B-ISDN/ATM Basics,
Protocol, and Structure
Basics
 Data Transmission Methods
 Asynchronous and synchronous
data transmission
 Asynchronous transmission: Characters
are transmitted as a series of bits, with
each character identified separately by
start and stop bits. For example,
RS-232C, X.21.
S12345678S
Start bit
Stop bit
 Synchronous transmission: Sender and
receiver derive clock frequency
information from the transmitted data.
Data are transmitted in a frame which
consists of synchronization characters,
start-of-message characters, control
characters, data, CRC checks, and
end-of-message characters.
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SYN SOM CTL DATA CRC EOM
 Asynchronous versus synchronous
transfer mode
 Synchronous transfer mode (STM) :
 Synchronous time division
multiplexing
 Each time slot represents a reserved
piece of bandwidth dedicated to a
single channel
 Asynchronous transfer mode (ATM)
 Synchronous time division
multiplexing
 Time slots are available to any user
who has data ready to transmit
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 Multiplexing
 Multiplexing: Multiple stream of
information share a common physical
transmission medium.
 Multiplexing methods:
 Space division multiplexing: physically
separate, e.g., multiple cables
interconnect equipment
 Frequency division multiplexing:
modulate each signal by a carrier
frequency
 Time division multiplexing: time is
divided into slots
 Address multiplexing: each packet of
information is prefixed by an address
that each node interpreted
 Switching
 Switching takes multiple instances of a
physical transmission medium containing
multiplexed information streams, and
rearranges the information streams
between input and output. Information
from a particular physical link in a specific
multiplex position is switched to another
output physical link usually in a different
multiplex position.
 Switching functions:
 point-to-point
 point-to-multipoint
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 Switching methods
 Space division switching
 Frequency/wavelength switching
(optical networks)
 Time division switching
 Address switching
 What drives ATM
 Technologies
 Protocol enhancements: decentralized,
peer-to-peer networking
 High-performance digital transmission:
simple protocols for more reliable
transmission medium
 Worldwide industry support: most sectors
of industry support ATM
 Power to the desktop: processing power
for multimedia transmission
 Standards and interoperability: fast
realization and industrywide agreement on
a common set of standards
 Applications
 Consumer service applications
 Entertainment imaging
 Work at home: telecommuting
 Home shopping
 Video-on-Demand
 Multimedia Email
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 Interactive multimedia applications and
games
 Broadcast public service applications
 Distance learning
 Digital library
 Video-on-demand for training
 Videoconferencing
 Business
 Evolution from shared medium to
high-performance switching
 Virtual networking
 Seamless interworking (Mixed voice,
video, data, wireless traffic)
 More bandwidth for less bucks
 Futureproofing investment
 Enabling new applications
 Benefits
 Integration of multiple traffic types
 Efficient bandwidth use by statistical
multiplexing
 Guaranteed bandwidth and resource
allocation
 Dynamic bandwidth management
 High service availability
 Multiple Quality of Service (QOS) class
support
 Suitability for both delay or loss sensitive
and delay or loss insensitive traffic
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 Seamless private and public network
technology
 Automatic configuration and failure
recovery
 Cost-effective fixed length cell processing
 Improved transmission utilization
 Futureproof investment
Evolution of packet switching
 X.25
 TCP/IP
 Frame Relay
 Switched Multimegabit Data Service
(SMDS)
ATM standards and specification
bodies
 International Telecommunications
Union (ITU)
 Formerly called CCITT is renamed as ITU-T
(Telecommunications)
 First BISDN standard: 1988 blue books
 Many study groups to work on different
topics
 American National Standards Institute
(ANSI)
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 Committee T1 is primarily involved in the
standardization of BISDN
 Close coordination with ITU-T, address
unique technologies to North America
 Subcommittees: T1E1: physical interface,
T1M1 maintenance, T1A1 performance,
