CS522 F2006 Midterm Exam

Enter your CS Unix machine login as login and the 9 digits of student ID as password and submit the midterm before 11:59pm 10/11/2006. You can work at home or at PC lab where you can access it through a web browser. For multiple-choice questions, you must choose either yes or no for each answer.

After filled in the answers in the text areas and selected the answers, please print a copy of the web page with your answers before you hit the submit button. Note that "save file" menuitem does not save the data you enter. It only saves the HTML source file. Submit your answers by pressing the submit button at the end of this web page. You will get a confirm web page with all your answers. Save or print the answer confirmation web page for your record. Print a copy of your answers before hitting the submit button. If you have problem accessing the web server for submitting the answer, slide your hard copy with answers under my office door Tuesday Morning.
Enter the following information. The password is used to verify the person submitting the answers.

Your name:
Your login on CS UNIX machines:
Your password (All nine digits of your Student ID; no dash):

Introduction, OSI Reference, Network Services/Applications

OSI seven layer model

The purpose of the data link layer is to establishe communications between directly connected machines and ensure the integrity of the received frame. Yes No
SSL is a session layer protocol on top of TCP. What values it provide to the application layer? Name two.

PDU encapsulation/decapsulation and Internet message formats
1. What field in the Ethernet protocol header is used by the Ethernet Driver to deliver the Ethernet payload to the right IP layer protocol entity?
2. What is the name of the Data Link Layer protocol data unit?
3. Which protocol header contains the Time to Live field?
4. Which protocol header contains a SYNC bit?
5. What is the purpose of including the src port number in the transport layer header?
6. For a typical IP packet, how many bytes can be used by an application layer to carry its header and data?

Network address and their format
A laptop with wireless 802.11abg interface and wired ethernet interface shows the following routing table:

Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0     128.198.80.1   128.198.80.66       25
          0.0.0.0          0.0.0.0    128.198.160.1  128.198.172.24       20
        127.0.0.0        255.0.0.0        127.0.0.1       127.0.0.1       1
     128.198.80.0    255.255.255.0    128.198.80.66   128.198.80.66       25
    128.198.80.66  255.255.255.255        127.0.0.1       127.0.0.1       25
    128.198.160.0    255.255.224.0   128.198.172.24  128.198.172.24       20
   128.198.172.24  255.255.255.255        127.0.0.1       127.0.0.1       20

The ipconfig command shows

Ethernet adapter Wireless Network Connection:

        Connection-specific DNS Suffix  . : eas.uccs.edu
        Description . . . . . . . . . . . : Intel(R) PRO/Wireless 3945ABG Network Connection
        Physical Address. . . . . . . . . : 00-13-02-02-B8-BE
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . : 128.198.80.66
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 128.198.80.1
        DHCP Server . . . . . . . . . . . : 128.198.160.72
        DNS Servers . . . . . . . . . . . : 128.198.160.66
                                            128.198.160.64
                                            128.198.1.250
        Primary WINS Server . . . . . . . : 128.198.1.51
        Secondary WINS Server . . . . . . : 128.198.1.73
        Lease Obtained. . . . . . . . . . : Wednesday, October 11, 2006 3:21:27PM
        Lease Expires . . . . . . . . . . : Wednesday, October 11, 2006 4:21:27PM

Ethernet adapter Local Area Connection:

        Connection-specific DNS Suffix  . : uccs.edu
        Description . . . . . . . . . . . : Intel(R) PRO/1000 PM Network Connection
        Physical Address. . . . . . . . . : 00-16-36-15-9C-A6
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . : 128.198.172.24
        Subnet Mask . . . . . . . . . . . : 255.255.224.0
        Default Gateway . . . . . . . . . : 128.198.160.1
        DHCP Server . . . . . . . . . . . : 128.198.160.72
        DNS Servers . . . . . . . . . . . : 128.198.1.250
                                            128.198.1.117
        Primary WINS Server . . . . . . . : 128.198.1.73
        Secondary WINS Server . . . . . . : 128.198.1.51
        Lease Obtained. . . . . . . . . . : Wednesday, October 11, 2006 11:55:10AM
        Lease Expires . . . . . . . . . . : Wednesday, October 11, 2006 7:55:10PM

The traceroute command shows

C:\Documents and Settings\chow>tracert 128.198.1.250

Tracing route to nx01.uccs.edu [128.198.1.250]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  128.198.160.1
  2    <1 ms    <1 ms    <1 ms  nx01.uccs.edu [128.198.1.250]

What are the CIDR notations for the wirelss network and wired network connected by this laptop?
As indicated by the traceroute command, the packets are currently route through the wireless network. Yes No
What will be the broadcast address sent to the wireless network?
What will be the source mac address of the ethernet frames sent?
What will be the destination mac address of the wireless frame received from the laptop?
Which routing entry will be matched for the returning http response? What is its inteface and gateway address?

Basic End Host Routing
On elan.uccs.edu (uccs IT web server), netstat -rn shows the following result:


elan.uccs.edu> /usr/sbin/netstat -rn
Routing tables
Destination      Gateway            Flags     Refs     Use  Interface

Route Tree for Protocol Family 26:

Route Tree for Protocol Family 2:
default          128.198.1.1        UGS       339 33421542  alt0      
10.0.0/24        10.0.0.2           U           5    17016  ics0      
10.0.0.2         10.0.0.2           UHL         2     6864  ics0      
10.1.0/24        10.1.0.2           U          34 134085364  ee0       
10.1.0.2         10.1.0.2           UHL         0        0  ee0       
127/8            127.0.0.1          UR          0        0  lo0       
127.0.0.1        127.0.0.1          UHL        24  5078257  lo0       
128.198.0/22     128.198.1.203      U          62  5672840  alt0      
128.198.0/17     128.198.1.1        UGS        51  7648718  alt0      
128.198.1.197    127.0.0.1          UH          0        0  lo0       
128.198.1.203    128.198.1.203      UHL         7    64157  alt0      
128.198.1.208    127.0.0.1          UH          1     1668  lo0       
128.198.1.212    127.0.0.1          UH          1      380  lo0       
128.198.1.230    127.0.0.1          UH          0        0  lo0       
128.198.1.233    127.0.0.1          UH          0        0  lo0       
128.198.128/17   128.198.1.1        UGS        24  3371453  alt0

For an outoging packet with 128.198.60.62 destination IP address, which gateway should the packet be sent?
For an outoging packet with 128.198.172.27 destination IP address, which gateway should the packet be sent?
What protocol is used by a machine to find out the MAC address of another machine in the same subnet?
A web server can run on port 443. Yes No
Only root user can runs servers with port numbers greater than 10000. Yes No

Protocol Engineering-specification, verification

Reachability Analysis. For the following two machines,

What are the buffer sizes we should prepare for C1 and C2?
Is there a deadlock? Yes No
Is there an unspecified reception? Yes No
Is there non-executable state? Yes No
Is there non-exeutable transition? Yes No
How many global states generated?

Protocol Programming/Implementation

Internet Domain Socket page 5.
1. Internet Domain Socket can be used to send messages to processes within the local host. Yes No
2. The 5th parameter in recvfrom() provides information about the sender's IP address and port number. The network software extracts the information from the incoming packet. Yes No
3. The 2nd parameter in listen() provides information about the sender's identity. Yes No
Stream vs. Datagram
1. The Stream socket does not deliver message boundary. It is possible to read the content of two packets sent by the sender in single read() or recv() function call if we specifies a buffer size bigger than that of two messages sent. Yes No
2. By default, stream connection uses TCP and guarantees packets to be delivered in sequence without loss.This implies that T
  CP implements timeout for retransmission to deal with packet loss and implement buffering to hold packets that arrive out of order.
  Yes No
3. The two subsequent packets reads from a datagram socket can be from different senders. Yes No
Forking or not?
Given that creating a child process using fork() takes 1 milliseconds,
1. For processing such as Internet crawling or search that requires long I/O, it is worth while to use fork to serve request on a stream connection. Yes No
2. A server, which performs a table lookup with 1 microseconds to satisfy each request, should create a child processes using fork() to serve each request. Yes No
Select() page 20.
1. In State 3 of our absend.c if we did not set the readfds and timeout values again before the next Select() call, what will happen?
2. If the timeout parameter of select() is null and no messages are coming, the select() will return immediately. Yes No

Transmission Fundamental
Given the following signal constellation diagram (16 signal set) and their bit pattern assignments.

If the modem is sending signals at the rate of 4800 baud, what is the bit rate this modem can achieve?
If the sending modem receives a byte with 01101001 bit pattern from the sending computer, what are analog signals that will be generated by the sending modem?
If the receiving modem receives two analog signal: one with amplitude of A and phase angle of 7/4pi followed by a signal of amplitude of 2A and phase angle of 1/4pi, what bit patterns should it sends to the receiving computer?

If you feel some of the questions are ambiguous, state the problem # and your assumptions on the answers.

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