1. ITEC4610 Network Switching and Routing
ดร. ประวิทย์ ชุมชู
หัวหน้าสาขาวิชาวิศวกรรมสารสนเทศและการสื่อสาร(ICE)
MUT
ห้องทำงาน: F402
เบอร์โทรศัพท์ที่ทำงาน: (02) ต่อ 220
เบอร์โทรศัพท์เคลื่อนที่:

2. Class II IP over ATM ดร. ประวิทย์ ชุมชู
หัวหน้าสาขาวิชาวิศวกรรมสารสนเทศและการสื่อสาร(ICE)
MUT
ห้องทำงาน: F402
เบอร์โทรศัพท์ที่ทำงาน: (02) ต่อ 220
เบอร์โทรศัพท์เคลื่อนที่:

3. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
The ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

4. ATM
Data
Voice
Video

5. IP over ATM

6. ATM Based on cell relay protocol designed by the “ATM Forum”
Asynchronous Transfer Mode (ATM) is a Broadband Integrated Services Digital Networks B-ISDN designed by the ITU‑T.
Based on cell relay protocol designed by the “ATM Forum”

7. ATM Cell ATM is packet switching technology
It uses short/fixed size packet, hence it is called cell technology
Long cells are better suited for data
Short cells are better suited for voice
As a compromise:
ATM cell is 48 bytes + 5 bytes header = 53 bytes

8. Protocol Architecture
Similarities between ATM and packet switching
Transfer of data in discrete chunks
Multiple logical connections over single physical interface
In ATM flow on each logical connection is in fixed sized packets called cells
Minimal error and flow control
Reduced overhead
Data rates (physical layer) 25.6Mbps to Mbps

9. Protocol Architecture (diagram)

10. Reference Model Planes
User plane
Provides for user information transfer
Control plane
Call and connection control
Management plane
Plane management
whole system functions
Layer management
Resources and parameters in protocol entities

11. Architecture of an ATM Network

12. Architecture of an ATM Network
User end points are connected through user-to-network interface (UNI) Switches are connected through network-to-network interface (NNI)

13. Multiplexing Using Different Packet Sizes
Variable delays: small packet served after long packet will experience longer delay as compared to a short packet

14. Multiplexing Using Cells
Multiplexing fixed, small size cells results in constant short delay

15. ATM Multiplexing
ATM is based on statistical (asynchronous) multiplexing
Asynchronous TDM (no empty slots) is more efficient than synchronous TDM (possible empty slots if user has no data to send)

16. TDM
Data rate of the transmission medium is greater than sending and receiving devices. Link is divided in time 1 4 4

17. Synchronous TDM
Synchronous: multiplexer allocates exactly the same time slot to each deviceb
Frame: consists of one complete cycle of time slots

18. Asynchronous (Statistical) TDM
Each time slot can be assigned to any input device. The number of time slots (m) in the frame is based on statistical analysis

19. Frames and Addresses a. Only three lines sending data
Address bits are needed for each time slots More overhead.
No empty slots in the frames. Higher efficiency
a. Only three lines sending data

20. Frames and Addresses
b. Only four lines sending data

21. Frames and Addresses
c. All five lines sending data

22. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

23. ATM Addressing
The ITU-T standard is based on the use of E.164 addresses (similar to telephone numbers) for public ATM (B-ISDN) networks.
The ATM Forum extended ATM addressing to include private networks. It decided on the subnetwork or overlay model of addressing, in which the ATM layer is responsible for mapping network layer addresses to ATM addresses.

24. ATM Addressing

25. ATM Address Fields
AFI—Identifies the type and format of the address (E.164, ICD, or DCC).
DCC—Identifies particular countries.
High-Order Domain-Specific Part (HO-DSP)—Combines the routing domain (RD) and the area identifier (AREA) of the NSAP addresses. The ATM Forum combined these fields to support a flexible, multilevel addressing hierarchy for prefix-based routing protocols.
End System Identifier (ESI)—Specifies the 48-bit MAC address, as administered by the Institute of Electrical and Electronic Engineers (IEEE).
Selector (SEL)—Is used for local multiplexing within end stations and has no network significance.
ICD—Identifies particular international organizations.
E.164—Indicates the BISDN E.164 address.

26. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

27. ATM Layers

28. ATM Layers ATM standard defines three layers
Application adaptation layer AAL
ATM layer
Physical layer
End points use all three layers
Switches use only the bottom two layers

29. ATM Layers in End-Point Devices and Switches

30. AAL Types

31. Application Adaptation Layer AAL
Allows existing networks (such as packet networks) to connect to ATM
AAL protocols accept transmissions from upper- layer services (e.g., packet data) and map them into fixed-sized ATM cells
Such transmission can be of any type (voice, data, audio, video) and can be of variable or fixed rates
At Rx, this process is reversed, e.g., segments are are reassembled into their original format

32. Data-Stream Types ATM deals with four types of data streams
Constant-bit rate (CBR): real time application, such as real-time voice (telephone calls), real-time video (TV) transmission delay must be minimal
Variable-bit-rate (VBR): bit rate may vary from section to section of transmission: compressed voice and video, data
Connection-oriented packet data: X.25, TCP protocol
Connectionless packet data: datagram applications: IP protocols

33. Application Adaptation Layer : AAL1
Supports applications at constant bit rate (CBR): voice, video, existing digital telephone networks (E-1, T-1)
AAL layer is divide into two sublayers:
Convergence sublayer (CS)
Segmentation and reassembly (SAR)
Convergence sublayer (CS): divides the bit stream into 47-byte segments and pass them to the SAR below

34. AAL1

35. Segmentation and reassembly (SAR)
Adds one-byte header to each 47-byte segment (payload) received from CS
This header consists of four fields:
CS identifier (CSI): one-bit for signaling purposes
Sequence count (SC): three-bit (modulo 8) sequence number for end-to-end error and flow control
CRC: three-bit cyclic redundancy check field calculated over the first four bits. Beside single and multiple bit error detection they can correct a single-bit error
Parity (P): one-bit parity calculated over the first seven bits (detects an odd number of errors)

36. AAL2

37. AAL2 Supports variable bit-rate (VBR) applications
SAR accepts 45-bit payload from the CS and adds one-byte header and two-byte trailer, the result is 48-byte data unit passed to ATM layer
The overhead consists of three fields in the header and two fields in the trailer
Header:
CS identifier (CSI): one-bit for signaling purposes
Sequence count (SC): three-bit (modulo 8) sequence number for end-to-end error and flow control
Information type (IT): 4 bits identifying the data segment as falling in the beginning, middle or end of message

38. ALL-2 (Trailer) The trailer
Length indicator (LI): The first six bits of the trailer are used with the final segment of a message (when the IT in the header of the message indicates the end of the message) to indicate the amount of padding in the final cell (LI indicates where in the segment those bits start)
CRC: last 10 bits are CRC of the entire data unit. Can correct single-bit error in the data unit

39. AAL3/4

40. AAL3/4
Initially, AAL3 was intended to support connection-oriented data services and AAL4 to support connectionless services
Combined later to a single format called AAL3/4
Convergence sublayer:
accepts data packet of no more than 65,535 (216-1) bytes from upper layer service
adds a header and trailer, which indicate the beginning and end of the message and how much of the final frame is padding (Padding size is bytes)
Message (including header/trailer/padding) is passed 1n 44-byte segment to the SAR layer

41. AAL3/4 CS header and trailer: Type (T): one byte T field set to zero
Begin tag (BT): one byte beginning flag (synchronization)
Buffer-allocation (BA): two bytes indicating the buffer size
Pad (PAD): indicates the three possible padding size:
If # of data in the final segment is 40 bytes, no padding
If # of data < 40 bytes, add padding to bring total to 40
If # of data is between 41 and 44, add padding ) 43 to 40 to bring the total to 84. The first 44 bytes make a complete segment, the next 40 bytes and the trailer make the last segment

