Multitech CommPlete MR9600-100, User Manual

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1 Introduction
CommPlete Communications Server 7
technology such as stackable hubs, coupled with the decreasing cost of switches, bridges, and routers,
allow the design of low-cost, efficient Fast Ethernet workgroups and enterprise LANs.
The following factors strongly influence the architecture of Fast Ethernet networks:
•
The EIA/TIA 568 Wiring Standard imposes a 100 meter limit on horizontal runs of twisted-pair cables;
that is, connections from the wiring closet to the end-station.
•
Fast Ethernet’s increased operational speed reduces the maximum distance between all elements of the
LAN (see below).
•
The EIA/TIA 568 Wiring Standard does not support the use of coaxial cables for horizontal wiring.
Network
The network diameter, which is the distance between two end-stations in the same collision domain, is the
primary difference between traditional Ethernet and Fast Ethernet. Due to the increased speed in Fast
Ethernet and adherence to the EIA/TIA 568 wiring rules, the network diameter of a Fast Ethernet collision
domain is limited to 205 meters; in contrast, the maximum 10BASE-T Ethernet collision domain diameter
can be up to 2500 meters.
Hubs
While 10BASE-T hubs are all functionally identical, Fast Ethernet hubs are divided into two distinct types:
Class I and Class II. A Class I hub repeats all incoming signals on one port to the other ports by first
translating them to digital signals and then retranslating them back to line signals. These translations are
necessary when connecting various network media to the same collision domain, such as when combining
two wire-pair 100BASE-TX media with four wire-pair 100BASE-T4 media. Only one Class I hub can exist
within the same collision domain, thus this type of hub cannot be cascaded. A Class II Hub (or
“repeater”), on the other hand, immediately repeats all incoming line signals on one port to the other
ports; no translations are performed. This type of hub connects identical media to the same collision
domain; for example, TX to TX. At most, two Class II hubs can exist within the same collision domain.
The cable used to cascade these hubs is called an inter-repeater link (IRL).
As mentioned earlier, stackable hubs can be used to increase the number of available nodes in a collision
domain. An entire hub stack counts as a single hub (repeater).
Connectivity Rules
•
The maximum length of a twisted-pair segment (that is, distance between a port in the hub to a single-
address network device such as a PC, server, or LAN switch) is 100 meters.
•
The maximum diameter in a collision domain is about 205 meters using two Class II hubs (or hub
stacks) and 200 meters using one Class I hub.
•
Between any two end-stations in a collision domain, there may be up to three segments and two Class
II hubs or two segments and one Class I hub.
Switching Technology
Switching is fast becoming the industry standard for pushing the limits of existing Ethernet networks. A
switch bridges Ethernet packets between Ethernet and Fast Ethernet LAN segments at the MAC address
level of the Ethernet protocol.