A computer network is a network of computers and other devices interconnected by communication channels . These channels are used to facilitate communication among users and enables the user to share and access resources on the network. Network can be classified based on their wide variety of characteristics depending on their physical scope.
Local area network(LAN):- a local area network is a network that is used to inter connect computers and other network devices in a limited geographic area such as school, house and buildings within a particular area.
Wide Area network(WAN):- is a computer network which covers a large geographical area such as a city or country. The network can also can be extended to intercontinental distance by using communication channels such as telephone lines , cables and air waves.
Back bone Network (BBN) :-is a part of a network which interconnects different piece of a network and gives path for exchange of information .
Metropolitan Network (MAN):- is a large network that spans over a city or campus.
Let us consider Metropolitan Area Network in detail.
Metro Ethernet is a computer network which is used to cover metropolitan area such as cities and large urban Areas based on the Ethernet standards. It is mostly used as a metropolitan access network to connect large users(subscribers) and businesses to the internet. It ‘s geographical scope is fall between Wide Area Network (WAN) and local area network (LAN). It also provides Internet connectivity to LAN in metropolitan region, and connects them to Wider area networks like the Internet. 1? 2?
Ethernet Standards- Ethernet standards as defined by the Institute for Electrical and Electronic Engineers(IEEE) standard 802.3 defines rules for configuring ethernet and the protocols used for communicating of computers over the network.
Overview of Metro Ethernet
Metro Ethernet network is a set-up that connects geographically separated LAN’s or WAN’s or backbone networks of internet service providers (ISP). Metro Ethernet Network provides network access across the globe through their core protocol called the Metro Ethernet. Metro Ethernet
is available in different packages of standard compliant interfaces like 10Mbps,100Mbps,1000Mbps and 10Gbps
Metro Ethernet’s predominant purpose is in the business sector where the necessity for high quality voice, video, as well as data transfer is a requirement. The existing technology infrastructure is based on SONET/SDH(Synchronous Optical Network/Synchronous Digital Hierarchy) architecture which is expensive and have problems of scalability and limited band width.
Metro Ethernet over comes these issues of the on SONET/SDH architecture and also provides more additional features such as
Easy to use:- since most devices on the network use Ethernet interface so that network administration and operation is simplified.
Cost effective:- Ethernet interfaces are much cheaper than that of SONET/SDH -Flexibility and Scalability:- MAN can provides many variety services and subscribers have the possibility to change their bandwidth as their interest. 3?
Service provider metro Ethernet is a collection of Layer 2 or layer 3 switches or routers connected through optical fiber with a various topologies like ring ,star,full or partially mesh networks.Metro Ethernet provides different types of deployments such as
pure Ethernet MAN:- this is the simplest and cheapest with less configuration requirement with shortcoming of MAC table over flow on the switches convergence of the SPT protocol. it includes only layer 2 network equipments
SONET/SDH based MAN:- this is established based on the existing SDH. and has an advantage of reliability due to the SDH owns protection mechanisms. with short coming of having limited traffic engineering and its is costly.
MPLS based Ethernet MANS:-this type of MANS are costly and requires extensive configuration but they have high scalability, and ability to aggregate in any type of traffic. 4?
Ethernet is a common communication protocol used to create a network or a Local Area Network (LAN).E thernet was developed at Xerox Parc between 1973 and 1975.
The basic need for metro Ethernet occurred when telecom companies had to inter-connect different Ethernet LAN’s. Previously dedicated point to point lines were used to connect these geographically disconnected LAN’s. A gateway router was configured on either side of the LAN network interconnected by a TCP/IP across private lines. This arrangement worked out very costly especially when the network was big.
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Gradually the point to point circuits were replaced by Frame relay and ATM.These protocols were very similar to private lines but relatively inexpensive. These connections were slow so companies started connecting their private LAN’s across cities through the internet. This had many loop holes in it as the connection was very insecure. As advancement telecom companies came up with “Private IP Networks”. This was available for long distance transport. But this process was too expensive and was not preferred by companies. This draw back was resolved with secure internet encryption protocols such as IPSec and firewall enhancements. Post to this the connection was still slow and the over head on IP headers were tremendous.
Companies upgraded their infrastructure and the internet emerged an excellent choice for interconnection of Ethernet LAN’s. Though there were a very few weak points to this methods such as VPN boxes being very expensive and hackers could intercept any network though firewalls were installed. This problem was solved through MPLS(Multi path Label Switch) private IP networks.
The Metro Ethernet was developed in concurrence with MPLS and resulted as a standard called Metro Ethernet Standards.5?
