Cabletron Systems TOKEN RING TECHNOLOGY OVERVIEW
NOTICE Cabletron Systems reserves the right to make changes in specifications and other information contained in this document without prior notice. The reader should in all cases consult Cabletron Systems to determine whether any such changes have been made. The hardware, firmware, or software described in this manual is subject to change without notice.
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CONTENTS CHAPTER 1 INTRODUCTION USING THIS MANUAL .................................................................................................... 1-1 RECOMMENDED READING.......................................................................................... 1-1 CHAPTER 2 TOKEN RING OVERVIEW INTRODUCTION............................................................................................................. 2-1 TOKEN RING TOPOLOGY ..............................................................
CONTENTS TOKEN RING MANAGEMENT......................................................................................2-22 FRAME TYPES .............................................................................................................2-25 Fill Sequence ..........................................................................................................2-25 Abort Format ...........................................................................................................2-26 Token Format .
Chapter 1 INTRODUCTION Welcome to the Token Ring Network Technology Overview. It provides an introduction to Token Ring network concepts and physical components. USING THIS MANUAL Chapter 1, Introduction, provides an overview of this document and lists several reference documents related to Token Ring networks. Chapter 2, Token Ring Overview, covers basic concepts related to Token Ring network operation and design.
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Chapter 2 TOKEN RING OVERVIEW This chapter introduces Token Ring features and describes characteristics that distinguish Token Ring from other Local Area Network (LAN) technologies such as Ethernet and FDDI. INTRODUCTION The Token Ring network protocol is non-contention based, which means that because only one station on the network can send data at one time, stations do not have to compete for access to the transmission medium. This is controlled by token passing.
TOKEN RING OVERVIEW TOKEN RING TOPOLOGY The Token Ring topology, or logical shape, is a ring. A ring topology is a point-to-point network in which the network devices are connected, machine to machine, in an unbroken unidirectional circle. The Token Ring topology uses an access method called token passing. No station may transmit unless that station first possesses the token.
TOKEN RING OVERVIEW LOCAL AREA NETWORK STANDARDS Networking standardization has one goal: to allow systems to communicate with each other. This is particularly relevant to LANs where the two primary objectives are to permit common resource sharing and to allow interconnection of many different systems to the same physical medium. To achieve this, each system must conform to the same standard for using the LAN.
TOKEN RING OVERVIEW Physical (Layer One) This layer interfaces directly to the physical medium and is responsible for sending and receiving a stream of bits across that medium. It defines the electrical, mechanical, and signal characteristics to the medium. Data Link (Layer Two) This layer controls the flow of information between systems and the next adjacent system on the path to the final destination.
TOKEN RING OVERVIEW Application (Layer Seven) This layer provides access to the OSI environment and provides communication based services to the end users. Typical of the services it provides are file-transfer services, file-directory operations, and electronic messaging. All the subordinate layers of the model exist to support, and make possible, the activities of this layer.
TOKEN RING OVERVIEW Access Method Communication between devices on a network requires that there be a common method for transmitting and receiving messages, and every device on the network must have the ability to talk at some point. Also, if two devices attempt to talk at the same time the data will become corrupted. Thus there are two conflicting requirements.
TOKEN RING OVERVIEW 8. Through the use of simple time-out circuits, the ring has a means of protection against a station that fails to pass the token on. 9. An Active Monitor station ensures that these rules are being followed and can detect and recover from violations of these rules. Advantages of Token Ring The main advantages of using Token Ring are as follows: • It provides a deterministic performance specification, by which the access time (i.e.
TOKEN RING OVERVIEW PHYSICAL LAYER The Token Ring topology is characterized as a logically circular, unidirectional transmission path without defined ends. The physical topology is a star wired system with each station having its own cable running back to a central point. Although wired as a star, tracing of the cable run will reveal a continuous ring. The ring is most typically constituted by sets of MSAUs interconnected via their Ring In/Ring Out (RI/RO) ports.
TOKEN RING OVERVIEW Lobe Cable The lobe cable is used to attach a station the TCU on an MSAU. In practice lobe cabling can consist of various cable segments constituting the lobe-to-TCU connections. Segments typically include patch cables from the TCUs to the main wiring panel, the lengths of the main wiring to the station locations, and then patch cables from floor/desk sockets to the stations.
