Advanced Data Communications Udhay Prakash Part 1

8/13/2019 Advanced Data Communications Udhay Prakash Part 1

1/69

Advanced

Data Communications

Udhay Prakash

uday3prakash@gmail[dot]com


2/69

Content for discussion

Data Communication Networks

Protocols & Standards

Standardizing Organizations

2


3/69

Data Communication

Can we imagine life without Communication? Why

Factors necessitating data Communication

Local/Remote Sharing/transmission of information

Telecommunication-Distant communication

Data = information+ redundancy

Data is represented by binary information units (bits)

3


4/69

Data Communication

Exchange of data (in the form of 0s & 1s) between twodevices via some form of transmission medium.

Communicating entities must be part of communication

System.

Effectiveness of data transmission depends on: Delivery to onlydesired destination(s)

Accuracy -error-freeness

Timeliness- more real-time, lesser the delay should be maintained

4


5/69

Components

of Data Communication System

5


6/69

Transmission modes-

Simplex, Half-duplex & Full Duplex

6


7/69

Data Transmission

7


8/69

Data Transmission-

Parallel transmission

8


9/69

Data Transmission-

Serial transmission

9


10/69

AsynchronousTransmission

10


11/69

SynchronousTransmission

11


12/69

Networks-

Channel

Set of devices/nodes connected by media links communication channels

Links connecting the devices

12


13/69

Networks-

Point to point links

13


14/69

Networks-

Multi-point links

14


15/69

NetworkTopology

15


16/69

Network Topology

Mesh

16


17/69

Network Topology-

Bus

17


18/69

Network Topology-

Ring

18


19/69

Network Topology-

Star

19


20/69

Categoryof Networks

20


21/69

Categoryof Networks-

LAN

21


22/69


LAN

22


23/69


MAN

23


24/69


WAN

24


25/69

Internet

25


26/69

Networks-

Distributed Processing

All tasks are divided among multiple entities/nodes.

Advantages

Security/encapsulation

limiting the kinds of interactions that a given user can have on entiresystem

Network (crash) security Distributed databases

No one system needs to store entire data of database. Ex: WWW

Faster problem solving

Multiple computers work on part of total problem

Security through redundancy

Multiple computers running same program at the same time

Collaborative Processing

26


27/69

Networks-

Network Criteria

Includes

Performance

No. of users

Type of transmission medium

Hardware

Software Reliability

Frequency of failure

Recovery time after failure

catastrophe

Security Unauthorized access

Malicious software

27


28/69

OSIModel

Necessity

The model

Functions of the layers

E l


29/69

Assume Maria and Ann are neighbors with a lot of commonideas. However, Maria speaks only Spanish, and Ann speaksonly English. Since both have learned the sign language in theirchildhood, they enjoy meeting in a cafe a couple of days perweek and exchange their ideas using signs. Occasionally, theyalso use a bilingual dictionary. Communication is face to faceand Happens in one layer as shown in Figure below.

Example

29

E l 2 2


30/69

Now assume that Ann has to move to another town because ofher job. Before she moves, the two meet for the last time in thesame cafe. Although both are sad, Maria surprises Ann whenshe opens a packet that contains two small machines. The firstmachine can scan and transform a letter in English to a secretcode or vice versa. The other machine can scan and translate aletter in Spanish to the same secret code or vice versa. Anntakes the first machine; Maria keeps the second one. The twofriends can still communicate using the secret code, as shownin Figure below.

Example 2.2

30

E l


31/69

Example

31


32/69

32

2-2 THE OSI MODEL

Established in 1947, the International StandardsOrganization ISO)is a multinational body dedicatedto worldwide agreement on international standards.Almost three-fourths of countries in the world arerepresented in the ISO. An ISO standard that coversall aspects of network communications is the OpenSystems Interconnection (OSI) model. It was firstintroduced in the late 1970s.


33/69

OSI MODEL

33

International Standards Organization (ISO)

Covers all aspects of network communications

Open Systems Interconnection (OSI) model.

ISO is the organ izat ion;

OSI is the model.


34/69

OSI Model

34


35/69

OSI Model

35


36/69

OSI Model

36

An Exchange Using the OSI Model


37/69

An Exchange Using the OSI Model

37


38/69

Physical Layer

38


39/69

Data Link Layer

39


40/69

Data Link Layer Example

40


41/69

Network Layer

41

T i Di d i h S i


42/69

Topics Discussed in the Section

Comparison between OSI and TCP/IP

Layers in the TCP/IP Suite

42

Figure 2.7 Layers in the TCP/I P Protocol Suite


43/69

43

Figure 2.7 Layers in the TCP/I P Protocol Suite

Figure 2.8 TCP/I P and OSI model


44/69

44

Figure 2.8 TCP/I P and OSI model

Figure 2.9 A private internet


45/69

45

g p

Figure 2.10 Communication at the physical layer


46/69

46

g p y y

A

Physicallayer

Physicallayer

R1 R3 R4 B

Source DestinationLegend

011 ... 101

011

...101

011 ... 101 011 ... 101

Link 3 Link 5 Link 6Link 1


47/69

47

The uni t of commun icat ion at thephys ical layer is a b it .

