CS372 - Week 8
Path Maximum Transmission Unit (Path MTU)
The largest amount of data, in bytes, which can be accommodated throughout a datagram's route from sender to receiver is called ________________
- host - host
The network layer manages communication from ______ to _______
False
The path MTU is the largest MTU on a path from sender to receiver
True
The transport layer header is encapsulated in the first fragmented IP datagram
It is the responsibility of a routing algorithm to determine a datagram's next hop information.
True
It is the responsibility of a routing algorithm to find a datagram's path through a network.
True
NAPT devices translate IP address and port numbers.
True
NAPT devices translate IP address and port numbers. (True)
True
The "Identification" header field is unchanged by IP datagram fragmentation.
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 "traceroute" application (on Windows) receives ICMP messages. (T/F)
True
The path MTU is the smallest MTU on a path from sender to receiver.
True
The path MTU is the smallest MTU on a path from sender to receiver. (T/F)
True
When a destination host's IP fragment timer expires, it drops all accumulated fragments corresponding to that timer.
True
When a destination host's IP fragment timer expires, it drops all accumulated fragments corresponding to that timer. (T/F)
True
The "traceroute" application (on Windows) sends ICMP messages by default.
True (Sends UDP by default on other OS with option to use ICMP echo requests)
Given an internet represented as a weighted undirected graph, the shortest path between node X and node Y is the path that...
has the smallest sum of edge weights
The path MTU is the largest MTU on a path from sender to receiver. (T/F)
False
The transport-layer header is encapsulated in every IP datagram fragment.
False
- Destination IP address - Destination port - Header checksum
For a TCP/IP datagram coming into a home network through a NAPT device, which header fields are altered?
- Source Port - Source IP address - Header checksum
For a TCP/IP datagram leaving a home network through NAPT device, which header fields are altered?
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
Suppose that a 2200-byte datagram (identification #40) must transit a network which has a 660-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? 260 bytes 5. What is the identification number of the second fragment? # 6. What is the fragment offset in the last fragment?
1. 4 2. 620 3. 640 4. 260 5. 40 6. 240
What is the longest common prefix for the following address range? 10011110 10111001 10011101 00000000 - 10011110 10111001 10011101 10000000
10011110 10111001 10011101
The Internet Protocol (IP) implements congestion control. (T/F)
False
Upon encountering a router with the following routing table: Prefix Match Port 10011110 00011110 10001111 0 10011110 00011110 10001111 000 1 10011110 00011110 10001111 01 2 10011110 00011110 10001110 0001 3 Default 4 A datagram with the destination IP address 158.30.142.90 would be routed to Port _____ .
4
Subnet
A group of hosts sharing a common address prefix, behind a router is called a __________
For a TCP/IP datagram leaving a home network through a NAPT device, which of the following header fields (IP and/or TCP) are altered? (Check all that apply) Destination IP address Source IP Address Header Checksum Destination Port Upper Layer Protocol Source Port Identification
Checksum Source IP Address Source Port
The Internet Protocol (IP) implements timing controls. (T/F)
False
For a TCP/IP datagram coming into a home network through a NAPT device, which of the following header fields (IP and/or TCP) are altered? (Check all that apply) Upper Layer Protocol Source Port Header Checksum Identification Destination Port Destination IP address Source IP Address
Destination Port Destination IP address Checksum
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, 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 alters IP to add new IP addresses. (T/F)
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 network layer manages communications from _____ to ______.
Host-to-host
- Through a connection relay service - Using universal plug and play (UPnP) - By using the NAPT devices IP address, and a port number pre-configured to correspond to the server
If hosting a server inside a NATed network, how do clients outside the NAPT router connect to the server?
- Subnet address - Broadcast address
In a subnet, the reserved addresses are the _____________ (with a lowest subnet IP address) and the ______________ (with a highest subnet IP address)
The "first hop" in a path to each of the networks known to the router
In addition to a default entry, routing tables in an internet store __________
Shortest Path
In network graph terminology, the __________ from A to B is the set of edges to traverse to reach B from A for the lowest total cost
Which of the following are benefits of a datagram network? Connection states are preserved. Less overhead than a VC network. Guaranteed timing. Guaranteed bandwidth. Faster delivery.
Less overhead than a VC network Faster delivery
The largest amount of data, in bytes, which can be accommodated by a particular network, link, or physical-layer is called the [a].
Maximum Transmission Unit (MTU)
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)
In network graph terminology, [a] represent routers.
Nodes
In a datagram network, the responsibilities of the network layer include: congestion control reliable delivery payload error correction packet routing connection setup/takedown flow control host-to-host communication packet forwarding
Packet routing Packet forwarding host-to-host communication
The destination host
Re-assembly of fragmented IP datagrams is handled by ....
In network graph terminology, a [a] from A to B is the set of edges to traverse to reach B from A for the lowest total cost.
Shortest Path
If hosting a server inside a NATed network, how do clients outside the NAPT router connect to the server? (Check all that apply) Using Universal Plug and Play (UPnP) By using the NAPT devices IP address, and a port number pre-configured to correspond to the server. By using the server's local IP address. Through a connection relay service
Using Universal Plug and Play By using the NAPT devices address.... Through a connection relay service
In network graph terminology, [a] represent costs.
Weights
- Multiple data flows requiring the same outbound link - Slow outbound link transmission rate
What can cause packet queuing at a router's output port?
- Output port contention - Head of line blocking - Slow outbound link transmission rate
What can cause queueing at a router's input ports?
- Routers - PCs - Laptops - Mobile devices
Where do network layer protocols run?
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
In network graph terminology, [a] represent direct connections between routers.
edges
The process of moving a datagram from a router's input port to output port is handled by the __________________.
switching fabric
Re-assembly of fragmented IP datagrams is handled by...
the destination host
The "time to live" field in a modern IPv4 datagram header specifies...
the number of remaining hops before the datagram is dropped