3Com 100 TX manual Classification, Repeaters

Classification of Repeaters 3-9

Classification of	The IEEE 802.3 standard defines two classes of repeaters for 100BASE-T
Repeaters	Fast Ethernet networks, as detailed below.

Class I Repeaters A Class I repeater is a hub with internal delay such that only one repeater can exist between any two DTE (data terminal equipment) devices within a single collision domain when two maximum-length cable segments are used.

The LinkBuilder FMS 100-TX Hub (product number 3C250-TX/1) is a Class I device only.

Internal delay is the time delay between the sensing of the first data bit received and the sensing of the first bit transmitted on a 100 Mbps CSMA/CD network. Propagation time delays also affect repeater classification. Class I repeater delays are longer than Class II repeater delays.

A Class I network topology consists of one hub (or hub stack) in a single collision domain existing between any two end stations. The stack of LinkBuilder FMS 100-TX Hubs in this configuration can contain up to eight hubs.

Figure 3-8 shows a single collision domain containing one Class I hub stack between two end stations, with the distance between end stations being 200 meters. If one of the hub-to-node segments is implemented with fiber cabling (by using the 100BASE-FX transceiver interface module), the total span can be 260.8 meters. That is, up to 100 meters can consist of UTP cabling, with up to 160.8 meters of fiber cabling.

200 meters: maximum UTP distance

(260.8 meters: mixed UTP and fiber cable)

100 meters maximum
(160.8 meters: fiber cable)	100 meters maximum

Class I configuration

Figure 3-8 Class I Hub