Computer Science 881
                         Quiz C           Name _______________________


1. TCP Vegas implements Fast/Restart and Fast/Recovery in a
   different way than Reno.. Under what condition does Vegas
   initiate a retransmission?





2. Vegas enthusiasts claim that another of its advantages is:

   a. Vegas will attain larger      b. Vegas can halve the cwnd
      cwnd values than will Reno       multiple times per RTT
                                       where Reno will only halve
   c. Reno can halve the cwnd         it once
      multiple times per RTT
      where Vegas will only halve
      it once

3. a. In a Vegas TCP suppose Base_RTT = 0.100 seconds and cwnd = 10000.
      What is the "expected" throughput



   b. Suppose the ack for segment number 400000 has just been received.
      snd.nxt = 408000 and the RTT is 0.125 seconds. What is the
      actual throughput during the period between the transmission
      of segment 400000 and the receipt of its ACK.



  c. What is N_extra in bytes?



  d. Suppose the MSS is 1000. Should Vegas increase cwnd, decrease
     cwnd, or hold it constant during the next RTT.



4. What two problems associated with the use of drop-tail
   gateways are early random drop gateways designed to fix?

   a -


   b -


5. Identify two characteristics that  distinguish Floyd's Random
   Early Detection gateways from prior Early Random Drop Gateways.

   a -




   b -



6. SNMP data is exchanged using:

  a. UDP datagrams.                  b. TCP connections

  c. Raw IP datagrams                d. A special protocol like ICMP


7. a. The formal language used to define the mib goes by a three
      letter abbreviation followed by a numeral.. What is it?




   b. The rules used to encode MIB elements into SNMP packets are
      also known by a 3 letter abbreviation. What is it?





8. There are three main classes of SNMP messages. One is Set Reply/Response
   is Get/GetNext/Request/Response. What is the third??









9. SNMP-1 provides a weak authentication scheme.  What is the
   term used for the "password".