Introduction to Networking
Dr. Mahdi Nasereddin
PPU
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Introduction
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Web Browser, e-mail, streaming audio, etc..
The Web browser
 http://www.google.com
 17 messages!!!
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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
The Basics
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Internetworking:
 Communication between two or more networks via a
router or gateway.
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Hub?
Switches?
Routers?
Hubs, Switches, and Routers
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Routers
 They are used to separate different networks
 Main function: to route packets across networks
 Deal with global addresses “IP addresses”
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Hubs
 Multi-port repeaters
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Switches
 Used within a network
 Smarter than hubs
 Deal with local addresses “Hardware or Mac
Addresses”
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Media
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10Base2
10Base5
10BaseT
100BaseTX
1000BaseT
1000BaseSX
1000BaseLX
Ethernet Cabling (Straight-Through Cable)
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Recommended use:
 Switch to router
 Switch/Hub to Computer
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Ethernet Cabling (Crossover Cable)
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Recommended use
 Switch/hub to Switch/hub
 Router to router
 PC to PC
 Router to PC
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Ethernet Cabling (Rolled Cable)
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Recommended use:
 Computer to console port of a switch or router
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Network Architecture
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Peer to Peer
Server based
Typical Networks
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Topologies
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Bus
Ring
Star
Mesh
Star-Bus
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
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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
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Makes complex systems easier to understand
In networking, there are two approaches:
 OSI
 The TCP/IP model
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The TCP/IP Model
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Process/Application Layer Protocols
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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”
Host to Host Layer Protocols
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Transmission Control Protocol “TCP”
User Datagram Protocol “UDP”
TCP versus UDP
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TCP
UDP
Sequenced
Not sequenced
Reliable
Not reliable
Virtual circuit
Low overhead
Windowing flow control
No flow control
Port Numbers
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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
Port Numbers to remember
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Port
Application
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ftp
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telnet
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DNS
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TFTP
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POP3
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HTTP
Internet Layer Protocols
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Internet Protocol “IP”
IP Address: 192.168.0.1
 Like a home address for the post office
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Network Address: 192.168.0.0/24
 Like a ZIP/Postal code for the post office
 Denotes a range of addresses
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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
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Class A (N.H.H.H)
 1-126
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Class B (N.N.H.H)
 128-191
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Class C (N.N.N.H)
 192-223
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Practice Makes Perfect
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What class does the following IPs belong to?
 132.25.23.12
 13.25.1.1
 200.20.3.6
 254.23.1.14
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Reserved IPs
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All 0s for the host address Network address
 Example: 132.12.0.0
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All 1s for the host address  Broadcast address
 Example: 132.12.255.255
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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)
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All 1s for the Network address All networks with this
host address
Subnet Mask
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Subnet Mask tells you what bits belong to host id
and what bits belong to network id
Why were they created?
NAT and PAT?
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Network Address Translation
Port Address Translation
Protocol: IPv6
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Internet Protocol, Version 6
 RFC 2460
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Advantages over IPv4
 More native security
 Increases available address space from 32 bits to 128 bits
 Easily extensible
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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
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