Review for Exam 4 School of Business Eastern Illinois University © Abdou Illia, Spring 2006

The Internet School of Business Eastern Illinois University

3 Host name n Host Names – The other network addressing system on the Internet – Easy to remember n microsoft.com n eiu.edu – Two or more text “labels” separated by dots eiu.edu

4 Host name n Host Names – Like nicknames n Not official addresses n Each host must have an IP address n But only some hosts have host names n If you give it a host name, your browser must look up IP address of host eiu.edu

5 Domain Name System (DNS)

6 n User’s computer sends a DNS host the target host’s host name in a DNS Request message n DNS host returns the target host’s IP address in DNS Response message Originating Host DNS Host eiu.edu

7 Domain Name System (DNS) n Organizations or ISPs have local DNS hosts n These hosts must know only local host names and IP addresses n For other host names, local DNS host passes request to another DNS host Originating Host Local DNS Host Remote DNS Host

8 Domain Name System (DNS) n Remote DNS host passes information back to the local DNS host n Local DNS host passes information back to user PC Originating Host Local DNS Host Remote DNS Host

9 Domain Name System (DNS)

10 Autoconfiguration n Every computer attached to the Internet is a host – Including desktop PCs n Every host must have an IP address n Some hosts, such as routers and webservers, get permanent IP addresses – So that they can be found easily

11 Autoconfiguration n User PCs do not need permanent IP addresses – They only need to be found within a use session – They usually are given temporary IP addresses each time they use the Internet – They may get a different IP address each time they use the Internet

12 Autoconfiguration n Request-Response Cycle – User software requests IP address for the user PC in Autoconfiguration Request message – Autoconfiguration Response message contains temporary IP address to use in current session

13 Autoconfiguration n Most popular autoconfiguration protocol is DHCP – Dynamic Host Configuration Protocol – Built into Windows after Win 3.1 – Supplies host with temporary IP address n DHCP can give more information too – Usually gives IP address of a default gateway (Microsoft terminology for router) – Can give IP address of a local DNS host – Can give other information as well

14 Summary Questions 1)a) When do we need DNS? b) What information do you send in a DNS request message? c) What information do you receive in a DNS response message? 2)a) What is autoconfiguration? b) What information do we get back, at a minimum, in an autoconfiguration response message? c) What other information may we get back?

Security School of Business Eastern Illinois University

16 Quiz n Check Quiz 3 (Part 1) questions

17 Summary Questions n Name a few kinds of systems attacks Answer (Security, Slide #3): Denial of Service attacks, Malicious content attacks and Intercepting messages. n Distinguish between Denial-of-Service (DoS) attack and Distributed Denial-of-Service (DDoS) attack Answer (Security, Slides #4, 5): In DoS attack, the attacker sends a stream of messages or an oversized message to the victim (usually a server) from a single computer connected to the network. In DDoS, the attacker hacks into multiple clients and plants Zombie programs on them. Then, he/she sends commands to Zombie programs which execute the attacks. n Name some techniques usually used to protect a communication against Intercepting messages. Answer: Symmetric key encryption/decryption methods, and Public key encryption/decryption methods

18 Summary Questions n Jason sends a message to Kristin using public key encryption. (a) What key will Jason use to encrypt the message? (b) What key will Kristin use to decrypt the message? (c) What key will Kristin use to encrypt the reply? (d) What key will Jason use to decrypt the reply? (e) Can the message and reply be long messages? Explain. Answer: a) Jason will encrypt the message with Kristin’s public key. b) Kristin will use her own private key to decrypt the message. c) Kristin will use Jason’s public key to encrypt the reply. d) Jason will use his own private key to decrypt the reply. e) No, public key encryption can only encrypt short messages. n Does public key encryption have a problem with secure key exchange for the public key? Explain. Answer: There is no problem distributing the public key, because it does not have to be distributed securely. You can even find companies’ public keys on their website.

19 Summary Questions 1. Briefly describe the various types of malicious content attacks Answer: See slide #6 in class notes 2. What headers and messages do Packet filter firewalls examine? Answer: See slide #10 in class notes 3. a) What part of a packet do Application firewalls examine? b) What do they look for? Answer: a) Application layer messages. b) They look for illicit content.

Network Management 2

21 Quiz n Check Quiz 3 (Part 2) questions

22 Summary Questions (Part 1) 1) List the main elements in centralized network management 2) Does the Manager communicate directly with the managed devices? Explain. 3) Explain the difference between a managed device and objects. 4) Where is the MIB (database) stored?

23 Summary Questions (Part 2) 1) In Manager-Agent communications, which device creates commands? Responses? Traps? 2) Explain the two types of commands. 3) What is a trap?