Asynchronous Transfer Mode - Data Communication

Asynchronous Transfer Mode (ATM) Presentation Overview:

This presentation explores Asynchronous Transfer Mode (ATM), a high-speed, cell-based switching technology used in telecommunications networks. It emphasizes ATM's role in supporting real-time voice, video, and data transmission, making it a versatile solution for broadband communication.

1. Asynchronous
Transfer Mode
REPORTERS:
ATINADO, RUSSELL VINCENT
DECREPITO, JAMAHL
RONDOVIO, CHERLJOHN NEO

2. Asynchronous
Transfer Mode
Is a relatively new data communications
technology that uses a high-speed form of
packet switching network for the
transmission media
ATM can handle all kinds of communications
traffic, including voice, data, image, video,
high-quality music, and multimedia.

3. Asynchronous
Transfer Mode
ATM Cell Structure

4. Asynchronous Transfer Mode
Payload- actual data being
transmitted in the packet
Header- packet that contains
the control information
necessary for the packet to be
transmitted over the network

5. ATM Protocol
Architecture

6. ATM Protocol Architecture

7. ATM Protocol Architecture
The physical layer is responsible for transmitting raw bits over the physical medium. This
layer defines the physical characteristics of the transmission medium, such as the voltage
levels, signaling rates, and physical connectors. The ATM protocol supports a variety of
physical media, including fiber-optic cable, twisted pair, and coaxial cable.

8. ATM Protocol Architecture
The ATM layer is responsible for segmenting data into fixed-size cells and routing these
cells through the network. The fixed-size cells are 53 bytes in length, consisting of a 5-
byte header and a 48-byte payload. The header contains information about the cell's
destination, the virtual circuit it belongs to, and the quality of service requirements for the
data. The ATM layer also provides traffic management functions to ensure that high-
priority traffic is given priority over lower-priority traffic.

9. ATM Protocol Architecture
The AAL (ATM Adaptation Layer) layer is responsible for adapting higher-layer protocols,
such as TCP/IP and MPEG, to the ATM protocol. The AAL layer performs segmentation
and reassembly of higher-layer data, and also provides error control and flow control
mechanisms to ensure reliable delivery of data.

10. ATM Protocol Architecture
User plane: Provides for user information transfer, along with associated controls (e.g.,
flow control, error control)
Control plane: Performs call control and connection control functions
Management plane: Includes plane management, which performs management functions
related to a system as a whole and provides coordination between all the planes, and layer
management, which performs management functions relating to resources and
parameters residing in its protocol entities

11. ATM LOGICAL
CONNECTIONS

12. ATM LOGICAL
CONNECTIONS
Logical connections in ATM are referred to as virtual channel connections (VCCs). A VCC is
analogous to a virtual circuit in X.25; it is the basic unit of switching in an ATM network. A
VCC is set up between two end users through the network and a variable-rate, full-duplex
flow of fixed-size cells is exchanged over the connection. VCCs are also used for user-
network exchange (control signaling) and network-network exchange (network
management and routing).

13. ATM LOGICAL
CONNECTIONS
For ATM, a second sublayer of processing has been introduced that deals with the
concept of virtual path (Figure 11.2). A virtual path connection (VPC) is a bundle of VCCs
that have the same endpoints. Thus, all of the cells flowing over all of the VCCs in a
single VPC are switched together.

14. ATM LOGICAL
CONNECTIONS
Several advantages can be listed for the use of virtual paths:
Simplified network architecture
Increased network performance and reliability
Reduced processing and short connection setup time
Enhanced network services

15. ATM LOGICAL
CONNECTIONS
• The virtual path control mechanisms
include calculating routes, allocating
capacity, and storing connection state
information.
• To set up a virtual channel, there must
first be a virtual path connection to the
required destination node with sufficient
available capacity to support the virtual
channel, with the appropriate quality of
service. A virtual channel is set up by
storing the required state information
(virtual channel/virtual path mapping).

16. ATM LOGICAL
CONNECTIONS

17. ATM LOGICAL
CONNECTIONS
VIRTUAL CHANNEL CONNECTION USES:
Between end users: Can be used to carry end-to-end user data; can also be used to carry
control signaling between end users, as explained later.
Between an end user and a network entity: Used for user-to-network control signaling, as
discussed subsequently.
Between two network entities: Used for network traffic management and routing
functions.

18. ATM LOGICAL
CONNECTIONS
VIRTUAL PATH/VIRTUAL CHANNEL CHARACTERISTICS:
Quality of service (QoS): A user of a VCC is provided with a QoS specified by parameters such as cell loss ratio (ratio of cells
lost to cells transmitted) and cell delay variation.

Switched and semi-permanent virtual channel connections: A switched VCC is an on-demand connection, which requires a
call control signaling for setup and tearing down.
Cell sequence integrity: The sequence of transmitted cells within a VCC is preserved.
Traffic parameter negotiation and usage monitoring: Traffic parameters can be negotiated between a user and the
network for each VCC.
Virtual channel identifier restriction within a VPC: One or more virtual channel identifiers, or numbers, may not be available
to the user of the VPC but may be reserved for network use.

19. ATM CELLS

20. ATM Cells
Network to
Network Interface
- connects two or
more networks
User to Network
Interface
- connect the
user to the
network
Cell Formats:
1.
2.

