info 203 chapters 3 and 4

Which of the following addresses can not be used by an interface in the 223.1.3.0/29 network? Check all that apply.

- 223.1.3.16/29 - 223.1.2.6/29 - 223.1.3.28/29

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 waits at a light and then turns left at the intersections - The gas stops at an intersection to 'gas-up' and take a 'bathroom break'

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.

- A router exchanges messages with another router, indicating the cost for it (the sending router) to reach a destination host - Routers send information about their incoming and outgoing links to other routers in the network

What is meant by an IP subnet?

- A set of device interfaces that can physically reach each other without passing through an intervening router. - A set of devices that have a common set of leading high order bits in their IP address.

Which of the following statements is true regarding an IP address? (Zero, one or more of the following statements is true).

- An IP address is associated with an interface - If a host has more than one interface, then it has more than one IP address at which it can be reached - If a router has more than one interface, then it has more than one IP address at which it can be reached

What are the principal components of the IPv4 protocol (check all that apply)?

- IPv4 datagram format - IPv4 addressing conventions - Packet handling conventions at routers (eg. segmentation/reassembly)

Which of the fields below are in a UDP segment header?

- Internet checksum - Source port number - Destination Port Number - Length (of UDP header plus payload)

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.

- Looking up address bits in an arriving datagram header in the forwarding table - Moving an arriving datagram from a router's input port to output port - Dropping a datagram due to a congested (full) output buffer

Check all of the services below that are provided by the TCP protocol.

- Reliable data delivery. - In-order data delivery - A congestion control service to ensure that multiple senders do not overload network links. - A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. - A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender.

Check all of the statements below where (in the network) the network layer is implemented that are true.

- The network layer is implemented in hosts at the network's edge. - The network layer is implemented in routers in the network core.

Computing the Internet Checksum (2). Compute the Internet checksum value for these two 16-bit words: 11110101 11010011 and 10110011 01000100

01010110 11100111

This field contains the number of available bytes in the TCP receiver's buffer.

Receiver advertised window

What is meant by transport layer demultiplexing?

Receiving a transport-layer segment from the network, extracting the payload (data) and delivering the data to the correct socket

This field contains the index in the sender-to-receiver byte stream of the first byte of that data in the payload carried in this segment.

Sequence number

This field contains the port number associated with the sending socket for this TCP segment.

Source port number

What is meant by transport layer multiplexing?

Taking data from one socket (possible many sockets), encapsulating a data chunk with header information - thereby creating a transport layer segment - and eventually passing this segment to the network layer

Over what set of bytes is the checksum field in the UDP header computed?

The entire UDP segment, except the checksum field itself, and the IP sender and receiver address fields

What is the purpose of the Dynamic Host Configuration Protocol?

To obtain an IP address for a host attaching to an IP network

Where is transport-layer functionality primarily implemented?

Transport layer functions are implemented primarily at the hosts at the "edge" of the network.

True or False: It is possible for two TCP segments with source port 80 to be sent by the sending host to different clients.

True

True or False: It is possible for two UDP segments to be sent from the same socket with source port 5723 at a server to two different clients.

True

True or False: On the sending side, the UDP sender will take each application-layer chunk of data written into a UDP socket and send it in a distinct UDP datagram. And then on the receiving side, UDP will deliver a segment's payload into the appropriate socket, preserving the application-defined message boundary.

True

True or False: The transport layer provides host-to-host delivery service?

True

True or False: When computing the Internet checksum for two numbers, a single flipped bit (i.e., just one of the two numbers) will always result in a changed checksum.

True

True or False: When multiple UDP clients send UDP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

True

Consider a TCP connection between Host A and Host B. Suppose that the TCP segments traveling from Host A to Host B have source port number x and destination port number y. Then the destination port number for segments sent out of Host B to Host A is:

X

What is the maximum # of interfaces which can be present in the 223.1.2.0/24 network?

254

What is the maximum # of interfaces in the 223.1.3.0/29 network?

6

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.

A DHCP request message is sent broadcast, using the 255.255.255.255 IP destination address - A DHCP request message may contain the IP address that the client will use - 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

Why is the UDP header length field needed?

Because the payload section can be of variable length, and this lets UDP know where the segment ends

Consider the TCP Telnet scenario below (from Fig. 3.31 in text). Why is it that the receiver sends and ACK that is one larger than the sequence number in the received datagram?

Because the send-to receiver segment carries only one byte of data, and after that segment is received, the next expected byte of data is just the next byte (i.e., has an index that is one larger) in the data stream.

This field contains the internet checksum of the TCP segment and selected fields in the IP datagram header.

Checksum

The transport layer sits on top of the network layer, and provides its services using the services provided to it by the network layer. Thus it's important that we know what is meant by the network layer's "best effort" delivery service. True or False: The network layer's best-effort delivery service means that IP makes its "best effort" to deliver segments between communicating hosts, but it makes no guarantees. In particular, it does not guarantee segment delivery, it does not guarantee orderly delivery of segments, and it does not guarantee the integrity of the data in the segments.

Correct! The network layer's best effort service doesn't really provide much service at all, does it?

The field contains application data that was written into a socket by the sender of this TCP segment.

Data (or payload)

Consider the method TCP estimates the RTT, Round Trip Time, as shown below. this method is called EWMA, Exponentially Weighted Moving Average, and calculated the nth value of the estimated RTT: EstimatedRTTn = (1- a)*EstimatedRTTn-1 + a*SampleRTTnTrue or False: with this EWMA algorithm the value of EstimatedRTTn has no dependence on the earlier sample, SampleRTTn-1

False

True or False: On the sending side, the TCP sender will take each application-layer chunk of data written into a TCP socket and send it in a distinct TCP segment. And then on the receiving side, TCP will deliver a segment's payload into the appropriate socket, preserving the application-defined message boundary.

False

True or False: When computing the Internet checksum for two numbers, a single flipped bit in each of the two numbers will always result in a changed checksum.

False

True or False: When multiple TCP clients send TCP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

False

Which one of the following operations is NOT performed by NAT.?

Generating ACKs back to the TCP sender and then taking responsibility for reliably delivery the segment to its destination, possibly using a non-TCP reliable data transfer protocol.

This field contains the number of bytes in the TCP header.

Header length field

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 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!

Compute the Internet checksum value for these two 16-bit words: 01000001 11000100 and 00100000 00101011Compute the Internet checksum value for these two 16-bit words: 01000001 11000100 and 00100000 00101011

10011110 00001111

If set, this segment cumulatively ACKs all data bytes up to, but not including, the byte index in the ACK value field of this segment.

ACK bit

This field contains the index in the byte stream of the next in-order byte expected at the receiver.

ACK number field