Q1: What is the use of Asynchronous Transfer mode switching(ATM)? ATM as a Backbone technology: ATM Devices: ATM network interface: User to Network Interface (UNI): Network to Node Interface (NNI): ATM reference model: ATM services: ATM Virtual Connections: ATM CLASS OF SERVICES: ATM CONCEPTS SERIVES CATEGORIES:

1. ASSINGMENT # 3
INTERNET ARCHITECTURE
AND PROTOCPL(IA&P)
NAME:
ARSLAN
ROLL NO:
17581556-012
SUBMITTED TO:
MAM SARA
SECTION:
‘A’
‘BSIT’
UNIVERISTY OF

2. Q1: What is the use of Asynchronous Transfer mode
switching(ATM)?
Asynchronous transfer mode (ATM) is a switching technique used by
telecommunicationnetworks.
Uses asynchronous time-division multiplexing to encode data into small,
fixed-sized cells.
This is differentfrom Ethernet or internet, which use variable packet sizes
for data or frames. ATM is the core protocolused over the synchronous
optical network (SONET) backbone of the integrated digital services
network (ISDN).
It operates at data link layer of OSI and has Huge impact developmentif
ISDN.
ATM cell formats 53 bytes
5
Header
48
Payload
UNI HEADER:
is used within private networks of ATM for communication between
ATM endpoints and ATM switches.
NNI HEADER:
Is used for communicationbetween ATM switches
It is ideal for real-time low latency data such as video as well as high-
throughput data transfer like file transfer.
Advantages of ATM:
It provides dynamic bandwidth that is particularly switched for bursty
traffic.
Small sized header reduces packet overload thus ensuring effective
bandwidth usage.

3. ATM as a Backbone technology:
ATM stands for Asynchronous Transfer Mode,is a high-speed,
broadband transmission data communication technologybased on packet
switching, which is used by telcos, long distance carriers, and campus-wide
backbone networks to carry integrated data, voice, and video information.

4. Asynchronous TransferMode (ATM) can be used as the underlying
technology for FiberDistributed Data Interface (FDDI), Synchronous
Optical Network (SONET), and other high-speed networks. Plus, ATM can
run on any media including coax, twisted-pair, or fiber-optic.
ATM Devices :

5. An ATM network is made up of an ATM switch and ATM endpoints.
An ATM switch is responsible for cell transit through an ATM network.
The job of an ATM switch is well defined. It accepts the incoming cell
from an ATM endpoint or another ATM switch. It then reads and
updates the cell header information and quickly switches the cell to an
output interface towards its destination. An ATM endpoint (or end
system) contains an ATM network interface adapter. Examples of ATM
endpoints are workstations, routers, digital service units (DSUs), LAN
switches, and video coder-decoders.
ATM network interface:

6. User to Network Interface (UNI):
Public UNI, Private UNI
Network to Node Interface (NNI):
Private NNI (P-NNI)
Public NNI = Inter-Switching System Interface (ISSI)
Intra-LATA ISSI (Regional Bell Operating Co)
Inter-LATA ISSI (Inter-exchange Carriers)
Broadband Inter-Carrier Interface (B-ICI)
Data Exchange Interface (DXI):
Between packet routers and ATM Digital Service Units (DSU)

7. ATM reference model :
1. PhysicalLayer: This layer correspondsto physical layer of OSI model. At
this layer, the cells are converted into bit streams and transmitted over the
physical medium. This layer has two sub layers: PMD sub layer (Physical
Medium Dependent) and TC (Transmission Convergence) sub layer.
2. ATM Layer: This layer is comparable to data link layer of OSImodel. It
accepts the 48 byte segments from the upper layer, adds a 5 byte header to
each segment and converts into 53 byte cells. This layer is responsible for
routing of each cell, traffic management, multiplexing and switching.
3. ATM Adaptation Layer (AAL): This layer correspondsto network layer of
OSI model. It provides facilities to the existing packet switched networks to
connect to ATM network and use its services. It accepts the data and
converts them into fixed sized segments. The transmissions can be of fixed
or variable data rate. This layer has two sub layers: Convergence sub layer
and Segmentation and Reassembly sub layer.
ATM endpoints: It contains ATM network interface adaptor. Examples
of endpoints are workstations, routers, CODECs, LAN switches, etc.

