dinisoft 1 Chapter 2 Networking Fundamentals Problem for Call us: Shahajahan babu 01716718039
Developed as a result of business applications that were written for microcomputer
The microcomputers were not connected so there was no efficient way to share data among them
It was not efficient or cost-effective for businesses to use floppy disks to share data
Businesses needed a solution that would successfully address the following three problems:
- how to avoid duplication of equipment and resources
- how to communicate efficiently
- how to set up and manage a network
Data networking solutions
The history of computer networking is complex
It has involved many people from all over the world over the past 35 years
In the 1940s computers were large electromechanical devices that were prone to failure
In 1947 the invention of a semiconductor transistor opened up many possibilities for making smaller, more reliable computers
In the 1950s large institutions began to use mainframe computers, which were run by punched card programs
In the 1960s mainframes with terminals and integrated circuits were widely used.
In the late 1960s and 1970s smaller computers called minicomputers were created
In the mid-1980s PC users began to use modems to share files with other computers. This was referred to as point-to-point, or dial-up communication
In 1977 the Apple Computer Company introduced the microcomputer, which was also known as the Mac.
In 1981 IBM introduced its first PC
The user-friendly Mac, the open-architecture IBM PC, and the further micro-miniaturization of integrated circuits led to widespread use of personal computers in homes and businesses
From the 1960s to the 1990s the U.S. Department of Defense (DoD) developed large, reliable, wide-area networks (WANs) for military and scientific reasons
Equipment that connects directly to a network segment is referred to as a device. These devices are broken up into two classifications. The first classification is end-user devices . The second classification is network devices .
A repeater is a network device used to regenerate a analog or digital signals that are distorted by transmission loss due to attenuation
A repeater does not make intelligent decision concerning forwarding packets like a router or bridge
Hubs concentrate connections
In other words, they take a group of hosts and allow the network to see them as a single unit
This is done passively, without any other effect on the data transmission
Active hubs concentrate hosts and also regenerate signals.
Bridges convert network data formats and perform basic data transmission management
Bridges provide connections between LANs
Bridges also check data to determine if it should cross the bridge
This makes each part of the network more efficient.
Switches add more intelligence to data transfer management
They can determine if data should remain on a LAN and transfer data only to the connection that needs it
Another difference between a bridge and switch is that a switch does not convert data transmission formats
Routers have all the capabilities listed above
Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers
They can also connect to a WAN, which allows them to connect LANs that are separated by great distances
None of the other devices can provide this type of connection
Network topology defines the structure of the network. The physical topology , which is the actual layout of the wire or media , and the logical topology , which defines how the media is accessed by the hosts for sending data.
A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone
A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.
A star topology connects all cables to a central point.
An extended star topology links individual stars together by connecting the hubs or switches .
A hierarchical topology is similar to an extended star. However, instead of linking the hubs or switches together, the system is linked to a computer that controls the traffic on the topology
Each host sends its data to all other hosts on the network medium
There is no order that the stations must follow to use the network
It is first come, first serve. Ethernet works this way as will be explained later in the course.
An electronic token is passed sequentially to each host
When a host receives the token, that host can send data on the network
If the host has no data to send, it passes the token to the next host and the process repeats itself
Examples: Token Ring and Fiber Distributed Data Interface (FDDI)
A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate
Protocol suites are collections of protocols that enable network communication from one host through the network to another host
Rules are created and maintained by many different organizations and committees:
- The Institute of Electrical and Electronic Engineers ( IEEE )
- American National Standards Institute ( ANSI )
- Telecommunications Industry Association ( TIA )
- Electronic Industries Alliance ( EIA )
- International Telecommunications Union ( ITU )
Operate within a limited geographic area
Allow many users to access high-bandwidth media
Provide full-time connectivity to local services
Connect physically adjacent devices
Network interface cards
Fiber distributed data interface (FDDI)
Integrated Services Digital Network (ISDN)
Digital Subscriber Line (DSL)
Asynchronous Transfer Mode (ATM)
T (US) and E (Europe) carrier series: T1, E1, T3, E3
Synchronous Optical Network (SONET)
Metropolitan - Area Networks (MANs)
A MAN is a network that spans a metropolitan area such as a city or suburban area.
A MAN usually consists of two or more LANs in a common geographic area.
Storage - Area Networks (SAN s )
A SAN is a dedicated, high-performance network used to move data between servers and storage resources
Because it is a separate, dedicated network, it avoids any traffic conflict between clients and servers
Virtual Private Networks (VPN s )
A VPN is a private network that is constructed within a public network infrastructure such as the global Internet
Benefits of VPNs
A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet.
VPNs maintain the same security and management policies as a private network.
They are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise customer's network.
There are three main types of VPNs:
Intranets and Extranets
Intranets are designed to permit access by users who have access privileges to the internal LAN of the organization
Extranets refer to applications and services that are Intranet based, but that use extended, secure access to external users or enterprises
Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time
Bandwidth is limited by the laws of physics and by the technologies used to place information on the media
Example: Bandwidth of a conventional modem is limited to about 56 kbps
Importance of Bandwidth
Two analogies that describe digital bandwidth
Width of a pipe
Number of lanes on a highway
Media bandwidth differences
Category 5 UTP – 100 meters maximum physical distance
Provide logical addressing which routers use for path determination
Examples: IP, IPX
The Lower Layers (cont.)
Combines bits into bytes and bytes into frames
Access to media using MAC address
Error detection not correction
Examples: 802.3/802.2, HDLN
Moves bits between devices
Specifies voltage, wire speed, and pin out cables
Examples: EIA/TIA-232, V.35
The OSI Model
Application – Think of browsers.
Presentation – Think of common data format.
Session – Think of dialogs and conversations.
Transport – Think of flow control and reliability.
Network – Think of path selection, routing, and logical addressing.
Data Link – Think of frames and media access control.
Physical – Think of signals and media.
For data to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination.
During this process, the protocols of each layer exchange information, called protocol data units (PDUs), between peer layers.
Each layer of communication on the source computer communicates with a layer-specific PDU, and with its peer layer on the destination computer.
The TCP/IP Reference Model
TCP/IP Protocol Graph
FTP – File Transfer Protocol
HTTP – Hypertext Transfer Protocol
SMTP – Simple Mail Transfer Protocol
DNS – Domain Name System
TFTP – Trivial File Transfer Protocol
OSI Model and TCP/IP Model
Use of the OSI Model in the CCNA Curriculum
Encapsulation The lower layers use encapsulation to put the protocol data unit (PDU) from the upper layer into its data field and to add headers and trailers that the layer can use to perform its function.
Names for Data at Each Layer
When the data link layer receives the frame, it does the following:
It reads the physical address and other control information provided by the directly connected peer data link layer.
It strips the control information from the frame, thereby creating a datagram.
It passes the datagram up to the next layer, following the instructions that appeared in the control portion of the frame.