The 8 Position 8 Contact (8P8C) modular plugs and sockets are communications connectors. Under the same naming scheme, an 8P6C connector has eight positions, with six positions containing conductors, and a 6P6C connector has six positions, all containing conductors. 8P8C connectors are typically used to terminate twisted pair cable.

These connectors are often referred to as RJ45 plugs and sockets. This is technically incorrect because the RJ45 standard specifies both the mechanical interface and a different wiring scheme than T568A/B, which is often used for Ethernet and telephones.

8P8C consists of two paired components: the male plug and the female socket. Each has eight equally-spaced conductors. On the plug, these conductors are flat contacts positioned parallel with the connector body. Inside the socket, the conductors are suspended diagonally toward the insertion interface. When an 8P8C plug is mated with an 8P8C socket, the conductors meet and create an electrical connection. Spring tension in the socket's conductors ensure a good interface with the plug and allow for slight travel during insertion and removal. The 8P8C connector is probably best known for its use in Ethernet. Since about 2000, it is nearly universal as the type of connector used on a cable that carries a single Ethernet network, and has replaced many older connector types. Older connectors have also been phased out as modern cables no longer have the high current and voltage requirements for which the bulkier connectors were designed.

Standardization

The shape and dimensions of an 8P8C modular connector are specified for U.S. telephone applications by the Administrative Council for Terminal Attachment (ACTA) in national standard ANSI/TIA-968-A. This standard does not use the short term 8P8C and covers more than just 8P8C modular connectors, but the 8P8C modular connector type is the eight position connector type described therein, with eight conductors installed.

For data communication applications (LAN, structured cabling), International Standard IEC 60603 specifies in parts 7-1, 7-2, 7-4, 7-5, and 7-7 not only the same physical dimensions, but also high-frequency performance requirements for shielded and unshielded versions of this connector for frequencies up to 100, 250 and 600 MHz, respectively.

Wiring

It is frequently terminated using the T568A or T568B pin/pair assignments that are defined in TIA/EIA-568-B. A cable that is wired as T568A at one end and T568B at the other (Tx and Rx pairs reversed) is a "crossover" cable. Such a cable often has a red sheath and, before the widespread acceptance of auto-MDI/MDIX capabilities, was needed to interconnect network equipment (such as hubs, switches, and routers) to one another. A cable wired the same at both ends is called a "straight-through" cable, because no pin/pair assignments are swapped.

Types

There are two types of 8P8C plugs, sockets, and diesets (used for crimping): Western Electric/Stewart Stamping (WE/SS) and Tyco/AMP. While both types look remarkably similar, they are exclusive and cannot be interchanged. Tyco/AMP 8P8C plugs are proprietary, and have smaller spacing between contacts than the WE/SS style. As a result, using a WE/SS 8P8C crimp dieset on a Tyco/AMP 8P8C plug will crush the top of the connector, and vice versa. While the WE/SS 8P8C plug is more common than Tyco/AMP, it is still important to know what style is being used to avoid damaging the plug during crimping.

WE/SS 8P8C plugs come in shielded and unshielded varieties, depending on the attenuation tolerance needed. All Tyco/AMP 8P8C plugs include a metal ferrule, and so shielding comes standard. Shielded plugs are more expensive, but have a lower attenuation and can reduce signal noise. WE/SS plugs are available from a large number of manufacturers, whereas Tyco/AMP plugs are produced exclusively by Tyco Electronics.

Termination

Termination of a cable with an 8P8C plug involves using a hand crimper or crimp machine containing an 8P8C dieset. An 8P8C crimp dieset usually looks similar to an 8P8C socket, except for the eight teeth lining the top portion of the die. When the tool is operated, the die compresses around the 8P8C plug. As the die compresses, these teeth force the plug contacts down into the conductors of the cable being terminated, permanently attaching the plug to the cable.

Applications

A common application is in computer networking, where the plug on each end is an 8P8C modular plug wired according to a TIA/EIA standard. These cables are typically used to connect Ethernet or Token Ring network interfaces. Most network communications today are carried over Category 5e or Category 6 cable with an 8P8C modular plug crimped on each end.

The 8P8C modular connector is also used for RS-232 serial interfaces according to the EIA/TIA-561 standard[1]. This application is commonly used as a console interface on network equipment such as switches and routers. Other applications include other networking services such as ISDN and T1.

In floodwired ^[1] environments the center (blue) pair is often used to carry telephony signals. Where so wired, the physical layout of the 8P8C modular jack allows for the insertion of an RJ11 plug in the center of the socket, provided the RJ11 plug is wired in true compliance with the U.S. telephony standards (RJ11) using the center pair. The formal approach to connect telephony equipment is the insertion of a type-approved converter.

The remaining (brown) pair is increasingly used for Power over Ethernet (PoE). Legacy equipment may use just this pair; this conflicts with other equipment as manufacturers used to short circuit unused pairs to reduce signal crosstalk. Some routers/bridges/switches can be powered by the unused 4 lines — blues (+) and browns (−) — to carry current to the unit. There is now a standardized scheme for Power over Ethernet.

Different manufacturers of 8P8C modular jacks arrange for the pins of the 8P8C modular connector socket to be linked to wire connectors (often IDC type terminals) that are in a different physical arrangement from that of other manufacturers: Thus, for example, if a technician is in the habit of connecting the white/orange wire to the "bottom right hand" IDC terminal, which links it to 8P8C modular connector pin 1, in jacks made by other manufacturers this terminal may instead connect to 8P8C modular connector pin 2 (or any other pin).

A router (pronounced /'rautər/ in the USA, pronounced /'ru:tər/ in the UK, or either pronunciation in Australia) is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding information. Routers generally contain a specialized operating system (e.g. Cisco's IOS or Juniper Networks JUNOS and JUNOSe or Extreme Networks XOS), RAM, NVRAM, flash memory, and one or more processors. High-end routers contain many processors and specialized Application-specific integrated circuits (ASIC) and do a great deal of parallel processing. Chassis based systems like the Nortel MERS-8600 or ERS-8600 routing switch, (pictured right) have multiple ASICs on every module and allow for a wide variety of LAN, MAN, METRO, and WAN port technologies or other connections that are customizable. Much simpler routers are used where cost is important and the demand is low, for example in providing a home internet service. With appropriate software (such as Untangle, SmoothWall, XORP or Quagga), a standard PC can act as a router.

Routers connect two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.^[1] The term layer 3 switch often is used interchangeably with router, but switch is really a general term without a rigorous technical definition. In marketing usage, it is generally optimized for Ethernet LAN interfaces and may not have other physical interface types.

Routers may provide connectivity inside enterprises, between enterprises and the Internet, and inside Internet Service Providers (ISP). The largest routers (for example the Cisco CRS-1 or Juniper T1600) interconnect ISPs, are used inside ISPs, or may be used in very large enterprise networks. The smallest routers provide connectivity for small and home offices.

A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are typically on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. A wireless LAN may exist using a different IEEE protocol, 802.11b or 802.11g. The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.

All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 40 Gbit/s.