CABLING GUIDELINES ---------------------- These guidelines explain token ring cabling guidelines that are based on Thomas-Conrad's laboratory testing and field experience. These guidelines should result in reliable network performance if you follow them carefully. If you need a more detailed explanation than you find in here, consult one of the following documents: * IBM Cabling System Planning and Installation Guide (document GA27-3710-3). * Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) publication number 568, Commercial Building Telecommunication Wiring Standard (July 1991). * EIA/TIA Technical System Bulletin TSB-36, November 1991. All TIA standards, including TSBs, are available for a fee by calling IBM Global Engineering Documents. Cable Types ------------- These guidelines contain information about using the following types of token ring cabling in a network: * Shielded twisted-pair (STP): Type 1 or 2 shielded twisted-pair data grade cable and Type 6 shielded twisted-pair patch cable. * Unshielded twisted-pair (UTP): Type 3 unshielded twisted-pair cable. UTP cable is classified into the categories shown below. Category 5 cable is the most suitable for longer cable runs and inter-MAU connections, because it has the greatest bandwidth and the least susceptibility to noise and interference. Category 3 UTP, 10MHz bandwidth Category 4 UTP, 20MHz bandwidth Category 5 UTP, 100MHz bandwidth General Design Guidelines ---------------------------- In general, you should observe the following rules when designing or expanding a token ring network: * Use all STP (Types 1, 2 and/or 6) or all UTP (Category 3, 4 and/or 5) cable in a particular network. Mixing UTP and STP cable causes electrical impedance imbalances, which can result in errors and poor performance. * Category 3 UTP cable is not suitable for use near devices that cause electromagnetic interference, such as fluorescent lighting, electrical motors or elevators. * Use STP (Types 1, 2 or 6) or Category 4 or 5 UTP cable to interconnect MAUs within a wiring closet. * Use Type 1 STP or Category 5 UTP cable between wiring closets. NOTE -------- Theese guidelines allow for one wall connector at each end of the MAU-to-node connection, and for one punchdown block in the wiring closet. Avoid introducing additional cable discontinuity (for example, patch cables between wall connectors or additional punchdown blocks in wiring closets). Doing so tends to decrease signal quality and to introduce data errors. Calculating the Ring Length ----------------------------- To calculate token ring cable length, take the steps shown below. Each step is explained in more detail later. STEP ACTION 1 Measure the total cable length used to interconnect MAUs. Also measure the length of the longest MAU-to-node connection. Keep cable lengths separated by cable type. 2 Convert cable lengths to their Type 1 equivalents. 3 Add the Type 1 equivalent of the MAUs on the network. 4 The sum of the Steps 2 - 4 is the total length of the cable in your network. This total should not exceed the values in the tables shown later in these guidelines. Step 1: Measure Cable Length by Type ---------------------------------------- Measure the length of each type of cable used in MAU-to-MAU connections, and in the longest MAU-to-node connection. You can add the length of Types 1 and 2 STP cable together, since they are equivalent in distance calculations. Keep other cable types in separate categories. Step 2: Calculate the Type 1 Cable Equivalence -------------------------------------------------- Convert the measured cable distance to a Type 1 equivalent using the conversion factors shown in Table 1. Step 3: Calculate the Type 1 MAU Equivalence ------------------------------------------------ Count the total number of non-retiming MAUs (such as the TC4050) on the network. Multiply the total number of MAUs by 25 feet and add it to the total from Step 2. Omit from your count any MAUs that actively retime and regenerate the data signal (such as the IBM 8250). Step 4: Calculate the Total Ring Length ------------------------------------------- The sum of Steps 2 and 3 is your network's total ring length. If your total ring length is greater than the allowable lengths shown in the tables later in these guidelines, you need to take steps to reduce the amount of cabling in the network. Call Thomas-Conrad Technical Support for additional assistance. Support is available toll-free 24 hours-a-day, 7 days-a-week at (800) 334-4112. Conversion Factors and Network Limits --------------------------------------- Table 1 below shows how to convert cable lengths to their Type 1 equivalents: Table 1. Type 1 Conversion Factors If the cable is of this type: The conversion factor for Type 1 is: Type 1 or 2 STP n/a Category 3 or 4 UTP 2.25 Type 6 STP or 1.3 Category 5 UTP Table 2 below shows the maximum allowable total ring length for 4Mbps and 16Mbps token ring networks, after adjustment for MAUs. Type 1 equivalent lengths are shown. Table 2. Maximum Total Ring Length Ring Speed Maximum Total Ring Length (MAX) 4Mbps 1200 feet 360 meters 16Mbps 550 feet 168 meters Table 3 shows limits for 4Mbps token ring networks in which passive concentrators (Note 1) such as TC4050s are used: Table 3. Limits: 4Mbps Networks, Passive Concentrators (Note 1) Cable Type Maximum number of nodes Maximum Lobe Length (MLL) Type 1 STP 260 1000 feet 305 meters Cat. 3 UTP 72 328 feet 100 meters Cat. 4, 5 UTP 132 328 feet 100 meters Table 4 shows limits for 16Mbps token ring networks in which passive concentrators (Note 1) such as TC4050s are used: Table 4. Limits: 16Mbps Networks, Passive Concentrators (Note 1) Cable Type Maximum number of nodes Maximum Lobe Length (MLL) Type 1 STP 260 550 feet 168 meters Cat. 3, 4, 5 UTP 72 250 feet (Note 2) 76 meters Table 5 shows limits for 4Mbps or 16Mbps token ring networks in which active retimed concentrators (such as IBM 8250s) are used: Table 5. Limits: 4/16Mbps Networks, Active Retimed Concentrators Cable Type Maximum number of nodes Maximum Lobe Length (MLL) Type 1 STP 260 1000 feet 305 meters Cat. 3, 4, 5 UTP 132 328 feet 100 meters Note 1 - "Concentrator" is synonymous with "MAU" as used elsewhere in this manual; however, "concentrator" is more consistent with proposed IEEE standards. Note 2 - Currently, the IEEE 802.5 specification and IBM guidelines do not include support for Category 3 UTP cabling at 16Mbps. The values shown in this table are based on Thomas-Conrad testing and experience. Other Calculations -------------------- If you are expanding an existing network, you can use the formulas below to determine the Maximum Lobe Length or the longest Main Ring Length allowable on your network. However, you must never exceed the maximum values shown in the tables on the previous pages. MLL = MAX - MRL MRL = MAX - MLL MLL = Maximum Lobe Length. The maximum allowable length of any lobe (connection from a MAU to a node) in a particular token ring. This value must include adjustments for cable type as shown in Steps 2 and 3. The MLL must never exceed the limits shown in the tables on the previous pages. MRL = Main Ring Length. The maximum allowable sum of cable distances on the main ring (i.e., this length does not include the MLL), adjusted for cable type and MAUs as shown in Steps 2 and 3. MAX = Maximum Total Ring Length.