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Pushing the envelope (January 01, 2006)

The phenomenal increase in networking speeds is driven by the need for data rate to support bandwidth-intensive multimedia applications.


January 1, 2006  


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There has been a steady increase in the speed of data networks over the last 15 years.

Ethernet networks have evolved from a shared network speed of 10 Mb/s over Category 3 cabling in the early 1990s to networks providing dedicated 1 Gb/s speeds to the work area over Category 5e / 6 copper cabling and 10 Gb/s speeds in the backbone over multimode and single mode optical fiber.

The next generation of Ethernet is moving to 10 Gb/s in the horizontal over augmented Category 6 cabling and 40 Gb/s in the backbone over laser optimized multimode or single mode fiber.

This phenomenal increase in networking speeds is driven by the constant need for data rate to support bandwidth-intensive multimedia applications encompassing voice, data, video and long-distance Storage Area Networks (SANs) — applications that are used down to the desktop level.

The next generation of networks will feature converged voice, data and video. To that end, networking and cabling performance are closely intertwined since higher network speeds demand higher performance cabling.

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What differentiates higher performance Category 6/6A cabling from lower performance cabling is the higher available bandwidth and higher Signal-to-Noise Ratio, which translates into a higher information capacity.

In order to better understand the network demands for different applications, let us look at different types of information such as text, pictures and video and determine how much information can be transported over a typical 100 Mb/s network.

Let’s start with text information. What’s in a word? A word contains an average of six characters. Each character can be represented by one byte or eight bits of information. 0ne page of information contains approximately 1,000 words and can be represented by 48,000 bits of information.

A networking speed of 100 Mb/s can transmit 2,000 text pages per second, which is a lot of text information and is sufficient for most needs. An 8 1/2-by-11-inch page excluding margins can be represented by 45,360,000 bits (grayscale) or 136,080,000 bits (colour) at 300 dots-per-inch (dpi) resolution.

A networking speed of 100 Mb/s can transmit approximately two pictorial pages per second (gray scale) or 40 pictorial pages per minute (colour). At a higher resolution of 600 dpi the throughput would be reduced by a factor of four. As you can see, at 100 Mb/s the network speed may not be sufficient for high throughput and output quality.

Now let’s look at the information capacity required for digital video. A streaming video signal is a series of images concatenated in time at a rate of 30 frames per second.

Because two adjacent frames in a motion picture sequence are usually very nearly identical, MPEG compression dramatically decreases the amount of storage space required to record motion picture sequences by eliminating redundant information. Meanwhile, when it comes to information capacity required for different video resolutions, a networking speed of 100 Mb/s can transmit simultaneously 1 HDTV signal and 2 studio quality TV signals. If other services were running concurrently on the same network, a higher networking speed would be required.

A high-speed information network would be useless without the means to store and retrieve the information.

For government and financial institutions as well as commercial businesses, information is a valuable asset and is an indispensable part of doing business.

SAN architecture is typically based on a 120MB/sec (1 Gbit/sec) interface that is designed to interconnect hundreds of devices in a reliable network fabric. There is a need for higher 10 Gb/s speeds for greater efficiencies and high traffic volumes.

Finally, we have the exponential increase in computing power, which doubles in speed every 18 months according to Moore’s Law.

However, the challenges of shrinking chips and higher clock speeds is that the chip designers are running into some physical barriers at the 4 GHz speed, namely power consumption, memory access times and circuit delays in signal transmission.

The answer to breaking this speed barrier is parallel computing, which involves the simultaneous use of more than one computer or processor to execute a program.

This means that the computers and processors are interconnected in a network fabric passing bits and pieces of information back and forth at a very high rate of speed, the faster the better to avoid waiting times and increase computing power.

In conclusion, 10Gb Ethernet is an evolutionary step, a killer enabler to faster, easier high-speed networking and more cost effective high-speed infrastructure for LANs and SANs.

Paul Kish is Director, Systems & Standards at Belden CDT. He is also vice chair of the TR-42 engineering committee.

Disclaimer: The information presented is the author’s view and is not official TIA correspondence.