Computer Science 825 Quiz 1 Name _______________________ Terminology: the very highest layer is the APPLICATION LAYER the very lowest layer is the PHYSICAL LAYER Suggestion: READ the questions carefully... some with minor changes in terminology from old quizzes have DIFFERENT ANSWERS from their counterparts. 1. What is the highest layer that must be implemented in every IMP in a store and forward network. 2. What is the lowest layer which is normally present in hosts but not in IMP's. 3. Protocol headers used by a layer N are handled by layer K (K > N) as follows: a. The are removed before b. They are treated as user data. the packet arrives at Layer K c. They are deleted by layer K. 4. A Layer N service definition is most closely related to specifying the way in which layer N interacts with: a. Layer N - 1 b. Layer N + 1 c. Layer N at other nodes in the network. 5. A Layer N protocol definition is most closely related to specifying the way in which layer N interacts with: a. Layer N - 1 b. Layer N + 1 c. Layer N at other nodes in the network. 6. Which two layers does the TCP / IP network architecture specify a. Data Link and Physical b. Application and Transport c. Network and Transport d. None of the above Turn page over... there's more fun on the back! 7. Identify the form of Transport service best suited for the following applications: ___ a. Very large file a. unreliable connectionless transfers b. reliable connection oriented ___ b. Audio & Video teleconferencing c. reliable connection less. ___ c. Electronic mail d. unreliable connection oriented. 8. At which layer is it most necessary that a common protocol be implemented within all nodes of a network. Computer Science 825 Quiz 2 Name _______________________ 1. The maximum useful BAUD rate on a 10,000 hz channel is: a. 10,000 baud b. 20,000 baud c. 5, 000 baud d. Unlimited 2. a. How many signalling levels are required to transmit 64,000 bits / second on a 4Khz bandwidth channel. b. What SNR in db is necessary for this scheme to work? 3. Associate each of the following constraints with the "natural law" that constrains it: ____ a. Maximum bit rate 1. Nyquist's Law ____ b. Maximum baud rate 2. Westall's Law ____ c. Maximum # signalling 3. Shannon's Law levels. 4. The use of a self-clocking modulation scheme is a. more important for asynchronous b. more important for synchronous than synchronous communication than asynchronous communication c. not important for either d. mandatory in both 5. Identify the physical layer transmission scheme used in each of the following interfaces: ____ a. Memory to U(S)ART a. Serial and modulated carrier ____ b. U(S)ART to modem b. Serial and baseband. ____ c. Modem to Modem c. Parallel and modulated carrier d. Parallel and baseband. 6. Which of the following best characterizes what is meant by the term "asynchronous communication" as discussed in class. a. The sender and receiver are b. The sender and receiver use completely unsynchronized. the same physical clock. c. The sender and receiver use d. The sender and receiver use independent clocks and resync independent clocks and resync every byte time. every bit time. 7. In the model of synchonous transmission that we described in class a. the sender and receiver b. the clocks in both USARTS USARTs and modems used and modems were derived 4 independently running from the clock in the clocks. sender USART. c. the clocks in both USARTSsed d. the clocks in both USARTS and modems were derived T. and modems were derived from the clock in the from the clock in the sender modem. receiver modem. 8. In the 1200 and 9600 b.p.s. modulation schemes that we presented in class which one of the 3 parameters of the expression for a general sine wave was NOT modulated? Computer Science 825 Quiz 3 Name _______________________ 1. Suppose a new "high fidelity" voice telephone service has a bit rate of 2 ^ 19 (512K) bits per second. Suppose that the system is designed to carry frequencies up to 16384 = (2 ^ 14)hz. Into how many discrete levels can the PCM signal be quantized. 2. Suppose a network has links that carry data at a rate of 10,000 bits per second. Suppose Node A and Node B are connected by a path that requires 20 hops (retransmissions). a. What is the minimum time required to send a 400,000 bit message if message switching is used. b. Suppose packet switching is used and no additional bits are required for headers. How long will it take to send the entire message if 5000 bit packets are used. c. Suppose a message is to be transmitted over a network in which all links run at the same speed and the time to transmit the message between any two nodes is T. Suppose that a path has length N hops and that T / N > (1 / bit rate). The time required to transmit a message over the entire path using packet switching when compared to message switching is: a. O(N * T) b. O(N / T) c. O(T / N) d. Independent of N (Hint: this is REALLY an easy question.) 