Black Box lt0007a-4u Guia De Especificaciones

Smart Lobe Access Units (RJ-45)

2-Port

UTP..................................................................LT0007A-2U

4-Port

UTP..................................................................LT0007A-4U
STP ...............................................................LT0007A-4SU

You may also need...
Unshielded Twisted-Pair Patch Cables (UTP) 

with Molded Boots, T568B, 4-Pair, RJ-45, CAT5e, PVC
Stranded, Beige..................................................EVNSL25E

Shielded Twisted-Pair Patch Cables (STP) 

with Snagless Boots, T568B, 4-Pair, RJ-45, CAT5, PVC
Stranded, Gray ......................................................EVNSL60

About Token Ring

Token Ring was developed in

the early 1980s by IBM

®

. In 1985,

the IEEE released document
number 802.5, which formally
accepted Token Ring as a
standard. Although its popularity
has been eclipsed by Ethernet,
Token Ring is nonetheless a
robust networking standard and is
still operating reliably in many
legacy networks.

Token Ring is most often used

in IBM mainframe environments.
IBM provides Token Ring
connections on much of its
mainframe computer hardware,
and its software enables PCs and
mainframes to act as peers on the
same network.

The name “Token Ring“ is

somewhat misleading. Although
its name implies a physical ring
shape, Token Ring is actually a
star-based topology. Logically, the
network operates as a ring—
“tokens“ bearing information are
passed from node to node until
the token travels completely
around the ring.

Token Ring networks are

interconnected via passive and
active hubs called Multistation
Access Units (MAUs). MAUs are
the fail-safe components of Token
Ring networks. If a cable or a
connection goes bad, the MAU
will drop that node from the ring.
This fail-safe hub arrangement
prevents a break from taking
down the entire network. Ring-
in/ring-out ports in each MAU can
be used to connect a ring to other
rings.

Token Ring repeaters are used

to extend distances within a ring.
Repeaters can increase either
main-ring or lobe lengths in a
Token Ring LAN. The main-ring
length is the distance between
MAUs. The lobe length is the
distance from MAU to
workstation.

The original Token Ring

specifications called for shielded
twisted-pair (STP) cable using
either a DB9 connector or a
unique square connector called
the IBM data connector. Later,
Token Ring was adapted to use
conventional unshielded twisted-
pair (UTP) cable with RJ-45
connectors. The most common
kinds of Token Ring cabling in use
to day are Type 1 and Type 6 STP
as well as Type 3 UTP.

Type 1 shielded twisted-pair

(STP) cable is the original wiring
for Token Ring. In Type 1 cabling,
each wire is constructed of 22
AWG solid copper. Type 1 cable is
not as flexible as Type 6 cable and
is generally used for long runs in
areas where twists and turns are
less likely, such as in walls or
conduits.

Type 6 Token Ring cable is a

lighter, more pliable version of
Type 1 cable. It’s constructed of
two stranded 26 AWG copper
pairs that are surrounded by an
overall braided shield. Type 6
cable is commonly used in offices
and open areas, and its flexible
construction enables it to
negotiate multiple twists and
turns.

Type 3 or UTP Token Ring

cabling uses the same twisted-
pair CAT3, CAT5, or CAT5e
cabling with RJ-45 connectors as
10BASE-T Ethernet.

Attaching older Type 1 Token

Ring to UTP Token Ring requires a
balun or adapter.
Two speeds

Token Ring operates at either

4 or 16 Mbps. While you can mix
speeds within one network, each
individual ring can operate at just
one speed. Simply put, you cannot
have 4- and 16-Mbps devices
operating in one ring.

Although it’s proven to be

reliable and fault-tolerant, Token
Ring has largely been supplanted
by Ethernet, and Token Ring
network devices are no longer
widely available. Additionally,
Ethernet LANs are less expensive
to build and operate than Token
Ring, Ethernet can provide far
greater bandwidth, and many
networking products simply do
not support Token Ring at all. The
sad reality is that Token Ring is
dying. Even IBM has walked away
from this standard.

For these reasons, system

administrators usually choose to
migrate their legacy Token Ring
networks to Ethernet by adding
new network segments as
Ethernet rather than Token Ring.

There are three different ways

to move from Token Ring to
Ethernet by interconnecting the
networks. The method you
choose depends on whether
you’re connecting a LAN or a
WAN and how much you want to
spend.

Keep in mind that no matter

how you connect the two
networks, they both must use the
same protocol. In other words,
they must speak the same
language, such as IP or IPX™.

An economical way to

combine Novell

®

IPX based Token

Ring and Ethernet networks is to
have them share a server. Just
install either a Token Ring NIC in
the Ethernet server or an Ethernet
NIC in the Token Ring server.
Then change the server’s
configuration to enable the
internal router program. While
this method is low cost, it adds
traffic and overhead to the server,
which can decrease overall
network performance.

An easy, standalone hardware

solution is to simply use an
Ethernet to Token Ring bridge
such as a BLACK BOX

®

Ethernet

to Token Ring Adapter (LBU9001-
US, LBU9002-US). Just connect
the bridge to your Token Ring
MAU and your Ethernet hub and
make sure that both networks
have the same network
identification— in essence, they
will become one logical network.
Also, since this is a solution for
LANs, both networks must be
close to each other.

Another choice for connecting

Token Ring and Ethernet is to use
a router to connect the two
networks over a wide-area link.
The router enables each network
to maintain its own unique
network identifier.