Metropolitan Area Network (MAN)

A metropolitan area network (MAN) is a computer network that interconnects users with computer resources in a geographic region of the size of a metropolitan area. The term MAN is applied to the interconnection of local area networks (LANs) in a city into a single larger network which may then also offer efficient connection to a wide area network. The term is also used to describe the interconnection of several local area networks in a metropolitan area through the use of point-to-point connections between them.

The MAN network (Metropolitan Area Network) is a high-speed network (broadband) that covers larger geographic area such as city (tens of kilometers) or districts than local area network (LAN) but smaller than wide area network (WAN) and providing the ability to integrate multiple services through the transmission of data, voice, and video, on transmission media such as copper, fiber optics, and microwaves.

The term is applied to the single network such as a cable television network, or it can be a way of connecting a certain number of LANs in a more extensive network so that resources can share from LAN to LAN and from device to device. For example, a company can use a MAN to connect the LANs of all its offices scattered around the city. Local libraries and government agencies often use a MAN to connect to citizens and private industries. It may also connect MANs within a larger area than LAN. The geographical limit of a MAN may span a city.

In MAN, different LANs connected through a local telephone exchange. Some of the widely used protocols for MAN are X.25, Frame Relay, Asynchronous Transfer Mode (ATM), ISDN (Integrated Services Digital Network), xDSL (Digital Subscriber Line), ADSL (Asymmetrical Digital Subscriber Line), WDM (Wavelength Division Modulation), etc. These protocols are quite different from those used for LANs.

A MAN can wholly own by a private company, which will be its operator, or it can be a service provided by a public service company, such as a local telephone company. Many telephone companies have a very popular MAN service called Multimegabit Data Switching Services (SMDS).

The copper pair technology positioned as the world’s largest network an excellent alternative for the creation of metropolitan networks, for its low latency (between 1 and 50 ms), excellent stability and the lack of radio interference, the MAN LOOP networks, offer speeds of 10 Mbit/s or 20 Mbit/s, on copper pairs and 100 Mbit/s, 1 Gbit/s and 10 Gbit/s through optical fiber.

The concept of the metropolitan area network represents an evolution of the concept of a local area network to a broader scope, covering larger areas that in some cases are not limited to an urban environment but can reach regional and even national coverage through the interconnection of different networks of the metropolitan area.

This type of networks is a larger version than the LAN and usually based on a technology similar to this one. The main reason to distinguish a MAN with a particular category is that a standard has adopted to make it work, which is equivalent to the IEEE standard.

WAN networks also applied in organizations, in groups of corporate offices near a city, these do not contain switching elements, which divert the packets by one of several potential output lines. These networks can be public or private.

The networks of the metropolitan area, comprise a specific geographical location “city, the municipality,” and its distance of coverage is greater than 4 km. They are networks with two unidirectional buses, each of which is independent of the other in terms of data transfer.

Applications of Metropolitan Area Network

The Metropolitan Area Network (MAN) has many and varied applications; the main ones are:

• Deployment of VoIP services (Voice over Internet Protocol), in the metropolitan area, allowing eliminating the “obsolete” traditional lines of analog or ISDN telephony, eliminating the current expenditure of these lines.
• Interconnection of local area networks (LAN).
• Deployment of Wi-Fi zones without wireless Backhaul (Femtocell) freeing all Wi-Fi channels for access, this in practice means more than 60% improvement in the connection of Wi-Fi users.
• Computer to computer interconnection.
• Local video surveillance systems.
• CAD / CAM transmission.
• Walkways for wide area networks (WAN).

They also allow the transmission of voice, data and video traffic with high latency guarantees, which is why it is necessary to install a metropolitan area network at the corporate level, for corporations that have multiple dependencies in the same capital area.

MAN public or private

A metropolitan area network can be public or private.

An example of a private MAN would be a large department or administration with buildings distributed throughout the city, transporting all voice and data traffic between buildings through its own MAN and routing external information through public operators.

The data could transport between the different buildings, either in the form of packages or over fixed bandwidth channels.

Video applications can link buildings for meetings, simulations, or project collaboration.

An example of public MAN is the infrastructure that a telecommunications operator installs in a city to offer broadband services to its customers located in this geographical area.

1. Network nodes

Citizen area networks allow to execute and exceed 600 access nodes to the network, which makes it very useful for public and private environments with a large number of jobs.

2. Network extension

The networks of metropolitan area allow to reach a diameter around 50 km, depending on the scope of network training of the type of cable used, as well as the technology used. This diameter is considered sufficient to house a metropolitan area. They cover a city and can connect many, forming more networks.

3. Distance between nodes

Metropolitan area networks allow distances between access nodes of several kilometers, depending on the type of cable. These distances are considered sufficient to connect different buildings in a metropolitan area or private camp.

4. High reliability

Reliability referred to the error rate of the network while it is in operation the error rate defined as the number of erroneous bits that transmitted over the network. In general, the error rate for optical fiber is lower than that of copper cable with equal length. The error rate not detected by the error detection mechanisms is of the order of 10-20. This feature allows metropolitan area networks to work in environments where errors can be disastrous, such as air traffic control.

The creation of municipal metropolitan networks would allow municipalities to have a high-performance infrastructure by providing them with a network similar to that of Internet service providers. In this way, the town hall can connect new offices, remote users, or video cameras on public roads.

5. High security

Fiber optic offers a safe means because it is not possible to read or change the optical signal without physically interrupting the link.

6. Real-time traffic

The metropolitan area networks guarantee minimum network access times, which allows for the inclusion of synchronous services necessary for real-time applications, where it is crucial that specific messages go through the network without delay even when the network load is high.

Between node and node, you can not have, for example, more than 100 kilometers of cable. Approximately 20 km of cable can approximate, but it not known at what moment information or data sent can be lost.

Synchronous services require a reservation of bandwidth; Such is the case of voice and video traffic. For this reason, metropolitan area networks are optimal networks for multimedia traffic environments, although not all metropolitan networks support isochronous traffic (information transmission at constant intervals).