other networks

How and when error and system messages are passed between devices

The setup and termination of data transfer sessions

Individual protocols in a protocol suite may be vendor-specific and proprietary.

Protocol Suites & Industry Standard

Many of the protocols that comprise a protocol suite reference other widely utilized protocols or industry standards Institute of Electrical and Electronics Engineers (IEEE) or the Internet Engineering Task Force (IETF).The use of standards in developing and implementing protocols ensures that products from different manufacturers can work together for efficient communications.

The Interaction of Protocols

Application protocol – HTTP. HTTP defines the content and formatting of the requests and responses exchanged between the client and server
Transport Protocol – TCP. TCP divides the HTTP messages into smaller segments. It is also responsible for controlling the size and rate of message exchange.
Internetwork Protocol – IP. It encapsulating segments into packets, assigning the appropriate addresses, and selecting the best path to the destination host.
Network Access Protocol – Protocols for data link management and the physical transmission of data on the media.

Using Layer Models

To visualize the interaction between various protocols, it is common to use a layered model.

Benefits of doing so:

  • Assists in protocol design, because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below.
  • Fosters competition because products from different vendors can work together.
  • Prevents technology or capability changes in one layer from affecting other layers above and below.
  • Provides a common language to describe networking functions and capabilities.

Protocol & Reference Model

A protocol model provides a model that closely matches the structure of a particular protocol suite. The hierarchical set of related protocols in a suite typically represents all the functionality required to interface the human network with the data network. Ex: TCP/IP model

A reference model provides a common reference for maintaining consistency within all types of network protocols and services. A reference model is not intended to be an implementation specification or to provide a sufficient level of detail to define precisely the services of the network architecture. The primary purpose of a reference model is to aid in clearer understanding of the functions and process involved. Ex: OSI model