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![Page 1: Basics of Networking and TCP/IP. Old Computing Model predominant in 1960-1985 utilizes a large mainframe computer connected to a set of terminals (host-terminal.](https://reader035.fdocuments.us/reader035/viewer/2022062500/5697bf881a28abf838c89889/html5/thumbnails/1.jpg)
Basics of Networking and TCP/IP
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Old Computing Model
predominant in 1960-1985 utilizes a large mainframe computer connected to a set of terminals (host-terminal setup).
Mainframe (IBM 360)
TC:Terminal Controller
low speed link
shared high speed link
Terminals (IBM 3270)
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Characteristics of the Old model
All processing is done at the host A terminal is simply an I/O device (Input: via
keyboard; output: via screen) The host computer is a bottleneck and a
central point of failure
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New Computing Model
1985-present; utilizes desktop computers connected by a Local Area Network (LAN).
Router
Network A
Network B
desktop computers
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Definition of a Computer Network
A computer network is a collection of autonomous (independent of each other) computers that are connected in such a way that data can be exchanged between any two computers.
an internetwork (or simply internet) is a collection of networks that are connected by routers. A router encompasses only the lowest three layers (physical layer, data link layer and network layer).
The Internet (with capital I) is a specific world wide internetwork that is managed by Internic and uses TCP/IP protocols.
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Benefits of Computer Networks Resource Sharing. Resources include hardware
devices such disk storage and printers and software (data + programs).
Higher Reliability. This is obtained by duplicating devices and replicating data.
Incremental and cheaper growth. Distributed processing. This comes about in
the form of client/server applications (e.g. web browser/web server) and clustering.
Promote communication among network users through resource sharing and e-mail.
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Design Goals of Networking
have two computers exchange data but account for the following. The two computers may be located in the same room or separated by thousands of miles. The two computers may have different manufacturers and different operating systems. The two computers may use different byte ordering for multi-byte data and may have different character encoding for text. Design must allow for continuing use of existing technology while embracing new technology
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ISO Protocol Layering International Standards Organization (ISO) model
was developed, based on its recommendation, in the form of seven layers.
The principles of layering: Each layer should represent a different abstraction level,
wherever needed Each layer should define well defined functions Information flow between layers should be minimum Number of layers should be optimum, not too many not
too few
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Transport Layer
Network Layer
Data Link Layer
Physical Layer
Packet
Frame
Signal (Bits)
Presentation Layer
Session Layer
ISO 7-Layer OSI Model
Application Layer
Computer A
Computer B
Protocol
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Presentation Layer
Session Layer
Application Layer
Interface
Data flow from A (Sender) to B (Receiver)
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Standards and Protocols A standard is an agreed-upon specification for some
type of product or service. Examples: A4 paper size, 2-feet florescent light,
PC serial (RS232C) and parallel port interfaces A protocol is an agreement (contract) between two
(or more) parties to conduct a joint task. Examples: two persons handshaking, passing
through traffic light.
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Network Communication Protocol
A network communication protocol (at the application or lower layers) specifies the format and meaning of messages that are exchanged between two peer (at the same layer) entities. Roughly a network protocol specifies the control header and its interpretation.
Examples: App. Layer Protocol: HTTP used between web browser and server Network Layer Protocol: Internet Protocol (IP)Data Link Layer Protocol: Point-to-Point Protocol (PPP) - used between two routers connected by phone lines
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Layering Principle Layered Protocols are designed so that layer n at the
destination receives exactly the same object sent by the layer n at the source.
Protocols are standards that specify how data is represented when being transferred from one machine to another.
Protocols specify how the transfer occurs, how errors are detected, and how acknowledgements are passed.
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Transport Layer
Network Layer
Data Link Layer
Physical LayerSignal (Bits)
Presentation Layer
Session Layer
Layers use Control Headers
Application Layer
Computer A
Computer B
Data flow from A (Sender) to B (Receiver)
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Presentation Layer
Session Layer
Application Layer
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Physical Layer Interfaces with the physical medium. Specifies bit to signal encoding such as voltage
levels and duration for 0/1. Transmits a stream of bits without boundaries.
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Data Link Layer Transmits frames - a frame is a delimited (has
a start and end markers) block of bits. The frame has a checksum to allow error
detection. Control access to the channel (medium),
especially over a broadcast (shared) channel. Implements flow control.
