Asynchronous Asynchronous Transfer Mode (ATM) Transfer Mode (ATM) Member’s Name: Member’s Name: Chen Sing Tiong Chen Sing Tiong (KL003676) (L) (KL003676) (L) Cheng Chin Tat Cheng Chin Tat (KL003832) (KL003832) Low Mei Ee Low Mei Ee (KL003796) (KL003796) Ng Shook Kien Ng Shook Kien (KL003795) (KL003795) Pang Yin Yee Pang Yin Yee (KL003719) (KL003719) Tan Lay Koon Tan Lay Koon (KL003809) (KL003809) Tan Wee Khoon Tan Wee Khoon (KL003844) (KL003844) Yong Yen Jen Yong Yen Jen (KL003797) (KL003797)
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Asynchronous Transfer Mode (ATM) Member’s Name:Chen Sing Tiong(KL003676) (L) Cheng Chin Tat (KL003832) Low Mei Ee(KL003796) Ng Shook Kien(KL003795) Pang.
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Asynchronous Transfer Asynchronous Transfer Mode (ATM)Mode (ATM)
Member’s Name:Member’s Name: Chen Sing TiongChen Sing Tiong (KL003676) (L)(KL003676) (L)Cheng Chin Tat Cheng Chin Tat (KL003832)(KL003832)Low Mei EeLow Mei Ee (KL003796)(KL003796)Ng Shook KienNg Shook Kien (KL003795)(KL003795)Pang Yin YeePang Yin Yee (KL003719)(KL003719)
Tan Lay KoonTan Lay Koon (KL003809)(KL003809)Tan Wee KhoonTan Wee Khoon (KL003844)(KL003844)
Yong Yen JenYong Yen Jen (KL003797)(KL003797)
What is ATM?What is ATM?• A transfer mode in which information is organised into cells
• International Telecommunication Union-Telecommunications Standards Section (ITU-T) standard for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells.
• Based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It was originally conceived as a high-speed transfer technology over public networks. – Operates at Layer 2 of the OSI-RM
• Switching technology in WAN backbone network
• Minimal functionality in the network
• Provide faster packet switching
– ATM Layer, common to all services and provides packet transfer capabilities:
• fixed size cells• logical connections
– ATM Adaptation Layer (AAL), that is service dependent:
• supports information transfer protocols not based on ATM, by mapping the information into ATM cells
ObjectivesObjectives
1.1. Explain the cell establishment Explain the cell establishment connection in ATM.connection in ATM.
2.2. Explain the protocol architecture of ATM Explain the protocol architecture of ATM in relation with OSI model.in relation with OSI model.
3.3. ATM cell structure and it effect on the ATM cell structure and it effect on the performance of ATM network.performance of ATM network.
ATM Cell EstablishmentATM Cell Establishment
• When an ATM device wants to establish a connection with another ATM device, it sends a signaling-request packet to its directly connected ATM switch. This request contains the ATM address of the desired ATM endpoint, as well as any Quality of Services parameters required for the connection.
The ATM Connection The ATM Connection Establishment ProcessEstablishment Process
• ATM signaling uses the one-pass method of connection setup. An ATM connection setup proceeds in the following manner:
- Source end system sends a setup message
- Send call proceeding message - Destination end system receives setup message - Send a connect message - Send acknowledge message
The ATM Connection The ATM Connection Establishment Process (Con’t)Establishment Process (Con’t)
• First, source end system sends a setup message
- a setup message is forwarded to the first ATM switch (ingress switch) in the network.
• Send call proceeding message - This switch sends a call proceeding message
and invokes an ATM routing protocol. The signaling request is propagated across the network
The ATM Connection The ATM Connection Establishment Process (Con’t)Establishment Process (Con’t)
• Destination end system receives setup message
- The exit switch (egress switch) that is attached to the destination end system receives the setup message.
• Send a connect message - The egress switch forwards the setup
message to the end system across its UNI, and the ATM end system sends a connect message if the connection is accepted.
The ATM Connection The ATM Connection Establishment Process (Con’t)Establishment Process (Con’t)
• Send acknowledge message - The connect message traverses back
through the network along the same path to the source end system, which sends a connect acknowledge message back to the destination to acknowledge the connection. Data transfer can then begin.
