What Are LAN Jacks?

By David Secor

LAN jacks can connect computers in a network to share files and printers.
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Nearly all of today's computers are designed to be connected to a network that provides access to the Internet as well as the ability to share files and printers locally. The Internet is an example of a wide area network, whereas access to local files and printers is performed through a local area network. Each computer that connects to a wired LAN requires a network card with a physical port, or jack, that accepts a compatible network cable. Over time, various types of LAN jacks have been used as network technology has evolved.

8P8C Jack

The 8 position 8 contact jack, colloquially known as the RJ-45 jack or Ethernet port, is essentially a wider telephone-style jack and is the most common LAN jack in use. In the original 10BASE-T Ethernet specification, the successor to coaxial-based 10BASE2 and 10BASE5 Ethernet, the 8P8C jack is used with an eight-conductor Category 3 cable that's terminated on both ends with an 8P8C plug. Using two pairs, or four of the eight total conductors, 10Base-T was capable of network speeds up to 10 megabits per second. The later 100Base-TX standard, the most common found on computers as of 2013, used the same jacks and plugs with Category 5 cable to reach 100Mbps. Switching to improved Category 5e cables, the increasingly-common 1000Base-T specification, known as Gigabit Ethernet, uses all eight conductors to further push the speed to 1,000 Mbps, otherwise written as 1Gbps. Finally, the latest standard, 10GBase-T replaces the Category 5 cable with Category 6, which has eight slightly larger conductors, to achieve a speed of 10,000Mbps, or 10Gbps. On home routers, there are typically four 8P8C jacks for the LAN and one 8P8C jack that's used for the WAN connection to the Internet.

N Connectors

N Connectors, combined with heavy coaxial cables similar to RG-8, were used in the early 10Base5 Ethernet specification to reach a maximum network speed of 10Mbps. The installation of this type of network was difficult due to the inflexibility of the cable, the requirement that network transceivers be placed at specific distance intervals, the difficulty of finding connection problems and the need for the cables to be properly terminated. Eventually, 10Base5 was replaced by the simpler and more cost-effective 10Base-T standard.

BNC Connectors

Found on 10Base2 Ethernet networks, BNC connectors were used on RG-58 coaxial cables to link computers. The maximum network throughput of 10Base2 was 10Mbps. It suffered from some of the same problems as 10Base5, including the difficulty of finding communication issues and the requirements for proper termination. Though it was common for a while to find network adapters with both ports, 10Base-T replaced 10Base2.

Optical Connectors

Designed mainly for use in large high-speed business networks such as data centers, optical fibers use beams of light to move data at faster rates than copper cables typically can. While there are many different optical connectors available, both the older SC connector and the smaller LC connector are typically used for Ethernet networks today, with speeds of 40Gbps and 100Gbps.