1. Asynchronous Transfer Mode
(ATM)

2. By.
P. Victer Paul
Dear,
We planned to share our eBooks and project/seminar contents
for free to all needed friends like u.. To get to know about more
free computerscience ebooks and technology advancements in
computer science. Please visit....
http://free-computerscience-ebooks.blogspot.com/
http://recent-computer-technology.blogspot.com/
http://computertechnologiesebooks.blogspot.com/
Please to keep provide many eBooks and technology news for
FREE. Encourage us by Clicking on the advertisement in these
Blog.

3. Agenda
 Definition
 Basic characteristics
 Why asynchronous
 How to access the network
 Service Categories
 Connections
 Protocol Architecture
 pros & cons
 Troubleshooting

4. ATM – definition
"A transfer mode in which information is
organized into cells; it is asynchronous in the
sense that the recurrence of cells containing
information from an individual user is not
necessarily periodic".

5. ATM Characteristics
 ATM uses packet switching with fixed length packet
of 53 bytes – CELLs. Each cell has a 5-byte header
and 48-byte payload
 ATM uses Virtual Circuits
 ATM can run over any physical layer. Often runs
over fiber optics using the SONET standard at speeds
of 155.52 Mbps, 622 Mbps and higher

6. ATM Characteristics
A Cell network uses the cell as the basic unit of data
exchange. A cell is defined as a small, fixed-sized
block of information
ATM uses asynchronous TDM – to multiplex cells
coming from different channels
 Uses fixed slots (size of cells)
 Fills a slot with a cell from any input channel that
has a cell
– slot is empty if none of the channels has a cell
to send

7. Asynchronous Transfer Mode
(ATM)
MUX
Wasted bandwidth
4 3 2 1 4 3 2 1 4 3 2 1

8. ATM Access
 ATM is a cell-switched network.
 The user access devices, called the endpoints, are
connected through a user-to-network interface (UNI)
to the switches inside the network.
 The switches are connected through network-to-
network interfaces (NNIs).

9. STDUCTURE Private ATM
network
Private
UNI
X X
Private
NNI Public ATM
X
network A
X X
NNI
Public X
UNI B-ICI Public ATM
network B
X
Public
UNI
X X

10. ATM Connections
 two levels of ATM connections:
virtual path connections
virtual channel connections
 indicated by two fields in the cell header:
virtual path identifier VPI
virtual channel identifier VCI

11. Virtual Paths
Physical Link
Virtual Channels

13. ATM Service Categories
 Real-time services
 Constant bit rate – uncompressed audio/video info
 Videoconferencing, TV, pay-per-view, VOD, etc.
 rt-Variable bit rate
 Non-real-time services
 nrt-VBR – high end system QoS, critical response time
 Bank transactions, airline reservations, etc.
 Unspecified bit rate – best-effort service
 e.g. text/image messaging, telecommuting
 Available bit rate – bursty apps requiring reliable end-to-end
connection
 e.g. LAN, router-to-router reliability

14. ATM Protocol Architecture
Management plane
Plane management
Control plane User plane
Layer management
Higher layers Higher layers
ATM adaptation layer
ATM layer
Physical layer

15.  adaptation layer: only at edge of ATM network
 data segmentation/reassembly
 roughly analogous to Internet transport layer
 ATM layer: “network” layer
 cell switching, routing
AAL user
 physical layer
ATM layer
Physical layer

16. Pros & cons
 higher transmission speeds
 quality of service
 bandwidth-on-demand
 application-independent
 Cost
 Complexity
 Availability

17. Troubleshooting
 Performing Basic Interface Checks
 Determining Network Connectivity
 Performing Loopback Tests
 Troubleshooting 155-Mbps and 622-Mbps Interfaces
 Troubleshooting T1 and E1 Interfaces
 Troubleshooting DS3 and E3 Interfaces
 Troubleshooting CBR T1 and CBR E1 Interfaces
 Troubleshooting 25-Mbps Interfaces

18. References:
1. Asynchronous Transfer Mode (ATM) fundamentals, white paper from Internation
Engineering Consortium
2. ATM tutorial-fnc educational services
3. Higher Layer Protocols:TCP/IP and ATM- Eytan Modiano,Massachusetts
Institute of Technology
4. ATM Switch Troubleshooting Guide-Cisco