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					ATM Networks                                                     CSE
Homework 1                                                       20

 1. Why do ATM networks use cell switching?[1]

 2. Why is virtual circuit switching critical for ATM networks? (Please
    list three reasons )[1]

 3. What are the "adaptation layers"? Are they in the switches? Are
    they in the end-hosts?[1]

 4. Is it practical to build a large (i.e., with lots of ports) input buffered
    ATM switch with fast links? Why or why not?[2]

 5. Is it practical to build a large (i.e., with lots of ports} outputbuffered
    ATM switch with fast links? Why or why not?[2]

 6. How many low-bit-rate calls can be supported by AAL2 in a single
    ATM connection?[2]

 7. Estimate the bit rate of the connection if an AAL2 carries the
    maximum number of calls carrying voice at 12 kbps.[2]

 8. Compare the overhead of AAL3/4 with that of AAL5 for a 64Kbyte

 9. Explain how the three-bit sequence number in the AAL1 header can
    be used to deal with lost cells and with miss inserted cells.[2]

 10. Suppose that an ATM connection carries voice over AAL-1.
     Suppose that the packetization delay is to be kept below 10
     ms.Calculate the percentage of overhead if the voice is encoded
     using PCM.[2]

 11. Explain how the header error checksum can be used to synchronize
     to the boundary of a sequence of contiguous ATM cells. What is the
     probability that an arbitrary five-odd block will satisfy the header
     error checksum? Assume bits are equally likely to be 0 or 1. What is
     the probability that two random five-octet blocks that correspond to
     two consecutive headers pass the error check?[3]

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