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Introduction to Networking

Dr. Mahdi Nasereddin

PPU

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Introduction

Web Browser, e-mail, streaming audio, etc.. The Web browser

http://www.google.com17 messages!!!

• 6 messages to translate www.google.com into an IP address• 3 messages to establish a TCP connection• 4 messages used by HTTP to send a get request• 4 messages to tear down the TCP connection

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The Basics

Internetworking:Communication between two or more networks via a

router or gateway. Hub? Switches? Routers?

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Hubs, Switches, and Routers

Routers They are used to separate different networksMain function: to route packets across networksDeal with global addresses “IP addresses”

HubsMulti-port repeaters

SwitchesUsed within a networkSmarter than hubsDeal with local addresses “Hardware or Mac

Addresses”

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Media

10Base2 10Base5 10BaseT 100BaseTX 1000BaseT 1000BaseSX 1000BaseLX

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Ethernet Cabling (Straight-Through Cable)

Recommended use:Switch to routerSwitch/Hub to Computer

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Ethernet Cabling (Crossover Cable)

Recommended useSwitch/hub to Switch/hubRouter to routerPC to PCRouter to PC

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Ethernet Cabling (Rolled Cable)

Recommended use:Computer to console port of a switch or router

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Network Architecture

Peer to Peer Server based

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Typical Networks

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Topologies

Bus Ring Star Mesh Star-Bus

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Bus Topology

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Simple Star Network

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Simple Ring Network

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Mesh Topology

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Star-Bus Topology

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Performance

How do we measure network performance?Bandwidth (Throughput)

• Number of bits that can be transmitted over a certain period of time (Ex. 10 Mbps)

Latency (Delay)• How long it takes a message to travel from one end of the

network to the other (Measured is Seconds)• RTT• Latency = Propagation + Transmit + Queue

– Propagation = Distance/Speed of light

– Transmit = Size/Bandwidth

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Beyond the basics:The Layered Approach

Makes complex systems easier to understand In networking, there are two approaches:

OSIThe TCP/IP model

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The TCP/IP Model

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Process/Application Layer Protocols

Telnet “Virtual terminal” File Transfer Protocol “FTP” Trivial File Transfer Protocol “TFTP” Network File System “NFS” Simple Mail Transfer Protocol “SMTP” Line Printer Daemon “LPD” X Windows Simple Network Management Protocol “SNMP” Domain Name Service “DNS” Dynamic Host Configuration Protocol “DHCP”

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Host to Host Layer Protocols

Transmission Control Protocol “TCP” User Datagram Protocol “UDP”

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TCP versus UDP

TCP UDP

Sequenced Not sequenced

Reliable Not reliable

Virtual circuit Low overhead

Windowing flow control No flow control

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Port Numbers

Used by TCP and UDP to communicate with upper layers keep track if different conversations crossing the network simultaneously

Sender port number start at 1024

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Port Numbers to remember

Port Application

21 ftp

23 telnet

53 DNS

69 TFTP

110 POP3

80 HTTP

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Internet Layer Protocols Internet Protocol “IP” IP Address: 192.168.0.1

Like a home address for the post office

Network Address: 192.168.0.0/24 Like a ZIP/Postal code for the post office Denotes a range of addresses

Format ‘Dotted-Quad’ notation: xxx.yyy.zzz.aaa Each dotted component is an 8-bit number

• Range is 0.0.0.0 to 255.255.255.255 The prefix length (/24), is the number of significant bits in a

network

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Addressing

Class A (N.H.H.H)1-126

Class B (N.N.H.H)128-191

Class C (N.N.N.H)192-223

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Practice Makes Perfect

What class does the following IPs belong to?132.25.23.1213.25.1.1200.20.3.6254.23.1.14

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Reserved IPs

All 0s for the host address Network address Example: 132.12.0.0

All 1s for the host address Broadcast address Example: 132.12.255.255

127.0.0.1 local node All 0s for the Network address This network

Example: 0.0.12.1 (If I am on network 169.23.0.0 then this is the same as my IP address 169.23.12.1)

All 1s for the Network address All networks with this host address

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Subnet Mask

Subnet Mask tells you what bits belong to host id and what bits belong to network id

Why were they created?

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NAT and PAT?

Network Address Translation Port Address Translation

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Protocol: IPv6

Internet Protocol, Version 6 RFC 2460

Advantages over IPv4 More native security Increases available address space from 32 bits to 128 bits Easily extensible

Disadvantages IPv4 is everywhere (cannot be replaced overnight) More protocol overhead (addresses are now 16 bytes instead of

4) IP routing protocols must be reworked to support it