Lesson #7: Exploring Token-Ring Specifications
Token-Ring networks uses a non-contention token-passing
architecture that adheres to the IEEE 802.5
standard. The topology is physically a star, but logically uses a ring to
pass the token from station to station. Each node must be attached to a
hub/concentrator called a multistation access unit
(MAU or MSAU).
Token-Ring network interface cards (NICs) can run at
4 Mbps or 16 Mbps. 4 Mbps cards can run only at that data rate.
However, 16 Mbps cards can be configured to run at 4 or 16 Mbps. All cards on
a given network ring must be running at the same rate.
All images are "clickable" links to larger, clearer images.
As shown above, each node acts as a repeater
that receives token and data frames from its nearest
active upstream neighbor (NAUN). After a frame is processed by
the node, the frame is passed (rebroadcast) downstream to the next attached
node. Each token makes at least one trip around the entire ring. It then
returns to the originating node. Workstations that indicate problems send a
"beacon" to identify an address of
the potential failure.
NOTE: On a Novell® LAN,
to find out if any beacon messages have been sent on your Token-Ring network,
review your System Error Log found in SYSCON through Supervisor Options.
As with the Ethernet cards, the node address on each NIC is
"burned in" (BIA) at the manufacturer and is unique
to each card. The node address in some cases can be overridden by vendor
specified software instructions (this is called a Locally Administered
Address - LAA). A maximum of two Token-Ring cards can be
installed in any node, with each card being defined as the primary or
alternate Token-Ring card in the machine. A typical Token-Ring card is shown
The common features of a Token-Ring NIC are:
- Interrupt (IRQ)
- I/O address (Primary or Secondary)
- Shared RAM address
- Shared RAM size
- Data Rate (4Mbps or 16Mbps)
- DMA channel
- 9-pin female connector
- (optional RJ-45 connector)
- Remote boot PROM socket
The interrupt (IRQ), I/O address, and
shared memory address on each Token-Ring NIC must be set to avoid
conflicts with all other components. The DMA channel
may or may not be sharable depending on your system.
Each Token-Ring NIC comes with a diagnostic disk that provides testing
for the adapter. Refer to the appropriate documentation for your card
for more detailed instructions.
IBM defines Token-Ring cabling in terms of two types of systems:
- Small movable
- Large non-movable
The Small Movable system supports up to
96 workstations and file servers and 12 MAUs. It uses Type 6 cable
to attach workstations and servers to IBM Model 8228 MAUs.
Type 6 cable is a shielded twisted pair (STP) cable with
stranded conductors. this cable is flexible,
but has limited distance capabilities. the characteristics of this cable
make it suitable for small networks and for patch cords (wiring
the large non-movable system supports
up to 260 workstations and file servers, with up to 33 MAUs. this network
configuration uses IBM Type 1 or Type 2 cable. these are
shielded twisted pair cables with solid-wire conductors
suitable for carrying signals greater distances than are possible
with Type 6. the large non-movable system also involves other wiring
needs such as punch panels or distribution panels, equipment racks for MAUs,
and wiring closets to contain the previously listed components.
the Multistation Access Unit (MAU) is the central cabling
component for IBM Token-Ring networks. the 8228 MAU
was the original wiring hub developed by IBM for Token-Ring networks.
the figure above shows an example of a network cabling several workstations
and 8228 MAUs. the distances noted in the figure are based on the rules for
the small, movable cabling system. Each 8228 has ten connectors,
eight of which accept cables to workstations or servers. the other connectors
are labeled RI (ring in) and RO (ring out)
. the RI and RO connectors are used to connect multiple 8228s to form
MAUs are mechanical devices that consist of relays and connectors. their
purpose is to switch workstations in and out of
the network. Each port is controlled by a relay powered by a voltage
sent to the MAU from the NIC. When an 8228 is first set up, each of these
relays must be initialized with a setup tool
(sometimes referred to as a phaser) shipped with the unit. the setup tool is
inserted into each port and held there until a light indicates that the port
is properly initialized (charged).
STUDY NOTE: Remember that when
talking about Token-Ring; MAU and MSAU both refer to Multistation Access
IBM Token-Ring networks use two (or three) types of connectors. NICs are
equipped with a female (DB-9) nine-pin
connector (only four pins are used) and/or an RJ-45 connector. MAUs,
repeaters, and most other equipment use a special IBM
Type-1 unisex data connector. (Newer Token-Ring cards and MAUs use
RJ-45 connectors and CAT5 UTP cabling).
IBM STP Cable|
Type 1 plus
(4) voice pairs
Two standard types of cables are employed as follows:
Patch cables have IBM data connectors at both ends.
these cables interconnect MAUs, repeaters, and most other Token-Ring
Token-Ring adapter cables have an IBM Type-1
unisex data connector at one end and a nine-pin connector at the other.
Adapter cables connect workstation and server NICs to other network
components that use IBM data connectors.
