Practice Exercise 23
  1. Encode the following byte values using NRZL, NRZI and Manchester encoding techniques. 
               a.)  00000000
               b.)  11111111
               c.)  10101010
  1. Using bit-stuffing (after 5 consecutive 1's, insert an extra 0), encode the following bit stream. 
               110111111110111111111110101011100000
  1. All the extra bits that surround the actual data in a packet have to be transmitted over the wire, too, so they consume time that could be spent transmitting real data. We call this the overhead that the protocol imposes. Consider the packet format in Section 3 of Chapter 25:
  1. How many bits will always get transmitted, even if there are 0 data bytes?

     

  2. If the maximum number of bytes are transmitted, how long will the entire packet be (in bytes?)

     

  3. What is the overhead of this longest packet in percent?

     

  4. If most packets only contain 1024 data bytes, what is the overhead (in percent)?
  1. Suppose that a particular connection-oriented protocol requires that an ACK be sent after each correct packet is sent. ACKs are 15 bytes long. Data packets can contain up to 4Kbytes of user data and contain 20 bytes of header each.
  1. How many packets would a 1 Megabyte data file be split into?

     

  2. Counting all the header bytes of all the packets, how many extra bytes would need to be transmitted just by the sender side to get this file over?

     

  3. How many bytes of ACKs would the receiver have to send, assuming there were no errors?
  1. For each of the following values of N, tell how many wires there would need to be for various network topologies. For meshes, the connectivity number is given as the minimum number of wires that touch each and every node. There may be more, but there must be at least this many. 
                                        N=5                     N=10
     ---------------------------------------------------------------------------
     fully connected
     
     ---------------------------------------------------------------------------
     token ring
     
     ---------------------------------------------------------------------------
     star
     
     ---------------------------------------------------------------------------
     mesh, con=2
     
     ---------------------------------------------------------------------------
     mesh, con=3
     
     ---------------------------------------------------------------------------
  1. What is the diameter of the following mesh network?

  1. If the routing tables did not have any default entries, how large would they be if there N nodes in the network?
  1. For the mesh network of Fig. 28 of Chapter 25, write out routing tables for nodes C, E and H. Try to distribute the packets somewhat evenly. You may use default entries if you like.