Metropolitan area network

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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 . [1] [2]

Computer network collection of autonomous computers interconnected by a single technology

A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi.

Metropolitan area region consisting of a densely populated urban core and its less-populated but economically-linked surroundings

A metropolitan area is a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metro area usually comprises multiple jurisdictions and municipalities: neighborhoods, townships, boroughs, cities, towns, exurbs, suburbs, counties, districts, states, and even nations like the eurodistricts. As social, economic and political institutions have changed, metropolitan areas have become key economic and political regions.

City Large and permanent human settlement

A city is a large human settlement. Cities generally have extensive systems for housing, transportation, sanitation, utilities, land use, and communication. Their density facilitates interaction between people, government organisations and businesses, sometimes benefiting different parties in the process.



By 1994, local area networks (LANs) were well established to provide data communication in buildings and offices.[ citation needed ] For the interconnection of LANs within a city, businesses relied primarily on the public switched telephone network. But while the telephone network was able to support the packet-based exchange of data that the various LAN protocols implemented, the bandwidth of the telephone network was already under heavy demand from circuit-switched voice, and the telephone exchanges were ill-designed to cope with the traffic spikes that LANs tended to produce. [3]

Local area network computer network that connects devices over a small area

A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits.

The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication. The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.

To interconnect local area networks more effectively, it was suggested that office buildings are connected using the single-mode optical fiber lines, which were by that time widely used in long-haul telephone trunks. Such dark fibre links were in some cases already installed on customer premises and telephone companies started to offer their dark fibre within their subscriber packages. Fibre optic metropolitan area networks were operated by telephone companies as private networks for their customers, and did not necessarily have full integation with the public wide area network (WAN) through gateways. [4]

Single-mode optical fiber

In fiber-optic communication, a single-mode optical fiber (SMF) is an optical fiber designed to carry light only directly down the fiber - the transverse mode. Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining Maxwell's equations and the boundary conditions. These modes define the way the wave travels through space, i.e. how the wave is distributed in space. Waves can have the same mode but have different frequencies. This is the case in single-mode fibers, where we can have waves with different frequencies, but of the same mode, which means that they are distributed in space in the same way, and that gives us a single ray of light. Although the ray travels parallel to the length of the fiber, it is often called transverse mode since its electromagnetic oscillations occur perpendicular (transverse) to the length of the fiber. The 2009 Nobel Prize in Physics was awarded to Charles K. Kao for his theoretical work on the single-mode optical fiber.

Dark fibre unused optical fibre

A dark fibre or unlit fibre is an unused optical fibre, available for use in fibre-optic communication. Dark fibre originally referred to the potential network capacity of telecommunication infrastructure. Dark fibre may be leased from a network service provider.

Wide area network Computer network that connects devices across a large distance and area

A wide area network (WAN) is a telecommunications network that extends over a large geographical area for the primary purpose of computer networking. Wide area networks are often established with leased telecommunication circuits.

Besides the larger companies that connected their offices across an metropolitan area, universities and research institutions also adopted dark fibre as their metropolitan area network backbone. In West Berlin the BERCOM project built up a multifunctional broadband communications system to connect the mainframe computers that publicly funded universities and research institutions in the city housed. The BERCOM MAN project could progress at speed because the Deutsche Bundespost had already installed hundreds of miles of fibre optic cable in West Berlin. Like other metropolitan dark fibre networks at the time, the dark fibre network in West Berlin had a star topology with a hub somewhere in the city centre. [5] The backbone of the dedicated BERCOM MAN for universities and research institutions was a optical fibre double ring that used a high speed slotted ring protocol developed by the GMD Research Centre for Innovative Computer Systems and Telephony. The BERCOM MAN backbone could thus support two times 280 Mbit/s data transfer. [6]

West Berlin Political enclave that existed between 1949 and 1990

West Berlin was a political enclave which comprised the western part of Berlin during the years of the Cold War. There was no specific date on which the sectors of Berlin occupied by the Western Allies became "West Berlin", but 1949 is widely accepted as the year in which the name was adopted. West Berlin aligned itself politically with the Federal Republic of Germany and was directly or indirectly represented in its federal institutions.

Deutsche Bundespost the state postal company in the Federal Republic of Germany

The Deutsche Bundespost was a German state-run postal service and telecommunications business founded in 1947. It was initially the second largest federal employer during its time. After staff reductions in the 1980s, the staff was reduced to roughly 543,200 employees in 1985. The corporation was dissolved in 1995 under the first and second postal reforms that took place in the German Post Office. Following the reforms, the former Deutsche Bundespost was broken into three publicly traded corporations: Deutsche Post AG, Deutsche Telekom, and Deutsche Postbank AG.

