Definition A new Technology Fixed size packets called CELLS Streamlined: minimal error and flow control Small cells compared to other technologies.

Definition

Definition

A new Technology

Fixed size packets called CELLS

Streamlined: minimal error and flow control

Small cells compared to other technologies

High speed multimedia networking; carry traffic at a speed up to 622Mbps

ATM Standards are done Primarily by the ATM Forum; Cisco systems, NET/ADAPTIVE, Northern Telecom, and Sprint in 1991.

End of Module

ATM Architecture

WAN& LAN

Common LAN/WAN Architecture

allowing ATM to be used consistently

from one desktop to another.

WAN

DS-3 ATM PROBE and OC-3 ATM PROBE have a job of a router

ATM Architecture

Multiple switches and interfaces connecting ATM devices

ATM Architecture

Two Types of Interfaces that interconnect ATM devices over point to point links:

User-Network Interface (UNI)

Network-Network Interface (NNI)

Third Type of Interface connect two public switches from different public networks:

Broadband Inter-Carrier Interface (BICI)

ATM Architecture

User-Network Interface

• UNI link connects an ATM end-system (client side) with an ATM switch (network site).

• ATM UNI standards specify how a user connects to the ATM network to access these services.

ATM Architecture

Network-Network Interface

• Also called Network Node interface (NNI).

• NNI link connect two ATM switches; in this case; both sides are network.

• NNI supports class of service-sensitive routing and bandwidth reservation.

• Parameters used as part of the path computation process include the destination ATM address, traffic class, traffic contract, QoS requirements and link constraints.

• (quality of service will be discussed later)

ATM Architecture

UNI and NNI are further subdivided into public and private UNIs and NNIs depending on the location and ownership of the ATM switch.

ATM Architecture

• A private UNI connects an ATM endpoint and private ATM switch.

• A private NNI connects two ATM switches within the same private network.

ATM Architecture

A router with an ATM interface processor (AIP) can be connected directly to the ATM switch, while the router without the ATM interface must connect to an ATM data service unit (ADSU) and from there to the ATM switch.

ATM Architecture

Without AIP

With AIP

•A public NNI connects two ATM switches within the same public network.

•a public UNI connects an ATM endpoint or private switch to a public switch.

• A third type of interface, the Broadband Inter-Carrier Interface (BICI) connects two public switches from different public networks.

ATM Architecture

End of Module

ATM

Fixed Length Cells

ATM Cell

• Fixed Size

• 5 bytes header

• 48 bytes information field

• small cells reduce delay for high priority cells, and transfer video and audio faster

• fixed size facilitates switching in hardware: carries payload-type information, virtual-circuit identifiers, and header error check.

ATM CellName of Part Length Description

Flow Control

4 bits Information Related to Flow Control

VPI 8 bits Whole connection is identified by VPI

VCI 16 bits When ATM creates physical connection, connection is identified by VCI.

Payload Type 3

3 bits Data Type:

Video, Sound

HEC/CRC 8 bits Error Control when needed

Priority 1 bit Priority of that cell

ATM Cell

The ATM Cell includes 5 Bytes Header; the header can be in either UNI or NNI format depending on the Interface.

ATM Cell Header—UNI Format

ATM Cell Header—NNI Format

ATM Cell

General Flaw Control: Provides local functions, such as flow control from end point equipment to the ATM switch.

Payload Type: Indicates in the first cell whether the cell contains user data or control data.

• If the cell contains user data, the second bit indicates whether congestion is experienced or not, and the third bit indicates whether the cell is the last in a series of cells that represent a single AAL5 (ATM adoption layer 5) frame.

• If the cell contains control data, the second and third bits indicates maintenance or management flow information.

ATM Cell

Cell Loss Priority: Indicates whether the cell should be removed if it encounters errors as it moves through the network.

Header Error Control: Contains Cyclic Redundancy Check (CRC) on the cell header.

Virtual Path Identifier (VPI): Identifies semi-permanent connections between ATM end points.

