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Overview of Data Communications and Networking

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Title: Overview of Data Communications and Networking


1
PART I
Overview of Data Communications and Networking
2
Overview
3
Definition of Data Communication
  • Is the exchange of data between two devices via
    some form of transmission medium exp, wire cable.
  • Communicating devices is a combination of
    hardware and software
  • 3 fundamental characteristics needs for make sure
    the effectiveness of D.C
  • Delivery deliver data to correct destination
  • Accuracy The data must be delivered accurately
  • Timelines the data must be sent in a timely
    manner.

4
1.1 Data Communication
Components Data Representation Direction of
Data Flow
5
Figure 1.1 Five components of data
communication
6
  • Message data- text,number,picture
  • Sender-device that send the message-computer,
    workstation, handphone etc
  • Receiver- device that accept the data
  • Medium- the physical path by which a message
    travel from sender to receiver, wire, wireless
  • Protocol- set of rules that governs D.C

7
Data Representation
  • Text
  • Numbers
  • Images
  • Audio
  • Video

8
Direction of flow
  • Communication between two devices can be
  • Simplex
  • Half-duplex
  • Full-duplex

9
Figure 1.2 Simplex
The communication is unidirectional-one way Exp
keyboards, traditional monitors
10
Figure 1.3 Half-duplex
Each station can both transmit and receive but
not at the same time Exp walkie-talkies
11
Figure 1.4 Full-duplex
Both stations can transmit and received at the
same time Exp telephone network
12
Networks
  • What is network?
  • It is a set of devices (nodes) connected by
    communication links.
  • Nodes?

13
1.2 Networks
  • Distributed Processing
  • Task is divided among multiple computers
  • Network Criteria
  • Performance, Reliability, Security
  • Physical Structures
  • Type of connection, Physical Topology
  • Categories of Networks
  • LAN,WAN,MAN

14
Figure 1.5 Point-to-point connection
15
Figure 1.6 Multipoint connection
16
Figure 1.7 Categories of topology
  • The topology of a network is the geometric
    representation of the relationship of all the
    links and linking devices to one another

17
Figure 1.8 Fully connected mesh topology (for
five devices)
18
Mesh
  • Every device has a dedicated point-to-point link
    to every other device
  • The link carries traffic only when the two
    devices is connected
  • A fully connected mesh network has n(n-1)/2
    physical channels to link n devices.

19
Continue.. Advantages
  • Use dedicated link- guarantees that each
    connection can carry its own data load, eliminate
    the traffic problems that can occur when links
    must be shared by multiple devices
  • Robust-if one link becomes unusable, it does not
    incapacitate the entire system.
  • Privacy/security-Only the intended recipient see
    the message
  • Easy to detect faulty in the nodes since using
    point-to-point

20
Continue..disadvantage
  • Use many cable and i/o port
  • Hard to install and reconfigure
  • Expensive and bulky

21
Figure 1.9 Star topology
22
Star
  • Each device has a dedicated point-to-point link
    only to a central controller/hub
  • Devices are not directly linked to one another
  • Does not allow direct traffic between devices
  • Controller/hubs acts as an exchange

23
Continue..advantages
  • Less expensive compared to mesh
  • Each device needs only one link and one i/o port
    to connect it to any number of others
  • Easy to install and reconfigure
  • Less cabling
  • Robustness-if one fails, only that link is
    affected-thus easy to identified fault and
    isolate it

24
Figure 1.10 Bus topology
25
Bus
  • Multipoint
  • One cable acts as a backbone to link all the
    devices in a network
  • Nodes are connected to the bus cable by drop
    lines and taps
  • Drop lines-connection running between the device
    and the main cable
  • Tap-a connector that either splices into the main
    cable or punctures the sheathing/covering of a
    cable to create a contact with the metallic core

26
Continue
  • Advantage
  • Ease of installation
  • Disadvantage
  • Difficult reconnection and fault isolation
  • Difficult to add new device
  • Signal reflection at the taps can cause
    degradation in quality
  • A fault in the bus cable stops all transmission
  • The damaged area reflects signals back in the
    direction of origin, creating noise in both
    directions.

27
Figure 1.11 Ring topology
28
Ring
  • Each device has a dedicate point-to point
    connection only with the two devices one either
    side of it.
  • A signal is passes along the ring in one
    direction, from device to device until it reaches
    its destination
  • Each device in ring incorporates a repeater
  • When a device receives a signal intended for
    another device, its repeater regenerates the bits
    and passes them along

29
Ring..continue..
  • Easy to install and reconfigure
  • Each device is linked only to its immediate
    neighbors
  • To add/delete a device requires changing only two
    connections
  • In a ring signal is circulating at all times, if
    one device does not receive a signal within a
    specified period, it can issue an alarm.
  • The alarm alerts the network operator to the
    problem and its location

30
Ring..continue
  • Disadvantage-unidirectional traffic
  • A break in a ring can disable the entire network
  • Solves using a dual ring or a switch capable of
    closing the break.