4. An RS-232 cable's data connections must be wired: a. 2 to 2 for modem to pc and b. 2 to 3 for modem to pc and 2 to 2 for pc to pc service 2 to 2 for pc to pc service c. 2 to 3 for modem to pc and 2 to 3 for pc to pc service 5. Select the most suitable multiplexing scheme (FDM, ATDM, STDM) for each of the following cases: a. Digital channels with very unbalanced loads. b. Analog channels. c. Digital channels with very well balanced loads. 6. The bit rate required by standard voice grade digital circuits is closest to: a. 4000 bps b. 8000 bps c. 64000 bps d. 1,544,000 bps 7. The class of data service provided by ISDN is best categorized as a. Connection oriented reliable b. Connection less unreliable bit stream. datagram. c. Connection oriented unreliable d. Connection oriented reliable bit stream. datagram 8. The main reason digital channels have much lower error rates than analog when used over very long distances is: a. Digital signalling is more c. Digital signals are regenerated powerful than analog. rather than amplified. b. Digital signals are amplified d. Digital channels have much higher rather than regenerated. SNR's than analog. 9. Which of the following best characterizes the relationship between digital and baseband signalling. a. All digital signals are baseband b. All digital signals are baseband but not all baseband signals and all baseband signals are are digital. digital. c. All baseband signals are digital but not all digital signals are baseband. Computer Science 825 Quiz 4 Name _______________________ 1. Measurements of an infinite user slotted aloha channel show that 60% of the slots are idle. a. What is the total load (mean number of transmission attempts per packet time) = G. b. What is the throughput?? c. Is the current load below or above the load required to obtain maximum throughput. 2. If K stations share a CSMA-CD bus and the probability that any station will transmit on a given contention slot is "p", then the probability that a successful transmission will take place in a slot is: a. p c. k * p * (1 - k) ** (p - 1) b. p * (1 - p) * (k - 1) d. None of the above. 3. The efficiency of a CSMA CD LAN is a function of the speed of light, the packet size, the bit transmission rate, and the length of the cable. Answer the following T or F. (Assume only the parameter indicated is being varied and all of the others remain fixed in each case). ___ a. Increasing the length of a CSMA CD LAN will increase the length of the contention interval and thus make the efficiency of the LAN higher. ___ b. Increasing the average packet size will tend to make the efficiency of a CSMA CD LAN higher. ___ c. Decreasing the bit transmission rate from 10 Mbps to 1 Mbps will make the contention interval longer and thus decrease the efficiency. 4. The main reason that an ethernet channel can support more packets / packet time throughput than a satellite based aloha system is that: a. The signal travels faster thru b. All stations hear every ethernet an ethernet cable than thru transmission but only the dest space. station hears an aloha transmission c. The signal propogation delay d. Only one station at a time is is far shorter in an ethernet allowed to transmit in an aloha than in a satellite net. network. 5. The main function of the CD portion of a CSMA-CD protocol is to: a. Reduce the probability that b. Reduce amount of wasted time a collision will occur. when a collision occurs. c. Ensure that no collisions d. Both a and b. occur at all. 6. Consider a p-persistent csma-cd lan. p persistent means that after a station senses the carrier idle it transmits with probability p and defers with probability (1 - p). Increasing the value of p will tend to: a. Reduce latency at low util. b. Increase latency at low util. and increase throughput at and increase throughput at high utilization. high utilization. c. Increase latency at low util. d. Reduce latency at low util. and increase throughput at and reduce throughput at high utilization. high utilization. 