Ring network network topology

A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node - a ring. Data travels from node to node, with each node along the way handling every packet.

Wavelength division multiplexing operating principle WDM operating principle.svg
Wavelength division multiplexing operating principle

The productive use of dense wavelength division multiplexing (DWDM) provided another impetus for the development of metropolitan area networks in the 2000s. Long haul DWDM, with ranges from 0 to 3000+ km, had been developed so that companies that stored large amount of data on different sites, could exchange data or establish mirrors of their file server. With the use of DWDM on the existing fibre optic MANs of carriers, companies no longer needed to connect their LANs with a dedicated fibre optic link. [7] With DWDM companies could build dedicated MANs using the existing dark fibre network of a provider in a city. MANs thus became cheaper to build and maintain. [8] The DWDM platforms provided by dark fibre providers in cities could allow for a single fibre pair to be divided into 32 wavelengths. One multiplexed wavelength could support between 10 Mbit/s and 10 Gbit/s. Thus companies that paid for a MAN to connect different office sites within a city could increase the bandwidths of their MAN backbone as part of their subscription. DWDM platforms also alleviated the need for protocol conversion to connect LANs in a city, because any protocol and any traffic type could be transmitted using DWDM. Effectively it gave companies wishing to establish a MAN choice of protocol. [9]

In computing, a file server is a computer attached to a network that provides a location for shared disk access, i.e. shared storage of computer files that can be accessed by the workstations that are able to reach the computer that shares the access through a computer network. The term server highlights the role of the machine in the client–server scheme, where the clients are the workstations using the storage. It is common that a file server does not perform computational tasks, and does not run programs on behalf of its clients. It is designed primarily to enable the storage and retrieval of data while the computation is carried out by the workstations.

Looking west over northern San Jose and other parts of Silicon Valley technology hub. Between 2002 and 2003 the Sprint Corporation built five Metro Ethernet rings to connect the metropolitan areas. AlumRockViewSiliconValley w.jpg
Looking west over northern San Jose and other parts of Silicon Valley technology hub. Between 2002 and 2003 the Sprint Corporation built five Metro Ethernet rings to connect the metropolitan areas.

Metro Ethernet, where a fibre optic ring within a larger city was built as MAN backbone carrying Gigabit Ethernet, became common. The ring topology was implemented using the Internet protocol (IP), so that data could be rerouted if a link was congested or one of the links that was part of the ring failed. [10] In the USA the Sprint Corporation was at the forefront of building fibre optic rings that routed IP Packets on the MAN backbone. Between 2002 and 2003 Sprint built three MAN rings to cover San Francisco, Oakland and San Jose, and in turn connected these three metro rings with a further two rings. The Sprint metro rings routed voice and data, were connected to several local telecom exchange points, and totalled 189 miles of fibre optic cable. The metro rings also connected many cities to the Internet that went on to become part of the Silicon Valley tech-hub, such as Fremont, Milpitas, Mountain View, Palo Alto, Redwood City, San Bruno, San Carlos, Santa Clara and Sunnyvale. By adopting IP routing for its metro Ethernet rings, Sprint could re-route traffic in its MANs within milliseconds in the event of fibre cuts or local power outages. [11]

Metro Ethernet

A metropolitan-area Ethernet, Ethernet MAN, or metro Ethernet network is a metropolitan area network (MAN) that is based on Ethernet standards. It is commonly used to connect subscribers to a larger service network or the Internet. Businesses can also use metropolitan-area Ethernet to connect their own offices to each other.

Gigabit Ethernet standard for Ethernet networking at a data rate of 1 gigabit per second

In computer networking, Gigabit Ethernet is the various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3ab standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks, as a result of being considerably faster. The cables and equipment are very similar to previous standards and have been very common and economical since 2010.

Sprint Corporation American telecommunications company

Sprint Corporation is an American telecommunications company that provides wireless services and is an internet service provider, based in Overland Park, Kansas. It is the fourth-largest mobile network operator in the United States and serves 54.5 million customers as of March 2019. The company also offers wireless voice, messaging, and broadband services through its various subsidiaries under the Boost Mobile, Virgin Mobile, and Assurance Wireless brands, and wholesale access to its wireless networks to mobile virtual network operators. The company is headquartered in Overland Park, Kansas. In July 2013, a majority of the company was purchased by Japanese telecommunications company SoftBank Group Corp., although the remaining shares of the company continue to trade on the New York Stock Exchange. Sprint uses CDMA, EvDO and 4G LTE networks.