ATM Devices Establish Connections Through the One-Pass Method
ATM Call EstablishmentATM Call Establishment
ATM Protocol ArchitectureATM Protocol Architecture• The ATM architecture is divided into 3 layers:
Functions of the B-ISDN in relation to the Protocol Reference Model.Source: ITU-T; I.371
B-ISDN and ATMB-ISDN and ATM• B-ISDN is based on ATM (ITU-T et
al:1984-1988)• ATM is used to implement B-ISDN• B-ISDN uses optical fibre• A service requiring transmission
channels capable of supporting rates greater than the primary rate (ITU-T)
Layered ArchitectureLayered Architecture
ATMATM
PHYPHY
AALAAL
ATMATM NetworkNetwork UNIUNIUNIUNI
ATMATM
AALAAL
PHYPHY
• Physical Layer (PHY)• User Network Interface (UNI)• Different AAL Protocols for Different Traffic Types (e.g., data, voice, video)
Cell SwitchingCell Switching
End Station End StationSwitch
VoiceVoice
DataData
VideoVideo
AAAALL
PHY
PHY
ATM
PHY
ATM
PHY
ATM
AAAALL
Voice
Data
Video
Cells
• AAL: Inserts/extracts information into 48 byte payload• ATM Layer: Adds/removes 5 byte header to payload• PHY: Converts to appropriate electrical or optical format
Low Bit Rate Voice (Real Time)Low Bit Rate Voice (Real Time)
-Variable Bit Rate (VBR)-Variable Bit Rate (VBR)
Time Invariant Data (bursty data)Time Invariant Data (bursty data)
““Simple” Data Simple” Data
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3/43/4
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•Provides Mapping Of Applications To ATM Service Of The Same Type•Segments/Reassembles Into 48 Payloads•Hands 48 Bytes Payloads To ATM Layer (4 Bytes to adapt)
AAL Sub-layersAAL Sub-layers• Segmentation and Reassembly (SAR)
– segment data in native format into fixed length ATM cells and vice versa
• Convergence Sub-layer (CS)– error checking, removal of corrupted
cells– service specific
ATM In UseATM In Use
DataDataCellCell
VideoVideoCellCell
VoiceVoiceCellCell
In DetailIn DetailATM Cell Creation TransmissionATM Cell Creation Transmission
AdaptationAdaptationLayerLayer
ATMATMLayerLayer
PhysicalPhysicalLayerLayer
Conversion Conversion to ATM Data to ATM Data Types, 48-Types, 48-
Byte LengthByte Length
Forward Forward Cell Cell
Through Through NetworkNetwork
Add 5-Byte Add 5-Byte HeaderHeader
Convert To Convert To Correct Correct
Electrical Electrical Or Optical Or Optical
FormatFormat
VoiceVoiceCellCell
DataDataCellCell
VideoVideoCellCell
Services
ATM Cell Structure (cont.)ATM Cell Structure (cont.)• Two types of header
– Generic Flow Control (GFC)- 4 bits. Used only for flow control protocols on shared medium user access networks. (UNI format only)
– Virtual Path Identifier- 8 (UNI) or 12 bits (NNI). Field constitute a routing field for the network. Allowing for more virtual paths to be supported within the network.
– Virtual Channel Identifier- 16 (UNI) or 20 bits (NNI). Field is used for routing to and from the end user.
ATM Cell Structure (cont.)ATM Cell Structure (cont.)– Payload Type - 3 bits. Used mainly for
Operations and Maintenance purposes.(5th edition, pg 335)
– Cell Loss Priority-1 bit. Used for congestion control purposes.
– Header Error Control (HEC)- 8 bits. Used for header error protection. Allows to correct single bit errors in the header. Also used in the cell delineation process (used to determine on which bit position the cell starts, i.e. cell synchronisation)
information field)• Small cells reduce queuing delay for high priority
cells• Small cells can be switched more efficiently• Easier to implement switching of small cells in
hardware
ConclusionConclusion•Asynchronous Transfer Mode is the cell relay protocol designed by the ATM forum and adopted by the ITU-T
•The ATM data packet is called cell and composed of 53 bytes
•The cell network is based on permanent virtual circuit routing
•The ATM standard define three layers
AAL
ATM
Physical layer
Conclusion (cont.)Conclusion (cont.)
•ATM can handle or minimize the severity of:
Out of sequence packets
Delay time between packets of a message
Bit errors
•ATM cell have 2 types
UNI
NNI
Questions and AnswersQuestions and Answers(1) What is the definition of ATM?Answer: A transfer mode in which information is
organised into cells; for cell relay wherein information for multiple service types, such as voice, video, or data, is conveyed in small, fixed-size cells.
(2) What is the method used by ATM signaling for setup connection?
Answer: one-pass method
Questions and Answers Questions and Answers (cont.)(cont.)
(3) What are the 3 lower layer of the OSI stack which the ATM specific function ca be found?
Answer: ATM adaptation Layer (AAL),ATM layer, and Physical layer
(4) In AAL, which types of services that required timing between source and definition?
Answer: Class A, and Class B.
Questions and Answers Questions and Answers (cont.)(cont.)
(5) What is the header field consist in UNI ATM cell format?
Answer: GFC, VPI, VCI, PT, CLP and HEC.
(6) What is the 2 types header in ATM cell structure?