02.Networking102.pdf

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Outline
• Next, we’ll look at specific protocols
–
–
–
–
–
SSH – secure shell
SSL
security on the Web
IPsec
security at the IP layer
Kerberos
symmetric key system
GSM
mobile phone (in)security
– You need to know the basic ideals and be able to analyze why they are
secure or not secure using what we covered in Chapter 9
• However, you are not required to know the implementation details
• If you are interested in the details, you can take the network security class or read
more about them
– If you have any questions, I will be more happy to help.
– Read Chapter 10
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1
OSI Reference Model
• The layers
– 7: Application, e.g., HTTP, SMTP,
FTP
– 6: Presentation
– 5: Session
– 4: Transport, e.g. TCP, UDP
– 3: Network, e.g. IP, IPX
– 2: Data link, e.g., Ethernet frames,
ATM cells
– 1: Physical, e.g., Ethernet media,
ATM media
• Standard software engineering
reasons for thinking about a
layered design
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2
TCP/IP Model
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Message Mapping to the Layers
L7 App
S
P
SVN update message
D
P
S
P
D
P
L4 TCP
Segment 1
Segment 2
L3 IP
S
A
S
M
D
A
D
M
S
P
S
A
D
P
D
A
Packet 1
S
P
D
P
S
A
Packet1
S
M
D
A
D
M
S
P
S
A
D
P
D
A
Pack
2
S
P
D
P
Pack
2
L2 Eth
Communications bit stream
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4
4
Network Layer - IP
• Moves packets between computers
– Possibly on different physical segments
– Best effort
• Technologies
– Routing
– Lower level address discovery (ARP)
– Error Messages (ICMP)
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