21. ATM Cells
Generic Flow Control
- Controls the flow of
traffic across the UNI
and into the network.
Virtual Path Identifier
- Identifies a particular
VP link.

22. ATM Cells
Virtual Channel Identifier
- Used for routing to
and from the end user.

23. ATM Cells
Payload Type
- Indicates the type of
information in the
information field.

24. ATM Cells
Payload Type

25. ATM Cells
Payload Type
First bit:
0 - Indicates user information
1 - Indicates that this cell carries network management or
maintenance information
Second bit:
- Indicates whether congestion has been experienced
Third bit:
- used to discriminate two types of Service Data Units associated
with a connection

26. ATM Cells
Cell Loss Priority (CLP)
- used to provide
guidance to the
network in the event of
congestion

27. ATM Cells
Header Error Control
- used to check the
validity of the ATM cell
control information

28. ATM Cells
Header Error Control

29. TRANSMISSION OF
ATM CELLS

30. TRANSMISSION OF ATM CELLS
ATM cells may be transmitted at one of several data
rates:
622.08 Mbps
155.52 Mbps
51.84 Mbps
25.6 Mbps
We need to specify the transmission structure that
will be used to carry this payload.

31. TRANSMISSION OF ATM CELLS
Cell-based physical layer
SDH (Synchronous Digital
Heirarchy) - based physical layer
Approaches:

32. TRANSMISSION OF ATM CELLS
Cell-based physical layer
- The interface structure consists of a continuous
stream of 53-octet cells.
- No framing is imposed so synchronization is
needed.

33. TRANSMISSION OF ATM CELLS
Synchronization:
1. HUNT State
2. PRESYNC State
3. SYNC State
Cell-based physical layer

34. TRANSMISSION OF ATM CELLS
Cell-based physical layer
1. HUNT State
A cell delineation algorithm is performed bit
by bit to determine if the HEC coding law is
observed.

35. TRANSMISSION OF ATM CELLS
Cell-based physical layer
2. PRESYNC State
A cell structured is now assumed. The cell
delineation algorithm is performed cell by cell
until the encoding law has been confirmed.

36. TRANSMISSION OF ATM CELLS
Cell-based physical layer
3. SYNC State
HEC is used for error detection and
correction. Cell delineation is assumed to be
lost if the HEC coding law is recognized as
incorrect.

37. TRANSMISSION OF ATM CELLS
Cell-based physical layer
Advantage:
Simplified interface that results when both
transmission and transfer mode functions
are based on a common structure.

38. TRANSMISSION OF ATM CELLS
SDH-Based Physical Layer
- Imposes a structure on the ATM cell
stream.
- Operates at a line rate of 155.52 Mbps
- Framing is imposed using the STM-1 (STS-
3) frame.

39. TRANSMISSION OF ATM CELLS
Advantage:
Can be used to carry either ATM-based or STM-
based
Can be circuit switched using an SDH channel
Several ATM streams can be combined to build
interfaces with higher bit rates than those
SDH-based physical layer

40. ATM SERVICE CATEGORIES
Contrast Bit Rate (CBR)
Variable BIt Rate (rt-VBR)
REAL-TIME SERVICE
non-real-time variable bit rate(nrt-VBR)
Available bit rate (ABR)
Unspecified bit rate (UBR)
Guaranteed frame rate (GFR)
NON-REAL-TIME SERVICE
aims to provide
quality of
service and
designed to
transfer
various data
types

41. REAL-TIME SERVICE
CONSTANT BIT RATE
(CBR)
VARIABLE BIT RATE
- continuous flow of
data

42. REAL-TIME SERVICE
CONSTANT BIT RATE (CBR)
require a fixed amount of
bandwidth and have strict
timing requirements. These
services are typically used for
applications that require a
continuous and predictable
flow of data
videoconferencing
television
video-on-demand
audio library
Examples:

43. REAL-TIME SERVICE
VARIABLE BIT RATE (rt-VBR)
applications transmit at a rate
that varies with time and source
can be characterized as
somewhat bursty
video streaming
audio streaming
Examples:

44. NON-REAL-TIME SERVICE
non-real-time variable bit rate(nrt-VBR)
Available bit rate (ABR)
Unspecified bit rate (UBR)
Guaranteed frame rate (GFR)
-does not require constant or
guaranteed bandwidth

45. NON-REAL-TIME SERVICE
NON-REAL-TIME VARIABLE BIT RATE(NRT-VBR)
can be used for data
transfers that have
critical response time
requirements.
airline reservations
bank transactions

46. NON-REAL-TIME SERVICE
AVAILABLE BIT RATE (ABR)
ABR specifies a peak cell
rate (PCR) that it will use
and a minimum cell rate
(MCR) that it requires.The
network allocates
resources so that all ABR
applications receive at
least their MCR capacity.
file transfer
lan interconnection

47. NON-REAL-TIME SERVICE
UNSPECIFIED BIT RATE (ABR)
does not allocate
bandwidth or provide any
priority scheme for
different types of traffic.
best-effort service
text
image transfer
messaging
email
web browsing

48. NON-REAL-TIME SERVICE
GUARANTEED FRAME RATE (ABR)
major goal of GFR is to
optimize the handling of
frame-based traffic that
passes from a LAN
through a router onto an
ATM backbone network
video conferencing
online games

49. THANK YOU