TDC 363 Spring 2008 Midterm Exam Study Guide and Pratice Exam John Kristoff Exam Format The midterm exam will consist of multiple choice, fill in the blank and short essay questions. The exam will take you about 1 to 1 1/2 hours to complete, but you have as much time as you need. If you are having an unreasonably difficult time with the exam, chances are others are as well. Do the questions you know best first and go back to the hard ones later. There is a grading curve for the final grade to correct any problems in the exam or my instruction that led up to the exam. You MAY bring a single 8.5" x 11" sheet of paper with crib notes and use that for reference on the exam. Whatever you can write or print on a single sheet, both sides OK, you can use. The exam is closed book, closed notes other than that one sheet, no calculators, computers, phones, or any devices of the sort. Only basic math skills that can be solved with pencil/pen and paper are required. You should have plenty of paper to work with, but if you need more blank sheets, ask. A final word of caution, DO NOT CHEAT. Topics Covered: Syllabus Weeks 1 through 4 inclusive All assigned reading, lecture topics and lab exercises is fair game for the exam. Be sure to study your book and review the lectures. Make sure you have gone through the lab exercises and undstand them. Sample Exam Match the best answer on the right with the term on the left. __e__ IEEE a. IEEE working group for wireless LANs __i__ IETF b. Thirteen in decimal __d__ CSMA/CD c. Used to map names to resources like IP addresses __g__ CSMA/CA d. Arbitration scheme used by wired Ethernet LANs __a__ 802.11 e. Standards group responsible for all 802 standards __j__ 802.3 f. Eleven in decimal __h__ IP g. Arbitration scheme used by wireless LANs __c__ DNS h. Internet's layer-3/network protocol __f__ 1011 i. Group responsible for writing Internet RFCs __b__ 1101 j. IEEE working group for wired Ethernet LANs Convert the following IP address in decimal to binary: 129.59.3.252 = 10000001.00111011.00000011.11111100 Which field in a IP header is maninpulated by the traceroute utility to discover the path packets take? time to live Which type of DNS resolver do most end stations use? stub resolver Name three types of cables that hvae been widely used in LAN systems: category 5 / unshielded twisted pair cable coaxial cable fiber optic cable Which of the following are not properly formed IPv4 addresses? a. 127.0.0.1 b. 256.256.256.256 c. 0.0,0.0 d. 10.1.10.100 e. 127.0.1.256 f. ff:ff:ff:ff:ff:ff answer: b, e and f What are the two fundamental tasks an Ethernet bridge performs? Address learning and making a forwarding decision It is impossible for a LAN switch to have active Ethernet ports at differing speeds (e.g. one at 10 Mb/s and one at 100 Mb/s). True or False? False Examine the diagram: .-----------------. LAN A +-----+ router/bridge 1 +------. LAN B '-----------------' | | .--------+--------. | router/bridge 2 | '--------+--------' | .-----------------. | LAN D +-----+ router/bridge 3 +------. LAN C '-----------------' Describe what happens if there is a host on LAN A that sends an Ethernet frame with destination ethernet address of another station on LAN D. Assume that all of the boxes are transparent bridges and they just came online and have nothing in their bridge address tables. answer: frame is first transmitted on LAN A, bridge 1 hears it, learns the source address of the sending station and adds an entry for it on its interface for LAN A in the bridge address table. It doesn't find the destination in its address table so it forwards it onto LAN B (floods it out all other ports). Bridge 2 sees the frame, doesn't have an entry for the destination in its address table so it forwards/floods it over to LAN C and adds the source address from the host on LAN A to its bridge address table, associating it with the bridge interface on LAN B. bridge 3 now sees the frame, doesn't recognize the destination so it floods it to LAN D and puts an entry for the source address in its bridge address table for LAN C. The host on LAN D should recognize its destination address in the frame the bridge forwarded and process it. explain in detail how a station arbitrates access to a shared Ethernet wired LAN. Assume a station has at least 3 consectutive collisions for that frame. Using CSMA/CD, carrier sense multiple access with collision detection, the station first queues the frame for transmission. It listens to see if the wire/channel is busy. When it is free, it begins transmission while listening on its rx line for any transmission that may have began when it did or shortly after from another station. Another station happened to be transmitting when it began (within the first 64 