DigiPoints Volume 1. Student Workbook. Module 12 Asynchronous Transfer Mode

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1 Asynchronous Transfer Mode Page 12.1 DigiPoints Volume 1 Module 12 Asynchronous Transfer Mode Summary This last chapter of, covers ATM, and provides an end-to-end data communications model that draws on all twelve chapters of this volume. Module Objectives Upon successful completion of the module, the student should be able to: Describe how ATM technology differs from a packet or Frame Relay system. Explain how Asynchronous Transfer Mode is carried on a synchronous transport such as SDH or SONET. Identify the six basic fields found in the ATM header. Explain how ATM fulfills bandwidth on demand. Identify the ATM Protocol Layers and relate them to the OSI Model. Explain the relationship of ATM to Broadband ISDN (B-ISDN). Explain the purpose of ATM Adaptation Layers, and identify the five ATM Adaptation Layer types. Describe the process and the network elements involved when sending data from a terminal with a dial-up connection to a terminal with a cable modem connection via the Internet. Prerequisites Read, Chapter 12.

2 Asynchronous Transfer Mode Page 12.2 A T M Cell Switched Technology Fixed Length - 53 bytes not SMDS Defacto Standard Multimedia capable Use with SONET or SDH How are the bytes in the ATM cell allocated? What is the difference between ATM and SMDS? How has ATM become the de facto standard in the industry? Can ATM be used outside the United States?

3 Asynchronous Transfer Mode Page 12.3 SONET Optical Carrier (OC) Rates and SDH Synchronous Transport Module (STM) Modules Line Rate (Mbps) SONET Level SDH Level OC OC-3 STM OC OC-12 STM OC OC-24 STM OC-36 STM OC-48 STM-16 What is the bit rate for the first point when SONET and SDH levels are equal? How many times per second is a SONET or SDH frame transmitted per second? How is an asynchronous signal, ATM, carried on a synchronous system?

4 Asynchronous Transfer Mode Page 12.4 What is the size of the STM-1 frame in bytes? In bits? What is the meaning of the following acronyms? SONET SDH OC-N STM-N How does the SDH STM frame differ from the SONET OC frame?

5 Asynchronous Transfer Mode Page 12.5 ATM Cell Structure Header Payload 5 Octets 48 Octets Bit Position Octet GFC VPI VPI VCI VCI VCI PTI HEC C L P VCI = Virtual Channel ID VPI = Virtual Path ID PTI = Payload Type Identifier GFC = Generic Flow Control CLP = Cell Loss Priority HEC = Header Error Control Where is the user information manipulated? How many bits are used for the VCI? What is their function? What type of error technique is used in the HEC What values can the CLP have and what do those values indicate?

6 Asynchronous Transfer Mode Page 12.6 Bandwidth Utilization User 1 User 2 User 3 User 1 User 2 User 1 User 2 User 1 User 2 User msec 250 msec 375 msec What is the significance of this utilization diagram to explain the concept of bandwidth on demand? Assuming the frame rate above continues to repeat, what are the respective line speeds for each of the three users?

7 Asynchronous Transfer Mode Page 12.7 ATM Protocol Layers OSI 7 Application B-ISDN Presentation Session Transport Convergence Sublayer Segmentation and Reassembly Sublayer A A L 3 2 Network Data Link ATM Layer Transmission Convergence Sublayer Physical 1 Physical Physical Medium Sublayer With respect to the ISO OSI Model, how was the ATM Protocol developed? What is the protocol from which the ATM Protocol evolved? How is ATM protocol similar to Frame Relay protocol?

8 Asynchronous Transfer Mode Page 12.8 ATM in B-ISDN Protocol Model Control Plane User Plane Higher Layers ATM Adaptation Layer ATM Layer Physical Layer L a y e r M g m t. P l a n e M g m t. Management Plane What does the Management Plane do? What are the layers of the within the ATM Protocol?

9 Asynchronous Transfer Mode Page 12.9 What is the function of the Physical Layer? PM TC What does the ATM Layer do? What are the basic functions of the ATM Adaptation Layer?

10 Asynchronous Transfer Mode Page AAL Types Class A Class B Class C Class D Synchronization between sender and Receiver Required Required Not Required Not Required Bit Rate Constant Variable Variable Variable Connection Mode Connection Oriented Connection Oriented Connection Oriented Connectionless AAL Type 1 2 3,4,5 4 Source: Adaptations of CCITT Recommendations How are AAL types aligned with ATM cells? What class of AAL is associated with voice telephony? Which class is associated with multimedia to include video? Which type of service offering is associated with Class C? Class D?

