Module 5 Flashcards
Suppose an application generates chunks of 60 bytes of data every second, and each chunk gets encapsulated in a TCP segment and then an IP datagram. What percentage of each datagram will contain application data.
60%
Consider sending a 1300 byte datagram into a link that has an MTU of 500 bytes.
Three fragments are created with offsets 0, 480 and 960.
In a router, queuing can occur
all of the above
In a high-performance router, shadow copies of the routing table are kept in
the input ports
Question 5:Suppose a router has n input ports each with identical line speeds, n output ports each with identical line speeds, and the line speed of an output port is at least n times as that of an input port. Further suppose that the switching fabric speed is at least n times as fast as an input line speed. Then
there is no queuing delay in the router
Suppose one IPv6 router wants to send a datagram to another IPv6 router, but are connected together by intervening IPv4 routers. If the two routers use tunneling, then
The sending IPv6 router creates an IPv6 datagram and puts it in the data filed of an IPv4 datagram.
TF: With a datagram network layer, each packet carries the address of the destination host.
True
TF: Suppose the computer in your office has been configured with an IP address, and you move (along with your computer) to an office down the hall. If after the move your computer is connected to the same IP network, then it is not necessary to reconfigure the IP address in your computer.
True
TF: The network portion of an IP address is the same for all the hosts on the same IP network.
True
TF: A gateway router must run both an intra-AS routing algorithm and an inter-AS routing algorithm.
True
TF: Single-homed hosts have one interface and routers typically have two or more interfaces.
True
Check all of the statements below about where (in the network) the network layer is implemented that are true.
The network layer is implemented in routers in the network core.
The network layer is implemented in hosts at the network’s edge.
Consider the travel analogy discussed in the textbook - some actions we take on a trip correspond to forwarding and other actions we take on a trip correspond to routing. Which of the following travel actions below correspond to forwarding? The other travel actions that you don’t select below then correspond to routing.
A car takes the 3rd exit from a roundabout.
A car stops at an intersection to “gas-up” and take a “bathroom break”
A car waits at light and then turns left at the intersection.
For each of the actions below, select those actions below that are primarily in the network-layer data plane. The other actions that you don’t select below then correspond to control-plane actions.
Moving an arriving datagram from a router’s input port to output port
Dropping a datagram due to a congested (full) output buffer.
Looking up address bits in an arriving datagram header in the forwarding table.
We’ve seen that there are two approaches towards implementing the network control plane - a per-router control-plane approach and a software-defined networking (SDN) control-plane approach. Which of the following actions occur in a per-router control-plane approach? The other actions that you don’t select below then correspond to actions in an SDN control plane.
Routers send information about their incoming and outgoing links to other routers in the network.
A router exchanges messages with another router, indicating the cost for it (the sending router) to reach a destination host.
Which of the following quality-of-service guarantees are part of the Internet’s best-effort service model? Check all that apply.
None of the other services listed here are part of the best-effort service model. Evidently, best-effort service really means no guarantees at all!
Match the names of the principal router components (A,B,C,D below) with their function and whether they are in the network-layer data plane or control plane.
(picture not included)
A: input ports, operating primarily in the data plane.
B: the switching fabric, operating primarily in the data plane.
C: output ports, operating primarily in the data plane.
D: the routing processor, operating primarily in the control plane.
Where in a router is the destination IP address looked up in a forwarding table to determine the appropriate output port to which the datagram should be directed?
At the input port where a packet arrives.
Where in a router does “match plus action” happen to determine the appropriate output port to which the arriving datagram should be directed?
At the input port where a packet arrives.
Suppose a datagram is switched through the switching fabric and arrives to its appropriate output to find that there are no free buffers. In this case:
The packet will either be dropped or another packet will be removed (lost) from the buffer to make room for this packet, depending on policy. But the packet will definitely not be be sent back to the input port.
What is meant by Head of the Line (HOL) blocking?
A queued datagram waiting for service at the front of a queue prevents other datagrams in queue from moving forward in the queue.
Packet scheduling (Scenario 1, FCFS).
(diagram and full question not included. Identify the answer by the Scenario name)
1 2 3 4 5 6 7
Packet scheduling (Scenario 1, Priority).
(diagram and full question not included. Identify the answer by the Scenario name)
1 2 3 5 4 7 6
Packet scheduling (Scenario 1, RR).
(diagram and full question not included. Identify the answer by the Scenario name)
1 3 2 4 5 6 7
What are the principal components of the IPv4 protocol (check all that apply)?
Packet handling conventions at routers (e.g., segmentation/reassembly)
IPv4 datagram format.
