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CS-461 Internetworking / Test #12
Department of Computer Science / March 6April 22, 2003
James Madison University / Time Allowed: 7560 Minutes
Name (PRINT) / SOLUTIONS
Score (Max 40 points)

Attempt ALL questions. Put your answers in the provided space.

Identify and circle the correct answers for questions 1 through 6 (23 points each)

Which of the following is true for the IP address 192.0.0.10In an OSPF autonomous system with n areas, how many areas are connected to the backbone area??

a.  The netID is 1921 / b.  nThe netID is 0.10 – 1
c.  nThe network address is 192.0.0.0 / nThe hostID 0.0.10
+ 1
d. 

2.  What destination address can be used to send a packet from a host of IP address 196.43.0.6 to all hosts on the networkA connectionless iterative server uses ______ports.?

a.  196.43.0.255ephemeral / b.  196.43.255.255well-known
c.  0.0.0.0active / d.  255.255.255.255
a and b

3.  The subnet mask for a class C network is 255.255.255.248. How many subnetworks are availableIn a connection-oriented concurrent server, the ______is used for connection only.?

a. 4infinite port / b. 8ephemeral port
c. well-known port16 / d. b and c32

4.  What does a router running proxy ARP and representing 10 hosts return as a target hardware address when replying to an ARP request inquiring about one these 10 hosts?The _____ system call adds the local socket address to an already created socket.

a.  Any of 10 different hardware addresses

b.  Any of 11 different hardware addresses

c.  Just the router’s hardware address

d.  Just the router’s IP addressaddress

e.  create

f.  bind

g.  socket

5.  An IP packet goes directly from the ______module of the ARP package to the data link layer if the state of the corresponding Cache Table entry is RESOLVED.The _____ system call creates a new socket for actual communication and connects the next client in line.

a. acceptcache-control / b. connectinput
c. bindoutput / d. createa and c.

6.  The _____ system call establishes an active connection to a remote process.

A time-exceeded ICMP message is generated if:

The round-trip time between hosts is close to zero

The time-to-live field of an IP packet has a zero value

Fragments of an IP packets do not arrive within a set time

b and c.

a. accept / b. bind
c. socket / d. connect

7.  (3 8 points) Find The netID and hostID of the following IP addressesA router has the following RIP routing Table:

DestinationIP address / Hop Count
NetID / Next Hop
Current / New / Current / New
Net_1a. 114.34.2.8 / 4 / 3 / B / C
b. 129.14.6.8Net_2 / 2 / 5 / C / C
Net_3 / 1 / 1 / F / F
Net_4c. 192.8.56.2 / 5 / 5 / G / G


What would be the content of the above table if the router receives the following RIP response message from router C:

Indicate your answer by filling the new “Hop Count” and “Next Hop” entries in the above table.

Destination / Hop Count
Net_1 / 2
Net_2 / 4
Net_3 / 3
Net_4 / 7

(3 4 points) What is the maximum number of subnets using the following masks?During an FTP session, two connections are established; these are

8. 

The Control connection, which is used for exchanging commands and responses

and the Data connection, which is used for transferring data files

Mask /

Class

/ Max. No. of Subnets
a. 255.255.224.0 / Class A
b. 255.255.224.0 / Class B
c. 255.255.255.240 / Class C

9.  (4 points) An organization is granted the block 130.56.0.0 in class B. The administrator wants to create 1024 subnets.

a.  Find the subnet mask.

b.  Find the number of addresses in each subnet.

c.  Find the first and last address in the first subnet.
1st address is:
last address is:

d.  Find the first and last address in the last subnet.
1st address is:
last address is:

10.  (4 points)
Using the network topology shown in the figure, construct the routing table for Router R5 by filling the provided table:

Mask / Destination / Next Hop / Flags (UGH)

11.  (4 points) An IP datagram with no options carries a payload data of 4500 bytes and has an identification number of 36,952. The packet is to be fragmented into three smaller fragments of sizes: 1600, 1600, and 1300 bytes, respectively. For each of the three fragments, provide some of the headers’ fields by filling the following table:

Fragment / Total Length / Identification / More Fragments bit / Fragmentation Offset / Payload Data Bytes
From / To
1
2
3

( 4 points) What are the source and destination ports shown in an SNMP response message from the agent to the manager?

Source port is: well-known port 161

Destination port is: ephemeral port

( 6 points) Decode the following BER-encoded data (show values in decimal format)

0A 40 04 23 51 62 71 02 02 14 12

Type / Tag (Hex) / Type / Tag (Hex)
INTEGER / 02 / IPAddress / 40
OCTET STRING / 04 / Counter / 41
OBJECT IDENTIFIER / 06 / Gauge / 42
NULL / 05 / TimeTicks / 43
Sequence, sequence of / 30 / Opaque / 44

The sequence:

IP address 35.81.98.113

12.  INTEGER 5138
(3 points) An ICMP message has arrived with the following header (in hexadecimal):
0303 1020 0000 0000
What is the type of the message?
What is the code?
What is the purpose of the message?

13.  (3 points) A TCP sender is using a window size of 10,000 bytes and the previous acknowledgement number that arrived from the receiver was 22,001. Draw a diagram showing the situation of the sender window.
The sender now receives a segment with acknowledgement number 24,001 and a window size of 11,000. Draw the new situation of the sender window

14.  (4 points) A TCP connection is in the SYN-SENT state. The following events occur one after another:

a.  A SYN+ACK segment is received

b.  A “close” message is received.

Draw a state transition diagram showing the state of the connection and the action taken after each event at both parties of this TCP connection.

Dr. Mohamed Aboutabl