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  1. Introduction
  2. Network Topology
  3. Hardware Connections
  4. TCP/IP Ports and Addresses
  5. Network Protocol Levels
  6. Data Link Layer and IEEE
  7. Network Protocol Categories
  8. Repeaters, Bridges, Routers
  9. ARP and RARP Address Translation
  10. Basic Addressing
  11. IP (Network)
  12. TCP (Transport)
  13. UDP (Transport)
  14. ICMP
  15. Hardware Cabling
  16. Wireless media
  17. Outside Connections
  18. Ethernet
  19. Token Ring
  20. ARCnet
  21. AppleTalk
  22. FDDI
  23. IPX/SPX
  24. NetBEUI
  25. AppleTalk
  26. SNA
  27. Others
  28. Simple Routing
  29. More Complex Routing
  30. IP Masquerading
  31. Firewalls
  32. Domain Name Service (DNS)
  33. Virtual Private Networking
  34. DHCP
  35. BOOTP
  36. RPC and NFS
  37. Broadcasting and Multicasting
  38. IGMP
  39. Dynamic Routing Protocols
  40. Simple Mail Transfer Protocol (SMTP)
  41. Simple Network Management Protocol
  42. Network Services
  43. Installing Drivers
  44. Network Operating Systems
  45. Applications
  46. Wide Area Networks
  47. Backing up the network
  48. Fault Tolerance
  49. Troubleshooting
  50. Commonly used Network Ports
  51. Networking Terms and Definitions
  52. Networking RFCs and Protocols
  53. Further Reading
  54. Credits

Token Ring

Developed by IBM, Token Ring, is standardized to IEEE 802.5. Token Ring uses a star topology, but it is wired so the signal will travel from hub to hub in a logical ring. These networks use a data token passed from computer to computer around the ring to allow each computer to have network access. The token comes from the nearest active upstream neighbor (NAUN). When a computer receives a token, if it has no attached data and the computer has data for transmission, it attaches its data to the token then sends it to its nearest active downstream neighbor (NADN). Each computer downstream will pass the data on since the token is being used until the data reaches its recipient. The recipient will set two bits to indicate it received the data and transmit the token and data. When the computer that sent the data receives the package, it can verify that the data was received correctly. It will remove the data from the token and pass the token to its NADN.

Characteristics

Maximum cable length is 45 meters when UTP cable is used and 101 meters when STP is used. Topology is star-wired ring. It uses type 1 STP and type 3 UTP. Connectors are RJ-45 or IBM type A. Minimum length between nodes is 2.5 meters. Maximum number of hubs or segments is 33. Maximum nodes per network is 72 nodes with UTP and 260 nodes with STP. Speed is 4 or 16 Mps. Data frames may be 4,000 to 17,800 bytes long.

Hubs

A token ring network uses a multistation access unit (MAU) as a hub. It may also be known as a Smart Multistation Access Unit (SMAU). A MAU normally has ten ports. Two ports are Ring In (RI) and Ring Out (RO) which allow multiple MAUs to be linked to each other. The other 8 ports are used to connect to computers.

Token Ring Connections

Cables

UTP or STP cabling is used as a media for token ring networks. Token Ring uses an IBM cabling system based on American Wire Gauge (AWG) standards that specify wire diameters. The larger the AWG number, the small diameter the cable has.

Token ring networks normally use type 1, type 3 or regular UTP like cable used on ethernet installations. If electrical interference is a problem, the type 1 cable is a better choice. Cable types:

TypeDescription
1Two 22 AWG solid core pair of STP cable with a braided shield. This cable is normally used between MAUs and computers.
2Two 22 AWG solid core pair with four 26 AWG solid core of STP cable.
3Four 22 or 24 AWG UTP cable. This is voice-grade cable and cannot transmit at a rate above 4Mbps.
4Undefined.
5Fiber-optic cable. Usually used to link MAUs.
6Two 26 AWG stranded core pair of STP cable with a braided shield. The stranded-core allows more flexibility but limits the transmission distance to two-thirds that of type 1.
7Undefined.
8Type 6 cable with a flat casing to be used under carpets.
9Type 6 cable with plenum-rating for safety.

Beaconing

The first computer turned on on a token ring will be the active monitor. Every seven seconds it sends a frame to its nearest active downstream neighbor. The data gives the address of the active monitor and advertised the fact that the upstream neighbor is the active monitor. That station changes the packets upstream address and sends it to its nearest active downstream neighbor. When the packet has traveled around the ring, all stations know the address of their upstream neighbor and the active monitor knows the state of the network. If a computer has not heard from its upstream neighbor after seven seconds, it will send a packet that announces its own address, and the NAUN that is not responding. This packet will cause all computers to check their configuration. The ring can thereby route around the problem area giving some fault tolerance to the network.