IPv4 addressing conventions.
Match each of the following fields in the IP header with its description, function or use.
Version field
Type-of-service field
Fragmentation offset field
Time-to-live field
Header checksum field
Upper layer field
Payload/data field
Datagram length field
( unique keywords in each answer to help identify)
Version field: version number
Type-of-service field: ECN
Fragmentation offset field: fragmentation/reassembly.
Time-to-live field: the packet must be dropped.
Header checksum field: Internet checksum
Upper layer field: demultiplexed
Payload/data field: UDP or TCP segment
Datagram length field: total number of bytes in datagram.
Which of the following statements is true regarding an IP address? (Zero, one or more of the following statements is true).
If a host has more than one interface, then it has more that one IP address at which it can be reached.
An IP address is associated with an interface.
If a router has more than one interface, then it has more that one IP address at which it can be reached.
What is meant by an IP subnet? (Check zero, one or more of the following characteristics of an IP subnet).
A set of devices that have a common set of leading high order bits in their IP address.
A set of device interfaces that can physically reach each other without passing through an intervening router.
What is the maximum # of interfaces in the 223.1.2/24 network?
256
What is the maximum # of interfaces in the 223.1.3/29 network?
8
Which of the following addresses can not be used by an interface in the 223.1.3/29 network? Check all that apply.
223.1.2.6
223.1.3.28
223.1.3.16
What is meant by saying that DHCP is a “plug and play” protocol?
No manual configuration is needed for the host to join the network.
Which of the following statements about a DHCP request message are true (check all that are true). Hint: check out Figure 4.24 in the 7th and 8th edition of our textbook.
The transaction ID in a DHCP request message will be used to associate this message with future DHCP messages sent from, or to, this client.
A DHCP request message may contain the IP address that the client will use.
A DHCP request message is sent broadcast, using the 255.255.255.255 IP destination address.
Which of the following fields occur ONLY in the IPv6 datagram header (i.e., appear in the IPv6 header but not in the IPv4 header)? Check all that apply.
The flow label field.
128-bit source and destination IP addresses.
What is the purpose of the Dynamic Host Configuration Protocol?
To obtain an IP address for a host attaching to an IP network.
Destination-based forwarding, which we studied in section 4.2, is a specific instance of match+action and generalized forwarding. Select the phrase below which best completes the following sentence:
“In destination-based forwarding, …”
… after matching on the destination IP address in the datagram header, the action taken is to forward the datagram to the output port associated with that destination IP address.
Which of the following match+actions can be taken in the generalized OpenFlow 1.0 match+action paradigm that we studied in Section 4.4? Check all that apply.
all EXCEPT
… after matching on the URL contained in an HTTP GET request in the TCP segment within the IP datagram, the action taken is to determine the IP address of the server associated with that URL, and to forward the datagram to the output port associated with that destination IP address.
Which of the following fields in the frame/datagram/segment/application-layer message can be matched in OpenFlow 1.0? Check all that apply.
IP destination address
Time-to-live field
IP type-of-service field
Upper layer protocol field
Consider the figure below that shows the generalized forwarding table in a router. Recall that a * represents a wildcard value. Now consider an arriving datagram with the IP source and destination address fields indicated below. For each source/destination IP address pair, indicate which rule is matched. Note: assume that a rule that is earlier in the table takes priority over a rule that is later in the table and that a datagram that matches none of the table entries is dropped.
picture not included
What is meant by generalized forwarding (as opposed to destination-based forwarding) in a router or switch?
Which of the following network devices can be thought of as a “middlebox”? Check all that apply.
HTTP load balancer
HTTP cache
Network Address Translation box
What protocol (or protocols) constitutes the “thin waist” of the Internet protocol stack? Check all that apply.
IP
Which of the statements below are true statements regarding the “end-to-end principle”? Check all that apply.
The end-to-end argument allows that some redundant functionality might be placed both in-network and at the network edge in order to enhance performance.
The end-to-end argument advocates placing functionality at the network edge because some functionality cannot be completely and correctly implemented in the network, and so needs to be placed at the edge in any case, making in-network implementation redundant.
(all but the shortest answer)
What is meant when it is said that the Internet has an “hourglass” architecture? See the picture below if you are unfamiliar with an “hourglass”.
The Internet protocol stack has a “thin waist” in the middle, like an hourglass. The Internet Protocol (IP) is the only network-layer protocol in the middle layer of the stack. Every other layer has multiple protocols at that layer.
In the US, which of the following services has been regulated by the Federal Communications Commission (FCC) going back into the 20th century?
Telecommunication services.
