LAN TECHNOLOGIES

S.T.D.Maduranga

• Ethernet• FIBER DISTRIBUTED DATA INTERFACE (FDDI)• Token Ring

Technology Options

Our Focus is Ethernet• History• Developed by Bob Metcalfe and others at Xerox PARC

in mid-1970s• Roots in Aloha packet-radio network• Standardized by Xerox, DEC, and Intel in 1978• LAN standards define MAC and physical layer

connectivity• IEEE 802.3 (CSMA/CD - Ethernet) standard – originally

2Mbps• IEEE 802.3u standard for 100Mbps Ethernet• IEEE 802.3z standard for 1,000Mbps Ethernet

Ethernet Standard Defines Physical Layer

Metcalfe’s originalEthernet Sketch

802.3 standard defines both MAC and physical layer details

Ethernet

• 10 Base 5 (Thicknet) (Bus Topology)

• 10 Base 2 (Thinnet) (Bus Topology)

• 10 Base T (UTP) (Star/Tree Topology)

• 10 Base FL (Fiber) (Star/Tree Topology)

Ethernet Technologies: 10Base2

10: 10Mbps; 2: under 185 (~200) meters cable length Thin coaxial cable in a bus topology

Repeaters used to connect multiple segmentsRepeater repeats bits it hears on one interface to its other interfaces: physical layer device only!

10BaseT and 100BaseT

• 10/100 Mbps rate• T stands for Twisted Pair• Hub(s) connected by twisted pair facilitate “star topology”• Distance of any node to hub must be < 100M

Fast Ethernet• 100 Mbps bandwidth• Uses same CSMA/CD media access protocol and packet format as in Ethernet.• 100BaseTX (UTP) and 100BaseFX (Fiber) standards • Physical media :-• 100 BaseTX - UTP Cat 5e• 100 BaseFX - Multimode / Singlemode Fiber• Full Duplex/Half Duplex operations.• Provision for Auto-Negotiation of media speed:

10 Mbps or 100Mbps (popularly available for copper media only).

• Maximum Segment Length• 100 Base TX - 100 m• 100 Base FX - 2 Km (Multimode Fiber)• 100 Base FX - 20 km (Singlemode Fiber)

Gigabit Ethernet• 1 Gbps bandwidth.• Uses same CSMA/CD media access protocol as in

Ethernet and is backward compatible (10/100/100 modules are available).

• 1000BaseT (UTP), 1000BaseSX (Multimode Fiber) and 1000BaseLX (Multimode/Singlemode Fiber) standards.

• Maximum Segment Length• 1000 Base T - 100m (Cat 5e/6)• 1000 Base SX - 275 m (Multimode Fiber)• 1000 Base LX - 512 m (Multimode Fiber) • 1000 Base LX - 20 Km (Singlemode Fiber)• 1000 Base LH - 80 Km (Singlemode Fiber

10 Gig Ethernet

• 10 Gbps bandwidth.• Uses same CSMA/CD media access protocol as in

Ethernet.• Propositioned for Metro-Ethernet• Maximum Segment Length• 1000 Base-T - Not available• 10GBase-LR - 10 Km (Singlemode Fiber)• 10GBase-ER - 40 Km (Singlemode Fiber)

IEEE 802.5 and Token Ring

• Proposed in 1969 and initially referred to as a Newhall ring.

• Token ring : a number of stations connected by transmission links in a ring topology. Information flows in one direction along the ring from source to destination and back to source.

• Medium access control is provided by a small frame, the token, that circulates around the ring when all stations are idle. Only the station possessing the token is allowed to transmit at any given time.

Token Ring Operation

• When a station wishes to transmit, it must wait for token to pass by and seize the token.

• One approach: change one bit in token which transforms it into a “start-of-frame sequence” and appends frame for transmission.

• Second approach: station claims token by removing it from the ring.• Frame circles the ring and is removed by the transmitting station.• Each station interrogates passing frame, if destined for station, it

copies the frame into local buffer. {Normally, there is a one bit delay as the frame passes through a station.}

Token Ring Networkwith star topology

IEEE 802.5 Token Ring

• 4 and 16 Mbps using twisted-pair cabling with differential Manchester line encoding.