31
Figure 1.12 Categories of networks
32

LAN
  • Privately owned and links the devices in a single
    office,building or campus
  • Designed to allow resources to be shared between
    pcs.
  • Beside size, LAN are distinguished from other
    networks by their transmission media and topology
  • Common topologies bus,ring,star
  • Traditionally LAN data rates 4-16 Mbps
  • Now up to 100Mbps

33
Figure 1.13 LAN
34
Figure 1.13 LAN (Continued)
35
MAN
  • Designed to extend over an entire city
  • It can be a single network i.e cable tv network
    or connecting a number of LANS into a larger
    network,i.e a company use a MAN to connect the
    LANs in all its office throughout a city.
  • It may be wholly owned and operated bya private
    company, service provided by a public company i.e
    local telephone company

36
WAN
  • Provides long-distance transmission of
    data,voice,image and video info over large
    geographic areas country continent, whole
    world.
  • May utilize public,leased or private
    communication equipment
  • WAN that is wholly owned and used by a single
    company known as enterprise network

37
Figure 1.14 MAN
38
Figure 1.15 WAN
39
1.3 The Internet
A Brief History The Internet Today
40
Figure 1.16 Internet today
41
What is the Internet?
  • Internet is a global network, which connecting
    millions of computers for the purpose of exchange
    data, news and opinions.
  • It is made up of thousands of smaller commercial,
    academic, domestic and government networks
  • Internet transmit data by packet switching using
    a standardized Internet Protocol (IP) and many
    other protocols
  • It carries various information and services, such
    as electronic mail, online chat and the
    interlinked web pages and other documents of the
    World Wide Web.

42
Internet(1)
  • Internet is decentralized by design. Each
    Internet computer, called a host, is independent.
  • Its operators can choose which Internet services
    to use and which local services to make available
    to the global Internet community.
  • Internet was conceived by the Advanced Research
    Projects Agency (ARPA) of the U.S. government in
    1969 and was first known as the ARPANET.

43
Internet(2)
  • Today, the Internet is a public, cooperative, and
    self-sustaining facility accessible to hundreds
    of millions of people worldwide
  • Physically, the Internet uses a portion of the
    total resources of the currently existing public
    telecommunication networks

44
The Internet as mapped by The Opte
Project (http//opte.prolexic.com/) on 15.
January 2005
45
1.4 Protocols and Standards
Protocols Standards Standards
Organizations Internet Standards
46
Protocols
  • Set of rules that governs D.C
  • 3 Key elements
  • Syntax-structure or format of the data, in order
    they were presented
  • Semantics- the meaning of each section of bits
  • Timing-when data should be sent and how fast it
    can be sent out

47
Standards
  • Need in creating and maintaining an open and
    competitive market for equipment manufacturers in
    making sure that devices make by different vendor
    able to be use/ work together
  • Exp organizations creates standards
  • ITU_T, ISO, CCITT,ANSI,IEEE

48
NetworkModels
49
2.1 Layered Tasks
Sender, Receiver, and Carrier Hierarchy Services
50
Figure 2.1 Sending a letter
51
2.2 Internet Model
Peer-to-Peer Processes Functions of
Layers Summary of Layers
52
Figure 2.2 Internet layers
53
Figure 2.3 Peer-to-peer processes
54
Figure 2.4 An exchange using the Internet model
55
Figure 2.5 Physical layer
56
Note
The physical layer is responsible for
transmitting individual bits from one node to the
next.
57
Figure 2.6 Data link layer
58
Note
The data link layer is responsible for
transmitting frames from one node to the next.
59
Figure 2.7 Node-to-node delivery
60
Example 1
In Figure 2.8 a node with physical address 10
sends a frame to a node with physical address 87.
The two nodes are connected by a link. At the
data link level this frame contains physical
addresses in the header. These are the only
addresses needed. The rest of the header contains
other information needed at this level. The
trailer usually contains extra bits needed for
error detection
61
Figure 2.8 Example 1
62
Figure 2.9 Network layer
63
Note
The network layer is responsible for the delivery
of packets from the original source to the final
destination.
64
Figure 2.10 Source-to-destination delivery
65
Example 2
In Figure 2.11 we want to send data from a node
with network address A and physical address 10,
located on one LAN, to a node with a network
address P and physical address 95, located on
another LAN. Because the two devices are located
on different networks, we cannot use physical
addresses only the physical addresses only have
local jurisdiction. What we need here are
universal addresses that can pass through the LAN
boundaries. The network (logical) addresses have
this characteristic.
66
Figure 2.11 Example 2
67
Figure 2.12 Transport layer
68
Note
The transport layer is responsible for delivery
of a message from one process to another.
69
Figure 2.12 Reliable process-to-process
delivery of a message
70
Example 3
Figure 2.14 shows an example of transport layer
communication. Data coming from the upper layers
have port addresses j and k (j is the address of
the sending process, and k is the address of the
receiving process). Since the data size is larger
than the network layer can handle, the data are
split into two packets, each packet retaining the
port addresses (j and k). Then in the network
layer, network addresses (A and P) are added to
each packet.
71
Figure 2.14 Example 3
72
Figure 2.15 Application layer
73
Note
The application layer is responsible for
providing services to the user.
74
Figure 2.16 Summary of duties
75
2.3 OSI Model
A comparison
76
Figure 2.17 OSI model
77
Note
The OSI model is briefly discussed in Appendix C.
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