DATA



Wired Networking

Network nodes may be directly connected by a multitude of physical carrier technologies.

They roughly fit into copper-based and fibre-based categories. Copper cables come in either coaxial or twisted pair configurations which carry electromagnetic waves while optical fibers transmit light impulses.

Wired networks feature a generally higher performance and are relatively more secure than wireless technologies. The reason lies in the fact that private cables are used for signal transmission which have a much lower attenuation than radio waves and they produce limited or no electromagnetic emmissions so it is harder for third parties to eavesdrop. Wired networks are easy to scale by adding more parallel cables, which is often not possible for wireless links due to a full frequency spectrum. Another benefit of wired networks is the fact that they are an unlicensed technology, so everyone can set up an infrastructure. The wireless spectrum is a scarce resource and only a very small band of frequencies is publicly available for unlicensed use.

Ethernet

The cheapest and most commonly used wired medium is Ethernet which utilizes 4 pairs of twisted copper wires and achives between 100 Mbit/s and 10 Gbit/s over different grades of cables. Twisted pair cables are classified by category and shielding where, for example, CAT5 unshielded twisted pair (UTP) is sufficient for a 100Mbit/s Ethernet connection over up to 100m distance. CAT5e, CAT6 and the shielded variants (STP) are required for Gigabit (GigE) and 10 Gbit/s Ethernet (10 GigE).

Optical fibre glass is superior to copper in throughput and cable length, but also more expensive, less flexible and less robust. Fibre can carry multiple wavelengths of light simultaneously and is immune to electromagnetic interference. It is commonly used in high-end media productions, for high-speed internet uplinks, undersea cables, and in industry automation.

DSL

Digital subscriber lines (DSL) are a network edge technology to connect private households via telephone lines. Because cable quality is poor the available frequency spectrum is very limited and noisy. The system design favours downlink capacity, hence the spectrum is asymmetrically shared between uplink and downlink, meaning a much wider frequency spectrum is available for downstream than for upstream. This also coined the name ADSL (asymmetric DSL). ADSL typically reaches 17Mbit/s in downstream capacity, but only 1Mbit/s for upstream. The more recent VDSL (very-high-bitrate DSL) keeps the asymmetric nature, but increases the overall data rate to 52Mbit/s downstream and 16Mbit/s upstream.

Performance Overview



Author: Alexander Eichhorn

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