Fddi
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FDDI Fiber Distributed Data Interface
By: Aziz Ur Rehman
FDDI Position in the OSI Reference Model
FDDI is defined as the two bottom layers of the seven-layer OSI reference model It provides a transport facility for higher-level protocols such as TCP/IP
Naser Tarhuni
2
FDDI Position in the OSI Reference Model Physical layer is subdivided into: physical-medium-dependent (PMD) sublayer defines the details of the fiber-optic cable used the physical (PHY) layer specifies encoding/decoding and clocking operation
Naser Tarhuni
3
Fiber Distributed Data Interface
Fiber Distributed Data Interface 100 Mbps token passing ring ANSI X3I9.5 not IEEE networks interconnecting computer systems and network FDDI applications include directly connecting workstations and servers in workgroups, and serving as a high-speed backbone to connect other networks in a building, in a campus environment, or in a city.
Naser Tarhuni
4
FDDI
FDDI networks are not used for wide area FDDI networks are not used for wide area networks where network radii typically exceed 100 km FDDI was very popular in networks that required 100 Mbps capability prior to 1996.
Naser Tarhuni
5
FDDI
Since 1996, 100 Mbps Ethernet/802.3 ( Fast Ethernet) and 1000 Mbps Ethernet/802.3( Gigabit Ethernet) technologies have displaced new FDDI installations. 100Mbps LAN and MAN applications Token Ring
Naser Tarhuni
6
FDDI MAC Frame Format
Naser Tarhuni
7
IEEE 802.3 Frame Format
Naser Tarhuni
8
Token Ring MAC Frame
Naser Tarhuni
9
Operation
Station seizes token by aborting token transmission Once token captured, one or more data frames transmitted New token released as soon as transmission finished (early token release in 802.5)
Naser Tarhuni
10
Naser Tarhuni
11
FDDI Physical Layer
Medium Optical Fiber Twisted Pair Data rate 100 100 Signaling 4B/5B/NRZI MLT-3 Max repeaters 100 100 Between repeaters 2km 100m
Naser Tarhuni
12
FDDI’s physical layer Specifications
FDDI’s physical layer is based on fiber-optic cable. Fiber runs cannot be longer than 2 km between nodes for multimode fiber and there is a total allowable distance of 100 km per FDDI ring ( two rings are allowed). Each ring consists of two fibers. Thus, two rings use four fibers. FDDI also supports copper cable via a related technology called CDDI, which stands for Copper Distributed Data Interface. CDDI supports both unshielded twisted-pair ( UTP) and shielded twisted-pair (STP).
Naser Tarhuni
13
FDDI’s physical layer Specifications
FDDI’s physical layer does not use Manchester encoding, which is used in Ethernet/802.3 and 802.5 LANs. FDDI uses a “group” encoding scheme known as the 4B/5B method, which stands for four bits in five baud, or four-bit to five-bit. The 4B/5B encoding method takes data in four-bit codes and maps them to corresponding five-bit codes. Naser Tarhuni
14
FDDI’s physical layer Specifications
These five-bit codes are then transmitted using a technique called NRZI, which stands for non-return to zero, invert on ones. FDDI Signaling
Uses an encoding scheme called 4B/5B Every four bits of data are sent as a 5 bit code Signal sources are LEDs or lasers
Naser Tarhuni
15
FDDI Rings
FDDI specifies dual rings for physical connections Traffic on each ring travels in opposite directions Rings consist of two or more point-to-point connections between adjacent stations Primary ring is for data transmission Secondary ring is for back up
Naser Tarhuni
16
Single-Attachment Stations
SAS Class B Attach to one ring ( primary) Attached through a concentrator. Provides connection for multiple SASs . Ensures that no one SAS can interrupt the ring
Naser Tarhuni
17
Single-Attachment Stations
Naser Tarhuni
18
Dual Attachment Stations
DAS Class A Attach to both rings Has two ports to connect to the dual ring Both ports connect to both the rings
Naser Tarhuni
19
Dual Attachment Stations
Naser Tarhuni
20
Advantages to FDDI
100 Mbps long cables are supported (up to 200 Km) built-in network management fair access through negotiation increased reliability of fiber optic, resistant to eavesdropping non-electric, maintains ground isolation between buildings cable cost comparable to UTP Naser Tarhuni
21
Disadvantages to FDDI
concentrators and boards are expensive substantial expertise needed to install and maintain
Naser Tarhuni
22
Differences: FDDI B/W 802.5
FDDI
802.5
Fiber, STP, UTP 100 Mbps MTU 4500 Bytes Fault Tolerant Dual Ring Distributed Clock Early Release
STP, UTP 4/16 Mbps MTU 4500-18K Bytes No fault tolerance built into spec Centralized Clock Release after receive
Naser Tarhuni
23
Support frames
To accommodate a mixture of stream and bursty traffic, FDDI is designed to handle two types of traffic:
Synchronous frames that typically have tighter delay requirements (e.g., voice and video) Asynchronous frames have greater delay tolerances (e.g., data traffic)
Naser Tarhuni
24
Applications
Mission critical requirements for fault tolerance LAN needs connectivity to MAN Need for high bandwidth Voice and video used where distance between stations are excess of 100 meter Locations where EMI and RFI Naser Tarhuni
25
Product and service providers
Cabletron systems DSI BayNetworks 3COM Madge
Naser Tarhuni
26
By: Aziz Ur Rehman
FDDI Position in the OSI Reference Model
FDDI is defined as the two bottom layers of the seven-layer OSI reference model It provides a transport facility for higher-level protocols such as TCP/IP
Naser Tarhuni
2
FDDI Position in the OSI Reference Model Physical layer is subdivided into: physical-medium-dependent (PMD) sublayer defines the details of the fiber-optic cable used the physical (PHY) layer specifies encoding/decoding and clocking operation
Naser Tarhuni
3
Fiber Distributed Data Interface
Fiber Distributed Data Interface 100 Mbps token passing ring ANSI X3I9.5 not IEEE networks interconnecting computer systems and network FDDI applications include directly connecting workstations and servers in workgroups, and serving as a high-speed backbone to connect other networks in a building, in a campus environment, or in a city.
