It is now certain that Wireless Internet is truly established in Seychelles.

 Back in December 2000 when Kokonet pioneered the service, it can be said that only the bold and the hard core home surfers along with the business community went for the technology. Now that wireless ‘broadband’ access is becoming more widely available, the customers can only benefit with this new development.

As part of its customer care program, Kokonet will be over the next four weeks, running a weekly article on the nuts and bolts of Wireless Internet and its benefits for the customers. The aim of the articles is to keep the internet community in tune with the technology and help speed up decision making when considering the service. 

Within the Internet society, as is almost always the case, speed and bandwidth are the first considerations when selecting an ISP.  Today, we will tackle the issue of latency (speed) and bandwidth (capacity).

Latency and bandwidth are commonly misinterpreted concepts in networking.  Often people believe that they are one and the same.  For example when asked, "what is the speed of your connection?", most answers will be '128K' or '512K' or something similar.  As can be seen this is the capacity of the service and not the speed.

Invariably the two together, combined, give the customers the perception of how fast data from the Internet can be transferred.  In a competitive environment, as always, a strong marketing pitch is developed and 'broadband' service providers’ expressions such as 'get high speed access' , 'get high capacity access' are commonly used.  Therefore it is important that the customers understand these terminologies.  The term broadband usually refers to the available bandwidth, not how fast the circuit.

In a network, latency, a synonym for delay, is an expression of how much time it takes for a packet of data to get from one designated point to another. This gives a clear indication of the speed of data transfer for that circuit. One of the most common methods used to measure latency is the utility 'ping' which measures how fast a packet of data is returned to the sender.  The round-trip time is considered the latency and it is normally expressed in milliseconds.  Typical latencies are shown  below:-

Analogue Modem  100-200ms
ISDN                     15-30ms
DSL                      10-20ms
E1                         2-5ms

Ethernet                 0.3ms

 

Here are some examples to compare speed & capacity:

1.       Imagine water running through a pipe. (Consider the pressure is latency, the width of the pipe is bandwidth).  Using a wide pipe but low pressure; you can move a large volume of water but at a slow rate.  On the contrary with a narrow pipe but high pressure; you can move less water but at a faster rate.

2.       Now imagine people in an aircraft.  (Consider the passengers are the data packets, the size of the aircraft is the bandwidth and the speed at which the aircraft travel is the latency).  Using a Boeing 747 and a 767, we find that the 747 can carry 400+ passengers and the 767 only 240+ passenger.  Both fly at about 500 knots.  Therefore if both leaves opposite airports (e.g. Singapore & Seychelles) they will arrive at their destination at approximately the same time.  Although they travelled at the same speed (latency), the 747 has a larger passenger capacity (bandwidth) and transferred more passengers (packets of data).

As can be seen from above examples the bandwidth is easier to understand than latency.  To increase transfer potentials, it is necessary to increase the bandwidth of your circuit.  Therefore 256K will provide the customers with larger transfer capabilities than a 64K bandwidth. We express this rate as the amount of data that can be transferred during a second and is normally expressed in bits per second, e.g. 64 Kbps or 256 Kbps.  

Therefore, it is easily seen that if the bandwidth is saturated then congestion occurs and latency increases.  On the other hand if the bandwidth is not being used totally, the latency will not change, which implies that bandwidth can be increased but latency cannot decrease below the optimum for a particular network.

The general assumption seems to be that data is transmitted instantly between one point and another and that there is no delay but in fact there are several factors that contribute to increase latency in a network as shown below:

∑       Propagation: Time taken for a packet of data to travel between one place and another at the speed of light.

∑       Transmission: The medium itself (be it wireless, DSL or others) introduces some delay due to it physical properties. The size of the packet of data introduces delay as a larger packet will take longer to send and receive than a short one.

∑       Processing (routers and others): Each gateway node must authenticate and possibly change a packet header.

∑       Storage (computer) delays: These type of delays are not accounted for when considering the backbone network but since your computer and its switching and bridging equipment form part of your connection to the network, data retrieval, storage and switching delays will increase overall latency.

Eventually the actual download and upload speed of your connection will vary according to the bandwidth you have subscribed for, the strength of the signal at your location, traffic conditions on your local network, and invariably how busy the traffic is on the world wide web. 

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