| 100VG AnyLAN was developed by Hewlett Packard along with others to be the
standard for Fast Ethernet. The IEEE gave that title to 100BASE T and 100VG AnyLAN wound
up getting its own standard of 802.12. It is not Ethernet but it is compatible with either
802.3 Ethernet or 802.5 Token Ring (depending on the manufacturer). 100VG
AnyLAN relies on the hub to control network access. The hub uses Token Passing,
a method where each station receives and passes the right to use the single shared channel
on the LAN. All stations are guaranteed access to the network at regular consistent
intervals. This provides support for time sensitive applications like voice, video and
multimedia. While Ethernet uses a CSMA/CD access scheme (see the Intro to Ethernet section
for more details) 100VG AnyLAN uses a Demand Priority access scheme. Demand
Priority allows one or more stations to send high priority
transmissions first. If the hub receives a high priority request, it completes its current
transmission and then immediately grants access to the high priority request. When all
high priority requests are dealt with, normal operation resumes. Preventing time outs is
simple: the hub grants temporary high priority status to normal priority requests. This
creates a collision free network and is designed for higher throughput. However, 100 BaseT
may be a better choice, depending on your needs. Cabling
on 100VG AnyLAN depends on your needs. 4 pair Category 3 or 4 UTP can be used for a
maximum segment length of 100 meters. 4 pair Category 5 can be used for a max
segment length of 200 meters. Type 1 STP can be used but you must also use a balun to
match impedance. Max Segment length is 100 meters. 62.5/125 micron duplex multimode fiber
optic cable can be used for a maximum segment length of 2km. This allows most existing
cabling to be used with the need for rewiring virtually eliminated. |
|
1. 100VG AnyLAN Hub
2. 100VG AnyLAN Network Card
3. 100VG AnyLAN Hub
4. 100VG to Ethernet Bridge
5.10/100 Mbps Ethernet Switch
6. 4pair Cat5 Color Coded Patch Cables
7. 4pair Cat5 UTP Cable
8. 10 Base-T Network Card |
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