TOKEN RING OVERVIEW Ring De-Insertion If the station’s hardware adapter experiences a non-recoverable error, the phantom current will drop causing the relay on the MSAU to open. This breaks the circuit for that lobe and the station is then bypassed from the ring. Typical causes for this condition are the station being powered off, the lobe cable being unplugged, or an adapter hardware failure.
TOKEN RING OVERVIEW With Differential Manchester Encoding the sequence of signal polarities is completely dependent on the polarity of the second half of the previous bit cell time. If a bit to be transmitted during any given bit cell time is a 0 (zero), then the polarity of the first half of that bit cell time is opposite to that of the previous bit cell time, consequently as polarity changes occur at the start of the bit cell time as well as the forced mid-bit time.
TOKEN RING OVERVIEW when the AM loses power. The process to select a new AM is known as Monitor Contention. The process to select the new AM begins with one of several timers expiring indicating that either the current AM has failed or that some other network parameter has not been corrected by the current AM. The Monitor Contention process can be started by any station on the ring and begins as timers expire. As stations time out they immediately begin broadcasting Claim Token frames.
TOKEN RING OVERVIEW its transmit clock. This problem is known as Accumulated Jitter and is one of the main reasons for the limitations on the number of stations and repeaters on a ring. To overcome Accumulated Jitter an elastic buffer is set up by the Active Monitor, in addition to the Latency buffer. For a 4 Mbps ring the buffer is initiated at 3 bits and can grow to 6 bits or shrink to 0 bits. For 16 Mbps, the buffer is initialized at 16 bits and can grow to 32 bits or shrink to 0 bits.
TOKEN RING OVERVIEW Station Insertion The act of powering up a station does not immediately enable it to become part of the ring. Certain tests are performed while the adapter is being initialized by the software drivers. The basic tests are known as insertion tests. These tests are made whenever an attempt is made to open the Token Ring adapter. Lobe Test The Lobe Test involves the station sending a string of Lobe Media MAC frames on that station’s lobe.
TOKEN RING OVERVIEW Ring Poll Process If there is no duplicate address on the ring, the station participates in neighbor notification by learning its Nearest Active Upstream Neighbor (NAUN) and identifying itself to its nearest active downstream neighbor. The AM initiates process by sending out a broadcast AMP frame to its downstream neighbor. The downstream neighbor sets the address recognized and frame copied bits, stores the AM address, and generates a broadcast SMP frame to its downstream neighbor.
TOKEN RING OVERVIEW The Standby Monitor All other stations are Standby Monitors (SMs). The SMs verify that the AM is on the ring and performing its duties. Each SM checks for good tokens using the “Good Token Timer” (2.6s); the SMs also verify that the AM is transmitting an Active Monitor Present MAC frame using the Receive Poll Timer (15s). If an SMs’ Good Token Timer or Receive Poll Timer expires, the station issues a Claim Token MAC frame.
TOKEN RING OVERVIEW Therefore, the station with the highest address eventually receives its own Claim Token MAC frame back, allowing it to reissue a sufficient number (3) of successive Claim Token MAC frames to ensure the integrity of the ring. It then becomes the new AM. To ensure that all stations receive information about the AM status, an AMP MAC frame is transmitted by the AM on a periodic basis. When this timer expires in 7 seconds, an AMP frame is released by the AM.
TOKEN RING OVERVIEW • Station B still has a frame to transmit but it cannot capture the present token, which is set to priority 3; it only has a priority 1. As the token passes through Station B it sets the Priority reservation field to 1 again. Stacking Station Station D captures the token and transmits its frame. Station D has raised the service priority of the ring to 3, and is termed the Stacking Station. It notes in its reservation register that R was set to 1.
TOKEN RING OVERVIEW Each station on the ring, as it receives the PRG frame, cancels all timers and resets to normal repeat mode, if the frame cannot be copied. If the frame can be copied, action is taken according to the information field of the MAC frame. The information field contains the address of the Nearest Active Upstream Neighbor (NAUN). If the PRG frame successfully makes it around the ring, the monitor has been properly reset on the ring. A new token would then be issued by the monitor.
TOKEN RING OVERVIEW SOURCE-ROUTE BRIDGING METHOD Source-route bridging is the predominant method used for linking Token Ring LANs. Source-route bridging is a process whereby the source device, or the sending station, rather than the bridge determines the route to other stations used for sending messages.