7. The motivation for dual persistence is that the probability that a collision will occur is: a. higher when a station has b. lower when a station has sensed the carrier busy and sensed the carrier busy and waited for it to become idle waited for it to become idle than when it initially senses than when it initially senses the carrier idle. the carrier idle. c. very low immediately after a collision. Computer Science 825 Quiz 5 Name _______________________ 1. A token bus system (not IEEE 802.4) works like this. When the token arrives at a station a timer is reset to 0. The station then transmits priority 6 frames unitl the timer reaches T6. It then switches to priority 4 until the timer reaches T4. This algorithm is repeated for with priority 2 and 0. If all stations use the values of 60, 100, 130, 150 for T6 through T0 what percent of the bandwidth will be dedicated to class 4 (assume all stations have an infinite backlog of each class.) 2. In IEEE 802.4 the value TRT4 specifies: a. The time dedicated to class b. The time left for transmission 4 traffic at each token of class 4 data when the time of possession. the last token rotation is subtracted from TRT 4 c. The time left for transmission d. Both a. and c. specify the of class 4 data when the time of same value. the last token rotation + time spent transmitting class 6 is subtracted from TRT 4 3. For the IEEE token bus match the control packets with the conditions underwhich they are used. (Some answers may or may not be used multiple times and some may or may not be used at all.) ____ a. A station is powered up, listens 1. SOLICIT_SUCCESSOR_2 for the token and doesn't hear one. 2. WHO_LEADS ____ b. A station wishes to leave the net. 3. WHO_FOLLOWS ____ c. A station transmits the token twice 4. RESOLVE_CONTENTION without hearing its successor transmit a token or a packet. 5. CLAIM_TOKEN ____ d. A station wishes to invite a new 6. SOLICIT_SUCCESSOR station to enter the network. 7. SET_SUCCESSOR ____ e. A station recognizes a WHO_FOLLOWS packet specifying its predecessors 8. WHO_KNOWS address. 9. LEAD_FOLLOW_OR_ ____ f. A station transmits WHO_FOLLOWS GET_OFF_THE_DAMN_BUS and receives no response. 4. The maximum length of an ethernet segment is: a. 5 meters b. 5 miles c. 500 miles d. 500 meters 5. Which of the following best characterizes the difference between an ethernet bridge and a repeater. a. Both bridges and repeaters b. Bridges forward all traffic but forward all traffic to repeaters attempt to forward only connected segments. those packets that need to go to the connected segment. c. Repeaters forward all traffic but bridges attempt to forward only those packets that need to go to the connected segment. 6. a. In a token ring LAN is the sender xor receiver responsible for removing a data packet from the ring? b. What is the BIGGEST problem associated with having the other party perform the function. 7. Suppose bit transmission rate is 4,000,000 b.p.s and signal propogation is 200,000 KM / sec. How long must a cable be to hold an entire 24 bit token. Computer Science 825 Quiz 6 Name _______________________ 1. Suppose the MLMA MAC protocol is being used and station addresses consist of 3 decimal numbers. If stations 610, 501, 403, 199 and and 197 all become ready at the same time. How many decades will be required to identify the ready stations. 2. The objective of the reservation based Aloha Schemes was to a. Act like TDM at both b. Act like Aloha at low loads high and low loads. and TDM at high. c. Act like TDM at high d. Act like Aloha at low loads loads and Aloha at lows. and Aloha at high. 3. Reservation aloha schemes collect consequtive packet slots into larger units called GROUPs. The size of a group: a. is unrestricted. b. must be no more than the two way propogation delay c. must be >= than the d. must be >= than the two way propogation delay one way propogation delay. 4. A disadvantage of the use of the reservation method that had all dynamically assigned slots (Crowther's method) was: a. It was not easy to add or b. One station could potentially hog delete stations while the the entire net's bandwidth for long network was active. periods of time unless special rules were devised. c. A station with much data d. Both b. and c. to send was not guaranteed access to its slot in all successive frames once it started transmitting. 5. Suppose a 15 bit codeword with ODD parity is being used in a single bit hamming ECC. Suppose the following codeword is received. 1 1 1 1 1 0 0 1 1 1 1 0 1 1 0 -------------------------------------------- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 a. Which bit if any is in error? b. Suppose a multiple bit error occurs. Circle the correct description of the result. 1. The fact that there is a multibit error can be detected, but the error can't be corrected. 2. The multibit error will be undetected and the value that results from the correction process will be a legal code word but it will be the wrong one. 3. The multibit error will be undetected and the corrected value will be either the wrong codeword or it might be the correct codeword. 