1. 1 Some TCP/IP Basics....NFSDNSTELNETSMTPFTP UDPTCP IP and ICMP Ethernet, serial line,..etc. Application Layer Transport Layer Network Layer Low-level & Physical Layer

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24. 24 Ports Each connection initiating from or arriving at the application layer is given a logical number, the so-called port number A TCP or UDP connection is defined by: Source IP address, Destination IP address, Sources port number, and Destination port number.

25. 25 Firewalls and Their Components To the Internet Host 1Host 2 Packet Filter- ing Router Allowed traffic Blocked Traffic

26. 26 Firewalls and Their Components Web request Host 1Host 2 Application Gateway With Web proxy

27. 27 A Firewall Example Internet Host 1Host 2 Application Gateway running Web and FTP proxies Packet Filter

28. 28 firewall Actual Traffic?

29. 29 http://rnd.aucegypt.edu/ids/dumps/ Assignment 0: