Workgroup Switches
T
o
k
e
n-Ring
www.networking.ibm.com
120
C
Investment Protection —
Asset Protection
The 8270 provides a cost-effective
alternative solution to address your
Token-Ring LAN performance
requirements. With a minimum
disruption to existing networks, and
only minimal additional investment
in network infrastructure components,
you can go a long way in addressing
current LAN performance
requirements.
Supports full-duplex
communication
The 8270 supports full-duplex commu-
nication with LAN stations equipped
with full-duplex Token-Ring adapters.
Full-duplex Token-Ring connections
can provide up to twice the bandwidth
(up to 32 Mbps) of standard half-duplex
connections. A typical bandwidth
would benefit using the IBM 8270 by
placing each of its high-volume
servers on workstations on shared
segments and placing client worksta-
tions on shared segments using
standard Token-Ring concentrators,
such as the IBM 8239 Token-Ring
Stackable Hub.
Source-routing switch
To support high-performance switch-
ing in source-route Token-Ring
networks, IBM has developed a new
technology called “source-route
switching”. This technology is opti-
mized to take advantage of the
inherent benefits of source routing
without forcing the user to manually
configure “ring and bridge” numbers
for each port on the Token-Ring switch.
The 8270 functions similarly to a
multiport bridge, forwarding frames
among its ports. One key advantage of
being a source-routing switch is that all
ports appear to be on the same logical
ring. This switch does not require any
ring and bridge number; therefore, the
8270 substantially reduces the
configuration burden on the network
administrator, for both initial setup as
well to support ongoing network
changes. IBM has taken a leadership
role within the IEEE in defining and
developing standards for source-route
switching technology.
Spanning tree support
The 8270 supports the transparent
Spanning Tree implementation that is
fully compliant with the IEEE 802.1d,
allowing the 8270 to effectively
participate in complex configurations.
It also provides the capability of having
several IBM 8270s interconnected with
redundant paths without having to
administer source-route bridging and
ring numbers. When more than one of
the ports are connected to the same
physical Token-Ring segment, the
Spanning Tree support in the 8270 will
configure only one of the ports in
forwarding mode; the rest of the ports
will be in blocking mode.
Source-route bridging
With the source-route bridging
function, an 8270 can transport frames
between Token-Ring LAN segments
with different ring numbers. The Token-
Ring LAN ports of a Token-Ring switch
can be divided into non-overlapping
groups called virtual switches. The
physical Token-Ring LAN segments
within a single domain all have the
same ring number. Ordinarily, no traffic
is switched between virtual switch
domains. However, when the source
route bridging function is enabled,
Token-Ring traffic can be transported
among any of the domains within a
switch. This function is comparable to
an internal, multiport source-route
bridge where each domain is con-
nected to the internal bridge via a
logical bridge port.
Auto-sense/auto-configure
With the 8270s adaptive cut-through
capabilities, it can be self-healing and
self-optimizing when media quality
problems arise, affecting overall
network reliability and performance.
Additionally, for each of its Token-Ring
ports, the 8270 will automatically sense
what type of Token-Ring connection is
being employed on each of its ports,
whether there are connections:
• To a shared media segment via a
Token-Ring concentrator
• To a dedicated media segment, directly
to a Token-Ring LAN station
• Operating in half-duplex or full-duplex
mode
•Operating at 4 Mbps or at 16 Mbps
• Another IBM 8270, 8272 or 8270 Module
in an IBM 8260
The auto-sense/auto-configure
capability minimizes the network
administrative burden associated with
both initial installation and ongoing
network changes and helps assure
that you can easily get optimum use of
your network without always having to
manage the large number of configura-
tion variables.
Installation and usability
The 8270 processor card has three
LEDs on its faceplate that indicate the
operational status of the switch as well
as a serial port that can be used for
status display and operational control.
Additionally, a four-character display is
provided on the Token-Ring processor
card faceplate that visually provides
more detailed information about the
operational status of the switch. The
8270 shipping carton has been
specifically designed for hot-staging in
the carton to allow the switch to be
configured and tested under power in
a staging location before shipment to a
final destination for installation.