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Network Layer Routing of packet over an internetwork. The network
layer examines the network destination address of an incoming packet and re-encapsulates the packet in a new frame that it sends down again through the data link layer of an (outgoing) link.
Provides software abstraction independent of communication hardware (for example, while data link layer addresses are permanently fixed in hardware, network layer address are dynamically configured through software).
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TCP/IP 5-Layer Model
Application
Transport
Network
Data Link
Physical
Application
Transport
Network
Data Link
Physical
Network
Data Link
Physical
Computer BComputer A IP Router
IP
TCP
The transport layer is an end-to-end layer. This means that the corresponding stations (hosts) are the actual source and actual destination of the application data.
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What is TCP/IP?
TCP/IP: Transmission Control Protocol / Internet Protocol TCP/IP is the name of a protocol suite (protocol stack). Applications interface with TCP layer to communicate with
other peer applications
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History of TCP/IP
TCP/IP is the brain child of ARPAnet which was developed by the USA DoD (Department of Defense) supported project (Advanced Research Project Agency).
TCP/IP was first defined in 1974, meant to be used for geographically distant communication. It has evolved with many improvements since then.
The University of Berkeley has incorporated TCP/IP in their BSD Unix. Since than it has been a very good marriage between the two.
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The Internet The Internet is a network of networks. Today, the Internet connects tens of thousands of
networks and millions of computer 1990: 3000 networks ( 200,000 users.) 1992: 992,000 hosts. Present: millions of networks, computers, and users.
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Why TCP/IP is Popular?
Popularity of TCP/IP simpler than ISO-OSI model provides an elegant solution to world wide data
communication. Open Protocol Standards, freely available, and
independent from any hardware platform.
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TCP/IP Features Independence from specific network hardware
Allows TCP/IP to integrate many types of networks (Ethernet, Token Ring, X.25, dial-up)
TCP/IP is used in both LANs and WANs Common addressing scheme
every host on the Internet has a unique address Standardized high-level protocols for world wide
available network services
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IP Protocol The primary network layer protocol of TCP/IP stack
Provides basic packet delivery service on which TCP/IP networks are built
Main functions Defines datagram (packet) format, basic unit of
transmission in the Internet Provides Internet addressing Routing of datagrams
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TCP Protocol
TCP facilitates process-to-process (i.e. application to application) communication. Any application that needs to send and receive via TCP is assigned an address (i.e. a TCP-port number).
Whereas IP is limited to providing a connectionless service (packets may be dropped at will), TCP provides a connection-oriented service (virtual circuit).
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IP
Data Link
Physical
IP
Data Link
Physical
IP
Data Link
Physical
Application
TCP
IP
Data Link
Physical
IP-Layer Operation
XA
B
C
Y
X
A B C
Y
Application
TCP
IP
Data Link
Physical
TCP is an end-to-end layer
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Application Layer Includes all software programs that use the Transport
Layer protocols to deliver data messages Examples of protocols:
Telnet: Network Terminal Protocol FTP: File Transfer Protocol SMTP: Simple Mail Transfer Protocol DNS: Domain Name Service WWW: World Wide Web
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Layer Decapsulation
Telnet
FTP
SMTP
HTT P
23 21 25 80
TCP Segments
IP Packets
Frames
Bits
Port Number, Destination (Source) Port identifies receiving (sending) application
Type, SAP, or other control info
MAC or WAN addressing
Applications
Transport
Network
Data Link
Physical
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LAN Hardware: Ethernet The most widely used LAN hardware. Developed originally in 1980 as 10 Mbps (10 million
bits per second) by Digital, Intel and Xerox Today, the mainstream Ethernet is known as Fast
Ethernet (100 Mbps) which uses HUB and Category 5 UTP wiring
Also Gigabit Ethernet (1000 Mbps) is available but limited in distance.
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Ethernet (Cont.)
Ethernet encompasses Data-Link and Physical Layers only
The Ethernet card is responsible for frame generation and reception
An Ethernet frame encapsulates a network layer packet
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Fast Ethernet Layout and Components
Fast Ethernet HUB
PC1 PC2 PCn
Category 5 UTP
An ordinary HUB is an active physical-layer device acting as signal repeater
Hubs can be cascaded
Each PC is equipped with Fast Ethernet Card (50 SR)
Hub Cost is proportional to the # of ports (25 SR per port)
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Break