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Some TCP/IP Basics

....NFSDNSTELNET SMTPFTP

UDPTCP

IP and ICMP

Ethernet, serial line, ..etc.

Application Layer

Transport Layer

Network Layer

Low-level& Physical Layer

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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.

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Firewalls and Their Components

To the Internet

Host 1Host 2

Packet Filter-ing Router

Allowed traffic

Blocked Traffic

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Firewalls and Their Components

Web request

Host 1Host 2

ApplicationGateway

With Webproxy

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A Firewall Example

Internet

Host 1 Host 2

ApplicationGateway running

Web and FTPproxies

Packet Filter

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firewall

Actual Traffic?

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http://rnd.aucegypt.edu/ids/dumps/

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