42. AAL3/4 CS header and trailer cont’d
Alignment (AL): one byte AL field to make the trailre 4 bytes long
Ending Tag (ET): one byte ending flag (synchronization)
Length (L): two-byte field indicates length of data
Segmentation and reassembly: accepts 44-byte pay load from CS and adds 2-byte header and 2-byte trailer. The resulting 48-byte data unit is passed to ATM for inclusion in the cell
SAR Header and trailer:
Segment type (ST): 2-bit ST indicates whether the segment belongs to the beginning, middle, or the end of a message, or is a single-segment message
Convergence sublayer identifier (CSI): one-bit for signaling purposes

43. AAL3/4 SAR Header and trailer cont’d
Sequence count (CS): three-bit (modulo 8) sequence number for end-to-end error and flow control
Multiplex identification (MID): 10-bit identifies cells coming from different data flows and multiplexed on the same virtual connection
Length indicator (LI): first 6-bit of the trailer indicate the amount of padding/message in the last segment.
CRC: last 10 bits of the trailer are the CRC of the entire data unit

44. AAL5 Called “simple and efficient application layer (SEAL)
Assumes that all cells travel sequentially and rest of functions provided by CS and SAR are already included in upper layers, hence no provision for addressing, sequencing or other CS and SAR heading information
Only padding and four-field trailer are added at CS
Padding and trailer are added to the end of the entire message of 65,536 bytes or less
Segments consist of 48 bytes of data, last segment has 40 bytes of data and 8 bytes overhead (trailer)

45. AAL5
Trailer:
Pad (PAD): between 0 and 47 bytes, making the message divisible by 48
User-to-user ID (UU): one byte UU field (user defined)
Type (T); one-byte T field (not defined)
Length (L): two-byte L fields indicates amount of padding/data
CRC: 4-byte error check for the entire data unit

46. AAL5

47. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

48. ATM Layer
Provides: routing, traffic management, switching, and multiplexing services
Accepts 48-byte segments from AAL sublayers and adds to them 5-bytes
headers

49. ATM Header

50. ATM Header Format
Two formats, one for user-to-user interface (UNI) and one for network-to-network interface (NNI)
Generic flow control (GFC): 4-bit field flow control at UNI level (flow control is not necessary for NNI, hence bits are added to VPI in the NNI header)
Virtual path identifier (VPI): 8-bit field for the UNI and 12-bit for the NNI
Virtual channel identifier (VCI): 16-bit field in both frames
Payload type (PT): 3-bit PT field, defines the payload as user data or managerial information

51. PT Fields
The interpretation of the last two bits depends on the first bit

52. ATM Header cont’d
Cell loss priority (CLP): one-bit CLP field for congestion control
Cells with CLP bit = 0 are cell of higher priority, they should not be discarded as long as there are cells with a CLP set to 1
Users who violate the rate assigned to them by sending at higher rate, the network will set the CLP to 1 to indicate that these cells must be dropped if the link becomes overloaded
Header error correction (HEC): one-byte field used for multiple bit error detection and a single-bit error correction over the first four bytes of the header

53. Header Error Control 8 bit error control field
Calculated on remaining 32 bits of header
Allows some error correction

54. Effect of Error in Cell Header

55. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

56. The ATM Physical Layer The ATM physical layer has four functions:
Cells are converted into a bitstream
the transmission and receipt of bits on the physical medium are controlled,
ATM cell boundaries are tracked
cells are packaged into the appropriate types of frames for the physical medium.
The ATM physical layer is divided into two parts: the physical medium-dependent (PMD) sublayer and the transmission convergence (TC) sublayer.
The PMD sublayer provides two key functions.
synchronizes transmission and reception by sending and receiving a continuous flow of bits with associated timing information.
specifies the physical media for the physical medium used, including connector types and cable.
Examples of physical medium standards for ATM include Synchronous Digital Hierarchy/Synchronous Optical Network (SDH/SONET), DS-3/E3, 155 Mbps over multimode fiber (MMF) using the 8B/10B encoding scheme, and 155 Mbps 8B/10B over shielded twisted-pair (STP) cabling.
The TC sublayer has four functions: cell delineation, header error control (HEC) sequence generation and verification, cell-rate decoupling, and transmission frame adaptation.

