Week 8 Summary Exercises

It is the responsibility of a routing algorithm to determine a datagram's next hop information.

True

NAPT devices translate IP address and port numbers.

True

The "Identification" header filed is unchanged by IP data fragmentation.

True

The "ping" application (on Windows) uses ICMP echo request/reply.

True

The "traceroute" application (on Windows) receives ICMP messages.

True

The path MTU is the smallest MTU on a path from sender to receiver.

True

When a destination host's IP fragment timer expires, it drops all accumulated fragments corresponding to that timer.

True

The transport-layer header is encapsulated in every IP datagram fragment.

False

ICMP can carry messages from ... (check all that apply) -Router to router -Destination host to source host -Source host to destination host -Router to sender host

-Router to router -Destination host to source host -Source host to destination host -Router to sender host

In a datagram network, the responsibilities of the network layer include: (check all that apply) -host-to-host communication -flow control -payload error correction -congestion control -reliable delivery -connection setup/takedown -packet forwarding -packet routing

-host-to-host communication -packet forwarding -packet routing

A private network uses a NAPT device at public IP address 128.100.116.1. The computers in the network use addresses of the form 10.0.0.x/22. Suppose that computer inside the NATed network sends a request with: Source Address: 10.0.0.4 Source Port: 932 Destination Address: 108.155.105.30 Destination Port: 22 The next available port number on the NAPT device is 12000. Part 1: What source and destination information do the request packet headers contain when the request is sent out by the sending host? 1. Source Address: ______________ 2. Source Port: ________________ 3. Destination Address: _____________ 4. Destination Port: ________________ Part 2: What source and destination information do the request packet headers contain when the request is sent out by the NAT box? 5. Source Address: ______________ 6. Source Port: ________________ 7. Destination Address: _____________ 8. Destination Port: ________________ Part 3: What source and destination information do the response packet headers contain when the response is received by the NAT box? 9. Source Address: ______________ 10. Source Port: ________________ 11. Destination Address: _____________ 12. Destination Port: ________________ Part 4: What source and destination information do the response packet headers contain when the response is received by the original sending host? 13. Source Address: ______________ 14. Source Port: ________________ 15. Destination Address: _____________ 16. Destination Port: ________________

1. 10.0.0.4 2. 932 3. 108.155.105.30 4. 22 5. 128.100.116.1 6. 12000 7. 108.155.105.30 8. 22 9. 108.155.105.30 10. 22 11. 128.100.116.1 12. 12000 13. 108.155.105.30 14. 22 15. 10.0.0.4 16. 932

Suppose that a 1600-byte datagram (identification #20) must transit a network which has a 740-byte MTU. Assume the minimum IP and TCP header sizes, i.e., the IP header is 20 bytes and the TCP header is 20 bytes. 1. How many fragments are created? 2. How many bytes of application data are carried in the first fragment? 3. How many bytes of application data are carried in the second fragment? 4. How many bytes of application data are carried in the last fragment? 5. What is the identification number of the second fragment? 6. What is the fragment offset in the last fragment?

1. 3 2. 700 3. 720 4. 140 5. 20 6. 180

What is the longest common prefix for the following address range? 10011110 10111001 10011101 00000000 - 10011110 10111001 10011101 10000000

10011110 10111001 10011101

IP datagram fragments cannot be fragmented again.

False

If an IP datagram fragmented into 1000-byte fragments, and later encounters a link with an 800-byte MTU, a special procedure (other than standard IP fragmentation) must be used.

False

If an IP datagram is fragmented into 1000-byte fragments, and later encounters a link with an 800-byte MTU, it is dropped.

False

In a fragmented IP datagram, the "offset" IP header field value is exactly equal to the number of bytes of fragmented data preceding this fragment.

False

It is the responsibility of a routing algorithm to correlate MAC addresses with IP addresses.

False

Network address translation alters IP to add new IP address.

False

Network address translation is strictly a Layer-3 protocol.

False

The "traceroute" application (on Windows) sends UDP messages by default.

False

The IP header is encapsulated in IP datagram fragments.

False

The Internet Protocol (IP) header may be 21 bytes long.

False

The path MTU is the largest MTU on a path from sender to receiver.

False

The largest amount of data, in bytes, which can be accommodated by a particular network, link, or physical-layer is called the ____________________.

Maximum transmission unit (MTU)

Given a router with 5 input ports and 5 output ports. If the switching fabric is 5 times as fast as the input/output line speed, queuing _____________ occur at an input port.

can

Given a router with 5 input ports and 5 output ports. If the switching fabric is 5 times as fast as the input/output line speed, queuing _____________ occur at an output port.

can

The process of moving a datagram from a router's input port to output port is handled by the __________________.

switching fabric