Welcome to Lesson 28. In this lesson, we're going to try our hands at applying the Cyber Assessment Risk Management Approach. CARMA stage 2 is identify cyberinfrastructure. Let us see if you can identify cyberinfrastructure by answering some questions about the abstracted Internet model I have displayed. Let's start by locating ISP8 on the diagram. Do you see it? Okay, question one, would you say ISP8 is a tier two or a tier 3 ISP? Remember, a tier two ISP is bigger than a tier three ISP. What do you think? I think it's clear from this diagram that ISP8 is a tier 3 ISP, as indicated by it's competitive size. Okay, got that? Let's confirmed. Question number 2. What other two ISPs shown on this diagram may also be considered tier 3 ISPs? Find them, I hope you see that ISP5 and ISP7 are clearly the other tier 3 ISPs in this diagram. Got it? Very good. So question three, now that we've identified the tier 3 ISPs, can you tell me how many customers they have combined? Take your time. Remember to pause this recording if necessary to consider your answer. Did everybody count six customers total? Excellent. Okay, now let's locate the tier 2 ISPs. Find them? Great. How many customers do the tier 2 ISPs have combined? Did you say 14? Great. I think you understand the different tiered ISPs. Let's now move on and look at how they're interconnected. Take a moment and locate customer number 18. Find it? Good, now locate customer number eight. Find it?, good, now answer me this. What is the minimum number of hops required for customer number 18 to send the data package for customer number 8? Take your time, remember to pause the recording if necessary to compose your answer. Are you ready? Do you have an answer? Did you count three hops? Fantastic. How did you find this answer? Well, you should count the first hope from customer number 18 to ISP number 8. Do you see it? The second hop then, is from ISP8 to ISP6. Okay, and finally the third hop is from ISP6 to customer number eight. Simple, right? Okay let's see if you truly got it. Answer me this, question number six. What is the minimum number of hops required for customer number one to send data to customer number three? Take you time. Do you have an answer? Do you count six? Excellent. Hop number one is from customer number one to ISP4. Hop two is from ISP4 to ISP1. Hop three is from IXP1 to ISP1. Hop four is from ISP1 to IXP3, and hop five is from IXP3 to ISP5. And finally, hop six is from ISP5 to customer number three. Again, this should be simple stuff. If not, rewind and review until it makes sense. Okay, let’s ask some questions of a more analytical nature. Take another look at this diagram. Question seven, as defected in the diagram which two customers are geographically closer C17 and C18 or C6 and C7? In terms of this diagram, geographic proximity is determined by the straight line distance between two nodes. Do you see it? Okay, what is your answer? Which two customers are geographically closer together? C17 and C18 or C6 and C7. Answer, I hope you said C6 and C7 are geographically closer to each other closer than C17 and C18 I hope you agree. Now, let me ask you this, which path is shorter? Is the path from C6 to C7 shorter? Where's the path from C17 and C18 shorter? Remember, you determine the size of a path by the number of hops. Which path has the least number of hops? Is it C6 to C7 or C17 to C18? Take your time. You have an answer? Yes, that is correct. Both paths are the same size. Both sets of nodes can be reached in the same number of hops. Both sets of nodes can be reached in seven hops. I hope you got that. Okay, let's now turn our attention to the ISPs. Question nine, which ISP has the most links? Take your time and count them. Do you have the answer? Yes, IXP2 and IXP3 are tied with four links each. Do you count that? Good, now one final question. Which IXP do you suppose carries the most traffic? By traffic we mean the number of packets that cross their network. Take your time to consider your answer. I'll give you a hint, it's one of the two IXPs with the most links. Do you think IXP two or IXP3 carries the most traffic? Figure it out? I'd say you're correct if you chose IXP2. IXP2 probably carries the most traffic. Why? ISP2 probably carries the most traffic because it is connected to 2 tier 1 and 2 tier 2 ISPs. ISP3 probably carries less traffic because it's connected to a 2 tier 2, 2 tier 1 but only one tier 2 ISPs IXP2 carries more traffic because it is connected to more large scale ISP's than IXP3. Copy that? Makes sense, right? I hope you agree. This concludes our look at CARMA stage two, which is to identify cyber infrastructure. Please join me in the next lesson as we move on and take a look at CARMA stage three, conduct cyber risk assessment. Thank you.