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Defining Other Standards of IEEE Models

© Muhammad Ahsan

We described 10Base2, 10Base5, 10BaseT, and Token Ring individually. There are some other standards of IEEE Ethernet, which can be used in the specific situations where coaxial or twisted-pair will not work well. Sometimes, speed of transmission is another requirement. For all those reasons, we have some other standards, which are as follow:

Contents:
1. 10BaseFL
2. 100VG-AnyLAN
3. 100BaseX


10BaseFL

10BaseFL is a specification for Ethernet over fiber-optic cables. The 10BaseFL specification calls for a 10 Mbps data rate using baseband.

The advantages of fiber-optic cable (and hence, the advantages of 10BaseFL) are discussed in my articles (see Fiber-Optic Cable). The most important advantages are long cabling runs (10BaseFL supports a maximum cabling distance of about 2,000 meters) and the elimination of any potential electrical complications.

In security zones, where usually entrance is prohibited (such as arm forces workhouses), only fiber-optic implementation can guarantee the safety of the data and its transfer to another security zone. That's all because data is transferred in the light-signals, in the result, it cannot be detected by any eavesdropping -equipment which is used to detect the electrical signals by placing the equipment onto the cable. It is possible for the e-robbers to break the cable but they can never get the data without authentication.

There are also some drawbacks. You need very expert professionals to install this standard. Another factor is cost.


100VG-AnyLAN

100VG-AnyLAN is defined in the IEEE 802.12 standard. IEEE 802.12 is a standard for transmitting Ethernet and Token Ring packets (IEEE 802.3 and 802.5) at 100 Mbps. 100VG-AnyLAN is sometimes called 100BaseVG. The 'VG' in the name stands for voice grade.

Demand Priority:

Demand priority is an access method used with the new 100 Mbps 100VG-AnyLAN standard. Although demand priority is officially considered a contention-based access method, demand priority is considerably different from the basic CSMA/CD Ethernet. In demand priority, network nodes are connected to hubs, and those hubs are connected to other hubs. Contention, therefore, occurs at the hub. (100VG-AnyLAN cables can actually send and receive data at the same time). Demand priority provides a mechanism for prioritizing data types. If contention occurs, data with a higher priority takes precedence.

As mentioned above 100VG-AnyLAN demand priority access method provides two priority levels when resolving media access conflicts.

100VG-AnyLAN uses a cascaded star topology, which calls for a hierarchy of hubs. Computers are attached to child-hubs, and the child-hubs are connected to higher-level hubs called parent-hubs.

The maximum length for the two longest cables attached to a 100VG-AnyLAN hub is 250 meters (820 ft). The specified cabling is Category 3, 4, or 5 twisted pair or fiber-optic. 100VG-AnyLAN is compatible with 10BaseT cabling.

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