ThickNet, also known as 10BASE5 or IEEE 802.3-1985, is an Ethernet standard that requires a specialized coaxial cable to transmit Ethernet frames at a rate of 10Mbps. It derives its nickname, which is a portmanteau of "Thick Ethernet," from the thick coaxial cable it uses, which is 0.375 inches in diameter.
The designation 10BASE5, assigned to the ThickNet standard by the Institute of Electrical and Electronics Engineers, provides a quick summary of the characteristics of its physical medium:
- "10" denotes its maximum data transmission rate of 10Mbps;
- "BASE" is shorthand for "baseband transmission," meaning the medium exclusively transmits Ethernet signals; and
- "5" means that it can transmit data at a maximum length of 500 meters before it experiences signal degradation.
The specialized coaxial cable used for a ThickNet computer network is sometimes referred to as "yellow cable" or "orange cable" because its outer insulation or jacket is made of either PVC (yellow) or Teflon (orange). This material makes the cable stiff and inflexible.
The cable contains a solid center conductor, and surrounding this conductor is an insulating filler made of foam, as well as a shielding braid. The cable must have a characteristic impedance of 50 ohms. Examples of coaxial cables made specifically for Ethernet include Belden numbers 9880 and 89880. ThickNet may also make use of RG-11 coaxial cable.
ThickNet employs a bus configuration as its network topology, meaning all nodes or devices are connected in a linear manner to one cable, known as a backbone, with 50 ohm resistive terminators at each physical end of the network. No more than 100 nodes may be connected to a ThickNet segment.
Transceivers, also known as Medium Attachment Units (MAU), were widely used in ThickNet networks. The term "transceiver" is a portmanteau of "transmiter" and "receiver," meaning it could both transmit and receive signals.
Transceivers were connected directly to cables through a device known as a "vampire tap," which is called such since it has spikes that pierce directly through the cable's outer jacket and into its center conductor. An N connector may also be used to connect a transceiver to a cable.
An Attachment Unit Interface (AUI) cable is used to connect a transceiver to a node. Transceivers may only be installed every 2.5 meters in order to not correspond to the wavelength of the signal. This minimizes echo and ensures that the reflections from multiple taps are not in phase.
ThickNet is the original Ethernet specification, although it was quickly superseded by 10BASE2 (also known as "ThinNet"). At present, it is considered obsolete computer networking technology.
ThinNet, also known as 10BASE2, IEEE 802.3, or "CheaperNet," is an early Ethernet standard that makes use of industry-standard RG-58 coaxial communications cables connected to BNC T-connectors. The standard has been nicknamed as such due to the thin and relatively inexpensive coaxial cables or "thinwire" used, which are 5 millimeters (0.2 inches) in diameter; "ThinNet" is a portmanteau of "Thin Ethernet."
The Institute of Electrical and Electronics Engineers (IEEE) has assigned ThinNet the identifier 10BASE2, as a quick summary on the following characteristics of the standards:
- "10" means it has a maximum transmission speed of 10Mbps;
- "BASE" is shorthand for "baseband transmission" or "baseband Ethernet," meaning that the medium only transmits Ethernet signals; and
- "2" refers to its maximum network segment length of 185 meters, rounded up to 200 meters.
Aside from its maximum segment length, it is of note that there is also a minimum length for this standard. Cables must not be any shorter than 0.5 meters. Other restrictions for ThinNet include: no more than 30 devices may be attached to a single ThinNet port per segment or "daisy chain"; no more than 3 repeater devices may be used to connect two network devices; and a maximum of 5 connected segments are allowed.
BNC T-connectors are used to connect each cable segment to a Medium Attachment Unit (MAU), LAN card or transceiver, which is then connected to the computer. In terms of network topology, a ThinNet network is usually arranged in a bus configuration, meaning each computer station or node is attached to the cable segment, which is ended by a terminator on either side to prevent interference caused by a radio frequency signal from being reflected back from the end. RG-58 coaxial cables have a nominal impedance of 50 Ohms, so 50 Ohm terminators are required for termination at the physical end of a network.
It is important to assure that everything in a ThinNet network is properly installed and connected, because connection flaws at any point of the network cabling tend to prevent all communications, and it very difficult to diagnose bad contacts or shorts (although a time-domain reflectometer may aid in finding problems).
Wall-mounted EAD-sockets can, however, provide more reliable connections. In this aspect, 10BASE-T networks are preferable because they are easier to maintain, but ThinNet does have a number of advantages over 10BASE-T: it has cheaper hardware costs, and wiring is easier since only a single wire run is needed. Thus, ThinNet is more ideal for smaller networks, while 10BASE5 or 10BASE-T are preferable options for larger networks.
Among 10Mbps Ethernet standards, ThinNet was the most popular for several years, widely used for home desktop machines, but it has since been superseded by standards featuring the low-cost Category 5 cable, wireless local area network (WLAN) standards, and Ethernet standards featuring much faster transmission rates (i.e. 100Mbps or higher). In present-day computer networking, ThinNet is considered obsolete technology.
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