TOKEN RING OVERVIEW Source Routing Upon receiving an SRF, a bridge looks for the following information in the RIF: • The ring number of the receiving port on the bridge • The bridge number • The ring number of the port on the bridge through which the bridge forwards the SRF If the bridge finds the above information, it transmits the SRF to the next ring. However, a bridge discards the SRF if any of the following situations exist: • The bridge does not find the above information.
TOKEN RING OVERVIEW TOKEN RING MANAGEMENT According to the IEEE 802.5 standards, each ring station or Network Interface Card (NIC) has the ability to perform the following network management functions: • Monitor soft and hard errors • Maintain details of the configuration, such as the Nearest Active Upstream Neighbor (NAUN) • Control various parameters such as the token priority, ring number, etc. The above functions are the normal features installed by each manufacturer.
TOKEN RING OVERVIEW Claim Token Process (CL_TK) All stations are capable of being the AM, while others remain as SMs. The establishment of an AM is achieved by a Ring Station (RS) detecting the absence of an AM and originates a Claim Token, also known as Monitor Contention. The conditions on which a Claim Token MAC frame are issued are when either the standby monitors Good Token Timer or Receiver Poll timers have expired.
TOKEN RING OVERVIEW Remove Ring Station (REMOVE) The CRS transmits this frame to a certain station when unconditional removal of that station is required. Report Error (ERROR) Any station transmits this frame to the REM when a timer expires. Report Active Monitor Error (ACTIVE-ERROR) When a Purge or AMP is received by the AM that it did not transmit, or when a Claim Token is received the AM transmits this frame to the REM.
TOKEN RING OVERVIEW Request Ring Station State (RQ_STATE) This frame is transmitted by any of the management servers to a station. It is a request for information of the state of the station. Response (RSP) This frame is transmitted by any station to acknowledge receiving, or to report errors in a MAC frame. FRAME TYPES Bit sequences are transmitted onto the ring in clearly defined groups known as frames. Most frames carry fields of information that are common to all frame types.
TOKEN RING OVERVIEW Abort Format This frame sequence shown in Figure 2-4 is used by a station to terminate its transmission prematurely. The Starting Delimiter (SD) and Ending Delimiter (ED) formats are the same as used for token and data frames. The sequence can be detected by any station at any stage in a frame transmission even if it does not occur in octet boundaries.
TOKEN RING OVERVIEW Starting Delimiter (SD) The SD is always the same pattern of 8 bits - J K 0 J K 0 0 0. Both J and K violate the Differential Manchester Encoding scheme since they have no mid-bit polarity transition. J has the same polarity as the previous bit and K has the opposite polarity of the preceding bit. Access Control (AC) The AC field shown in Figure 2-5 has the following format: PPP | T | M | RRR Where PPP are the priority bits.
TOKEN RING OVERVIEW Ending Delimiter (ED) The ED has the following format: JK1JK1|I|E The first 6 bits, J K 1 J K 1, are always the same. Note that the J and K bits are non-data symbols and violate the Differential Manchester Encoding scheme. I is the Intermediate Frame bit which notes if the frame is part of a multiple frame transmission. If this bit is set to 0 then the frame is the last or only frame in the transmission sequence. If set to ‘1’ then it is the first of several or an intermediate frame.
TOKEN RING OVERVIEW SD AC FC DA SA INFO FCS ED FS FCSC SFS EFS SFS = Start of Frame Sequence FCSC = Frame Check Sequence Coverage EFS = End of Frame Sequence Figure 2-6. Data Frame Structure Start of Frame and End of Frame Sequences The SD and AC fields are referred to as Start of Frame Sequence (SFS), and the ED and FS fields as the End of Frame Sequence (EFS). Frame Control (FC) The Frame Control field shown in Figure 2-7 defines the type of frame and certain MAC and information frame functions.
TOKEN RING OVERVIEW SD AC FC DA SA INFO FCS ED FS Note that ‘r’ bits are reserved. FF ZZZZZZ FF = Frame Bits 1x = reserved 01 = Data Frame 00 = MAC Frame with vector identifier ZZZZZZ = Control Bits Undefined rrrYYY = PDU priority rrrYYY = control value for each of 25 MAC frames and 17 extended IBM MAC frames Figure 2-7. Frame Control Field Format Destination Address (DA) The DA field shown in Figure 2-8 contains the address of the station or stations for which that frame is intended.
TOKEN RING OVERVIEW SD AC FC DA SA INFO FCS ED FS I/G U/L Ring# Station Address I/G bit = 0 - Individual station address I/G bit = 1 - Group node address U/L bit = 0 - Universal addressing, 46 bits in each station’s MAC PROM.