Naser Tarhuni
4
FDDI
FDDI networks are not used for wide area FDDI networks are not used for wide area networks where network radii typically exceed 100 km FDDI was very popular in networks that required 100 Mbps capability prior to 1996.
Naser Tarhuni
5
FDDI
Since 1996, 100 Mbps Ethernet/802.3 ( Fast Ethernet) and 1000 Mbps Ethernet/802.3( Gigabit Ethernet) technologies have displaced new FDDI installations. 100Mbps LAN and MAN applications Token Ring
Naser Tarhuni
6
FDDI MAC Frame Format
Naser Tarhuni
7
IEEE 802.3 Frame Format
Naser Tarhuni
8
Token Ring MAC Frame
Naser Tarhuni
9
Operation
Station seizes token by aborting token transmission Once token captured, one or more data frames transmitted New token released as soon as transmission finished (early token release in 802.5)
Naser Tarhuni
10
Naser Tarhuni
11
FDDI Physical Layer
Medium Optical Fiber Twisted Pair Data rate 100 100 Signaling 4B/5B/NRZI MLT-3 Max repeaters 100 100 Between repeaters 2km 100m
Naser Tarhuni
12
FDDI’s physical layer Specifications
FDDI’s physical layer is based on fiber-optic cable. Fiber runs cannot be longer than 2 km between nodes for multimode fiber and there is a total allowable distance of 100 km per FDDI ring ( two rings are allowed). Each ring consists of two fibers. Thus, two rings use four fibers. FDDI also supports copper cable via a related technology called CDDI, which stands for Copper Distributed Data Interface. CDDI supports both unshielded twisted-pair ( UTP) and shielded twisted-pair (STP).
Naser Tarhuni
13
FDDI’s physical layer Specifications
FDDI’s physical layer does not use Manchester encoding, which is used in Ethernet/802.3 and 802.5 LANs. FDDI uses a “group” encoding scheme known as the 4B/5B method, which stands for four bits in five baud, or four-bit to five-bit. The 4B/5B encoding method takes data in four-bit codes and maps them to corresponding five-bit codes. Naser Tarhuni
14
FDDI’s physical layer Specifications
These five-bit codes are then transmitted using a technique called NRZI, which stands for non-return to zero, invert on ones. FDDI Signaling
Uses an encoding scheme called 4B/5B Every four bits of data are sent as a 5 bit code Signal sources are LEDs or lasers
Naser Tarhuni
15
FDDI Rings
FDDI specifies dual rings for physical connections Traffic on each ring travels in opposite directions Rings consist of two or more point-to-point connections between adjacent stations Primary ring is for data transmission Secondary ring is for back up
Naser Tarhuni
16
Single-Attachment Stations
SAS Class B Attach to one ring ( primary) Attached through a concentrator. Provides connection for multiple SASs . Ensures that no one SAS can interrupt the ring
Naser Tarhuni
17
Single-Attachment Stations
Naser Tarhuni
18
Dual Attachment Stations
DAS Class A Attach to both rings Has two ports to connect to the dual ring Both ports connect to both the rings
Naser Tarhuni
19
Dual Attachment Stations
Naser Tarhuni
20
Advantages to FDDI
100 Mbps long cables are supported (up to 200 Km) built-in network management fair access through negotiation increased reliability of fiber optic, resistant to eavesdropping non-electric, maintains ground isolation between buildings cable cost comparable to UTP Naser Tarhuni
21
Disadvantages to FDDI
concentrators and boards are expensive substantial expertise needed to install and maintain
Naser Tarhuni
22
Differences: FDDI B/W 802.5
FDDI
802.5
Fiber, STP, UTP 100 Mbps MTU 4500 Bytes Fault Tolerant Dual Ring Distributed Clock Early Release
STP, UTP 4/16 Mbps MTU 4500-18K Bytes No fault tolerance built into spec Centralized Clock Release after receive
Naser Tarhuni
23
Support frames
To accommodate a mixture of stream and bursty traffic, FDDI is designed to handle two types of traffic:
Synchronous frames that typically have tighter delay requirements (e.g., voice and video) Asynchronous frames have greater delay tolerances (e.g., data traffic)
Naser Tarhuni
24
Applications
Mission critical requirements for fault tolerance LAN needs connectivity to MAN Need for high bandwidth Voice and video used where distance between stations are excess of 100 meter Locations where EMI and RFI Naser Tarhuni
25
Product and service providers
Cabletron systems DSI BayNetworks 3COM Madge
Naser Tarhuni
26
