FDDI is a 100 Mbps dual-ring fiber optic network that uses counter-rotating primary and secondary rings. It uses single-mode or multi-mode fiber, with single-mode using lasers and multi-mode using LEDs. FDDI defines MAC, PHY, PMD and SMT specifications. ISDN is an international standard for digital phone lines that supports up to 64 Kbps data transfer for basic rate interface and higher for primary rate interface, allowing transmission of voice and data over phone lines.

1. FDDI & ISDN
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2. FDDI
The Fiber Distributed Data Interface (FDDI) specifies a 100-Mbps
token-passing, dual-ring LAN using fiber-optic cable.
FDDI is frequently used as high-speed backbone technology
FDDI uses a dual-ring architecture with traffic on each ring flowing in
opposite directions.
The dual-rings consist of a primary and a secondary ring.
During normal operation, the primary ring is used for data transmission,
and the secondary ring remains idle.
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CSED, TU

3. FDDI
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4. FDDI uses counter-rotating primary and secondary rings
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5. Fiber is Immune
FDDI uses optical fiber as the primary transmission
medium, but it also can run over copper cabling (CDDI).
In particular, security, reliability, and performance all are
enhanced with optical fiber media because fiber does not
emit electrical signals.
Fiber is immune to electrical interference from radio
frequency interference (RFI) and electromagnetic
interference (EMI).
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CSED, TU

6. Mode
FDDI defines two types of optical fiber: single-mode and
multi-mode.
A mode is a ray of light that enters the fiber at a particular
angle
Multi-mode fiber uses LED as the light-generating devices,
while single-mode fiber generally uses lasers.
Modal Dispersion
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CSED, TU

7. Light sources differ for single-mode and multi-mode fibers
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CSED, TU

8. FDDI's four specifications
Media Access Control (MAC):- Defines how the medium is accessed,
including frame format, token handling, addressing, algorithms for
calculating cyclic redundancy check (CRC) value, and error-recovery
mechanisms
Physical Layer Protocol (PHY):- Defines data encoding /decoding
procedures, clocking requirements, and framing
Physical-Medium Dependent (PMD):- Defines the characteristics of the
transmission medium, including fiber-optic links, power levels, bit-error
rates, optical components, and connectors.
Station Management (SMT):- defines FDDI station configuration, ring
configuration, and ring control features
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CSED, TU

9. FDDI Station-Attachment Types
FDDI defines three types of devices:-
Single-attachment station (SAS)
Dual-attachment station (DAS)
Concentrator
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CSED, TU

10. A concentrator attaches to both the primary and
secondary rings
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CSED, TU

11. A Ring recovers from a station failure by wrapping
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12. A Ring also wraps to withstand a Cable failure
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13. The optical bypass switch uses internal
mirrors to maintain a network
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CSED, TU

14. A Dual-homed configuration
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CSED, TU

15. FDDI Frame Format
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16. FDDI Frame Fields
Preamble---A unique sequence that prepares each station for an upcoming frame.
Start Delimiter---Indicates the beginning of a frame.
Frame Control---Indicates the size of the address fields and whether the frame contains asynchronous
or synchronous data.
Destination Address---Contains a unicast (singular), multicast (group), or broadcast (every station)
address. As with Ethernet and Token Ring addresses.
Source Address---Identifies the single station that sent the frame.
Data---Contains control information.
Frame Check Sequence (FCS)---Filed by the source station with a calculated cyclic redundancy
check value dependent on frame contents (as with Token Ring and Ethernet). The destination address
recalculates the value to determine whether the frame was damaged in transit. If so, the frame is
discarded.
End Delimiter---Indicate the end of the frame
Frame Status---Allows the source station to determine whether an error occurred and whether the
frame was recognized and copied by a receiving station.
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CSED, TU

17. ISDN
Integrated Services Digital Network
An international communications standard for sending voice, video,
and data over digital telephone lines or normal telephone wires.
ISDN supports data transfer rates of 64 Kbps (64,000 bits per second).
There are two types of ISDN.
Basic Rate Interface (BRI)
Primary Rate Interface (PRI)
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CSED, TU

18. ISDN
ISDN is a circuit-switched telephone network system, which also
provides access to packet switched networks, designed to allow digital
transmission of voice and data over ordinary telephone copper wires,
resulting in potentially better voice quality than an analog phone can
provide.
Delta-channel, the channel in an ISDN connection that carries control
and signaling information.
Bearer-channel, the main data channel in an ISDN connection. Basic
Rate ISDN (BRI) service consists of two 64 Kbps B-channels
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CSED, TU

19. Reference
http://www.pulsewan.com/data101/fddi_basics.htm
http://www.webopedia.com/TERM/F/FDDI.html
http://www.webopedia.com/TERM/I/ISDN.html
http://en.wikipedia.org/wiki/Integrated_Services_Digital_Network
http://www.webopedia.com/TERM/B/B_channel.html
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CSED, TU