8. ATM switch : It transmits cells through the ATM networks. It accepts the
incoming cells from ATM endpoints (UNI) or another switch (NNI), updates
cell header and retransmits cell towards destination.
ATM cell formats 53 bytes:
5
header
48
Payload
UNI HEADER:
is used within private networks of ATM for communication between
ATM endpoints and ATM switches.
NINI HEADER:
Is used for communicationbetween ATM switches
It is ideal for real-time low latency data such as video as well as high-
throughput data transfer like file transfer.

9. ATM services:
ATM makes virtual connection between nodes or devices to communicate.
There are two types of virtual circuits:
1. Permanent Virtual Circuit, or (PVC). A circuit or connection is
planned out and coded into the switches. Example: A server in Denver
has a PVC connection to the accounting server in San Diego
in ACME Widgets, Inc.
2. Switched Virtual Circuit, or (SVC). A circuit between devices is
established to transfer data, then the virtual circuit is deleted.
Example: Alexis in Denver downloads the latest sales figures from the
San Diego server to her office workstation.
ATM Virtual Connections:
ATM standard defines two types of ATM connections: virtual path connections
(VPCs), which contain virtual channel connections (VCCs) as shown in Fig. 4.6.6.
A virtual channel connection (or virtual circuit) is the basic unit, which carries a
single stream of cells, in order, from user to user. A collection of virtual circuits
can be bundled together into a virtual path connection. A virtual path connection
can be created from end-to-end across an ATM network. In this case, the ATM
network does not route cells belonging to a particular virtual circuit. All cells
belonging to a particular virtual path are routed the same way through the ATM
network, thus resulting in faster recovery in case of major failures. In this case, all
the switches within the ATM network are only VP switches, i.e. they switch the
cells only on the basis of VPIs. Only the switches, which are connected to the
subscribers are VP/VC switches, i.e. they use both VPIs and VCIs to switch the
cell. This configuration is usually followed so that the intermediate switches can do
switching much faster.

10. An ATM network also uses virtual paths internally for the purposeof bundling
virtual circuits together between switches. Two ATM switches may have many
different virtual channel connections between them, belonging to different users.
These can be bundled by two ATM switches into a virtual path connection. This
can serve the purposeof a virtual trunk between the two switches. This virtual
trunk can then be handled as a single entity by perhaps, multiple intermediate
virtual paths cross connects between the two virtual circuit switches.
ATM CLASS OF SERVICES:
There are 4 classes:
CLASS A:
Constant bit rate(CBR).
Connection oriented
Strict timing relation between source and destination i.e voice
CLASS B:
Variable bit rate(VBR).

11. Connection oriented
Strict timing e.g packet-mode video for video conferencing
CLASS C:
Connection oriented VBR.
Not strict timing e.g LAN data transfer application such as Frame
relay
CLASS D:
Connection less VBR. Not strict timing e.g LAN data transfer
application such as IP
ATM CONCEPTS SERIVES CATEGORIES:
ABR:
---Source follows network feed back
---Available bit rate
---Max throughput with minimum loss
UBR:
---Unspecified bit rate
---User sends whenever it wants. No feedback. No guarantee. Cells may
be dropped during congestion
CBR:
--- Constant bit rate
--- User declares required rate
--- Throughput. Delay and delay variation guarrented.
VBR:
--- Variable bit rate
--- Declare avg and max rate.
--- rt –VBR(Real time):conferencing.
-max delay guarranted
--- nrt –VBR(Non-real time):stored video

12. s