4. The multibit error will be undetected and the corrected value MAY be an illegal code word. c. Suppose an odd parity Hamming code is being used on a 3 bit codeword. Assuming the ECC bits are allocated as described in class which are the 2 legal codewords? 6. Suppose the following bit sequence has been subject to standard bit stuffing.. Write actual sequence of data bits. Last bit --> 111001111101111011111000 <- First bit transmitted 7. In the standard bit stuffing framing the loss of a start flag (framing character can be detected by (hint: Loss => RECEIVER failed to change states when it should have. ) a. The appearance of some 0's b. The appearance of some 1's where where there should only be 1's there should only be 0's. c. The appearance of all 1's d. The appearance of all 0's where where there should be a mix of there should be a mix of 1's 1's and zeros. and 0's. should only be 1's 8. In the standard bit stuffing framing the loss of an end flag (framing character can be detected by: a. The appearance of some 0's b. The appearance of some 1's where where there should only be 1's there should only be 0's. c. The appearance of all 1's d. The appearance of all 0's where where there should be a mix of there should be a mix of 1's 1's and 0's and 0's. Computer Science 825 Quiz 7 Name _______________________ 1. Suppose 2000 bit code words are to be transmitted and it is desired to use a Hamming code to correct error bursts of up to 40 bits. How many of the 2000 bits must be used for ECC. 2. Consider the following shift register: a. What will be the contents of the shift register after the input digits 1 and 0 are processed. b. What generator polynomial is represented by this shift register. c. Does this shift register represent standard long division or is it the pre-multiplying version? (Yes in not the correct answer). 3. Suppose a CRC generator polonomial G(x) is x ^ 2. Answer the following T or F. ___ 1. This polynomial can detect all single bit errors. ___ 2. This polynomial can detect no single bit errors. ___ 3. This polynomial can detect some (at least 1) double bit errors. 4. Any polynomial that has (x + 1) as a factor is guaranteed to detect a. All errors of 2 bits b. All errors in which an odd # or less of bits are inverted. c. All errors in which d. Both a. and b. an even number of bits are inverted. 5. The size of the largest error burst that a CRC can guarantee detection of is: a. The number of terms in the c. 32 generator b. The degree of the generator d. The degree of the generator + 1 6. The main advantage of using the pre-multiplying shift register is: a. The logic is simpler so b. The CRC is available as soon each cycle can be faster. as the last bit of the message has been put into the register. c. The CRC is available after all of the messages bits and the "r" appended 0 bits have been processed. 7. The premultiplying shift register for a degree 4 generator will work correctly a. Only if initilized to 0 b. Only if initialized with the and the 1st 4 message bits first 4 message bits. fed in 1 at a time. c. Both of the above will yield the same answer. 8. In protocol 1 in the book, frames didn't carry sequence #'s and no ACKS or CRC's were used. Which of the following is NOT a disadvantage of the use of protocol 1. a. A fast sender could overrun b. Undetected duplications of a slow receiver packets could take place. c. Packets could be lost. d. Damaged packets could be accepted. 9. In protocol 2, ACK's were used but no sequence numbers were used on frames or ACK's. Which of the following problems could occur. a. Lost frames would go b. Lost ACK's would result in undetected. lost frames c. Lost acks would result in d. Lost frames would result in duplicate frames. duplicate frames. Computer Science 825 Quiz 7 Name _______________________ 1. In protocol 3, frames's had sequence numbers but ACKS did not. Protocol 3 could fail in the presence of: a. ACK's that were lost b. ACK's that were excessively delayed c. Frames that were lost. d. Either a or b 2. Show how a sliding window protocol that uses a 2 bit sequence number, a sender window size of 3, and a receiver window size of 2 can fail. 3. Suppose that a satellite channel is in use and the EARTH to SATELLITE propogation delay is 120 ms. Suppose bit transmission rate is 100,000 bits per second and packets are 1000 bits long. a. What will the efficiency of this channel be if stop and wait protocal is used. b. How large (in packets) must the SWS be in order to obtain 100% efficiency if the channel is guaranteed error free. (i.e. give me the MINIMUM SWS). c. How large (in packets) must the RWS be in order to obtain 100% efficiency if the channel is guaranteed error free. d. Suppose the channel is chock full of errors. How if at all does your answers to part b. and c. change. b.? c? e. How many bits should the sequence number be if the channel is chock full of errors? 