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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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Ethernet Cabling (Crossover Cable)
Recommended useSwitch/hub to Switch/hubRouter to routerPC to PCRouter to PC
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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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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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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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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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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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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