CIS 304
LAN Hardware/Wiring & Installation

Lesson 7 - Exploring Token Ring Specifications

Instructor: Michael P. Harris

  Key Terms  
Token Ring
IEEE 802.5
MAU
4 & 16 Mbps
node repeater
NAUN
beacon
BIA, LAA
IRQ, I/O addr
Shared RAM
DMA channel
Data Rate
boot ROM
non-contention
token-passing
8228 MAU
RI, RO
relay switch
setup tool
DB-9 connector
Type-1 connector
RJ-45 connector
patch cables
adapter cables
IBM Type 1, 2, 3
IBM Type 6, 8, 9,
small movable
large non-movable
stranded conductors
solid-wire conductors
UTP Token Ring
min patch cable
max patch cable (MAUs)
max patch cable (ALL MAUs)
max patch cable (MAU & node)
maximum nodes (both)
maximum MAUs (both)
cable types (both)
media filter
Application: Token Ring Cable (LAB)
All images are "clickable" links to larger, clearer images.

[Top] Token Ring

Token Ring 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.

As shown below, 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.

[Top] Token Ring Board Settings

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 below.

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 card comes with a diagnostic disk that provides testing for the adapter. Refer to the appropriate documentation for your card for more detailed instructions.

[Top] Token Ring Cabling

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 closet jumpers).

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 larger networks.

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 Units.

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 PAIRS AWG USE
1 Solid,
twisted
22 Data
2 Type 1 plus
(4) voice pairs
22 Data &
Voice
6 Stranded,
twisted
26 Patch
8 Solid,
parallel
26 Under
carpet
9 Solid,
twisted
26 Plenum

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 components.

  • 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.

[Top] Node/Distance/MAU limitations

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.

[Top] Token-Ring Trouble Shooting

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 source.

  • 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 the MAU.

  • 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 is used.

  • 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.

[Top] Application Project:

We will be building a typical Token Ring adapter cable for this lesson project.

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.


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Last modified Aug 15
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