4. Under what combinations of propogation delay (Short..Long) and error rate (Low..High) would each of the following protocols be good choices. There may be protocols in the following list that would NEVER be particularly good choices. If so, say so. a. Stop and Wait b. Go back N c. Selective repeat d. Selective reject. 5. Match the amount of channel time lost each time an isolated error occurs in each of the following environments: ____ a. Go Back N 1. The two way propogation delay ____ b. Selective repeat 2. One way propogation delay. ____ c. Selective reject 3. One packet time 4. The timeout interval 5. Two times the timeout interval 6. Which best describes the constraints on the relationship between REASONBLE receiver and sender window sizes. a. They must always be b. Sender size may be larger the same size. than receiver size but not vice versa. c. Receiver size may be larger than sender d. Either one can be larger but not vice versa. than the other. Computer Science 825 Quiz 9 Name _______________________ 1. Identify two deficiencies of the protocol 5 implementation that would HAVE TO BE corrected before it could be successfully used in a real network. a. b. 2. The queuemsg process waited on two counting semaphores. What did the counts in each of these semaphores represent? a. b. 3. The address byte in an SDLC packet always carries the address of a. The sender b. The receiver c. The primary station. d. The secondary station. 4. Select the description which most accurately matches the use of the P/F bit in SDLC. a. 1 -> Poll and 0 -> Final b. The bit means poll or not poll when a secodary sends final or not final when a primary sends. c. The bit means poll or not d. The bit means poll or not poll poll to the sender final when the primary sends final or or not final to the receiver not final when a secondary sends. 5. Unnumbered frames in SDLC carry a. Both sequence numbers and b. Sequence numbers but no ack ack numbers. numbers c. Ack numbers but no sequence d. No numbers at all. numbers. 6. Which of the following is NOT a use of supervisory frames in SDLC a. Sending a standalone ack b. Seeing if another station is back up after a crash. b. Polling d. Telling another station to temporarily stop sending. 7. Which of the following messages has suitable semantics for the unnumbered protocol. Hint: This question is NOT asking what specific frame types are in SDLC. It IS asking what limitations are on the semantics of messages in protocols in which frames and acks carry no numbers. a. Set current seq # to 0. b. Add 1 to current seq #. c. Both a and b. d. Neither a nor b. 8. Suppose unnumbered frames were given sequence numbers and ACK numbers just like data frames and that the receiver of an out of sequence unnumbered frame would discard it just as it would an out of sequence data frame. Would this make the functions performed with unnum frames work: a. Much better and more b. Work worse and less reliably. reliably. c. Make no appreciable difference. 9. Identify the class of service provided to the transport layer by each of the following network layers. ___ a. IBM SNA a. Unreliable connection oriented ___ b. Internet Protocol b. Reliable connection oriented ___ c. BISDN c. Unreliable connectionless d. Reliable connectionless Computer Science 825 Quiz A Name _______________________ 1. For each of the following routing strategies identify its worst problem. Some answers may be used more than once, others not at all. _____ a. Static tables 1. Too slow _____ b. Hot potato 2. Works well for small networks but scales poorly for large nets. _____ c. Flooding 3. Susceptible to single pt failure. _____ d. Centralized 4. Can cause severe congestion 5. Not robust, packets may loop forever. 2. Let N = number of nodes in a network and M = the average number of links / node. a. The number of routing packets transmitted throughout the entire network at each routing exchange in Bellman-Ford is proportional to: 1. M 2. N 3. N ** 2 4. N * M b. In terms of computational complexity the SPF algorithm as performed by a single node is of order. 1. M 2. N 3. N ** 2 4. M ** 2 5. N * M c. The minimum number of routing packets transmissions at each complete exchange in SPF within the entire network is proportional to: 1. M 2. N 3. N ^ 2 4. M ^ 2 5. N * M d. Routing information exchanges in the SPF ARPANET scheme take place at least as often as once a 1. Second 2. Minute 3. Hour 4. Day e. Routing information exchanges in the Bellman Ford ARPANET scheme took place. 