When you are connecting a Token-Ring network, make sure that you
do the following:
Initialize each port in the 8228 MAU by using the setup tool shipped
with the MAU (wait for the click) before connecting a cable.
If using more than one MAU, connect the ring out (RO) port of each MAU
with the ring in (RI) port of the next MAU in the loop. this must
physically complete the ring.
A variety of rules must be observed when configuring a Token-Ring LAN. the
following rules apply to Token-Ring networks:
these additional configuration rules apply to a
small movable Token-Ring cable system:
A large non-movable Token-Ring cable system is
subject to the following rules:
- Maximum 260 nodes
- Maximum 33 MAUs
- Uses Type 1 or Type 2 cable
NOTE: Token-Ring networks also
can be cabled using UTP (CAT5) cable. the IEEE 802.5
standard describes 4 Mbps Token-Ring using IBM Type 3 UTP cable (equivqlent
to CAT3). However, CAT4 or CAT5 cable must be used for 16 Mbps Token-Ring.
When using UTP wiring with older non-UTP cards, a
media filter must be installed between the NIC and the UTP
cable. Some newer Token-Ring NICs have built-in media filters and RJ-45
jacks ready to interface with UTP wiring.
When trouble shooting Token-Ring networks, look for the following:
Any base I/O, DMA shared memory, or Interrupt conflicts
with other boards.
the version of the workstation or server software driver
to make sure that its revision level is compatible with your NIC. Drivers
are different for file servers and workstations.
Make sure that the MAUs are connected properly, with ring
out ports connecting to ring in ports throughout the ring.
Some MAUs other than the 8228 are active and require a
power supply. these MAUs fail if they have a blown fuse or a bad power
Check that patch cables are correctly attached to the
adapter cable. Patch cables connect MAUs together. Another type of
connecting cable is called an adapter cable which connects the NIC to
You may have a failed NIC. try substituting another one
known to work properly.
Determine if the MAU or the MAU port is bad. Ports may
need to be reinitialized with the setup tool.
Check to see if a 16 Mbps card is inserted into a 4 Mbps
ring or vice versa. Neither situation is correct.
Determine if the wrong type of cable for speed of network
Examine the pins on the adapter cable to see if they are
bent or broken.
If you are overriding the burned-in network addresses, it
is possible that duplicate node addresses may be set.
If connecting to a 4 Mbps twisted pair network, check the
Type 3 media filter.
We will be building a typical Token-Ring adapter cable for this
From your LAN-Wire materials kit locate the:
- 6' length of IBM Type 6 cable
- 1 IBM unisex data connector
- 1 DB-9 male (pin) connector
- 1 DB-9 hood
- 4 (or more) DB male pins
- 1 DB Insertion/Extraction tool
the unisex IBM Type-1 data connector is on both sides of a patch cable or
on one side of an adapter cable. this unique IBM connector is unisex
in that two of the same connector with attach to each other. You will find
these connectors on the standard IBM 8228 MAU, in patch panels, and in the
walls of most pre-wired token-ring installations. Installing the unisex IBM
data connector is a learning experience even for the most ardent cable
installer. Some data connector kits come with 45, 90, and 180 degree cable
exit strain reliefs. You will only use one. this snap-together kit looks easy
to assemble at first, and is easy after you develop a little
finesse. Do make sure that the cable color coded wire pairs for the
"Christmas Pair" (receive) and "Halloween Pair" (transmit)
are correctly inserted into the built-in punch-down block (use the punch-down
block slide as a color code guide). A common mistake is to leave out the
metal ferrule strain relief or the strain relief collar. You may have to
assemble/disassemble this data connector several times. When done properly
the snap-together unit looks clean and is very rigid. Two pieces in the kit
can be ignored until after assembly, the dust cover (with attachment loop)
and the installation lock (usually beige in color).
the node side of the Token-Ring adapter cable is a standard DB-9 male
connector using only pins 1, 5, 6, & 9 (the outside narrow edge pins).
Assembling this end of the cable is the same as installing any DB type
connector. Make sure you follow the wiring diagram and connect the
"Christmas Pair" (Red &
Green) to pins 1 & 6 respectively and the
"Halloween Pair" (Black & Orange
) to pins 5 & 9 respectively. You will need to use a pin crimp
tool to install the male pins. Be sure to crimp the rear fingers of the pin
around the insulation of the stripped wire for strain relief and crimp the
front fingers around the conductor for a positive connection. After all four
pins have been crimped on and inspected, use the Insertion/Extraction tool to
insert the pins into the DB-9 connector as per the color code diagram. Be
sure to inspect and re inspect the color coding at the data connector end and
the DB-9 end. After the pins have been inserted and inspected, attach the
DB-9 hood. Be sure to secure the strain relief of the hood.
We will test the Token-Ring adapter cable two ways. First, you will use
the digital multimeter to test for continuity and correct wiring. Second,
you will disconnect one of the adapter cables from one of the nodes on the
Token-Ring LAN, reconnect your cable, power up the workstation,
and log on to the file server.