3com 100 TX Manual De Usuario

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

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. 

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.

Figure 3-8   Class I Hub 

®

3C12345

®

3C12345

®

3C12345

®

3C12345

®

3C12345

®

3C12345

®

3C12345

®

3C12345

Class I configuration

200 meters: maximum UTP distance

(260.8 meters: mixed UTP and fiber cable)

100 meters maximum

(160.8 meters: fiber cable)

100 meters maximum