2-Broadband Networks and ATM

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IEEE Communications standards*

Standard Also known as Medium Access Topology /frequency band

IEEE 802.3 LAN/Eathernet Metcalfe /Xerox CSMA/CD Star to olo

IEEE 802.4 LAN (developed by General motors) Token Bus Bus topology

IEEE 802.5 LAN (developed by IBM) Token Ring Ring topology

  . . .

IEEE 802.15.1

IEEE 802.15.4

PAN/Bluetooth (developed by

Ericsson)

PAN/ZigBee/WSN (Wireless Sensor

--   ISM band at 2.4GHz

ISM bands**

 RF

 &

 2.4GHz

e wor s --

IEEE 802.16d 

IEEE 802.16e

IEEE 802.16j

BWA/Fixed WiMAX

BWA/Mobile WiMAX

BWA/Relay WiMAX

OFDM

OFDMA

OFDMA

2 GHz to 66 GHz (initially 10 GHz

to 66 GHz was allocated for LOS

 but to support NLoS 2 GHz to 11

IEEE 802.16m BWA/Very high data rate OFDMA GHz was allocated later)

IEEE 802.20 MBWA/Mobile-Fi ( Will support

connectivity up to 250 km/h mobile

-- Licensed Bands (below 3.5 GHz)

*IEEE provides communication standards for Physical & MAC layer only

** ZigBee operating frequencies 868 MHz in Europe, 915 MHz in the USA and Australia, and 2.4 GHz rest of  the world

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• Broadband networks can be classified as

 –  Wide Area Network (WAN) (Transports signals over longdistances)• Optical fiber backbone network

• ease nes

• Satellites Communication

• Telecommunication networks (BS to BS or backbone network)

 – Access network (BS or local exchange to customer • Cable modem , DSL & ADSL

•  

• WiMAX

• Telecommunication Networks from BS to MS (3G networks likeUMTS/CDMA 2000)

BS=Base StationMS= Mobile Station

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  . as tec no ogy

• WiMAX stands for Worldwide Interoperability for Microwave Access

• WiMAX forum is a non-profitable group

• WiMAX forum ensures the interoperability of devices developed by various

vendors using IEEE 802.16 specifications

• WiMAX forum Promote the development and deployment of WiMAX

systems

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• CBR constant bit rate:

• VBR(Variable bit rate)• ABR (Available Bit Rate:-minimum guarantee rate)

• UBR (Unspecified bit rate: Traffic is allocate to all)

• Services based on type of QoS (Quality of Service)

 –  UGS (Unsolicited Grant Service)

 –  ert s extended real time ollin service

 –  rtps (real tile polling service)

 –  nrtps (non real time polling service)

 –   

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CIF/SIFD= connection

 Identifier/Subscriber

 identifier

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•

• Internet

• ATM

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• Developed by Metcalfe's (Xerox company got patent)

• MAC address (48 bits) is used as address of a device.• CSMA/CD is used for multiple access.

•  

• Pure Eathernet is no more in use, at present combination of Eathernet andn erne s use n .

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• Develo ed b IETF

• TCP/IP protocol suite covers network and transport layers.

• IP address are used for addressing of devices.

• Packet size is variable

• Two versions IPv4 (32 bits) and IPv6 (128 bits) are available

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 • Developed by ITU-T

• Combination of best features of circuit switched & acket

switched networks• It uses asynchronous time division multiplexing

• Packet size is fixed (53 Bytes = 5 header +48 payload)

• ATM is a vital part of B-ISDN, SONET and several

telecommunication backbone/backhaul network technolo ies.

• It’s a Virtual Circuit switched network (connection oriented)

(three phases are Set-up connection, transfer data and tear down

connection)

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• The ATM reference model is com osed of the followin lanes

which span all layers: –  Control —This plane is responsible for generating and managing

.

 –  User —This plane is responsible for managing the transfer of data.

 –  Mana ement — This 

lane contains

 two

 com onents:

• layer management that manages layer‐specific functions, such as the 

detection of  failures and protocol problems 

•  

system.

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 • The ATM reference model is composed of three ATM layers:

 –  h sical la er: mana es the medium-de endent transmission 

 –  ATM Layer: provides cell multiplexing, cell-switching and routing services. To dothis, it uses the VPI and VCI information in the header of each ATM cell.

 –  ATM adaptation layer: segments the data into 48-byte cell payloads.

