<< Home

Industrial Training
@
MTT Network (Pvt) Ltd

Data Communication

9.1 Networking

This is another main area of operation of MTT. MTT is providing Wide Area Networking infrastructure to its customers with the Nortel Passport 6480 Frame Relay Network.

9.2 Frame Relay Network

MTT Frame Relay network consists of three Frame Relays located at Mullariyawa, Mahagalkanda and Gongala base stations. These Frame Relays are connected through 2 x 2 Mbit/s radio links. The Fig 9.1 shows the MTT Frame Relay network. 

Fig 9.1 Frame Relay Network

            Most of the customers are connected to Mullariyawa Frame Relay. The Frame Relay used in MTT is Nortel Passport 6480

9.3 Frame Relay

Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model. Frame Relay originally was designed for use across Integrated Services Digital Network (ISDN) interfaces. Today, it is used over a variety of other network interfaces as well.

Devices attached to a Frame Relay WAN fall into two general categories: data terminal equipment (DTE) and data circuit terminating equipment (DCE). DTEs generally are considered to be terminating equipment for a specific network and typically are located on the premises of a customer. In fact, the customer may own them. Examples of DTE devices are terminals, personal computers, routers, and bridges.

DCEs are carrier-owned internetworking devices. The purpose of DCE equipment is to provide clocking and switching services in a network, which are the devices that actually transmit data through the WAN. In most cases, these are packet switches. Fig 4-4 shows the relationship between the two categories of devices.

     Frame Relay provides connection-oriented data link layer communication. This means that a defined communication exists between each pair of devices and that these connections are associated with a connection identifier. This service is implemented by using a Frame Relay virtual circuit, which is a logical connection created between two data terminal equipment (DTE) devices across a Frame Relay packet-switched network (PSN).

Virtual circuits provide a bi-directional communications path from one DTE device to another and are uniquely identified by a data-link connection identifier (DLCI). A number of virtual circuits can be multiplexed into a single physical circuit for transmission across the network. This capability often can reduce the equipment and network complexity required to connect multiple DTE devices.

A virtual circuit can pass through any number of intermediate DCE devices (switches) located within the Frame Relay PSN. Frame Relay virtual circuits fall into two categories: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).

9.4 Data-Link Connection Identifier (DLCI)

Frame Relay virtual circuits are identified by data-link connection identifiers (DLCIs). DLCI values typically are assigned by the Frame Relay service provider (for example, the telephone company). Frame Relay DLCIs have local significance, which means that the values themselves are not unique in the Frame Relay WAN. Two DTE devices connected by a virtual circuit, for example, may use a different DLCI value to refer to the same connection.

9.5  Routers

A Router is an intelligent networking node. Routers connect Ethernet LANs to WANs via ISDN, asynchronous serial and synchronous serial connections, supporting Frame Relay, leased lines, Switched 56 and X.25.

Routing is the act of moving information across an Internet work from a source to a destination. Routing involves two basic activities: determining optimal routing paths and transporting information groups (typically called packets) through the Internet work. To aid the process of path determination, routing algorithms initialize and maintain routing tables, which contain route information.

9.6 Web, Wap & DNS Servers

MTT has its own web, wap and DNS servers and their server setup is as shown in the following Fig 9.2

Fig 9.2 Server Setup

DNS stands for Domain Name Service and it is the one maps IP addresses to URL’s
The following is a sample DNS Configuration:

SOA – Start of Authority
NS – Name Server  
A – Name to IP Address mapping  
CNAME- Canonical Name / Alias

Conclusion >>