Previously we had to connect to the internet through the dial up connection. There was many criticism on dial up connections as they did not provide a steady connection, the dial up was not affordable for the common man and it was overpriced.
As technology evolved dial up connections gave way for Metro Ethernets. Metro Ethernets were available at different speeds for customized needs which benefited the business sector tremendously. Since metro Ethernets did not use telephone line connections this resulted in not having to install additional phone lines in order to use both the telephone and connect to the internet simultaneously. The significant factor of Metro Ethernets is it is available in different packages from which end users could choose their required package. Metro Ethernets offers constant speed in during peak hours of network traffic irrespective of the number of users using the same connection.6?
Metro Ethernet Service types-
Metro Ethernet Forum (MEF) provides the most basic service type
STRUCTURE- Let us consider a ethernet work in a city owned by a particular ISP owner. A customer equipment (CE) is provided on the subscriber side which is used to connect to a network with a UNI. The UNI is a standard ethernet interface. The customer is concerbed only with his particular UNI interface to connect to the internet . The various communication technologies involved in communication such as transport,application layer protocols do not concern the customer.This communication technique is easy and simple. This technique is scalable and trust worthy.
EVC (Ethernet Virtual Connection)- EVC is a defined as an instance of an asscociation of two or more UNI’s through which data is passed in the form of ethernet frames 10?. The main functions of EVC are
Connecting client UNI’s on either side and transmitting data as ethernet frames between them safely and securely.
The ethernet frames are delivered similar to how they were sent with same MAC address and and other parameters.
The Metro Ethernet forum has defined two basic service types
1. Ethernet line service type-
The E-Line service provides at point to point Ethernet virtual Connection (EVC) between two User network Interfaces (UNI). The E-Line is used as point to point connectivity.
2. Ethernet LAN Service type-
The Ethernet LAN service provides multipoint connectivity. The E-LAN service can connect two or more interfaces. Each UNI is connected to a multipoint Ethernet Virtual Connection (EVC).As more UNI’s are added they are connected to the same EVC thus simplifying the process of provisioning and service activation.8?
Figure 2 : E-LAN ->9?
Limitations of Ethernet in MEN when compared to ATM and Frame relay are
1. End to End QOS guarantees-
Connection admission for new service requests with specific QOS is admitted readily?
Scheduling and policing of packets to maintain proper usage of bandwidth in spite of competition to the resource?
Ensuring optimal path establishment through the network?
2. Protection Mechanisms-
Slow failure recovery in ether networks as compared to automatic packet switching (APS) or SONET network.
There is no mechanism to quarantine faulty routes in the network as in the case of SONET network.8?
1. Multi protocol Label Switch (MPLS) provides traffic engineering capability, guaranteed bandwidth and runs on any Ethernet transport.
2. To address problems like slow recovery multiple spanning tree is a proposal to allow more than one loop free path in a VLAN environment.8?
Standards of MEF-
The Metro Ethernet Forum (MEF) identifies itself as the standard defining body for Carrier Ethernet. To address these limitations the MEF is currently focusing on
Services and testing
The above mentioned areas have sub teams working on each of them to deliver documents, agreements, frameworks and interoperability content to support Metro Ethernet as the common network by choice globally.8?
Carrier Ethernet- Carrier ethernet is an extension to ethernet services necessary for ISP providers to provide ethernet services to end customers.
Definition-Carrier Ethernet is defined as a ubiquitous, standardized, carrier-class Service and Network defined by five attributes that distinguish Carrier Ethernet from familiar LAN based Ethernet 11?
As referred in 9 the global market for Ethernet equipment reached
$3.8 billion in 2004 and doubled in four years to $7.6 billion in 2008 and
expected to grow at similar rates. As the MEF defines more standards to define carrier class Ethernet services, the market for “carrier Ethernet” switches and routers are also expected both Ethat a extravagant rate.Ethernet-over-Sonet market. Adva is the second in the Ethernet-over-WDM. Cisco systems comes third in both markets.
Nortel networks lead the worldwide market for ernet-over-Sonet equipment and Ethernet-over-wavelength-division-multiplexing (WDM). Alcatel is the second in
The biggest market for Ethernet was Asia back in 2004 which contributed to 39% of the total market revenue last year. North America contributed to 35% of the revenue while Europe, Central and Latin America contributed to 5% of the market revenue.9?
We can thus wrap up our digest on Metro Ethernet by saying that Metro Ethernet has great global requirement and though it has not been utilized globally many service providers are beginning to implement it due to the many advantages it possesses .
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