Definition

DefinitionA new TechnologyFixed size packets called CELLSStreamlined: minimal error and flow controlSmall cells compared to other technologiesHigh speed multimedia networking; carry traffic at a speed up to 622MbpsATM Standards are done Primarily by the ATM Forum; Cisco systems, NET/ADAPTIVE, Northern Telecom, and Sprint in 1991.

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ATM ArchitectureWAN& LAN

Common LAN/WAN Architecture allowing ATM to be used consistently from one desktop to another.

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

ATM ArchitectureMultiple switches and interfaces connecting ATM devices

ATM ArchitectureTwo 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 ArchitectureUNI 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 ArchitectureA 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 ArchitectureWithout AIPWith 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

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ATM Fixed Length Cells

ATM CellFixed Size5 bytes header48 bytes information fieldsmall cells reduce delay for high priority cells, and transfer video and audio fasterfixed size facilitates switching in hardware: carries payload-type information, virtual-circuit identifiers, and header error check.

ATM Cell

Name of PartLengthDescriptionFlow Control4 bitsInformation Related to Flow ControlVPI8 bitsWhole connection is identified by VPIVCI16 bitsWhen ATM creates physical connection, connection is identified by VCI.Payload Type 33 bitsData Type:Video, SoundHEC/CRC8 bitsError Control when neededPriority1 bitPriority of that cell

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

ATM Cell HeaderNNI 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 CellCell 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 CellATM 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.

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ATM Protocol Architecture

ATM Protocol ModelATM Protocol Model has 3 planes:UserControlManagement

ATM Protocol Model

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ATM Services

ATM Services:There are three general ATM services:Permanent Virtual Connection (PVC): Leased LineSwitched Virtual Connection (SVC):Telephone callConnectionless Service

ATM Services:

Type of ServiceAdvantages DisadvantagesPVCThe guaranteed availability of connection Static connectivity and that they require manual administration to set upSVCConnection flexibilityExtra time and overhead required to set up the connection

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QoS Quality of Service

Short for Quality of Service A networking term that specifies a guaranteed throughput levelOne of the biggest advantages of ATM over competing technologies such as frame relay and fast EthernetIt 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 serviceunchanged amount of bandwidth to the virtual channelspecially 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 serviceProvides bandwidth only as needed up to a specified maximum ratespecially 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 serviceAdjust the amount of bandwidth based on the amount of traffic in the networkAimed at data traffic such as file transfer and Email

Unspecified Bit Rate (UBR)ATM QoS:D quality serviceDoes not have any traffic parameters; does not specify the bandwidth for the PVCWhen enable PVC for UBR, the PVC uses the cell left over CBR or VBRThe only limit to UBR is the total bandwidth of the port

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SummaryATM is a new WAN and internet backbone technology.ATM high performance due to, small fixed cells, Packet switched, multiple QoSSmall cells reduce delay for high priority cells, and transfer video and audio faster at a speed up to 622 MbpsATM cell is 53 bytes, 48 bytes information field and 5 bytes headerATM Protocol Model has 3 planes: User, control, and managementATM 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.

ATM Technology Fundamentals CISCO Sys Inc. Jan 22,2003, April 29,2003

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