IA&P

1. Broadband ISDN
&
Asynchronous Transfer Mode (ATM)
Submitted to:Mam Sara Sarwar
Presented by: Group#4
Muhammad Saqlain(19011556-062)
Muhammad AbuBkar(19011556-058)
Touseeq Zulfiqar(19011556-055)
Abrar Ahmad(19011556-063)

2. ISDN
(Integrated Services Digital
Network)
Presented by:
Muhammad Saqlain(19011556-062)

3. ISDN (Integrated Services Digital Network)
Communication standards Integrates
Voice communication
Data ( Pictures, videos)
Dialup
Public Switched Telephone Network
• Circuit Switched Network
• Packet Switched Network

5. ISDN Supports Variety of Services

6. ISDN Defines Three Channels Types
B Channel: A Bearer channel is define at a rate of 64 kbps. It is the basic user
channel and can carry any type of "Digital Information" in full duplex mode as
long as the required transmission rate does not exceed 64 kbps.
D Channel: A data channel can be either 16 or 64 Kbps, depending on the
primary function of D channel is to carry "control signaling" for the B channels.
H Channel: It is available with data rates of 384 kbps (HO), 1536 kbps (H11) or
1920 kbps (H12). These are used for "high data rate applications" such as video,
teleconferencing and so on.

7. ISDN Interfaces

8. Basic Rate Interface (BRI)

9. Basic Rate Interface
There are two data-bearing channels ('B' channels) and one
signaling channel ('D' channel) in BRI to initiate connections. The B
channels operate at a maximum of 64 Kbps while the D channel
operates at a maximum of 16 Kbps. The two channels are independent
of each other. For example, one channel is used as a TCP/IP connection
to a location while the other channel is used to send a fax to a remote
location.
The basic rate interface (BRI) specifies a digital pipe consisting
two B channels of 64 Kbps each and one D channel of 16 Kbps. This
equals a speed of 144 Kbps. In addition, the BRI service itself requires
an operating overhead of 48 Kbps. Therefore a digi pipe of 192 Kbps is
required.

10. Primary Rate Interface (PRI)

11. Primary Rate Interface
Primary Rate Interface service consists of a D channel and either
23 or 30 B channels depending on the country you are in. A digital pipe
with 23 B channels and one 64 Kbps D channel is present in the usual
Primary Rate Interface (PRI). Twenty-three B channels of 64 Kbps each
and one D channel of 64 Kbps equals 1.536 Mbps. The PRI service uses
8 Kbps of overhead also. Therefore PRI requires a digital pipe of 1.544
Mbps.

12. ATM
(Asynchronous Transfer Mode)
Presented by:
Muhammad AbuBkar(19011556-058)
Touseeq Zulfiqar(19011556-055)
Abrar Ahmad(19011556-063)

13. Asynchronous Transfer Mode(ATM)
• ATM is a high speed network technology that is designed for both
WAN & LAN.
• It is a connection oriented switching technology, meaning that a
dedicated path is setup between two end systems before a
communication session can begin.
• It transmits all information including multiple service types such as
data, video, or voice which is conveyed in small fixed-size packets
knows as cells.
• All cells follow the same path to the destination.
• Also called Cell Relay.
• ATM operates at the data link layer—Layer 2 in the OSI MODEL

14. ATM Cell Format
• As information is transmitted in ATM in the form of fixed-size units
called cells.
• Each cell is 53 bytes long which consists of a 5 bytes header and 48
bytes payload.

15. ATM Multiplexing
• Multiplexing, or muxing, is a way of sending multiple signals or streams of
information over a communications link at the same time in the form of a single,
complex signal. When the signal reaches its destination, a process
called demultiplexing, or demuxing, recovers the separate signals and outputs
them to individual lines.

16. ATM Devices
• ATM networks are built around two types of devices
1. ATM End-Point
2. ATM Switch
• Examples of ATM end points are
 Pc
 Workstations
 Servers
 LAN Switches
 Routers

17. ATM Devices
• An ATM switch can be connected either another ATM switch or and
ATM endpoint.
• INGRESS SWITCH
The first ATM switch which is attached directly to the source ATM
point.
• EGRESS SWITCH
The exit switch that is attached to the destination end system.

18. ATM Switches and Interfaces
• ATM switch supports two types of Interface
• User-Network Interface(UNI)
• Connects an ATM end-point to a Switch
• Network-Network Interface(NNI)
• Connects two ATM Switches

19. Architecture of ATM Network

20. ATM Cell Formats
• An ATM header can have one of two formats - User-Network Interface (UNI) or Network-Node
Interface (NNI). UNI is used for communication between end systems and switches. NNI is used for
communication between switches.

