1. FDDI

2. FDDI was produced by ANSIX 379.5 during 1980.
It is used to connect the local area network such as [ethernet and token ring].with high speed connectivity of computers in local area.
In FDDI we use an optical fiber for transmission of data.
It has high security ,reliability and speed,long distance of transmission of data.

3. FDDI stands for fiber distributed data interface .
FDDI uses a ring topology of multimode or an single mode optical fiber transmission.
It permits upto 500 stations.
It employs dual counter –rotating ring.
16/48 bit address are allowed.
FDDI is observed by station and released as soon it completes frame transmission.

4. It releases token after transmission.
Transmission on optical fiber requires ASK.(AMPLITUDE SHIFT KEYING)
Coding is done in the presence or absence of {Intensity modulation}.
1300 nm wavelength specified.
Dual ring transmit in an opposite direction.
Normally second ring is idle used for for automatic repair or backup .

5. FDDI DUAL RINGS
FDDI DUAL RING ARCHITECTURE
MARCH 6, 2003
FDDI 5

6. RINGS PRIMARY RING : it is used for the data transmission.
SECONDARY RING: it is always idle and it is used as backup when the primary ring fails.

9. MEDIA ACCESS CONTROL [MAC]: defines how an mediun is accessed it includes an frame format,error recovery mechanism,addressing.
PHYSICAL LAYER PROTOCOL [PHY]: defines data encoding and decoding procedure.
PHYSICAL LAYER MEDIUM [PMD]: it defines the characteristics of transmission medium,fiber optic links ,power levels,connectors etc..
STATION MANAGEMENT [SMT]: it tells about an fddi configuration ring configuration fault tolerances.

10. MODES
Modes are bundle of light rays entering into the fiber at a particular angle.
There are two modes of transmission of data they are 1)single mode 2).multimode
Single mode: allows only one mode of light to propagate through the fiber.
Multimode : it allows more than one mode of light to propagate through the fiber.

11. SINGLE MODE In single mode it has higher bandwidth .
Greater cable run distance.
Used in inter building connectivity.
Light generating device is LASERS.
Eg : transmission of data through a single mode optical fiber from a larger distance.

12. MULTIMODE MODE It has lower bandwidth.
And it is able to connect to only to a shorter distance.
Used in an intra building connectivity.
Light generating device is LED.

13. FRAME FORMAT

14. Preamble—Prepares each station for the upcoming frame.
Start delimiter—Indicates the beginning of the frame. It consists of signaling patterns that differentiate it from the rest of the frame

15. Frame control—Indicates the size of the address fields, whether the frame contains asynchronous or synchronous data, and other control information
Destination address—Contains a unicast (singular), multicast (group), or broadcast (every station) address. As with Ethernet and Token Ring, FDDI destination addresses are 6 bytes

16. Source address—Identifies the single station that sent the frame
Source address—Identifies the single station that sent the frame. As with Ethernet and Token Ring, FDDI source addresses are 6bytes.
Data—Contains either information destined for an upper-layer protocol or control information

17. Frame check sequence (FCS)—Filled by the source station with a calculated cyclic redundancy check (CRC) value dependent on the frame contents (as with Token Ring and Ethernet). The destination station recalculates the value to determine whether the frame may have been damaged in transit. If so, the frame is discarded.

18. End delimiter: Contains non data symbols that indicate the end of the frame.
Frame status: Allows the source station to determine if an error occurred and if the frame was recognized and copied by a receiving station.

19. FAULT TOLERANCES
FDDI provides a number of fault-tolerant features. The primary fault-tolerant feature is the dual ring.
If a station on the dual ring fails or is powered down or if the cable is damaged, the dual ring is automatically “wrapped” (doubled back onto itself) into a single ring.
In this figure, when Station 3 fails, the dual ring is automatically wrapped in Stations 2 and 4, forming a single ring.
Although Station 3 is no longer on the ring, network operation continues for the remaining stations.

21. FAILED WIRING

22. OPTICAL BYPASS SWITCH

23. Optical bypass switches can be used to prevent ring segmentation by eliminating failed stations from the ring.

24. TRAFFIC TYPES
Synchronous traffic can consume a portion of the 100-Mbps total bandwidth of an FDDI network, while asynchronous traffic can consume the rest.
Synchronous bandwidth is allocated to those stations requiring continuous transmission capability.
Such capability is useful for transmitting voice and video information, for example.
Other stations use the remaining bandwidth asynchronously. The FDDI SMT specification defines a distributed bidding scheme to allocate FDDI bandwidth.

25. ASYNCHRONOUS
Asynchronous bandwidth is allocated using an eight-level priority scheme. Each station is assigned an asynchronous priority level.
FDDI also permits extended dialogues, where stations may temporarily use all asynchronous bandwidth. The FDDI priority mechanism can essentially lock out stations that cannot use synchronous bandwidth.
Eg data traffic

26. Features of fddi Optical fiber. 100 mbps. Reliability specified.
4b/5b encoding.
Distributed clocking.
Target token rotation time.
New token after transmit.

27. FDDI APPLICATIONS Backbones for the factory automation.
Office automation at the desk top.
Work group and departmental LANS
Integrated transport for multimedia applications.
Campus LAN interconnection.

28. FDDI BENIFITS Higher bandwidth ( 10 times more than the ethernet).
It has very low attenuation.
Very difficult to tap the signals from the fiber cable.
No interference from the external radio frequencies and the electromagnetic noises.

30. Fddi limitations
High cost of optical components for the transmission and the reception of signals .(especially for single mode fiber networks).
More complex to implement than the existing of low speed LAN technologies such as an IEEE and IEEE 802.5

31. COMPARISON WITH OTHER NETWORKS
FEATURES
FDDI
ETHERNET
TOKEN RING
Transmission rate
Data rate
Maximum coverage
Maximum nodes
Signal encoding
125 mbaud
100 mbps
100 km
500
4B/5B
20 mbaud
10 mbps
2.5 km
1024
manchester
8 & 32 mbaud
4 & 16 mbps
Configuration dependant
250
Differential manchester