T1S1.5: networking, signaling, layering,
AAL, …
 European Telecommunications
Standards Institute (ETSI)
 Generate more detailed specifications for
European
 ATM Forum
 Formed in October, 1991 by Northern
Telecom, Sprint, SUN, DEC
 Three types of membership: principle,
auditing, user
 Three types of committees: Technical,
market awareness, end user
 info@atmforum.com,
http://www.atmforum.com
 Internet Engineering Task Force (IETF)
 Concerns with interoperable implementations
using IP
 draft -> RFC -> stnadard
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 Frame Relay Forum and SMDS Interest
Group
 Both work very closely with the ATM Forum
to specify Frame Relay/ATM interworking
and SMDS over ATM UNI
The process of creating standards
Users, Vendors, Providers
Work Plan
Problems
Meetings
Comment
Resolution
Review
Drafting
Voting & Approval
Acceptance & Interoperability
Accepted
Current standards and specifications
 ITU-T
I.113
Vocabulary for B-ISDN
I.121
Broadband aspects of ISDN
I.150
B-ISDN Asynchronous Transfer Mode Functional Characteristics
I.211
General service aspects of B-ISDN
I.311
B-ISDN general network aspects
I.321
B-ISDN protocol reference model and its application
I.327
B-ISDN functional architecture
I.350
General aspects of quality of service and network performance in digital
networks, including ISDN
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I.356
B-ISDN ATM layer cell transfer performance
I.361
B-ISDN ATM layer specification
I.362
B-ISDN ATM adaptation layer (AAL) functional description
I.363
B-ISDN ATM adaptation layer (AAL) specification
I.364
Support of connectionless data service on a B-ISDN
I.365.1 Frame relaying bearer service specific convergence sublayer (FR-SSCS)
I.371
Traffic control and congestion control in B-ISDN
I.413
B-ISDN user network interface
I.432
B-ISDN user network interface - physical layer specificaiton
I.555
Frame relay bearer service interworking
I.580
General arrangements for interworking between B-ISDN and 64kbs ISDN
I.610
B-ISDN OAM principles and functions
G.804 ATM cell mapping into plesiochronous digital hierarchy (PDH)
 ANSI
 T1.624-1993 : BISDN UNI: rates and
formats specification
 T1.627-1993 : BISDN ATM functionality
and specification
 T1.629-1993 : BISDN ATM adaptation layer
3/4 common part functionality and
specification
 T1.630-1993 : BISDN - adaptation layer for
constant bit rate service functionality and
specification
 T1.633 : Frame relay bearer service
interworking
 T1.634 : Frame relay service specific
convergence sublayer (FR-SSCS)
 T1.635 : BISDN ATM adaptation layer type
5 (AAL5)
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 ATM Forum
 ATM User-Network Interface (UNI) version
2.0, 3.0, 3.1, 4.0
 ATM Private Network-Network Interface
(PNNI) specificaiton version 1.0
 ATM Data eXchange Interface (DXI)
version 1.0
 ATM Broadband-InterCarrier Interface
(B-ICI) version 1.0
 IETF
 RFC 1483 : Multiprotocol Encapsulation
over ATM
 RFC 1577 : Classical IP over ATM
B-ISDN protocol model and
architecture
 User plan: Physical layer, ATM layer,
AAL (1-5), higher layers
 Control plan: Physical layer, ATM layer,
AAL (SAAL), higher layers
 Management plan: layer management
and plan management
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Management plane
Control plane
Higher Layers
User plane
Higher Layers
ATM Adaptation Layer
ATM Layer
Virtual Channel Functions
Plane management
Virtual Path Functions
Layer management
Physical Layer (PMD)
A
A
L
P
H
Y
Layer Name
Function
Higher Layers
Higher Layer Function
Convergence
Sub-layer (CS)
Service Specific (SS)
Common Part (CP)
SAR Sub-layer
Segmentation and Re-assembly
Generic Flow Control
Cell Header
Generation/Extraction
ATM
Cell VCI/VPI
Translation
Cell Multiplexing/
De-multiplexing
Transmission
Cell Rate Decoupling
Convergence (TC) Cell Delineation
Transmission Frame Adaption
PMD
Bit Timing, Phy. Medium
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Physical Medium Dependent (PMD)
Sublayer
 PMD provides actual clocking of bit
transmission over the physical medium
 ANSI T1.624 standards
 SONET-based interface
 STS-1 at 51.84 Mbps
 STS-3c at 155.52 Mbps
 STS-12c at 622.08 Mbps
 PLCP of DQDB
 DS3 at 44.756 Mbps
 ITU-T I.432
 STM-1 at 155.520 Mbps
 STM-4 at 622.08 Mbps
 DS1, E1, DS2, E3, DS3, E4
 ATM Forum
 DS3, STS-3c
 FDDI at 100 Mbps
 Fiber Channel at 155.52 Mbps
 STP at 155.52 Mbps
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