21. ATM Cell Formats(Header)
• GFC (Generic Flow Control) - the Generic Flow Control field provides local
functions such as identifying multiple stations that share a single ATM
interface (it is typically not used, and is set to a default value of 0).
• VPI(Virtual Path Identifier)
It is the Routing field for the network to define the path
8 bits are used for UNI
12 bits are used for NNI
• VCI(Virtual Connection Identifier) - It defines routing between end
users(16-bits)

22. ATM Cell Formats(Header)
• Payload Type(PT) - Indicates the type of information in the information
field e.g. user info or Network Management
 Bit Information
 1st Bit
0 : User Information
1 : Indicate Network Management or Maintenance Information
 2nd Bit indicates Congestion: 0-NO 1-YES
 3rd Bit indicates SDU type

23. ATM Cell Formats(Header)
• CLP(Cell Loss Priority) - Cell Loss Priority provides guidance to the
network in the event of congestion. CLP = 0 indicates a cell of high
priority which should not be discarded. CLP = 1 indicates a cell that is
subject to discard.
• HEC(Header Error Control) - the Header Error Control field contains a
checksum calculated on the first 4 bytes of the header. It can be used
to correct a single bit error in these bytes, preserving the cell rather
than discarding it, or to detect multi-bit header errors (in which case
the cell is dropped).

24. ATM Services
SVC (Switched Virtual Circuit)
PVC (Permanent Virtual Circuit)

25. SVC (Switched Virtual Circuit)
• Re-establish the connection
• Temporary path

26. SVC (Switched Virtual Circuit)

27. PVC (Permanent Virtual Circuit)
Available permanently
Manual
Link-by-link

28. ATM reference model

29. ATM reference model

30. ATM reference model layers
• ATM reference model comprises of three layers:
i. Physical layer
ii. ATM layer
iii. ATM Adaptation layer

31. Physical layer
This layer corresponds to 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 sub layer (Transmission Covergence) sub
layer.

32. ATM layer
This layer is comparable to data link layer of OSI model. 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.

33. ATM Adaptation layer
This layer corresponds to 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.

35. Connection Establishment
• If a device wants to communicate with another device in an ATM
network across multiple switches.
• Device A sends a connection set-up request to its directly connected
switch
• Request signaled across UNI
• Includes information about QOS requirements and destination
address

37. Connection Establishment
• The switch decides if it can support these requirements?
• If “yes” then it determines if it can locate the destination address?
• If both conditions are true, the connection is set-up
• The switch sends a message to devices A informing that a connection
is established

39. Connection Establishment
• The switch also assigns a VPI/VCI value to the connection
VPI(Virtual Path Identifier):
The path data takes across a network
VCI(Virtual Channel Identifier):
A segment of the VCI
• Then forwards the request to next switch using NNI.

41. Connection Establishment
• The next switch performs same action as the first switch
• It again determines that if it can support QOS requirements and
locate destination address.
• If “yes” then assigns a VPI/VCI value and forward the request.
• This process is repeated till the last switch sends request to device B
using UNI

42. Connection Establishment
• Device B after accepting the request, sends a message to Device A
• Once the source (Device A) receives the message, data is sent.
• It may look like a long process but in most networks, it takes less than
a second.

43. Question
What happens when a switch fails during connection?

44. ATM Classes of service
• ATM service is divided into different classes or categories. The four
basic categories are as follows:
i. CBR
ii. VBR
iii. ABR
iv. UBR

45. CBR(Constant Bit Rate)
• As the name implies, This category is defined to support traffic
requiring a constant bit rate.
• Constant bit rate means a steady bandwidth allocation.
• This category has the highest priority.
• Primarily, the CBR service category is used to support voice
communication and is also sometimes called circuit emulation. This is
because the service provided emulates, or acts like, a dedicated
physical circuit.

46. VBR(Variable Bit Rate)
• This category has a priority below that of CBR
• It is defined to support traffic types that require a variable bit rate.
• Variable bit rate means the amount of traffic sent by the application
varies over time, so the contract defined by this service category must
accept data at different bandwidths.
• Video communications commonly uses this type of service.

47. ABR(Available Bit Rate)
• Available bit rate is a little more complex than the rest and is defined to
support plain data.
• The first two methods, CBR and VBR, define the bandwidth needs, and the
network supports them.
• With ABR, the application can determine how much bandwidth is available
on the network and use as much of it as possible.
• When using ABR, the transfer rate is constantly changing as the
transmitting station adjusts its transmission in accordance with available
bandwidth.
• ABR depends upon VBR-when VBR traffic needs more bandwidth, ABR gets
less, and vice versa.

48. UBR(Unspecified Bit Rate)
• And finally, with essentially no priority, is Unspecified Bit Rate, or UBR
• UBR traffic has no guarantees, so all other traffic takes priority.
• If the network gets congested, UBR traffic gets discarded first, and the
originating station is required to re-send it.

49. MCQs
1. Information bearing channels in ISDN are called :
a) D channels b) Data channels
c) B channels d) Voice channels
Ans : c) B channels
2. ISDN is a:
a) packet switched network b) circuit switched telephone network
c) packet switched and circuit switched telephone network
d) None
Ans : c) packet switched and circuit switched telephone network

50. MCQS
3. ATM also called:
a) Frame Relay
b) Cell Relay
c) TDM
Answer: b) Cell Relay
4. The Header size of an ATM Cell is
a) 53
b) 48
c) 5
Answer: c) 5 bytes

51. MCQS
5. The Interface of ATM switch are
a) NNI
b) UNI
c) Both a & b
Answer: c) Both a & b
6. Which is not ATM reference model layer
a) physical layer b) ATM adoption layer
c) ATM layer d) Datalink layer
Ans: d) Datalink layer

52. MCQs
7. Which switching technique establish path for short session
a) permanent virtual circuit b) Switched virtual circuit
c) both a&b d) None of these
Ans: b) Switched virtual circuit