TOKEN RING OVERVIEW MAC INFORMATION FIELD MAC LLID MAC Subvector 4 bytes Variable Length MAC Subvector Variable Length Major Vector Length (LL) Variable Length Major Vector ID (MVID) Class Byte 2 bytes MAC Subvector Dest. Class Source Class 1/2 byte 1/2 byte Command Byte Specific Code Point 1 byte Figure 2-9. MAC LLID Field Format The Major Vector consists of a MAC length and ID (LLID) and 0, 1, or more MAC sub-vectors.
TOKEN RING OVERVIEW If the frame type is a MAC frame, all stations on the ring act on the state of ZZZ control bits of the Frame Control field. There are 25 MAC frames detailed in the standard. For example, 0002 indicates a beacon frame, 0005 is an AM present frame. MAC frames are used for network operation rather than transfer of higher layer data. Table 2-1 shows the YYY Control Bit values and functions. Table 2-1.
TOKEN RING OVERVIEW Table 2-1. YYY Control Bit Values and Functions (Continued) Major Vector ID (Hex) 2-34 MAC Frame Frame Control Field (Hex) Destination Class Source Class Subvector (HEX) 0C Change Parameters 00 Station Config. Report Server 03, 04, 05, 06, 07, 09 0D Initialize Ring 00 Station Ring Parameter Server 03, 04, 05, 09 0E Request Ring Station Address 00 Station Config. Report Server 09 0F Request Ring Station State 00 Station Config.
TOKEN RING OVERVIEW Table 2-1. YYY Control Bit Values and Functions (Continued) Major Vector ID (Hex) MAC Frame Frame Control Field (Hex) Destination Class Source Class Subvector (HEX) 28 Report Active Monitor Error 00 Ring Error Monitor Station 02, 0B, 30 29 Report Soft Error 00 Ring Error Monitor Station 02, 0B, 2D, 2E 2A Report Transmit Forward 00 Config.
TOKEN RING OVERVIEW Ring Parameter Server The ring Parameter Server is a network management function that resides on every ring in which the operational parameters are centrally managed. It serves two (2) purposes for the Token Ring network: • Target for all Request Initialization MAC frames that are sent by ring stations during attachment to the ring.
Chapter 3 TOKEN RING DEVICES AND APPLICATIONS This chapter lists severalToken Ring products available from Cabletron Systems and presents examples of how Token Ring devices can be used in a Token Ring network. These examples help clarify features of the devices and applications and do not illustrate all possible applications. Contact Cabletron Systems Technical Support Department if you have questions related to your specific network applications. Cabletron offers a variety of Token Ring network products.
TOKEN RING DEVICES AND APPLICATIONS Management Slot MIM Slots Management Slot MIM Slots MIM Slots MMAC-M3FNB Management Slot MMAC-M5FNB MMAC-M8FNB Figure 3-1. MMACs Concentrators Modular concentrators install in the MMAC and provide multi-station access to the main Token Ring network through lobe cabling connected at Trunk Coupling Unit (TCU) ports. These devices provide multiple TCU (or lobe) ports.
TOKEN RING DEVICES AND APPLICATIONS Media Flexibility and Conversion Token Ring networks can be wired with different types of media. Cabletron Systems series of Token Ring Port Interface Modules (TPIMs), shown and listed in Figure 3-2, provide a method to interchange port interfaces supporting different media types for devices that support TPIM installation. TPIM-F2/F3 TPIM-T2/T4 TPIM-T1 Figure 3-2. TPIMs TPIM specifications are listed in Table 3-1.
TOKEN RING DEVICES AND APPLICATIONS Token Ring Management Modules Cabletron provides network management modules that allow a network manager to monitor and control the Token Ring networks configured in the MMAC. These modules each provide one or more RS-232 communication ports from which management applications can be accessed with a VT-series terminal or a PC running a VT-series emulation program either directly via a console-cable connection or from a remote modem connection.
TOKEN RING DEVICES AND APPLICATIONS Ring In Ring Out Ring In MMMM MicroMMAC-T & STH Stack MMAC Ring Out Figure 3-3. Expanded Token Ring Network MULTIPLE TOKEN RINGS IN ONE MMAC More than one Token Ring can be configured in an MMAC. Cabletron Systems provides a variety of Media Interface Modules (MIMs) to provide flexibility in configuring and managing separate rings in an MMAC.