57. ATM Logical Connections
Virtual channel connections (VCC)
Analogous to virtual circuit in X.25
Basic unit of switching
Between two end users
Full duplex

58. ATM Logical Connections Cont’d
Fixed size cells
Data, user-network exchange (control) and network-network exchange (network management and routing)
Virtual path connection (VPC)
Bundle of VCC with same end points

59. ATM Logical Connections
Virtual channel connections (VCC)
Analogous to virtual circuit in X.25
Virtual path connection (VPC)
Bundle of VCC with same end points
Advantages of Virtual Paths:
Simplified network architecture
Increased network performance and reliability
Reduced processing
Short connection setup time

60. Example of VPs and VCs 8 endpoints are communicating using 4 VCs
1st two VCs share the same virtual path from switch I to switch III, hence these two VCs are bundled to form one VP
Other two VCs share same path from I to IV and hence combined by another VP

61. Call Establishment Using VPs

62. Connection Identifiers
A virtual connection is identified by a pair of numbers: the VPI and VCI

63. Virtual Connection Identifiers
in UNIs and NNIs
256 x = 16,777,216 VCs
4096 x = 268,435,456 VCs

64. An ATM Cell

65. SVC Setup PVC (permanent virtual circuited) SVC
( swithed virtual circuits)
Connection less

66. Routing with a VP Switch
VP switch routes cells using only VPI
Switch routing decision is based on four piece of information stored in switching table: (1) arrival interface number, (2) VPI, (3) corresponding o/g interface number and (4) the new VPI

67. A Conceptual View of a VP Switch

68. Routing with a VPC Switch
VPC switch routes cells using both VPI and VCI
Switch routing decision is based on six piece of information stored in switching table: (1) arrival interface number, (2) i/c VPI, (3) i/c VCI (4) corresponding o/g interface number, (5) o/g VPI and (6) o/g VCI

69. A Conceptual View of a VPC Switch

70. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

71. LAN Emulation (ELAN)
Stations attached via ATM the same capabilities that they normally obtain from legacy LANs, such as Ethernet and Token Ring

72. LAN Emulation (ELAN)

73. Outlines ATM Architectures ATM Addressing ATM Adaptation layers
ATM Layer
The ATM Physical Layer
LAN Emulation (ELAN)
IP over ATM

74. IP Over ATM Objectives Upon completion you will be able to:
Review the features of an ATM WAN
Understand how an a datagram can pass through an ATM WAN
Understand how an IP packet is encapsulated in cells
Understand how cells are routed in an ATM network
Understand the function of ATMARP

75. IP over ATM and LAN Emulation

76. An ATM WAN in the Internet

77. ATM layers in routers and switches

78. Note:
End devices such as routers use all three layers, while switches use only the bottom two layers.

79. AAL5

80. The AAL layer used by the IP protocol is AAL5.
Note:
The AAL layer used by the IP protocol is AAL5.

81. ATM layer

82. ATM headers

83. Fragmentation
Tr=000, not last cell
Tr=001,last cell

84. Note:
Only the last cell carries the 8-byte trailer added to the IP datagram. Padding can be added only to the last cell or the last two cells.

85. Note:
The value of the PT field is 000 in all cells carrying an IP datagram fragment except for the last cell; the value is 001 in the last cell.

86. ATM cells

87. Entering-point and exiting-point routers

88. ATMARP
ATMARP finds (maps) the physical address of the exiting-point router given the IP address of the exiting-point router. No broadcasting is involved.

89. ATMARP packet

90. Table OPER field

91. Note:
The inverse request and inverse reply messages can bind the physical address to an IP address in a PVC situation.

92. Binding with PVC

93. Binding with ATMARP

94. Note:
The request and reply message can be used to bind a physical address to an IP address in an SVC situation.

95. Note:
The inverse request and inverse reply can also be used to build the server’s mapping table.

96. Building a table

97. LOGICAL IP SUBNET (LIS)
An ATM network can be divided into logical (not physical) subnetworks. This facilitates the operation of ATMARP and other protocols (such as IGMP) that need to simulate broadcasting on an ATM network.

98. LIS

99. Note:
LIS allows an ATM network to be divided into several logical subnets. To use ATMARP, we need a separate server for each subnet.

100. Summary
ATM
IP over ATM
IP over Ethernet
IP over Pla. Pla.