Computer Networks: Types of computer networks

The following is a sample chapter from the e-Book Computer Networks: An Introduction.  Enjoy reading!

Computer science is no more about computers than astronomy is about telescopes.” Edsger Dijkstra

It all started as a need to share resources! What existed as a concept and as an attempt to design the first computer network back in the 50’s, it was achieved in the ’60s by connecting some of the universities of that time. Over time, the desire to implement the first computer network as a result of curiosity had already been converted to a need that would fulfill the requirements. Precisely, it also led to the development and advancement of computer networking technologies. Thus, the need to connect and interconnect more computers into computer networks and with it more locations in itself resulted as the need to define topologies, architectures, technologies and computer networking categories. In that way, computer networks like personal area network (PAN), local area network (LAN), the metropolitan area network (MAN), and wide area network (WAN) were born.

Personal Area Network (PAN)

Back in time, in our society it wasn’t easy to own a home computer and that was mainly associated with material welfare since personal computers have been quite costly. In contrast, nowadays with the decrease of total cost of ownership of owning a computer have enabled many families to own a home computer. That said, as a result of a dynamic life and the need to communicate, besides home computer, households have printers, laptops, tablets, smartphones, and the Internet connection. Add to this the devices such as VoIP phone, smart TV, cable and satellite set-top box, surveillance cameras and other household devices with an interface to get connected into home computer network. Then all these connected devices in a computer network together with the media gateway, where usually are stored data files like audio and video, make up the personal area network (PAN). That said, PAN is defined as a computer network which is used to connect and transmit data among devices located in a personal area like home environment. Occasionally, from time to time, this computer network is often called home are network (HAN).

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Figure 1. The personal area network (PAN)

Local Area Network (LAN)

Now that we know what a personal area network (PAN) is, it will help us to understand in a more clearly and the easiest way the local area network (LAN). In fact, looking from the physical and logical topology perspectives these computer networks hardly differ at all. So, the same is true for the communication technology (i.e. Ethernet or 802.3) that is utilized by both types of networks. Now this brings up the following question: if these networks are almost identical then why we have two definitions? As I mentioned at the beginning, for the sake of understanding the definition about local area network (LAN), the comparison with personal area network (PAN) will take place. When comparing the participating devices in these two computer networks, we find that the personal area network (PAN) is dominated by portable devices (i.e. mobile), while the local area network (LAN) mainly consists of fixed devices. Both computer networks are covering local area, however LAN has a greater coverage than PAN because LAN’s usually cover the floor of the building, several floors of the building, an entire building, or even few buildings which are close to one-another. Another difference is that PAN’s are mainly organized around an individual, while LAN’s are organized around the organization, business or legal entity. This then precisely defines the local area network (LAN) as the computer network where employees share network resources with one-another. In summary, the local area network (LAN) is a computer network that connects two or more computers in a local area for the purpose of sharing resources. Figure 2 shows an example of the local area network (LAN):

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Figure 2. The local area network (LAN)

Metropolitan Area Network (MAN)

From the standpoint of coverage, the metropolitan area network (MAN) is greater than the local area network (LAN) and smaller than the wide area network (WAN). While from the viewpoint of data transmission speed, the metropolitan area network (MAN) is faster than the local area network (LAN) and the wide area network (WAN). As it was with PAN and LAN networks, the reason for the metropolitan area network (MAN) existence is the need for the allocation of resources in the city or metro. Therefore, the definition of metropolitan area network (MAN) is as follows:

  • a group of local area networks (LAN) connected within the geographical boundary of the town or city

The Figure 3 shows the metropolitan area network (MAN):

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Figure 3. The metropolitan area network (MAN)

Wide Area Network (WAN)

Areas which are not covered by the local area network (LAN), or metropolitan area network (MAN) are covered by wide area network (WAN). That said, wide area network (WAN) is a computer network covering a wide geographic area using dedicated telecommunication lines such as telephone lines, leased lines, and satellites. So to say, while other computer networks have geographic restrictions of their physical reach, wide area network (WAN) has no geographical limitations. From this definition we understand that the composition of the wide area network (WAN) is made up of local personal area networks (PAN), local area networks (LAN), and the metropolitan area networks (MAN). With that in mind, the best example of the wide area network (WAN) is the Internet, which connects all computer networks mentioned in this chapter. The Figure 4 shows wide area network (WAN):

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Figure 4. The wide area network (WAN)

In Conclusion

From the above definitions, you’ve learned about the characteristics of each of the types of computer networks. Although the differences may be significant both from the geographical scope and the communications technology, again the main element which brings these computer networks together is the very purpose of their existence. Therefore, as a reminder, the main purpose of computer networks existence is the resource sharing concept.

Take your time to share your experience with computer networks within Comment’s section. Thank you!

Hope you’ll find this post informative.

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What is Metropolitan Area Network?

