IEEE Standards,FDDI,

Collision Free Protocols

Taranum Shaikh-45

Samidha Rane-40

Deepali Patil-34

Priyanka Warekar-57

IEEESTANDARDS

802.3

The Institute of Electrical and Electronics Engineers (IEEE) publish widely accepted LAN- recommened standards

IEEE 802

IEEE 802.1 (Inter-

networking)

IEEE 802.2 (LLC)

IEEE 802.3 (Ethernet CSMA/CD)

IEEE 802.4 (Token Bus)

IEEE 802.5 (Token Ring)

IEEE 802.6 ( DQDB )

ETHERNET : IEEE 802.3

To fully understand IEEE802.3 standard , it is important to understand where it fits in a layered design and how it relates to other topics.

Network operations mainly performed on lowest 3 layers of OSI model.

The Data Link Layer perform services for the network layer & assumes the existence of the physical layer.

The DDL is responsible for accurate communication between 2 nodes in a n/w.

This involves frame formats, error checking and flow control.

DDL further divided into 2 sublayers:1. Logical Link control(LLC)2. Medium Access Control(MAC)

Network Layer

LLC

MAC

Physical Layer

IEEE 802.2 standard

Data link layer

IEEE 802.2 standard

Fig. Data Link Layer refinement

MEDIUM ACCESS SUBLAYER

1. Pure Aloha

2. Slotted Aloha

3. Carrier Sense Multiple Access (CSMA)

4. CSMA with Collision Detection

IEEE 802.3 (CSMA/CD)

The best known scheme for controlling a LAN on bus structure is CSMA/CD.

Many people incorrectly use the name ‘Ethernet’ to refer all CSMA/CD protocols,even though it really refers to a specific product that implements 802.3 stds.

ETHERNET: - It is a type of cabling & signaling specification - It uses a cable sharing process called CSMA/CD.- The media access protocols deal with the data collisions that can occur

when different nodes on the n/w attempt to send the data at the same time.

Advantages: # Inexpensive way to get highspeed upto 100 Mbps.# Supports various wiring technologies.# Easy to install

DLL provides the logic to control the CSMA/CD network. Its functions are: - Data Encapsulation / Decapculation: It provides source & destination address . Keeps track of error detection & error correction field.

- Media Access Mgmt .: It transmits frame into physical layer & receives from it. It provides buffers to frame.

- Data Encoding / Decoding: At transmitting side it encodes binary data stream to self clocking code. At receiver side, it decodes to binary code.- Channel Access : Senses a carrier on channel indicating channel status. Detects collision on channel on transmission station.

Fig. Table IEEE 802.3 Cable Standards

Medium option

Transmission Media

Signaling Technique

Data rate (Mbp)

Max. seg. Length(m)

1 10Base5 Coaxial Cable Baseband (Manchester)

10 500

2 10Base2 “ “ “ “ 10 185

3 10Base5 Unshielded Twisted pair

“ “ 1 250

4 10BaseT “ “ “ “ 10 100

5 10Broad36 Coaxial Cable Broadband (DPSK)

10 3600

6 10BaseF Fiber optics Baseband 10 2000

Format of IEEE 802.3 CSMA/CD frame

SFD DA SA length LLC data pad FCSpreamble

Preamble:7-octet pattern of alternating 0 and 1’sSFD:start frame delimeterDA:destination addressLength:length of LLC data fieldLLC Data:data unit supplied by LLCPad:octets added to ensure that the frame is of size appropriate for CD operationFCS:frame check sequence

IEEESTANDARDS

802.4

IEEE STANDARD 802.4:TOKEN BUS

TOKEN BUS

• LAN standards

• Arranged in a logical ring

• Highest numbered station may send the first frame

• Passes permission to its immediate neighbor

• Used a special control frame called token

90 50 120

400

75

PHYSICAL TOPOLOGY

50

75

90120

400

LOGICAL SEQUNCE OF TOKEN PROCESSING

TOKEN BUS FRAME FORMAT

IEEESTANDARDS

802.5

IEEE STANDARD 802.5-TOKEN 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.

