ATM Full

1. Computer Communication &
Networking
Mcs 1st A

2. Group Members
Iqra Muzaffar # Cell Structure
Zahida Batool # Multiplexing
Fakhira Abbas # ATM Layer
Rubba Kainat # ATM Switching

3. ATM (Asynchronous data
mode)
 ATM network are cell oriented . ATM
integrates the multiplexing and
switching function. High performance.
 ATM was design earlier in 1990s.
 It transfer data into small cells.

4. Asynchronous data transfer
 Goals:
 Universal service – for all subscribers.
 Support for all uses _ voice , videos
and data.
 A single unified infrastructure (no
separate LANs and WANs)
 Gurrantee service .

5. Architecture
 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 net- work. The
switches are connected through
network-to-network interfaces (NNIs).

6. ATM Cell Structure
 The most basic data transfer units are
called cell.
 At data link layer the data transfer
units are known as frames.
 A size of cell is 53 bytes . 5 bytes are
of header and 48 bytes are of
payload.

7. 53 bytes cell
structure
ATM Cell Format

8. Multiplexing
 Variety of frame size makes the traffic
unpredictable.
 Another problem is to provide
consistent data rate delivery when
frames size are unpredictable

9. Before multiplexing ATM

10. ATM Multiplexing

11. ATM Multiplexing

12. ATM Layers

13. Physical layer
 The lowest layer in the ATM protocol.
 It describe the physical transmission
media.
 We can use shielded or unshielded
twisted pair,coaxial cable, fiber optic
cable.

14. ATM Layer
 It perform all functions related to
routing or multiplexing of cell.
 It generates a header to the segment
streams generated by the AAL.
 To perform all these functions, ATM
layer maintain a table which contains
a list of VCIs.

15. ATM Adaptation layer
 AAL layer are the top layer in ATM
protocol .
 It convert the submitted information
into streams of 48 octet segments and
transport these segments and
transport these in payload field of
multiple ATM cells .

16.  Currentley five services have been
define. They are reffered as AAL 1-5.
AAL1 or AAL2 are connection
oriented. AAL1 provide constant bit
rate(CRB)service. AAL2 provides
variable bit rate(VBR) service.AAL3
provide connection oriented or VBR
service. Later, this service was
dropped and now merged with AAl4.
Both AAL4 and AAL5 provides similar
connectionless VBR service.

17. ATM switching
 A packet switching technology that allows
voice, data, image, and video traffic to be
combined into evenly sized cells for high-
speed transmission over one access circuit.
 ATM switching differs from conventional
switching because of the high-speed
interfaces (50 Mbps to 2.4 Gbps) to the switch,
with switching rates up to 80 Gbps in the
backplane .

19.  ATM networks are linked together by a
series of ATM switches that take in cells
from various sources and switch them out
again.
 The main task is to perform the routing of
data cells, signaling and management cell.
 It receives cells on an incoming port,
reads the VPI/VCI value, and identifies an
appropriate outgoing port for the next
node that is to receive the traffic.

20. ATM Switching techniques
 Cell Switch Fabric - to relay ATM cells
as quickly as possible and
accomplishes this by performing 2
major functions:
 Concentration, expansion,
multiplexing/demultiplexing of traffic
 Routing and buffering of traffic

21. THANK YOU..