• Maximum number of stations is 250.• Waits for last byte of frame to arrive before reinserting token on

ring {new token after received}.• 8 priority levels provided via two 3-bit fields (priority and

reservation) in data and token frames.• Permits 16-bit and 48-bit addresses (same as 802.3).

Token Ring

• Under light load – delay is added due to waiting for the token.

• Under heavy load – ring is “round-robin”• The ring must be long enough to hold the

complete token.• Advantages – fair access • Disadvantages – ring is single point of failure,

added issues due to token maintenance

Networks: Token Ring and FDDI

A

E

DC

B

FDDI Token Ring

FIBER DISTRIBUTED DATA INTERFACE (FDDI)

• PROJECT INITIATED IN OCTOBER 1982 BY JAMES HAMSTRA AT SPERRY (NOW UNISYS)

• TWO PROPOSALS FOR MEDIA ACCESS CONTROL (MAC) & PHYSICAL (PHY) LAYERS SUBMITTED IN JUNE 1983

• FDDI MAC BECAME AN ANSI STANDARD IN LATE 1986

• FDDI PHY WON ANSI STANDARDIZATION IN 1988• FDDI - II PROPOSAL WAS MADE IN EARLY 1986• FIRST PUBLIC DEMONSTRATIONS AT ADVANCED

MICRO DEVICES (AMD) IN 1989

FDDI BASIC PRINCIPLE• TOKEN RING NETWORK LIKE IEEE 802.5• TOKEN: A SPECIAL SEQUENCE OF BITS• TOKEN CIRCULATES AROUND THE RING• A STATION REMOVES THE TOKEN FROM RING BEFORE TRANSMISSION• AFTER TRANSMISSION, THE STATION RETURNS THE TOKEN TO THE RING• COLLISIONS ARE PREVENTED AS THERE IS ONLY ONE TOKEN IN THE RING

FIBER DISTRIBUTED DATA INTERFACE (FDDI)

FDDI ARCHITECTURAL MODEL

• ACCORDING TO THE OSI-RM, FDDI SPECIFIES LAYER 1 (PHYSICAL LAYER) AND PART OF LAYER 2 (DATA LINK CONTROL LAYER)

• THE PHYSICAL LAYER HANDLES THE TRANSMISSION OF RAW BITS OVER A COMMUNICATIONS LINK

• THE DATA LINK CONTROL (DLC) LAYER IS RESPONSIBLE FOR MAINTAINING THE INTEGRITY OF INFORMATION EXCHANGED BETWEEN TWO POINTS

FDDI - II

• SAME FEATURES AS BASIC FDDI (FDDI - I), INCLUDING MAXIMUM NUMBER OF MODES, 100 MBPS DATA TRANSFER BIT RATE, AND THE DUAL RING

• DEFINES THE PHYSICAL LAYER AND THE LOWER HALF OF THE DATA LINK LAYER SIMILAR TO FDDI-I

• FDDI-I SUPPORTS ONLY PACKET MODE (SYNCHRONOUS AND ASYNCHRONOUS) TRAFFIC, FDDI-II SUPPORTS BOTH PACKET DATA AS WELL AS ISOCHRONOUS DATA TRAFFIC (IN FDDI ISOCHRONOUS INDICATES A CLASS OF TRAFFIC FOR VOICE AND VIDEO

• THE SIMULTANEOUS SUPPORT OF BOTH PACKET AND ISOCHRONOUS TRAFFIC IS CALLED THE HYBRID MODE OF OPERATION

A FDDI BACKBONE NETWORK EXAMPLE

FEATURES FDDI ETHERNET TOKEN RING

TRANSMISSION RATE

125 MBAUD 20 MBAUD 8 & 32 MBAUD

DATA RATE 100 MBPS 10 MBPS 4 & 16 MBPS

SIGNAL ENCODING

4B/5B (80% EFFICIENT)

MANCHESTER (50%

EFFICIENT)

DIFFERENTIAL MANCHESTER

(50% EFFICIENT)

MAXIMUM COVERAGE

100 KM 2.5 KM CONFIGURATION DEPENDENT

MAXIMUM NODES

500 1024 250

MAXIMUM DISTANCE BETWEEN NODES

2 KM (MULTIMODE FIBER)

40 KM (SINGLE-MODE FIBER)

2.5 KM 300 M (RECOMMENDED

100 M)

COMPARISON WITH OTHER NETWORKS

………. THANK YOU ……….