An alternative to Fast Ethernet that provides 100-Mbps communications based on technology developed by Hewlett-Packard. 100VG-AnyLan is based on the 802.12 specifications of Project 802 developed by the IEEE. 100VG-AnyLan is informally named 100BaseVG.
Graphic 0-7. A 100VG-AnyLan network.
100VG-AnyLan networks are wired together in a star topology using unshielded twisted-pair (UTP) cabling, shielded twisted-pair (STP) cabling, or fiber-optic cabling with supporting 100-Mbps hubs or Ethernet switches. If UTP cabling is used, it can be category 3 cabling, category 4 cabling, or category 5 cabling - with category 5 (CAT5) cabling or enhanced category 5 cabling preferred. 100BaseVG uses all four pairs of wires in UTP cabling. When using UTP category 3 cabling, category 4 cabling, or STP cabling, the maximum length of a segment is 100 meters. With UTP category 5 cabling, the maximum length of a segment is 200 meters. When using multimode fiber-optic cabling, the maximum length is 2000 meters.
100VG-AnyLan differs from Fast Ethernet by not using the traditional Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method for media access used in Ethernet and Fast Ethernet networks; instead, 100VG-AnyLan uses the demand priority method for media access, which eliminates the overhead of collisions. 100VG-AnyLan uses a special coding scheme called quartet signaling, which makes it possible to transmit data over all four pairs of wires in a UTP cable simultaneously. This means that special 100VG-AnyLan hubs are required to support demand priority media access. Otherwise, the frame format, topology, and other specifications of 100VG-AnyLan are the same as for Ethernet.
100VG-AnyLan is also being developed to support token ring networks.