100BaseVG

100VG ANYLAN is a standard that was developed by Hewlett -Packard and AT & T and standardized by the IEEE 802.12 committee and had set itself the goal of becoming the successor of 10Mbit Ethernet. It was originally developed under the name 100BaseVG.

100BaseVG was specified for operation over four pairs of an otherwise only for 10 Mbit / s appropriate category 3 cable ( CAT3 ), as it was installed at the time of development, especially in the United States on a large scale. These cables are also known as "voice grade", ie phone cord, called - hence the acronym " VG ". The term " ANYLAN " pointed out that the standard was also provided the transport of Token Ring frames.

The standard was adopted in 1995. Due to the higher cost of 100VG - components and their limited availability to 100Base -TX standard reached no special acceptance, from about 1998, the corresponding products were taken off the market.

Operation

100VG - Anylan used a deterministic access method whereby collisions were avoided like the classic Ethernet with common medium:

• Each connected device / node communicates with the central hub and tells him its send request. Two priorities are available: Normal and High.
• If the hub decides that the device 's turn to send, it tells him that it is allowed to send now.
• The stroke passes through the units in a cyclic order, and allowed them each a packet to send ( round- robin ).
• It all high-priority devices are treated first, before the low-priority treatment.
• All devices that have not filed an application for transmission are ignored.
• In order to prevent high-priority devices block the network, the hub maintains a priority timer for each device. The timer is started when the device for the first time provides a normalpriorigen transmission request. If the timer expires before the device gets a chance to send his request is promoted to a high-priority transmit request.