Note

Figure 2.11 Communication at the data link layer


48/69

48

g y

A

Physical Physical

Data linkData link

R1 R3 R4 B

Source Destination DataD Header HLegend

Link 1 Link 3 Link 5 Link 6

FrameD2 H2

Frame

D

2H2

Frame

D2 H2Frame

D2 H2


49/69

49

The un i t of commun icat ion at the datal ink layer is a frame.

Note

Figure 2.12 Communication at the network layer


50/69

50

A

Physical Physical

Data linkata link

R1 R3 R4 B

NetworkNetwork


Datagram

D3 H3

Datagram

D3 H3


51/69

51

The uni t of commun icat ion at thenetwork layer is a datag ram.

Note

Figure 2.13 Communication at transport layer


52/69

52

A

Physical Physical

Data linkData link

R1 R3 R4

B

NetworkNetwork

Transport Transport


Segment

D4 H4

Segment

D4 H4


53/69

53

The uni t of commun icat ion at thetranspo rt layer is a segment, user

datagram , or a packet, depending on the

speci f ic p roto co l used in th is layer.

Note

Figure 2.14 Communication at application layer


54/69

54

A

Physical Physical

Data linkData link

R1 R3 R4

B

NetworkNetwork

Transport Transport

ApplicationApplication Source Destination DataD Header HLegend

MessageD5 D5

D5 D5

Message


55/69

55

The uni t of commun icat ion at theappl icat ion layer is a message.

Note


56/69

56

2-4 ADDRESSING

Four levels of addresses are used in an internetemploying the TCP/IP protocols: physical address,logical address, port address, and application-specific address. Each address is related to a onelayer in the TCP/IP architecture, as shown in Figure2.15.



57/69

57


Physical Addresses

Logical Addresses

Port Addresses

Application-Specific Addresses

Figure 2.15 Addresses in the TCP/I P protocol sui te


58/69

58

Example 2.3


59/69

59

In Figure 2.16 a node with physical address 10 sends a frame to anode with physical address 87. The two nodes are connected by alink a LAN). At the data link layer, this frame contains physical link)addresses in the header. These are the only addresses needed. Therest of the header contains other information needed at this level. Asthe figure shows, the computer with physical address 10 is thesender, and the computer with physical address 87 is the receiver.The data link layer at the sender receives data from an upper layer. Itencapsulates the data in a frame. The frame is propagated throughthe LAN. Each station with a physical address other than 87 drops theframe because the destination address in the frame does not matchits own physical address. The intended destination computer,however, finds a match between the destination address in the frameand its own physical address.

p

Figure 2.16 Example 2.3: physical addresses


60/69

60

Data87 10 1 packet

accepted Data87 10

4

Example 2.4


61/69

61

As we will see in Chapter 3, most local area networks use a 48-bit 6-byte) physical address written as 12 hexadecimal digits;every byte 2 hexadecimal digits) is separated by a colon, asshown below:

p

07:01:02:01:2C:4B

A 6-byte (12 hexadecimal digits) physical address

Example 2.5


62/69

62

Figure 2.17 shows a part of an internet with two routers connectingthree LANs. Each device computer or router) has a pair of addresseslogical and physical) for each connection. In this case, eachcomputer is connected to only one link and therefore has only onepair of addresses. Each router, however, is connected to threenetworks. So each router has three pairs of addresses, one for eachconnection. Although it may be obvious that each router must have a

separate physical address for each connection, it may not be obviouswhy it needs a logical address for each connection. The computerwith logical address A and physical address 10 needs to send apacket to the computer with logical address P and physical address95. We use letters to show the logical addresses and numbers forphysical addresses, but note that both are actually numbers.

p

Figure 2.17 Example 2.5: logical addresses


63/69

63

DataA P20 10 DataA P20 10

Physicaladdresses

changed

DataA P33 99

DataA P33 99

Physicaladdresseschanged

DataA P95 66 DataA P95 66


64/69

64

The physical add resses w i ll change fromhop to hop , bu t the log ical add resses

remain the same.

Note

Example 2.6


65/69

65

Figure 2.18 shows two computers communicating via theInternet. The sending computer is running three processes atthis time with port addresses a, b, and c. The receivingcomputer is running two processes at this time with portaddresses j and k. Process a in the sending computer needs tocommunicate with process j in the receiving computer. Note thatalthough both computers are using the same application, FTP,for example, the port addresses are different because one is aclient program and the other is a server program.

Figure 2.18 Example 2.6: port numbers


66/69

66

A Sender Receiver P

Internet

a DatajA PH2

a DatajA P

a Dataj

Data

a DatajA PH2

a DatajA P

a Dataj

Data


67/69

67

The physical add resses change fromhop to hop , bu t the logical and po rt

add resses usual ly remain the same.

Note

Example 2.7


68/69

68

As we will see in future chapters, a port address is a 16-bitaddress represented by one decimal number as shown.

753A 16-bit port address represented as one single number


69/69

Reference

Behrouz A. Forouzan, Sophia Chung Fegan, Data

Communications and Networking, ISBN 978-0-07-325032-8.

Behrouz A. Forouzan, Sophia Chung Fegan, TCP/IP: Protocol

Suite, ISBN 978-0-256-24166-2.

Documents

Advanced Data Communications Udhay Prakash Part 1