The metro Ethernet rings that did not route IP traffic, instead used one of the various proprietary spanning tree protocol implementations, so that each MAN ring had a root bridge. [12] Because layer 2 switching can not operate if there is a loop in the network, the protocols to support L2 MAN rings all need to block redundant links and thus block part of the ring. [13] Capsuling protocols, such as Multiprotocol Label Switching (MPLS), were also deployed to address the drawbacks of operating L2 metro Ethernet rings. [14]

Metro Ethernet was effectively the extension of Ethernet protocols beyond the local area network (LAN) and the ensuing investment in Ethernet led to the deployment of carrier Ethernet, where Ethernet protocols are used in wide area networks (WAN). The efforts of the Metro Ethernet Forum (MEF) in defining best practice and standards for metropolitan area networks thus also defined carrier Ethernet. [15] While the IEEE tried to standardise the emerging Ethernet based proprietary protocols, industry forums such as the MEF filled the gap and in January 2013 launched a certification for network equipment that can be configured to meet Carrier Ethernet 2.0 specifications. [16]

Metropolitan Internet Exchanges

Stealth Fiber Crew installing a 432-count dark fibre cable underneath the streets of New York City. Fiber-Optic Installation in New York City.jpg
Stealth Fiber Crew installing a 432-count dark fibre cable underneath the streets of New York City.
An optical fiber photonic switch at the AMS-IX AMS-IX optical patch panel.jpg
An optical fiber photonic switch at the AMS-IX

Internet Exchanges (IXs), also known as Exchange Points (XPs), have historically been important for the connection of metropolitan area networks (MANs) to the national or global Internet. The Boston Metropolitan Exchange Point (Boston MXP) enabled metro Ethernet providers, such as the HarvardNet to exchange data with national carriers, such as the Sprint Corporation and AT&T. Exchange points also serve as low-latency link between campus area networks, thus the Massachusetts Institute of Technology and the Boston University could exchange data, voice and video using the Boston MXP. Further examples of metropolitan Internet Exchanges in the USA that were operational by 2002 include the Anchorage Metropolitan Access Point (AMAP), the Seattle Internet Exchange (SIX), the Dallas-Fort Worth Metropolitan Access Point (DFMAP) and the Denver Internet Exchange (IX-Denver). [17] Verizon put into operation three regional metropolitan exchanges to interconnect MANs and give them access to the Internet. The MAE-West serves the MANs of San Jose, Los Angeles and California. The MAE-East interconnects the MANs of New York City, Washington, D.C., and Miami. While the MAE-Central interconnects the MANs of Dallas, Texas, and Illinois. [18]

In larger cities several local providers may have built a dark fibre MAN backbone. In London the metro Ethernet rings of several providers make up the London MAN infrastructure. Like other MANs, the London MAN primarily serves the needs of its urban customers, who typically need a high number of connections with low bandwidth, a fast transit to other MAN providers, as well as high bandwidth access to national and international long-haul providers. Within the MAN of larger cities, metropolitan exchange points now play a vital role. The London Internet Exchange (LINX) had by 2005 built up several exchange points across the Greater London region. [19]

Cities that host one of the international Internet Exchanges have become a preferred location for companies and data centres. The Amsterdam Internet Exchange (AMS-IX) is the world second largest Internet Exchange and has attracted companies to Amsterdam that are dependent on high speed internet access. The Amsterdam metropolitan area network has benefited too from high speed Internet access. [20] Similarly Frankfurt has become a magnet for data centres of international companies because it hosts the non-profit DE-CIX, the largest Internet Exchange in the world. [21] DE-CIX has gone on to establish carrier neutral metropolitan Internet Exchanges in New York, Madrid, Dubai, Marseille, Dallas, Hamburg, Munich, Duesseldorf, Berlin, Istanbul, Palermo, Lisbon, Mumbai, Delhi, Kolkata, Chennai, and Moscow. [22] The business model of the metro DE-CIX is to reduce the transit cost for local carriers by keeping data in the metropolitan area or region, while at the same time allowing long-haul low-latency peering globally with other major MANs. [23]

See also

Related Research Articles

Ethernet computer networking technology

Ethernet is a family of computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3, and has since retained a good deal of backward compatibility and been refined to support higher bit rates and longer link distances. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.