1. More often than the SPF 2. Less often than the SPF Arpanet scheme. arpanet scheme. 3. At the same rate as the SPF scheme. 3. Suppose the Bellman-Ford routing algorithm is being used and station B receives the following routing updates from neighbors A, C and E A C E Cost VIA A 0 6 1 | --------------------------------- B 6 11 2 | -------------------------------- C 3 0 4 | -------------------------------- D 8 5 2 | -------------------------------- E 2 8 0 | -------------------------------- F 11 2 7 | -------------------------------- Suppose BA delay = 3, BC delay = 2 and BE delay = 5. Complete the routing table for B. (Break ties alphabetically) 3. In another network that uses SPF suppose a station constructs the following cost matrix. Draw the optimal routing tree from node B to all destinations. Label each arc with the order in which it is made permanent in the SPF algorithm. (Break ties alphabetically) T o A B C D E F A 0 3 - 3 4 r B 5 0 6 - - o C - 1 0 7 3 m D 1 - 3 0 2 E 4 - 2 1 0 4. Suppose a new virtual circuit is to be set up and that it goes from the host at switch E to the host at switch B following the route A -> B -> F -> D -> C. Update the VC assignment tables. Computer Science 825 Quiz B Name _______________________ 1. We discussed several methods of broadcast routing. From reverse path forwarding, spanning tree, flooding, and multidestination identify the one that would cause the most and the least number of packet transmissions. Most - Least - 2. A minor problem with the token based (also called isarithmic) congestion control scheme was how to initially inject tokens into the network. Identify two other major problems of the scheme. 1 - 2 - 3. The hierarchical buffer allocation algorithm of Merlin and Schweitzer was designed to: a. Prevent reassembly deadlocks. b. Reduce congestion in connection less networks. c. Prevent store and forward deadlocks. 4. For this algorithm to work correctly the number of buffers at each routing node has a greatest lower bound of: a. 1 b. The number of nodes in the network. c, The maximum number of packets d. The maximum length in hops of in the network at any one time. of any route in the network. 5. The most important factor in determining whether or not preallocation of resources is a suitable way to do congestion control is: a. Whether or not the network b. Whether or not the network layer is reliable or layer is connection oriented unreliable. or connection less. c. Both of the above are d. Neither of the above is equally important. significant at all. 6. Choke packets are sent: a. from an imp experiencing b. To an IMP experiencing congestion to the source congestion from the source host of a packet. host of a packet. c. From an IMP experiencing d. To an IMP experiencing congestion to the dest congestion from the dest host of a packet. host of a packet. 6. The most important factor in determining whether or not packet discarding is a suitable way to do congestion control is: a. Whether or not the network b. Whether or not the network layer is reliable or layer is connection oriented unreliable. or connection less. c. Both of the above are d. Neither of the above is equally important. significant at all. 7. When flow control is used as a congestion control mechanism we said it generally works better if it was implemented in a coarse grain mode rather than fine grain. This statement assumes that: a. All sessions have near b. Sessions generate bursty traffic constant traffic rates. and the aggregation of traffic of multiple sessions appears equally c. Sessions generate bursty bursty (the fractal model). traffic but the aggregation of traffic of multiple stations is less bursty (the non fractal model). 8. The focus of Raj Jain's talk on Friday was: a. ATM performance issues. b. Optimizing TCP/IP routing. c. Object oriented protocol d. Implications of the halting implementation in DECNet. problem on SNA. 9. Which of the following did he NOT identify as a requirement for the commercial success of a networking architecture. a. Low cost b. High performance c. Interoperability with d. Must be designed by Microsoft. existing networks. Computer Science 825 Quiz C Name _______________________ 1. Recall that ATM Cells carry 48 data bytes and that the data rate required for voice is 64KB/sec. Suppose the telephone company decided to offer 100 MBit / Second service to your home at a cost of $10 per Giga-cell (no monthly minimum required). a. How much would a 20 minute long distance phone call cost. b. Now suppose you NFS mount a disk on your friend's computer in California and in the course of a few hours work transfer 16,000,000 MB of data. How much does that cost? c. Finally, suppose you want to watch a movie over the same system. Screen resolution is 480 x 640 pixels. Each pixel requires 3 bytes and frame rate is 40 frames / second. Suppose you can get 10 to 1 compression of the video stream. How much will a two hour movie cost? 2. Which routing algorithm is used by the spanning tree bridge if the location of the destination node is unknown? a. Spanning tree. b. Flooding c. Backward learning. d. Shortest past first. 