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
