Comparison of WAN Technologies
The advances technologies such as ISDN, Frame Relay, ATM and SDH/SONET are being integrated for the data and voice traffic being transmitted over the internet. In olden days the telephone lines used carried voice traffic in the form of analog and were know as Plain Old Telephone System (POTS), but at present the telephones and the computers use digital technology for the voice and data traffic. Devices like modems are being used to convert analog into digital and vice versa. As more and more peoples are using internet the data and voice traffic is being transmitted over the same line. In my report I will focus on some of the modern technologies for voice and data traffic and the devices that are being used for the purpose in the Wide Area Network. At present the most emerging technology being used in the Wan is VOIP. It transmits voice over the internet using the packets. The users can transmit audio and video over a data network. The analog signal is converted into digital using the modem. The modem converts analog signals into small digital packets to be transmitted over the network. At the receiver end the data is demodulated and the file is converted into an AVG file. This procedure is being used in VOIP, Video conferencing and streaming of audio and video clips on the internet. With this the WAN technologies are emerging and many WAN devices are being used.
WIDE AREA NETWORKS:
Several Local Area Network connected is know as Wide Area Network. This helps in transmitting data to longer distances using a single network. Better example for this would be different branches of a company around the world are interconnected using the Wide Area Network. The branches use LAN in the branch and WAN between different branches which helps the business to grow at a faster pace and with security.
The various WAN devices available in the market are being manufactured on the lines of reliability and security of the network. Some of them are
In the network a router helps to connect one or more than one computers. Normally for home users they are helpful in taking a single broadband connection and spreading
it to other computers. Backbone of an internet is usually by industrial routers which are used in the telecom industry. Each router has a table configured to make connections which lead to a group of IP addresses. The routing table also have the rules to handle different types of traffic.
A switch is every so often called a ‘intelligent hub’, and at the present that they are no longer considerably more costly than the hubs they have roughly replaced them completely. A switch works alike as a hub, with the aim of to connect devices to let them to work as a single segment. However, it does not repeatedly transmit traffic to each and every port. Whenever a frame of data enters into the switch, it save the physical address (MAC address) and the port it come from in its MAC address table. Then it checks the target MAC address in the table, and if it recognises it sends the frame to the suitable port. If the address is not the table, or address is a broadcast address (intended for every machine on the local network), then it do the equivalent as a hub and transmits the frame throughout every port apart from the originating port.
A hub is a tool for connecting various Ethernet devices (usually PCs) to outline a single segment – a part of a network that is unconnected from other parts of the network. It has several ports throughout which devices are joined, and while it receives data it send it out over through every port apart from the one it come in through. Initially Ethernet networks use coaxial cables. Each computer was fixed with a transceiver, which is connected straight into a long part of coaxial cable – a bus. This means that the traffic flowing on the network is visible to every one on the network.
The short form for modulator and demodulator is Modem. It converts digital frequencies of the computer in to analog to make it transmit over the telephone or cable lines. At the receiver end the modem successfully demodulates the analog into digital and gives it to the computer to carry out appropriate functions.
The replacement for old age analog technology is the ISDN. It was implemented to create a more reliable and faster transport mechanism. It is cheaper than a leased line and it takes seconds to install it. The standard ISDN, Broadband ISDN is the version most people are aware of which is the ATM.
The end equipment protocol is defined by the ITU I and the switch/network protocol is defined by the ITU Q series.
Structure of ISDN
The protocol model for ISDN is represented in the following diagram:
Figure: Structure of ISDN
With the beginning of PCM tools in the 1960s, communications networks are steadily transformed to digital technology above the next few years (Werner, Fundamentals and SONET testing). To deal with the stipulate for ever high bit rates, a multiplex hierarchy called the plesiochronous digital hierarchy (PDH) evolve. The bit rates begin with the fundamental multiplex rate of 3 Mbit/s with additional stages of 8, 34 and 140 Mbit/s. The 1980s see a start in the growth of the synchronous digital hierarchy (SDH), with the purpose to eliminate the disadvantage inbuilt in PDH. SDH bring the subsequent advantages to network provider.
- High transmission rates
Transmission rates of up and about 10 Gbit/s can be achieve in current SDH systems.
- Simplified add and drop function
When compared to the old PDH system, it is a lot easier to take out and insert low-bit rate channels on or after or into the high-speed bit streams in SDH.
Modern SDH networks consist of various repeated back-up and repair mechanism to deal with system faults.
- Future platform for advanced services.
