Token Ring Cabling

Token Ring Cabling

Traditional Token Ring networks use twisted-pair cable. The following are standard IBM cable types for Token Ring:

Type 1. A braided shield surrounds two twisted-pairs of solid copper wire. Type 1 is used to connect terminals and distribution panels or to connect between different wiring closets that are located in the same building. Type 1 uses two STPs of solid-core 22 AWG wire for long, high data-grade transmissions within the building’s walls. The maximum cabling distance is 101 meters (331 feet).
Type 2. Type 2 uses a total of six twisted-pairs: two are STPs (for networking) and four are UTPs (for telephone systems). This cable is used for the same purposes as Type 1, but enables both voice and data cables to be included in a single cable run. The maximum cabling distance is 100 meters (328 feet).
Type 3. Used as an alternative to Type 1 and Type 2 cable because of its reduced cost, Type 3 has unshielded twisted-pair copper with a minimum of two twists per inch. Type 3 has four UTPs of 22 or 24 AWG solid-core wire for networks or telephone systems. Type 3 cannot be used for 16 Mbps Token Ring networks. It is used primarily for long, low data-grade transmissions within walls. Signals don’t travel as fast as with Type 1 cable because Type 3 doesn’t have the shielding that Type 1 uses. The maximum cabling distance (according to IBM) is 45 meters (about 148 feet). Some vendors specify cabling distances of up to 150 meters (500 feet).

Type 3 cabling (UTP) is the most popular transmission medium for Token Ring. A Token Ring network using Type 3 (UTP) cabling can support up to 72 computers. A Token Ring network using STP cabling can support up to 260 computers.

The minimum distance between computers or between MSAUs is 2.5 meters (8 feet).

A patch cable is a cable that connects MSAUs. Patch cables are typically IBM Type 6 cables that come in standard lengths of 8, 30, 75, or 150 feet. (A Type 6 cable consists of two shielded 26-AWG twisted-pairs.) You can also get patch cables in custom lengths. You can use patch cables to extend the length of Type 3 cables or to connect computers to MSAUs. Patch cables have an IBM connector at each end.

Token Ring adapter cables have an IBM data connector at one end and a nine-pin connector at the other end. Adapter cables connect client and server network adapters to other network components that use IBM data connectors. The type of connectors you’ll need for a Token Ring network depends on the type of cabling you’re using. Type 3 cabling uses RJ-11 or RJ-45 connectors. (Media filters, if necessary, can convert the network adapter to RJ-11 or RJ-45 format.) Meanwhile, Type 1 and 2 cabling use IBM Type A connectors.

Token Ring networks come in a few sizes and designs. A small movable Token Ring system supports up to 12 MSAUs and uses Type 6 cable to attach clients and servers to IBM Model 8228 MSAUs. Type 6 is flexible but has limited distance capabilities. The characteristics of Type 6 cable make it suitable for small networks and for patch cords.

A large nonmovable system supports up to 260 clients and file servers with up to 33 MSAUs. This network configuration uses IBM Type 1 or Type 2 cable. The large nonmovable system also involves other wiring needs, such as punch panels or distribution panels, equipment racks for MSAUs, and wiring closets to contain the previously listed components.

The MSAU is the central cabling component for IBM Token Ring networks. The 8228 MSAU was the original wiring hub developed by IBM for Token Ring networks. Figure 4.16 shows 8228 MSAUs. Each 8228 has ten connectors, eight of which accept cables to clients 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.

8228s are mechanical devices that consist of relays and connectors. Their purpose is to switch clients in and out of the network. Each port is controlled by a relay powered by a voltage sent to the MSAU from the client. When an 8228 is first set up, each of these relays must be initialized with the setup tool that is shipped with the unit. Insert the setup tool into each port and hold it there until a light indicates that the port is properly initialized.

Figure 4.16 shows an example of a network cabling several clients and MSAUs. The distances noted in the figure are based on the rules for the small movable cabling system.

When you connect a Token Ring network, make sure you do the following:

1.	Initialize each port in the 8228 MSAU by using the setup tool shipped with the MSAU.
2.	If you’re using more than one MSAU, connect the RO port of each MSAU with the RI port of the next MSAU in the loop. Complete the loop so that the MSAUs form a circle or ring.