1. Protocols and the TCP/IP Suite Asynchronous Transfer Mode (ATM)
Chapter 5
Asynchronous Transfer Mode
(ATM)
Chapter 5 Asynchronous Transfer Mode
Chapter 2

2. Protocols and the TCP/IP Suite
Introduction
ATM Protocol Architecture
Logical connections
ATM Cells
Service categories
ATM Adaptation Layer (AAL)
Chapter 5 Asynchronous Transfer Mode
Chapter 2

3. ATM Protocol Architecture
Protocols and the TCP/IP Suite
ATM Protocol Architecture
Fixed-size packets called cells
Streamlined: minimal error and flow control
2 protocol layers relate to ATM functions:
Common layer providing packet transfers
Service dependent ATM adaptation layer (AAL)
AAL maps other protocols to ATM
Chapter 5 Asynchronous Transfer Mode
Chapter 2

4. Protocol Model has 3 planes
Protocols and the TCP/IP Suite
Protocol Model has 3 planes
User
Control
Management
Chapter 5 Asynchronous Transfer Mode
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5. Protocols and the TCP/IP Suite
Figure 5.1
Chapter 5 Asynchronous Transfer Mode
Chapter 2

6. Protocols and the TCP/IP Suite
Logical Connections
VCC (Virtual Channel Connection): a logical connection analogous to virtual circuit in X.25
VPC (Virtual Path Connection): a bundle of VCCs with same endpoints
Chapter 5 Asynchronous Transfer Mode
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7. Protocols and the TCP/IP Suite
Figure 5.2
Chapter 5 Asynchronous Transfer Mode
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8. Advantages of Virtual Paths
Protocols and the TCP/IP Suite
Advantages of Virtual Paths
Simplified network architecture
Increased network performance and reliability
Reduced processing and short connection setup time
Enhanced network services
Chapter 5 Asynchronous Transfer Mode
Chapter 2

9. VPC/VCC Characteristics
Protocols and the TCP/IP Suite
VPC/VCC Characteristics
Quality of Service (QoS)
Switched and semi-permanent virtual channel connections
Cell sequence integrity
Traffic parameter negotiation and usage monitoring
(VPC only) virtual channel identifier restriction within a VPC
Chapter 5 Asynchronous Transfer Mode
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10. Protocols and the TCP/IP Suite
Control Signaling
A mechanism to establish and release VPCs and VCCs
Methods to request for a VC:
Semi-permanent VCCs
Request as needed
Chapter 5 Asynchronous Transfer Mode
Chapter 2

11. Protocols and the TCP/IP Suite
ATM Cells
Fixed size
5-octet header
48-octet information field
Small cells reduce delay for high-priority cells
Fixed size facilitate switching in hardware
Chapter 5 Asynchronous Transfer Mode
Chapter 2

12. Protocols and the TCP/IP Suite
Header Format
Generic flow control
Virtual path identifier (VPI)
Virtual channel identifier (VCI)
Payload type
Cell loss priority
Header error control
Chapter 5 Asynchronous Transfer Mode
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13. Protocols and the TCP/IP Suite
Figure 5.4
CLP = Cell Loss Priority bit
Chapter 5 Asynchronous Transfer Mode
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14. Protocols and the TCP/IP Suite
Generic Flow Control
Control traffic flow at user-network interface (UNI) to alleviate short-term overload conditions
When GFC enabled at UNI, 2 procedures used:
Uncontrolled transmission
Controlled transmission
Chapter 5 Asynchronous Transfer Mode
Chapter 2

15. Protocols and the TCP/IP Suite
Header Error Control
8-bit field calculated based on remaining 32 bits of header
For error detection
In some cases, error correction of single-bit errors in header
Chapter 5 Asynchronous Transfer Mode
Chapter 2

16. Protocols and the TCP/IP Suite
Service Categories
Real-time service
Constant bit rate (CBR)
Real-time variable bit rate (rt-VBR)
Non-real-time service
Non-real-time variable bit rate (nrt-VBR)
Available bit rate (ABR)
Unspecified bit rate (UBR)
Guaranteed frame rate (GFR)
Slides with details for these?
Chapter 5 Asynchronous Transfer Mode
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17. Protocols and the TCP/IP Suite
Figure 5.8
Chapter 5 Asynchronous Transfer Mode
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18. ATM Adaptation Layer (AAL)
Protocols and the TCP/IP Suite
ATM Adaptation Layer (AAL)
Support non-ATM protocols
Maps to ATM cells
AAL Services
Handle transmission errors
Segmentation/reassembly (SAR)
Handle lost and misinserted cell conditions
Flow control and timing control
Chapter 5 Asynchronous Transfer Mode
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19. Applications of AAL and ATM
Protocols and the TCP/IP Suite
Applications of AAL and ATM
Circuit emulation (e.g., E-1/T-1 synchronous TDM circuits)
VBR voice and video
General data services
IP over ATM
Multiprotocol encapsulation over ATM (MPOA)
LAN emulation (LANE)
Chapter 5 Asynchronous Transfer Mode
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20. Protocols and the TCP/IP Suite
AAL Protocols
AAL layer has 2 sublayers:
Convergence Sublayer (CS)
Supports specific applications using AAL
Segmentation and Reassembly Layer (SAR)
Packages data from CS into cells and unpacks at other end
Chapter 5 Asynchronous Transfer Mode
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21. Protocols and the TCP/IP Suite
Figure 5.9
Chapter 5 Asynchronous Transfer Mode
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22. Protocols and the TCP/IP Suite
Figure 5.10
(CBR source)
CBR Service
(connectionless
or connection-oriented)
VBR Service
(higher-layer
connection-oriented services)
Connection-oriented Service
Chapter 5 Asynchronous Transfer Mode
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23. Protocols and the TCP/IP Suite
AAL Type 1
Constant-bit-rate source
SAR simply packs bits into cells and unpacks them at destination
Sequence Number (SN) used in reassembling SAR PDUs
Sequence Number Protection (SNP) provides error detection/correction
No CS PDU since CS sublayer primarily for clocking and synchronization
Chapter 5 Asynchronous Transfer Mode
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24. Protocols and the TCP/IP Suite
AAL Type 3/4
May be connectionless or connection oriented
May be message mode or streaming mode
Chapter 5 Asynchronous Transfer Mode
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25. Protocols and the TCP/IP Suite
AAL Type 5
Streamlined transport for connection oriented protocols
Reduce protocol processing overhead
Reduce transmission overhead
Ensure adaptability to existing transport protocols
Chapter 5 Asynchronous Transfer Mode
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26. Protocols and the TCP/IP Suite
Figure 5.13
Chapter 5 Asynchronous Transfer Mode
Chapter 2