1 some tcp/ip basics....nfsdnstelnetsmtpftp udptcp ip and icmp ethernet, serial line,..etc....
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1
Some TCP/IP Basics
....NFSDNSTELNET SMTPFTP
UDPTCP
IP and ICMP
Ethernet, serial line, ..etc.
Application Layer
Transport Layer
Network Layer
Low-level& Physical Layer
24
Ports
Each connection initiating from or arriving at the application layer is given a logical number, the so-called port numberA TCP or UDP connection is defined by:
Source IP address,Destination IP address,Sources port number, andDestination port number.
25
Firewalls and Their Components
To the Internet
Host 1Host 2
Packet Filter-ing Router
Allowed traffic
Blocked Traffic
27
A Firewall Example
Internet
Host 1 Host 2
ApplicationGateway running
Web and FTPproxies
Packet Filter
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