IEEE 802 is a family of IEEE standards dealing with local area networks and metropolitan area networks.

Fiber Distributed Data Interface standard for data transmission in a local area network

Fiber Distributed Data Interface (FDDI) is a standard for data transmission in a local area network. It uses optical fiber as its standard underlying physical medium, although it was also later specified to use copper cable, in which case it may be called CDDI, standardized as TP-PMD, also referred to as TP-DDI.

London Internet Exchange internet exchange point in London

The London Internet Exchange ("LINX") is a mutually governed Internet exchange point (IXP) that provides peering services and public policy representation to over 820 Internet service providers (ISPs) and other network operators. LINX operates IXPs in London, Manchester, Edinburgh, Cardiff in the UK, and Northern Virginia in the USA.

AARNet organization

AARNet provides Internet services to the Australian education and research communities and their research partners.

Add-drop multiplexer

An add-drop multiplexer (ADM) is an important element of an optical fiber network. A multiplexer combines, or multiplexes, several lower-bandwidth streams of data into a single beam of light. An add-drop multiplexer also has the capability to add one or more lower-bandwidth signals to an existing high-bandwidth data stream, and at the same time can extract or drop other low-bandwidth signals, removing them from the stream and redirecting them to some other network path. This is used as a local "on-ramp" and "off-ramp" to the high-speed network.

The next-generation network (NGN) is a body of key architectural changes in telecommunication core and access networks. The general idea behind the NGN is that one network transports all information and services by encapsulating these into IP packets, similar to those used on the Internet. NGNs are commonly built around the Internet Protocol, and therefore the term all IP is also sometimes used to describe the transformation of formerly telephone-centric networks toward NGN.

IPFC stands for Internet Protocol over Fibre Channel. It governs a set of standards created in January 2006 for address resolution (ARP) and transmitting IPv4 and IPv6 network packets over a Fibre Channel (FC) network. IPFC makes up part of the FC-4 protocol-mapping layer of a Fibre Channel system.

An edge device is a device which provides an entry point into enterprise or service provider core networks. Examples include routers, routing switches, integrated access devices (IADs), multiplexers, and a variety of metropolitan area network (MAN) and wide area network (WAN) access devices. Edge devices also provide connections into carrier and service provider networks. An edge device that connects a local area network to a high speed switch or backbone may be called an edge concentrator.

Optical networking is a means of communication that uses signals encoded onto light to transmit information among various nodes of a telecommunications network. They operate from the limited range of a local-area network (LAN) or over a wide-area network (WAN), which can cross metropolitan and regional areas all the way to national, international and transoceanic distances. It is a form of optical communication that relies on optical amplifiers, lasers or LEDs and wave division multiplexing (WDM) to transmit large quantities of data, generally across fiber-optic cables. Because it is capable of achieving extremely high bandwidth, it is an enabling technology for today’s Internet and the communication networks that transmit the vast majority of all human and machine-to-machine information.

In a hierarchical telecommunications network, the backhaul portion of the network comprises the intermediate links between the core network, or backbone network, and the small subnetworks at the edge of the network.

In audio and broadcast engineering, Audio over Ethernet is the use of an Ethernet-based network to distribute real-time digital audio. AoE replaces bulky snake cables or audio-specific installed low-voltage wiring with standard network structured cabling in a facility. AoE provides a reliable backbone for any audio application, such as for large-scale sound reinforcement in stadiums, airports and convention centers, multiple studios or stages.


EMMAN was a company limited by guarantee and jointly owned by its members, eight Higher Education Institutions in the East Midlands region of the United Kingdom.

Nextgen Networks

Nextgen Networks is a wholly owned subsidiary of Vocus Group, an Australian-based international telecommunications company.

Fiber media converter

A fiber media converter is a simple networking device that makes it possible to connect two dissimilar media types such as twisted pair with fiber optic cabling. They were introduced to the industry in the 1990s, and are important in interconnecting fiber optic cabling-based systems with existing copper-based, structured cabling systems. They are also used in metropolitan area network (MAN) access and data transport services to enterprise customers.


ACOnet is the name of the national research and education network in Austria. The ACONET association promotes the development and use of that network. ACOnet is not managed and operated by ACONET, but by a unit in the Computing Centre of the University of Vienna that also operates the Vienna Internet Exchange. The University of Vienna represents ACOnet internationally, for example as a member of TERENA and as a participant in the project that funds the European backbone network GÉANT.


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