11 Asynchronous Transfer Mode Page Higher Layer Application Sublayers within Adaptation Layers Message Convergence Sublayer AAL - SDU AAL Header Payload Trailer CS PDU Segmentation and Reassembly Sublayer Header Payload Trailer SAR PDU 48 Bytes (Octets) ATM Layer Header Payload ATM PDU 53 Bytes (Octets) Source: CCITT Recommendation I.363 The AAL has two sublayers. What are those sublayers and what are their functions? How does the SAR PDU differ from the regular ATM PDU? Why? What does this mean?

12 Asynchronous Transfer Mode Page AAL-1 & AAL-2 SAR PDU AAL-1 SN SNP SAR-PDU Payload 4 bits 4 bits 47 Bytes (Octets) SAR PDU Header AAL-2 SN IT SAR-PDU Payload LI CRC SAR PDU Header SAR PDU Trailer There are four Service Classes (A, B, C, D) and how many AAL PDU cell types? How does AAL-2 differ from AAL-1? In Type I AAL, what is the significance of the receiver recovering clocking from the transmitter?

13 Asynchronous Transfer Mode Page AAL- 3/4 SAR PDU SN IT MID SAR-PDU Payload LI CRC SAR PDU Header SAR PDU Trailer How does AAL 3/4 differ from AAL 2? What is the significance of this? What takes place in AAL 3/4 SAR PDU? How much actual user data can be carried in each AAL 3/4 PDU What is the significance of the Service Specific Coordination Function sublayer and the Service Specific Connection Oriented Protocol sublayer?

14 Asynchronous Transfer Mode Page ATM Summary End-to-end multimedia communications Standards Instability ATM in Public Network Backbones ATM in Private Network Backbones ATM-LAN Interfaces ATM in CATV Networks When was ATM first proposed? What is meant by Standards Instability? Where is ATM found today?

15 Asynchronous Transfer Mode Page End to End Data Communications Using Commercial ISPs User A Corporate LAN CORPORATE ISP CABLE ISP Head End V.34 Telephony Telco Central Office Router Public ATM Network The Internet Other TCP/IP Networks Frame Relay Network Router Cable Termination System Cable User B What is the difference of the Physical Layer for USER A s access and USER B? What three types of network technologies are displayed as being used for the Internet? What does the acronym ISP represent?

16 Asynchronous Transfer Mode Page End to End Data Communications Sending Using Commercial ISPs User A V.34 Telephony Telco Central Office Corporate LAN Router CORPORATE ISP Public ATM Network The Internet Other TCP/IP Networks Frame Relay Network CABLE ISP Router Head End Cable Termination System User Telco CO LAN Router ISP ATM Frame Relay ISP Off Hook Signaling Dialtone Digits Call Routing Answer (Trip Ringing) Setup Tones Message Ethernet PDUs Frame Relay over T-1 ATM PVCor SVC ATM or Frame Relay PVC or SVC Frame Relay PVC or SVC Cable User B

17 Asynchronous Transfer Mode Page End to End Data Communications Retrieval Using Commercial ISPs User A Corporate LAN CORPORATE ISP CABLE ISP Head End V.34 Telephony Telco Central Office Router Public ATM Network The Internet Other TCP/IP Networks Frame Relay Network Router Cable Termination System Cable User B Signaling ISP Router Logon Request Logon Confirm Request Establish Connection PVC to ISP or SVC Cable Termination System RF Mod/ Demod RF Mod/ Demod RF Mod/ Demod Cable Logon Request Logon Confirm User Request Connection to ISP

18 Asynchronous Transfer Mode Page Summary Asynchronous Transfer Mode SONET/SDH ATM Cell Bandwidth on Demand ATM Protocol Layers B-ISDN Protocol Adaptation Layer End-to-End Data Communications

19 Asynchronous Transfer Mode Page Study Questions 1. Describe the ATM cell. Include the function of each of the fields in the ATM cell header. 2. What is the difference between the Plesiochronous Digital Hierarchy and the Synchronous Digital Hierarchy? Give an example of each. 3. Derive the STM-1 signal bandwidth from its repetition rate. 4. What is the mechanism for communication operations and maintenance information in ATM? 5. If the ATM transport mechanism provides a 125 microsecond frame, calculate the number of ATM cells per frame needed to provide Mbps of bandwidth. Do the same for 384 kbps. of bandwidth.

20 Asynchronous Transfer Mode Page What are the three basic layers to the B-ISDN protocol, and what are their purposes? 7. How and where in the B-ISDN protocol is Frame Relay Service provided over ATM? 8. You have been asked by your management to set up a data communications network for moving data from a PC attached to a cable modem to a public switched ATM network. What factors must you consider as you begin your design?