bytes of the frame transmission otherwise it would be a late collision). A collision occurs, but bother stations detect it. They continue sending for at least 64 bytes of the frame, this is known as the jam signal to make sure everyone hears the transmission. The stations that collided then go into exponential back-off. They first both choose a random number between 0 and 1 inclusive. If one chooses 0 and the other chooses 1, then the one choosing 0 will transmit right away while the other delays for 1 slot time (512 bits or 64 byte time). If they both choose the same random number, they will probably collide again. A station that has collided a second time in a row will now choose a random number between 0 and 3 inclusive and delay for that length of slot time. A third successive collion and it will choose a slot wait between 0 and 7 inclusive. What is the difference between unicast, multicast and broadcast transmission? unicast is one-to-one, multicast is one to a group and broadcast is one to all. Which command would someone most likely use to test basic IP network connectivity between two hosts on the Internet (assume no firewalls or packet filtering is occuring)? ___ nslookup ___ whois _x_ ping ___ impossible to determine Which of the following is a popular OS virtualization software implementation? ___ telnet _x_ vmware ___ mozilla ___ nmap ___ icann What does the program wireshark allow you to do? Describe in a brief sentence or two. It allows you to capture and analyze raw network packets. If your network adapter permits promiscuous mode you can capture all packets on the local network otherwise you can capture packets only addressed to or from your network adapter. List the and label the seven layers of the OSI Reference Model. 7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical Ethernet is a physical ___star___ wired topology and a logical ___bus___ topology. The spanning tree algorithm permits redundant bridge links that activate when topology changes allow it. True or False. True Typical Ethernet LAN MAC layer addresses use fewer bits than an IP version 4 network layer address. True or False. False The IEEE is responsible for standardizing the Internet Protocol (IP). True of False. False A local area network is a network that never span more than 100 meters. True or false. False Which mode of transmission requires token ring transmission. ___ Unicast ___ Multicast ___ Broadcast _x_ Irrelevant The term "switch" and the idea of "cut-through" switching were both _x_ successful marketing campaigns ___ invented by the IETF ___ made obsolete with the development of Ethernet ___ added to the final Internet Protocol version 6 specification In a spanning tree there is ___ active root bridge(s). _x_ only one ___ at least two ___ up to eight ___ an unlimited number of Ethernet LANS have commonly run over which of the following physical media: ___ Unshielded twisted pair (UTP) ___ Coaxial cable ___ fiber optic cable _x_ All of the above Describe in your own words what typically differentiates a WAN from a LAN. A local area network is typically confined to a relatively small and singularly owned/operated property. Often LANs span a single building, floor or wing. However, LAN technology such as high-speed wired Ethernet connectivity can be strung between buildings or campuses using third party equipment and cables. We typically think of WANs as spanning larger distances such as between cities, states or countries. WANs are often typified through the requirement of leasing part of the transmission service from a communications provider who has right of ways between the communicating entities. Unshielded twisted pair comes in two basic flavors. One where the copper wires are "stranded" and the other where the copper wires are "solid core". What is the difference and when do you use one over the other? Stranded copper is meant to be used for the short runs, or patches at the end of the of the entire LAN link. They are relatively cheap, flexible and easy to work with. Solid core cables are generally installed permanently and have better transmission properties. They tend to account for the longest part of a communications link between a wall jack and a panel in the structured cabling wiring closet. Rank the transmission properties, with 1 being the highest and 4 being the lowest, of the following cabling systems with respect to capacity (bandwidth) and resistance to electro-magnetic interference. _2_ coaxial cable _1_ fiber optic cable _3_ category 5 unshieled twisted pair _4_ plain old telephone system (POTS) wiring (category 3 or lower) Classful IP addressing is obsolete, true or false. True [ in progress ] $Header: midterm-guide.txt,v 1.5 2008/06/05 16:11:42 jkristof Exp $