Virtual Channel Identifier (VCI): Have only local significance on the link between ATM nodes.

ATM Cell

• ATM is essentially a packet switched network with packets called cells.

• ATM Cells are switched, based on a Virtual Path Identifier (VPI), and Virtual Channel Identifier (VCI).

• A connection in an ATM network is achieved by tying together a series of VPIs/VCIs at multiple Interfaces.

End of Module

ATM

Protocol Architecture

ATM Protocol Model

ATM Protocol Model has 3 planes:

1. User

2. Control

3. Management

ATM Protocol Model

End of Module

ATM Services

ATM Services:

There are three general ATM services:

1. Permanent Virtual Connection (PVC):

Leased Line

2. Switched Virtual Connection (SVC):

Telephone call

3. Connectionless Service

ATM Services:

Type of Service Advantages Disadvantages

PVC The guaranteed availability of connection

Static connectivity and that they require manual administration to set up

SVC Connection flexibility Extra time and overhead required to set up the connection

End of Module

QoS

Quality of Service

Short for Quality of Service A networking term that specifies a guaranteed

throughput level One of the biggest advantages of ATM over

competing technologies such as frame relay and fast Ethernet

It allows ATM providers to guarantee to their customers that end-to-end latency will not exceed a specified level

ATM QoS:

ATM QoS:

ATM Provides the following QoS:

• Constant Bit Rate (CBR)

• Variable Bit Rate (VBR)

• Unspecified Bit Rate (UBR)

• Available Bit Rate (ABR)

ATM QoS:

Constant Bit Rate (CBR)

• A quality service

• unchanged amount of bandwidth to the virtual channel

• specially suitable for voice-over-IP (Transfer fixed rate uncompressed video), and other traffic that requires steady, guaranteed throughput

ATM QoS:

Variable Bit Rate (VBR)

• B quality service

• Provides bandwidth only as needed up to a specified maximum rate

• specially suitable for LANs and “bursty” data traffic such as transmitting compressed video or audio to the end user

Available Bit Rate (ABR)

ATM QoS:

• C quality service

• Adjust the amount of bandwidth based on the amount of traffic in the network

• Aimed at data traffic such as file transfer and Email

Unspecified Bit Rate (UBR)

ATM QoS:

• D quality service

• Does not have any traffic parameters; does not specify the bandwidth for the PVC

• When enable PVC for UBR, the PVC uses the cell left over CBR or VBR

• The only limit to UBR is the total bandwidth of the port

End of Module

Summary

• ATM is a new WAN and internet backbone technology.

• ATM high performance due to, small fixed cells, Packet switched, multiple QoS

• Small cells reduce delay for high priority cells, and transfer video and audio faster at a speed up to 622 Mbps

• ATM cell is 53 bytes, 48 bytes information field and 5 bytes header

• ATM Protocol Model has 3 planes: User, control, and management

• ATM has multiple QoS: CBR, VBR, ABR, UBR

Sources

“Online Education” Internationa Engineering Consortium. April 20,2003. www.iec.org/online/tutorials/atm_fund/index.html

Trinity University. April 20, 2003. www.trinity.edu/~rjersen/245glosf.html

www.webopedia.com

“Searchable glossary dictionary” Glossarist. April 25,2003,www.glossarist.com/gsearch.asp

“A Configurable Visualization and Simulation Tool for ATM Switches” VISTA, April 25,2003. <vip.cs.utsa.edu/systems/pubs/nrtthesis.html>

“ATM Technology Fundamentals” CISCO Sys Inc. Jan 22,2003, April 29,2003 <www.cisco.com/univercd/cc/td/doc/product/atm/c8540/12-0/13-19/atg/basics.htm#1020131>

George C. Sackett, Christopher Metz, "ATM and Multiprotocol Networking," McGraw- Hill, January 1997 pages 10-15

David E. McDysan, Darren L. Spohn, "ATM Theory and Applications," McGraw-Hill, September 1998 Pp23