Fig: A Ring Network

Unidirectional ring

Stations

Ringinterface

Token Ring Operation

• Token Passing Method– When any station wants to send the frame , it seizes the token & transmit

the frame to intended station.

• Priority and Reservation– Station which wants to transmit the frame may reserve the token by

entering its priority code in Access Control(AC) field of the token or data frame

• Time Boundation– For each station, the token holding time is 10 milliseconds.

• The Monitor Station– Monitor Station sets the timer on– If the token does not regenerate in the allotted time , it is assumed to be

lost & then monitor station generates a new token.

Wire Center

Bypass relay

Fig: 4 Stations Connected via Wire Center

Wire Center• Token ring has one difficulty that all stations have to be ON for

passing token.• This problem is solved using Wire Center

IEEE 802.5-Token Ring Frame FormatToken Frame Format

• SD - Starting Delimiter• AC - Access Control

– Four subfields• Priority bit field• Token bit field• Monitor bit field• Reservation bit field

• ED - Ending Delimiter

SD AC ED

1 1 1

Data Frame Format

• FC Frame Control– Consist of two bit fields

• First bit indicates type of information• Remaining seven bits contains information about token ring logic

• Destination address & Source Address– Consists of physical address

• Data– Contains data to transfer

• Checksum– Used to detect errors

• FS – Frame Status

SD AC FC Destination Address

Source Address Data Checksum ED FS

~ ~~ ~

1 1 1 2 or 6 2 or 6 No limit 4 1 1

IEEESTANDARDS

802.6

IEEE STANDARD 802.6-DISTRIBUTED QUEUE BUS (DQDB) MAN

• DQDB specification designed to be used in MAN• Architecture of DQDB

1 2 3 N

Bus A

Bus B

Direction of flow on Bus A

Direction of flow on Bus BHeadend

Headend

FDDI

FIBER DISTRIBUTED DATA INTERFACE

+

FDDI Network that Data flows

Same Network after the station has failed

FDDI Frame Format

Preamble

Destination Address

Source Address

Data Checksum

Byte

>= 8 2 or 6

No limit2 or 6

4 11

Frame control

Starting Delimiter

Frame Status

Ending Delimiter

• Preamble:-Preamble field is 8 bytes long. It is used to synchronize the

receiver’s clock with sender’s clock.• Starting Delimiter(SD) and Ending Delimiter(ED):

- The starting delimiter and ending delimiter fields mark the frame boundaries.

• Frame Control -FC field defines the frame type (whether data or control frame).

• Destination Address(DA) and Source Address(SA):-DA and SA fields are 2 bytes or 6 bytes or 6 bytes of length and

both are same as ……• Data • Checksum

COLLISION FREE PROTOCOLS

Collision Free Protocols

Bit-Map Protocol Binary Countdown

A Bit- map protocol

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

8 Contention Slots

Frames

8 Contention Slots

Frames

1 11 1 3 7 1 511

A Bit- map protocol

0 1 2 3 4 5 6 7

1 4

0 1 2 3 4 5 6 7

1 1 1 1 11 0 1 2 3 5 7

d

N slots

N/2 slots

• Reservation protocols.• Low numbered station must wait on average 1.5N slots.• At low loads only d/(d+N) efficient.

• High numbered station must wait on average 0.5N slots.• At high loads d/(d+1) efficient.

Binary Countdown

0 0 1 0

0 1 0 0

1 0 0 1

1 0 1 0

Station

0 1 2 3

Bit Time

0

0

1

1

0

0

0

1 0

Result 1 0 1 0

• It was used in data kit.

• Higher numberes station have higher priority.

• The channel efficiency is d/(d+ log2N)

Binary Countdown

• Mok and Ward(1979)– Variation of binary countdown using parallel

interface– Virtual station numbers

Binary Countdown

Station

7 6 5 4 3 2 1 0Priority

Station

Priority 7 6 5 4 3 2 1 0

C H D A G B E F

C H A G B E F D

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