3Com TR - Manual (Page 24)

1-14 C HAPTER 1: O VERVIEW
High-speed Cascade Connectors
These connectors provide a high-speed cascade con-
nection between Switch 2000 TRs in a stack. You can
connect multiple units to form a single switched
domain. You can connect up to six Switch 2000 TRs
with these connectors.
A stack of Switch 2000 TRs act as a single multiport
switch. The setup configuration parameters are
shared among switches and the entire stack can be
managed and downloaded as a single IP entity.
Token Ring Switching Concepts
This section describes Token Ring Switching and
unique features of the Switch 2000 TR, including:
■ Why Token Ring Switching?
■ Source Route Bridging
■ Transparent Bridging
■ Source Route Transparent Bridging
■ Spanning Tree (802.1d and IBM)
■ Store-and-Forward
■ Cut-through
■
Dynamic Cut-through
■ Congestion Control
■
Workgroups
Why Token Ring Switching?
Existing Token Ring networks are built around shared
media technology and typically operate at 16 Mbps
wire speed. This 16 Mbps of bandwidth is shared
between all stations on the ring. As applications
become more sophisticated, or as work-stations
become more powerful, or as the number of users
per ring grows, the demand for bandwidth increases.
As a result, stations are limited not by their own pro-
cessing power but by the limitations of the physical
network.
In an effort to reduce the traffic per ring and increase
the overall bandwidth availability, existing rings have
been divided into multiple smaller rings. This division
provides more bandwidth per station.
With an optional FDDI or ATM downlink module,
Token Ring switching also solves problems found in
client-server applications where a shared 100 Mbps
(FDDI) or 155 Mbps (ATM) pipeline can provide easy
access to servers and WAN links.
The major benefits of Token Ring switching are:
■ Bandwidth relief
■ Migration path to high-speed technologies
■ Cost-effective method for achieving LAN intercon-
nectivity
Source Route Bridging (SRT)
Source Route Bridging is a method of allowing a ring
station (node) on a Token Ring network to communi-
cate with another ring station on a different ring
interconnected by bridges. The “source” ring station,
in other words, the node initiating the communica-
tion, is responsible for dynamically determining and
then maintaining information about the “route” to