Download Introduction to Computer Networking

Introduction to Computer Networking
AE6382
Introduction to Computer Networking
Computer Networks
AE6382
Introduction to Computer Networking
How do you transfer data between two computers?
?
AE6382
Introduction to Computer Networking
Carry your data on a memory stick, floppy, or 9 track
computer tape from one computer to the other.
• slow
• limited distance
• secure
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Introduction to Computer Networking
A better solution is to send data over a wire. Use a direct
connection between each computer. Point-to-point
connection.
• fast
• convenient
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Introduction to Computer Networking
Now add a third computer.
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Introduction to Computer Networking
And a fourth computer.
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Introduction to Computer Networking
The problem is that this solution
does not scale. A very large
network would look like this.
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Introduction to Computer Networking
An alternative form is a tree structure.
F
D
E
A
C
B
G
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Introduction to Computer Networking
A star structure is a more flexible alternative.
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Introduction to Computer Networking
This arrangement forms the basis of modern computer
networks.
• The center node directs traffic from a source computer to a
destination computer. A virtual point-to-point connection is
created.
• The center node is a switch in an Ethernet based network
and a router in an IP based network.
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Introduction to Computer Networking
The Internet today is a combination of both the star and tree
structure. Local networks are configured as stars (ethernet)
and these are interconnected in a tree (IP).
Computers on the local ethernet network are connected by
way of an ethernet switch.
Each of these local networks are connected by way of
routers.
Each packet will travel from end to end of the virtual
connection created between two nodes.
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Introduction to Computer Networking
Protocols
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Introduction to Computer Networking
Protocols are the rules that govern how data travels over the
computer network.
• how data is packaged into discrete increments (packets/frames)
• what the packet components mean
• proper sequence of packet transmission and reply
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Introduction to Computer Networking
Ethernet is a low level protocol. It is used to implement
networks of closely located computers – LAN or Local Area
Network.
Ethernet is transmitted in frames.
An ethernet address is 48 bits long.
00:1a:a0:b3:42:79
each digit is hexadecimal, 0-f
each ethernet adapter has a unique address, this is the
MAC address
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Introduction to Computer Networking
Two types of ethernet frames, IEEE 802.3 is commonly used
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Introduction to Computer Networking
IP is a higher level protocol. It is normally used on top of
ethernet. It has the advantage of being able to operate over
very large networks. It is the basis of the Internet.
IP is transmitted in packets.
An IP address is 32 bits in length
172.16.0.100
each component ranges from 0-255
there is a network and host part
each address is unique
the “center node” for IP is a router
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Introduction to Computer Networking
An IP packet
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Introduction to Computer Networking
TCP is an even higher level protocol. It is used on top of IP.
It is a connection oriented protocol with reliable delivery.
TCP is transmitted in packets.
An TCP address (port) is 16 bits in length
each port addresses a service on a computer
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Introduction to Computer Networking
A TCP packet
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Introduction to Computer Networking
The relationship between the 3 protocols just presented is as
follows:
• The data you are sending is packaged into the data part of a TCP packet
with the port address of the destination specified.
• The resulting TCP packet is then inserted into the data part of an IP
packet. The IP address of the destination computer is specified here.
• Finally, the combined TCP/IP packet is inserted into the data section of
an ethernet frame. The frame is transmitted to the computer with the
specified destination MAC address.
At the destination the reverse process is performed until the
original data is presented to the receiving program.
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Introduction to Computer Networking
The actual sequence is more complex. There are also even
higher levels, application protocols, inserted inside of a TCP
packet’s data field.
Example application protocols
• ssh 22
secure shell, encrypted communications
• http 80
web access
• https 443 encrypted web access
• rdp 3389 Windows remote desktop
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Introduction to Computer Networking
Domain Name Service
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Introduction to Computer Networking
Domain Name Service (DNS) refers to the mechanism used
to map names with IP addresses.
Examples
128.61.191.2
Î www.ae.gatech.edu
128.61.191.51
Î asdl.ae.gatech.edu
C:\>nslookup www.google.com
Server: gw-asdl00.asdl.ae.gatech.edu
Address: 172.16.0.1
Non-authoritative answer:
Name: www.l.google.com
Addresses: 74.125.45.103, 74.125.45.104, 74.125.45.147, 74.125.45.99
Aliases: www.google.com
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Introduction to Computer Networking
Reverse lookups can also be performed
C:\>nslookup 130.207.244.120
Server: gw-asdl00.asdl.ae.gatech.edu
Address: 172.16.0.1
Name: newweb.gatech.edu
Address: 130.207.244.120
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Introduction to Computer Networking
Some Basic Network Tools
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Introduction to Computer Networking
Windows Network Commands
• ipconfig – a command that will display configuration of all network devices (see
ipconfig /help)
• ipconfig /all
• ipconfig /release and ipconfig /renew
• route – a command that will configure and display the current route tables on
your computer (see route help)
• route add 192.168.10.0 mask 255.255.255.0 192.168.10.50 this will setup a
static route
• route print
• netstat – a command to display current network connections (see netstat help)
• netstat – default to display current TCP connections
• netstat –a – display all connections, including listening
• tracert – this command will display the path to the target host
• tracert www.ae.gatech.edu
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Introduction to Computer Networking
Windows Network Commands
• ping – send a ping packet to the remote host (some hosts do not respond)
• ping www.ae.gatech.edu
• nbtstat – display MS specific network info (see nbtstat help)
• nbtstat –A asdlserver.asdl.ae.gatech.edu
• nslookup – perform DNS name and IP number mapping lookups
• nslookup www.ae.gatech.edu
• nslookup 128.61.191.2
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Introduction to Computer Networking
Windows - ipconfig
•
The ipconfig command will display the
current IP configuration of a windows
computer.
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Introduction to Computer Networking
Windows - nbtstat
The nbtstat command displays information about other Windows systems on the
network. It accepts either DNS name or NetBIOS name.
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Introduction to Computer Networking
Windows - netstat
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Introduction to Computer Networking
Windows - netstat
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Introduction to Computer Networking
Windows - netstat
:
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Introduction to Computer Networking
Windows - arp
:
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Introduction to Computer Networking
Windows - tracert
:
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Introduction to Computer Networking
Linux/Unix network commands
• ifconfig – configure and display network devices
• ifconfig eth0 – display configuration of eth0
• route – configure and display the hosts route tables
• route – display route table
• ip – multi-purpose network command
• ip addr – display network configurations
• ip route – display route table
• netstat – display current network connections
• netstat – display all current tcp and udp connections
• netstat –at – display all current tcp connections including listening ports
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Introduction to Computer Networking
Linux/Unix network commands
• traceroute – display the path to remote host
• traceroute www.ae.gatech.edu
• ping – send a ping to the remote host
• ping www.ae.gatech.edu
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