At present, SDH is the suitable platform for the advanced services ranging from ISDN, POTS through to data communications (LAN, WAN).
SDH makes it easy to install or set up new gateways in between various network providers and SONET systems.
Figure: SDH Layer Model
Difference between SDH and SONET:
SDH is the synchronous digital hierarchy that is use every where apart from in the USA, Canada and Japan. SONET (Synchronous optical network) is the American counterpart of SDH. Designs of this transmission technology in America begin as far back as 1985. The SONET basic bit rate is 51.48 Mbit/s and is named STS-1 (synchronous transport signal). If the bit rate is transmit above an optical cable system, the signal is named as OC-1 (optical container)
Table: Levels in Hierarchy
Public Data Network:
The people around the world use public network to send and receive data which is also know as internet. If a user is making a call using the internet then its priority will be high because the user is using an expensive technology. If its security and reliability is ignored then more and more private networks will be formed by different companies which will lead to congestion of the network The common carrier subscriptions which own telecom services are known as public networks. It supports the transmission of voice traffic over the internet using the modems through the telephone sockets and gain automated access to users around the world. In this there is no wastage of bandwidth as the calls are being made over the internet and this will be a reliable and suitable for small companies
ATM is the short form for Asynchronous Transfer Mode. Circuit switching usually requires that packets are placed into position in recurring frames, i.e. synchronous, in time, in step according to use and/or network clocks. Asynchronous transmission allow cells to be placed anywhere in the data stream. ATM at present has speeds of 155Mbps (OC-3 ports), 622Mbps (OC-12 ports), 1.2 Gbps and 2.5 Gbps. Since the cells are rigid in length (53 octets, or bytes) quite than variable such as an Ethernet frame, they can be switch in hardware to a certain extent than software and these accounts for the high speeds that can be attain than Ethernet, Token Ring and FDDI.
ATM is very lithe and allow the transmission of a variety of media type such as voice, video, data files etc. all demanding the network in changed ways, video, for example can be extremely subject to a sudden slowdown in network routine as altering speed video is very disturbing. ATM allows committed circuits with certain bandwidths and differing needs to be set up at the same time (http://www.rhyshaden.com/atm.htm). Quality of Service (QoS) can be locate up and is certain at connection stage by means of parameter such as delay, delay jitter and error rate base on the function and the position of the network at the moment of connection. Two priority for traffic are defined; High priority and Low priority. Low priority traffic force is leftover if around are switch congestion trouble. Particularly voice and video traffics include to be transferred by means of previous methods such as MPLS over ATM and IP over ATM, where QoS maintain advantages of the ATM are subjugated in exacting (Cemal Kocak, et.al, 2007). There is no joint media or conflict based protocols in ATM, each machine has 155Mbps all to itself. In ATM you be able to multiplex ‘cell streams’ so as to may be for totally different application, the structure works in ‘connection oriented’ form thereby guarantee cell sequencing for those cells in a exacting connection.
It is developed by the values or technology base on ISDN (Piliouras, 2005). The communication is among end users by following the interface of public network and private network (Taylor, 2000). It handles high traffic on internet at high speeds and on the whole handles data networking issue at high speed by functioning on following principles:
Solution for errors like congestion occurs, discarding frames and means to improve errors at end user method. It works on applications of data and is based on packet switching (Smith, 1996). The data is distributed into frames of variable length similar as in packet switching, which is sent to target through frame relay networks. The difference between frame relay and packet switching is that frame relay is second layer protocol of OSI where as packet switching is third layer protocol but frame relay is quite straightforward compared to packet switching linking locations all the way through access circuit to networks (Green, 2000). Carrier information rate (CIR) is the element which is used to charge and it guarantees the transporting the carrier through, Access Circuit cost is classify by LEC and port speed which is a manifold of 64 Kbps.
The idea of information backdrop, issue concerning technology, in force scenarios and advance to protocols management for WAN technologies and a lot of unresolved promotion and technological questions concerning coexist of conventional communications of voice. The WAN technology should further develop earlier than the considerable possible acceptance and also customer service and billing methods. Additional determine execution of WAN and efficient structure of billing method for calls using VOIP system and also sophisticated procedures. Advancement or adoption of WAN technologies will in the end resolve services, price efficiency and Quality of Service. The trouble for session timeout, issue of reliability and solution of feeble slow link have to be resolve. The mixing of data protection system is necessary for errors correction and dependable to run the arbitrary data or voice traffic over the internet internet.
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