Advanced Network Security

Activity 2-1: Viewing RFC-793 Time Required: 30 minutes make use of Request for Comments (RFC) documents. Enter ACTIVITY Objective: Examine the details of components of a TCP segment and how to Description: For an IT security professional, the amount of information that's available can be overwhelming. To protect an organization's resources (or "assets," as they're commonly called), you're expected to be skillful in many areas. To gain the necessary skills, you should know where to look for technical information that helps you better understand a particular technology. Want to know how the Domain Name System (DNS) works? Want a better under- standing of Dynamic Host Configuration Protocol (DHCP)? Reading the RFCs on these topics can answer any questions you might have. In this activity, you examine the details of a TCP segment and get an overview of some TCP header components. You don't have to memorize your findings. This activity is merely an introduction to the wonderful world of RFCs. 1. Start your Web browser, and go to www.ietf.org 2. On the Internet Engineering Task Force home page, click the RFC Pages link on the left. (If time permits, you might want to navigate to the many other selections for informa- tion on useful topics.) 3. Read the instructions on the RFC page, click the RFC Search Page link, and then type 793 in the RFC number text box and click Search. Now, click ASCII or PDF under Files to view the RFC. Note the title page of this RFC. 4. Scroll down the document and read the table of contents to get an overview of this document's information. Read Sections 2.6, 2.7, and 2.8 to get a better idea of how TCP works. (Note that Section 2.6 discusses reliable communication.) 5. Scroll down to Section 3.1, "Header Format." The diagram might not be what you're used to seeing in computer documentation, but it's typical of what you see in an RFC The numbers at the top make it easier for you to see the position of each bit. For example, the upper 0, 1, 2, and 3 show you that there are a total of 32 bits (0 to 31) across this segment. Note that the source port and destination port fields are 16 bits long, and both the ISN and the acknowledgment number are 32 bits long. 6. Read Section 3.1, and note the use of the binary numbering system. This information should help solidify your knowledge of binary and hexadecimal numbering. These topics are also reviewed in "Overview of Numbering Systems" later in the chapter 7. Scroll down to Section 3.4, "Establishing a connection," and skim the description of three-way handshake. The author does a nice job of simplifying this process and adds a lit tle humor about why an ACK doesn't occupy sequence number space. Many RFC authors have a knack for explaining complex material in an easy-to-understand manner 8. Scroll through the rest of the document to get an overview of what's covered. You can read the entire document later, if you like. When you're finished, exit your Web browser. Activity 2-1: Viewing RFC-793 Time Required: 30 minutes make use of Request for Comments (RFC) documents. Enter ACTIVITY Objective: Examine the details of components of a TCP segment and how to Description: For an IT security professional, the amount of information that's available can be overwhelming. To protect an organization's resources (or "assets," as they're commonly called), you're expected to be skillful in many areas. To gain the necessary skills, you should know where to look for technical information that helps you better understand a particular technology. Want to know how the Domain Name System (DNS) works? Want a better under- standing of Dynamic Host Configuration Protocol (DHCP)? Reading the RFCs on these topics can answer any questions you might have. In this activity, you examine the details of a TCP segment and get an overview of some TCP header components. You don't have to memorize your findings. This activity is merely an introduction to the wonderful world of RFCs. 1. Start your Web browser, and go to www.ietf.org 2. On the Internet Engineering Task Force home page, click the RFC Pages link on the left. (If time permits, you might want to navigate to the many other selections for informa- tion on useful topics.) 3. Read the instructions on the RFC page, click the RFC Search Page link, and then type 793 in the RFC number text box and click Search. Now, click ASCII or PDF under Files to view the RFC. Note the title page of this RFC. 4. Scroll down the document and read the table of contents to get an overview of this document's information. Read Sections 2.6, 2.7, and 2.8 to get a better idea of how TCP works. (Note that Section 2.6 discusses reliable communication.) 5. Scroll down to Section 3.1, "Header Format." The diagram might not be what you're used to seeing in computer documentation, but it's typical of what you see in an RFC The numbers at the top make it easier for you to see the position of each bit. For example, the upper 0, 1, 2, and 3 show you that there are a total of 32 bits (0 to 31) across this segment. Note that the source port and destination port fields are 16 bits long, and both the ISN and the acknowledgment number are 32 bits long. 6. Read Section 3.1, and note the use of the binary numbering system. This information should help solidify your knowledge of binary and hexadecimal numbering. These topics are also reviewed in "Overview of Numbering Systems" later in the chapter 7. Scroll down to Section 3.4, "Establishing a connection," and skim the description of three-way handshake. The author does a nice job of simplifying this process and adds a lit tle humor about why an ACK doesn't occupy sequence number space. Many RFC authors have a knack for explaining complex material in an easy-to-understand manner 8. Scroll through the rest of the document to get an overview of what's covered. You can read the entire document later, if you like. When you're finished, exit your Web browser