Basics of Networking and TCPIP

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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).

low speed link
Mainframe (IBM 360)
TCTerminal Controller
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).

Network A
desktop computers
Router
Network B
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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 in 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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ISO 7-Layer OSI Model
Computer A
Computer B

Application Layer
Application Layer
Presentation Layer
Presentation Layer
Session Layer
Session Layer
Transport Layer
Transport Layer
Packet
Network Layer
Network Layer
Data Link Layer
Frame
Data Link Layer
Physical Layer
Physical Layer
Signal (Bits)
Protocol
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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Layers use Control Headers
Computer A
Computer B
Application Layer
Application Layer
Presentation Layer
Presentation Layer
Session Layer
Session Layer
Transport Layer
Transport Layer
Network Layer
Network Layer
Data Link Layer
Data Link Layer
Physical Layer
Physical Layer
Signal (Bits)
Data flow from A (Sender) to B (Receiver)
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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 (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
TCP
Network Data Link Physical
IP
Computer B
Computer A
IP Router

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What is TCP/IP?

• TCP/IPTransmission Control Protocol/ Internet
  Protocol
• TCP/IP is the name of a protocol suite.
• 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 Layer

• Heart of TCP/IP
• 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 Layer

• An end-to-end layer. This means that the
  corresponding stations are the actual source and
  actual destination of the application data.
• Whereas the IP layer is limited to providing a
  connection-less service (packets may be dropped
  at will), the TCP layer provides a
  connection-oriented service (virtual channel).

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IP-Layer Operation
B
Y
X
C
A
X
Y
Application TCP IP Data Link Physical
Application TCP IP Data Link Physical
TCP is end-to-end layer
IP Data Link Physical
IP Data Link Physical
IP Data Link Physical
A
B
C
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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
T e l n e t
F T P
S M T P
D N S
Applications Transport Network Data
Link Physical
23 21 25 53
Port Number Protocol Number Type, SAP, or
other control info MAC or WAN addressing
TCP UDP 6 17
IP Packets
Frames
Bits
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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 Layer and Physical
  Layer
• 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
Category 5 UTP
PC1
PC2
PCn

• 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