• There are five types of ATM Adaptation Layers (AAL)

 –  AAL1: (CBR) used for voice and videoconferencing

 –  AAL2: (VBR) real time or non real time voice or video bursts in nature

 –  AAL3 and AAL 4:VBR services, supports both connection‐oriented and 

connectionless data

 –  AAL5: used for Data services, supports both

 connection

‐oriented

 and

 connectionless data, example IP over ATM.

• Which AAL is used in a cell is not encoded in the cell, it is negotiated

 between end devices prior to data transmission

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ATM Virtual Connections

Virtual Paths

Physical Link

Virtual Channels

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Exam le of Virtual ath & Virtual Channel in ATM

NN: Network Node

CPN: Customer

 Premise

 Node

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1. ATM network is organized as a hierarchy.

User’s e ui ment connects to networks via a U I User-Network  

Interface). Connections between provided networks are made through NNI

- .

2. ATM is connection-oriented .

A connection (an ATM channel) must be established before anycell/Packet transmission.

3. Two levels of ATM connections:

virtual channel connections

4. Indicated by two fields in the cell header:

virtual path identifier (VPI)

virtual channel identifier (VCI)

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Private 

UNI

Private ATM 

network ATM Network Architecture

X   X

Private 

NNI Public ATM 

X   X

network A

X

NNI

Public 

UNI

     X

B‐ICI Public ATM 

network B

     X     X

Public 

UNI

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ATM Network Architecture Two types of networks are included in the ATM architecture:

Private Networks: Customer Premises Networks, permit the use of lower

traffic speed

Public Networks : supports Wider area

UNI: User to Network Interface

 NNI: Network to Network Interface (Three types of NNI)

 NNI-ISSI   Inter‐Switchin

 S stem

 Interface

 that connects switches in the

same Local Transport Area

 NNI-ICI (Inter Carrier Interface) that connects ATM networks of different

carriers

Private NNI that connects different switches in a private network.

BICI: Broadband Inter Carrier Interface

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UNI Cell Format

GFC (4 bits) VPI (4 bits)

VPI (4 bits) VCI (4 bits)

VCI (8 bits)

CLP 

ATM cell header

VCI  4  its PT  3  its(1 bit)

HEC (8 bits)

Payload 

(48 bytes)

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 GFC (4 bits): Generic Flow Control

"uncontrolled access" this field is set to all zeroes

controlled access t is ie is set to all ones w en congestion as occurre .

VPI (8 bits): Virtual Path Identifier VCI (16 bits): Virtual Channel Identifier 

PTI 3 bits : Pa load T e

use information or Layer Management Information

CLP (1 bit): Cell Loss Priority

Indicates the cell's priority in the ATM selective loss algorithm. Set by the initiatingequ pmen , w en s se o , e ce s g ven pre erence over ce s w se o

1 during cell discarding (loss) process.

HEC (8 bits): Header Error Control

Provides a capability to correct all single bit errors in the cell header as well as the

detection of the majority of multiple-bit errors.Payload (48 Bytes): User or management Data

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Pa load T e 3 bits) 

cont.

•The first bit indicates the type of ATM cell that follows. A first bit set to

0 n cates user ata; a t set to 1 n cates operat ons, a m n strat on &

management (OA&M) data.

 journey from source to destination. This bit is also called the Explicit

Forward Congestion Indication (EFCI) bit. The second bit is set to 0 by

cell, it sets the bit to 1. After it is set to 1, all other switches in the path

leave this bit value at 1.

Destination ATM end oints can use the EFCI bit to im lement flow

control mechanisms to throttle back on the transmission rate until cellswith an EFCI bit set to 0 are received.

•The third bit indicates the last cell in a block for AAL5 in user ATM

cells. For non-user ATM cells, the third bit is used for OA&M functions.

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 VPI (12 bits): Virtual Path Identifier 

VCI (16 bits): Virtual Channel Identifier 

PTI (3 its): Pay oa Type

use information or Layer Management Information

CLP 1 bit : Cell Loss Priorit

Indicates the cell's priority in the ATM selective loss algorithm. Set by the initiating

equipment, when this set to 0, the cell is given preference over cells with CLP set to 1.

  s : ea er rror on ro

Provides a capability to correct all single bit errors in the cell header as well as the

detection of the majority of multiple-bit errors.

Payload (48 Bytes): User or management Data

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Data transmission through ATN network 

User 

information

User 

information

AAL   AAL

ATM   ATMATM   ATM

PHYPHY   PHY   PHY

…

End system   End

 systemNetwork

Cell Switching and Routing is performed in ATM Layer