With the speed test you can see what speed you have right now. The measured speed is indicative, and will typically be lower than the speed you have purchased. There are several reasons for this.
We recommend that the test is not carried out with a Wireless Access Point. The wireless signal can be influenced by its surroundings and therefore test results can be misleading.
What speed can you expect
Please note that when sending data over the internet there is from 15 to 33% overhead.
What is overhead?
Overhead is a measure of loss for data transport. Eg. the quantity of a network connection raw capacity that spilled to transferring unnecessary data. The problem is that IP packets can contain up to 64 kB, while Ethernet can only transmit packets of 1500 bytes .
So when one computer sends such a packet to another, the 64 kB broken up into packets of 1500 B. Each of These packets carry some necessary information (sender and modtageraddresse), after which they are sent away. The first package is of course necessary, but it is believed some of what information is passed 40-50 times, which really is not necessary. This waste is called overhead. The problem becomes even greater if one uses other standards , eg. provides TCP / IP over ATM an overhead around 10 - 33%.
Another example of overhead is encoding binary data so it can be transferred seamlessly between servers on the Internet. Base64 is used for example. SMTP and NNTP , can be above 33% overhead. That is to be transported 4 bytes for each 3 byte net.
Minimum speed to expect with overheads in Mbits (down/up)
In Kbits
1Mbit/1000 Kbits
0.670/0.08
670/80
3Mbits/3000 Kbits
2.010/0.17
2010/171
5Mbits/5000 Kbits
3.335/0.17
3335/171
'Wrapping paper'
When anything is sent over the Internet the information is divided into packets. Each packet needs to have extra data attached to make sure the packet ends up in the right place. It might sound simple but that is only half the story.
Application layer
The application layer is the program used to create the file, this could be Outlook, Word, Photoshop etc.
Transport layer
The transport layer is also known as TCP and it handles the port numbers and sorts out errors with the connection. Each packet send over the internet will be allocated a transport layer so if it does not arrive at its destination it will be sent again.
Web layer Also known as IP, this is will make sure the packet arrives at the correct place, and also knows if the packet is being sent or recieved. Each packet from the transport layer is attached to the personal information of the physical address of the network.
Network layer
When the modem and central computer are talking there will also be used space on error correction and packets divided into even smaller binary chunks which can be physically dispatched through the connection.
The measured speed
All in all, with this extra information that is occupying the datastream, it will bring the measured speed to work lower than the physical speed.
Sources: AT&T (America), Deutch Telecom, TDC (Denmark). This information is applicable to all Internet Providers WorldWide.