TOKEN RING DEVICES AND APPLICATIONS TRMMIM Ring Managed by TRMMIM TRMM Ring Managed by TRMM TRMM-4 Ring 1 Ring 2 Ring 3 Four Rings Managed by TRMM-4 Ring 4 Ring 4 Ring 3 Ring 2 Ring 1 TRMM Multiple Rings Configured via TRMM Chassis Management Application Figure 3-4.
TOKEN RING DEVICES AND APPLICATIONS Media interface Module 16 Mbps Ring Physical Bridge Link TRBMIM-T 4 Mbps Ring Figure 3-5.
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Chapter 4 TOKEN RING NETWORK CABLING This chapter provides an overview of the different cable types used for Token Ring networks. It covers basic cabling terminology and also performance and design specifications for shielded twisted pair (STP), unshielded twisted pair (UTP), and fiber optic cable types as specified by the ANSI/TIA/EIA-568-A standard. Figure 4-1 illustrates how different cable types can be used in a Token Ring network installation composed of Cabletron Systems Token Ring network products.
TOKEN RING NETWORK CABLING TERMINOLOGY This section covers some of the basic terminology used in reference to Token Ring cabling concepts. Attentuation Attenuation is the loss of signal strength in a cabling system. It is typically expressed in dB per unit lengths. The attenuation of PVC insulated cable varies significantly with temperature. At temperatures greater than 40°C, we strongly recommend that you use plenum-rated cables to ensure that cable attenuation remains within specification.
TOKEN RING NETWORK CABLING Patch Panel A patch panel is a device that serves as a junction for interconnecting lobeand trunk-cable segments. RJ Connector A RJ, or registered jack, connector is the original telephone-line connector now used extensively in networks. The RJ connector predominantly used for Token Ring implementation is the RJ45 connector. Station A station is any device on the ring, which can include a terminal, PC, bridge, or router, for example, capable of transmitting and receiving data.
TOKEN RING NETWORK CABLING STP CABLE SPECIFICATIONS The following is a summary of cable specifications that apply to STP cabling used with Cabletron Systems Token Ring products. Product changes could produce differences between this summary and the individual product specifications. Always refer to the specific product installation guide for current specifications.
TOKEN RING NETWORK CABLING Table 4-1.
TOKEN RING NETWORK CABLING Cable Connectors Medium Interface Connector (MIC) The MIC, shown in Figure 4-3, is typically found on IBM Type 6 and 9 patch cables. It has the capability to loop the transmission path back through the cable when it has been disconnected. Pinouts EMALE DB-9 RECEPTACLE Black TX- 1 Orange TX+ 6 2 7 Green RX- 3 8 Red RX+ 4 9 5 Hermaphroditic (Genderless)Media Interface Figure 4-3.
TOKEN RING NETWORK CABLING RJ45 Connector The 8-pin telephone type RJ45 connector shown in Figure 4-5 is found on STP cable used for lobe and trunk connections to Cabletron Systems Token Ring products. The RJ45 port on the device wraps upon disconnection. RX+ 5 TX+ 6 7 8 4 RX3 TX2 1 Figure 4-5. RJ45 Connector and Pinouts UTP CABLE SPECIFICATIONS The following is a summary of specifications for UTP cabling used with Cabletron Systems Token Ring (UTP) products.
TOKEN RING NETWORK CABLING Recommended Maximum Cable Lengths and Stations Table 4-3 lists recommended trunk (RI/RO) and lobe lengths for UTP cable types used with active and passive Cabletron Systems products at 4 and 16 Mbps. It also lists maximum station supported. Table 4-3. Recommended Maximum Cable Lengths and Stations UTP Cat. 3/4 UTP Cat.
TOKEN RING NETWORK CABLING Fiber Optic Construction A fiber optic cable is composed of a pair of strands, one used for transmit and the other for receive. Each strand is composed of a core of glass or plastic enveloped in a layer of glass or plastic called cladding. The cladding is further enveloped in multiple layers of plastic or other materials that provide protection and reinforcement to the core and the cladding.
TOKEN RING NETWORK CABLING Multimode There are two types of multimode fiber optic cable: step index and graded index. Both types are typically used for short-distance communications, shorter distances than are possible with single-mode fiber optic cable, that is. Step index fibers have an abrupt change in the index of refraction going from the core into the cladding, whereas graded index fibers have an index of refraction that decreases gradually going from the core to the cladding.