3. Which routing algorithm does the spanning tree bridge employ to avoid having destination unknown occur very often? a. Spanning tree. b. Flooding c. Backward learning. d. Shortest past first. 4. Since a spanning tree is computed every few seconds why do destination unknown situations EVER occur after the spanning tree has been constructed for the first time? 5. Which routing algorithm is used by the source routing bridge in routing "discovery" packets to the destination. a. Spanning tree. b. Flooding c. Backward learning. d. Shortest past first. 6. Identify the network layer at which each of the following interconnects is used (in the terminology of the text). a. Bridge b. Repeater 7. The LAN architecture in which intra-architecture bridging has the LEAST number of complicating factors is: a. 802.3 to 802.3 b. 802.4 to 802.4 c. 802.5 to 802.5 d. All are equally complicated. 8. Identify one complicating factor in bridging 802.5 to 802.5 9. Suppose the following is a diagram of an SNA network: A D / \ / \ Z C F \ / \ / B E Answer the following T or F. ___ a. Nodes B and C can't both have explicit routes with the identity (3, F). ___ b. For node A to have a functional explicit route with identity (3, F), node C must also have an explicit route with identity (3, F). ___ c. Nodes A and B can't both have explicit routes with the identity (3, F) where A's (3,F) passes through D and C's (3, F) passes through E. ___ d. Nodes A and B can both have explicit routes to F with A's called (3, F) and B's called (4, F) where A's (3,F) passes through D and B's (4, F) passes through E. Computer Science 825 Quiz D Name _______________________ 1. A VR manager receiving a packet with the Change Window Reply Indicator must: a. Stop sending immediately b. Set the current pacing group size to the minimum pacing group size. c. Decrement the current d. Increment the current pacing group pacing group size. size. 2. Suppose Tomlinson's clock proposal is used with a 12 bit sequence number and a clock that ticks 100 times a second. Suppose maximum packet lifetime is 6 seconds. a. What is the MINIMUM amount of time that can elapse before sequence number resynchronization must occur. b. How often will synchronization be needed if a packet is generated every 40 milliseconds. c. Suppose the bit transmission rate is 100000 bits per second and that all packets are the same size. What is the minimum packet size that permits full channel untilization WITHIN THE CONSTRAINTS IMPOSED BY TOMLINSONS algorithm. d. Which aspect of Tomlinson's alg does TCP NOT use. 3. Suppose a TCP connection has SND.UNA = 2200 and SND.NXT = 3450 and a packet arrives with ACK = 3000 and WINDOW = 4000. What size are the offered and usable windows now? offered - usable - Suppose a 3 way handshake is being used to establish a connection. Let SYN-1 represent a packet that carries SYN and no ack. Let SYN-2 represent a packet that carries both SYN and ACK that is sent in response to a SYN. 4. A delayed duplicate SYN2 received the SYN sent state is detected because: a. The SEQ number is wrong. b. The ACK number is wrong. c. Both SEQ and ACK are d. SYN2 is an unexpected packet known to be wrong. in the SYN sent state. 5. A delayed duplicate SYN1 received in the CLOSED / LISTEN state is a. detected because of wrong b. Detected because of wrong ACK SEQ number. number. c. Undetected and responded d. Responded to with a SYN 1. to with a SYN2. 6. A delayed duplicate SYN1 received in the ESTABLISHED state is: a. Responded to with RESET. b. Responded to with a data packet specifying current ACK and SEQ. c. Responded to with SYN2 d. Always causes TCP to crash. 7. Which class of net does a node whose address is 140.115.17.139 belong to. a. A b. B c. C d. Reserved 8. The function of the "protocol" byte found in the IP header? a. Identify the version of b. Identify the network IP being used. layer protocol being used. c. Identify the transport d. Identify the application protocol being used. protocol being used.