Computer science is no more about computers than astronomy is about telescopes.” Edsger Dijkstra

Introduction

It all began as a need to share resources. What existed as a concept and as an attempt to create first computer networks in the 1950’s, was achieved in the 1960’s by connecting few Universities. With the time passing by, the desire of early times for creating computer networks as an act of a curiosity had been converted to a need which will satisfy the demand. This then lead to advancements and enhancements in networking technology. With this said the need for connecting and interconnecting more computers to networks brought in itself the necessity to define topologies, architectures, technologies and categories of computer networks. This way the computer network types such as PAN (Personal Area Network), LAN (Local Area Network), MAN (Metropolitan Area Network), and WAN (Wide Area Network) were born.

As with the other types of computer networks, there are several definitions existing today for MANs as well. Among those, Harte (2003) describes MAN as “the group of interconnected LANs within the geographical border of a particular town or city.” It’s a computer network that is bigger then LAN, and smaller then WAN, in terms of covered area. In terms of transmission speed, MAN is a high-speed and high-bandwidth network infrastructure compared to both LAN and WAN which are slower. As with the other types of computer networks, the only and most important purpose that brought MANs into being is a need to share resources both hardware and software among users within an area that Young (2006) is calling a “metro region.”

Figure 1. Metropolitan Area Network (source: Harte, 2003)

Figure 1. Metropolitan Area Network (source: Harte, 2003)

Technologies

Since, MAN sits in between LAN and WAN thus acting as a bridge in between them, then a technology from both network infrastructures can be adopted for creating MANs. Among the legacy technologies used even nowadays to create MANs are: SONET-based TDM, ATM, FDDI, DQDB, and SMDS. Since all these technologies are non-IP based networks coming from Telecoms industries, proved to be expensive and complex to design, implement and maintain high-speed and high-bandwidth computer networks such as MANs. To overcome the issue of cost and complexity, new technologies for creating MANs are invented. Among such technologies that have emerged more and more nowadays are Gigabit Ethernet and 10 Gigabit Ethernet based on DWDM technology. With this said DWDM is becoming a driving force for Gigabit and 10 Gigabit Ethernet when it comes to designing speedy and wide MANs. The strong reason for adoption of DWDM technology by Ethernet networking technologies is the fact explained by Minoli and Johnson (2000):

Proponents of Dense-Wavelength Division Multiplexing (DWDM) make the claim that acceptance of the technology will drive the expansion of the optical layer throughout the telecommunications network and enable service operators to exploit the bandwidth capacity that is inherent in optical fiber but that has gone largely untapped until now. (p. 260)

Topologies

Among the existing computer networks physical topologies of nowadays, the most used for designing MANs undoubtedly is Mesh Topology. This is due to the fact that Mesh Topology of the MAN provides high availability of services in such networking environment.

That indeed MANs are a mixture of ingredients, does not speak for itself only physical topology, but also the networking media used in its design as well. With this said, obviously the mostly used networking media to create MANs links, in general it’s a mixture of fiber, wired and wireless technologies.

Same applies to logical topology as well, which enriches the list of mixture ingredients needed to design MANs. Thus, when it comes to transmitting data among networking devices of MAN, the most used protocols are the ones that are operating at Data-Link layer of the OSI model. In general, it would be protocols which are defined by the organizations such as IEEE, ITU-T, and proprietary standards as well as knowing that they share an acceptable percentage in designing MANs.

Figure 2. Computer network topologies (source: CS Odessa corp., 2015)

Figure 2. Computer network topologies (source: CS Odessa corp., 2015)

Benefits

It’s all about benefits reason why a particular campus, town, city of metro would go for a MAN. According to Cisco, MAN is a computer network infrastructure which facilitates the communications among local government, private businesses, organizations, utilities, educational institutions, libraries, and citizens within a specific physical area. Obliviously, one of the strong reasons why MANs are in expansion nowadays is all due to its enormous benefits. Besides allowing access to resources available in this networking infrastructure, lately majority of service providers in MANs networks are providing for its users the Internet access as well. Looking this from a philosophic point of view, it would be that the benefit alone is the existence of MAN itself. This in turn, facilitates the process of establishing an IT oriented society.

Dear readers, hope you find this post informative.

peace and blessings,

Bekim

References:

CS Odessa corp. (2015). Network Topologies.  Retrived March 30th, 2015 from http://www.conceptdraw.com/How-To-Guide/network-topologies

Harte, L. (2003). Introduction to Data Networks – PDN, LAN, MAN, WAN, and Wireless Data Technologies and Systems. Althos.

Minoli, D., Johnson, P., & Minoli, E. (2000). SONET-Based Metro Area Networks: Planning and Designing the Next-Generation Provider Network. New York, NY: McGraw-Hill

Young, R. (2006). Metro Ethernet as a Wide Area Technology and Why It Must Be Secured. Belcamp, MD: SafeNet, Inc.