MarkdownNotes

View the Project on GitHub JungAn2/MarkdownNotes

4.1-1 THE NETWORK LAYER - WHERE IS IT?

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

4.1-2 FORWARDING VERSUS ROUTING.

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.

4.1-3 THE CONTROL PLANE VERSUS THE DATA PLANE.

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.

4.1-4 WHAT TYPE OF CONTROL PLANE?

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.

4.1-5 BEST EFFORT SERVICE.

Which of the following quality-of-service guarantees are part of the Internet’s best-effort service model? Check all that apply.

4.2-1 WHAT'S INSIDE A ROUTER?

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.

4.2.1

4.2-2 WHERE DOES DESTINATION ADDRESS LOOKUP HAPPEN?

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?

4.2-3 WHERE DOES "MATCH+ACTION" HAPPEN?

Where in a router does "match plus action" happen to determine the appropriate output port to which the arriving datagram should be directed?

4.2-4 LONGEST PREFIX MATCHING.

Consider the following forwarding table below. Indicate the output to link interface to which a datagram with the destination addresses below will be forwarded under longest prefix matching. (Note: The list of addresses is ordered below. If two addresses map to the same output link interface, map the first of these two addresses to the first instance of that link interface.) [Note: You can find more examples of problems similar to this here.]

4.2.4

Note:
    Since this is in order, just set which ever come first at the top to be first destination.

4.2-5 PACKET DROPPING.

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:

4.2-6 HOL BLOCKING.

What is meant by Head of the Line (HOL) blocking?

4.2-7 SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under FCFS scheduling. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1). [Note: You can find more examples of problems similar to this here.]

4.2.7

Note:
    First come first serve

4.2-8 SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under priority scheduling, where red packets have higher priority. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1).

4.2.7

Note:
    Red has more priority than green

4.2-9 SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under round robin scheduling, where red starts a round if there are both red and green packets ready to transmit after an empty slot. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1).

4.2.7

Note:
    Alternate between red and green

4.2-10 PACKET SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under FCFS scheduling. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1).

4.2.10

4.2-11 PACKET SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under priority scheduling, where red packets have higher priority. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1).

4.2.10

4.2-12 PACKET SCHEDULING.

Consider the pattern of red and green packet arrivals to a router’s output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under round robin scheduling, where red starts a round if there are both red and green packets ready to transmit after an empty slot. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1).

4.2.10

4.3-1 WHAT IS THE INTERNET PROTOCOL?

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

4.3-2 THE IPV4 HEADER.

Match each of the following fields in the IP header with its description, function or use.

4.3-3 WHAT IS AN IP ADDRESS ACTUALLY ASSOCIATED WITH?

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

4.3-4 WHAT IS A SUBNET?

What is meant by an IP subnet? (Check zero, one or more of the following characteristics of an IP subnet).

4.3-5 SUBNETTING.

Consider the three subnets in the diagram below.

4.3.5

What is the maximum # of interfaces in the 223.1.2/24 network?

4.3-6 SUBNETTING.

Consider the three subnets in the diagram below.

4.3.5

What is the maximum # of interfaces in the 223.1.3/29 network?

4.3-7 SUBNETTING.

Consider the three subnets in the diagram below.

4.3.5

Which of the following addresses can not be used by an interface in the 223.1.3/29 network? Check all that apply.

4.3-8 PLUG-AND-PLAY.

What is meant by saying that DHCP is a "plug and play" protocol?

4.3-9 DHCP REQUEST MESSAGE.

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.

4.3-10 IPV4 VERSUS IPV6.

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.

4.3-11 PURPOSE OF DHCP.

What is the purpose of the Dynamic Host Configuration Protocol?

4.4-1 DESTINATION-BASED MATCH+ACTION.

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, ..."

4.4-2 GENERALIZED MATCH+ACTION.

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.

4.4-3 WHAT FIELDS CAN BE MATCHED IN GENERALIZED MATCH+ACTION.

Which of the following fields in the frame/datagram/segment/application-layer message can be matched in OpenFlow 1.0? Check all that apply.

4.4-4 MATCH+ACTION IN OPENFLOW 1.0.

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.

4.4.4.jpg

4.4-5 CRAFTING NETWORK-WIDE FORWARDING USING FLOW TABLES.

Consider the network below. We want to specify the match+action rules at s3 so that only the following network-wide behavior is allowed: traffic from 128.119/16 and destined to 137.220/16 is forwarded on the direct link from s3 to s1; traffic from 128.119/16 and destined to 67.56/16 is forwarded on the direct link from s3 to s2; incoming traffic via port 2 or 3, and destined to 128.119/16 is forwarded to 128.119/16 via local port 1. No other forwarding should be allowed. In particular s3 should not forward traffic arriving from 137.220/16 and destined for 67.56/16 and vice versa. From the list of match+action rules below, select the rules to include in s3's flow table to implement this forwarding behavior. Assume that if a packet arrives and finds no ddmatch rule, it is dropped.

4.4.5.jpg

4.4-6 CRAFTING NETWORK-WIDE FORWARDING USING FLOW TABLES (MORE).

Consider the network below. We want to specify the match+action rules at s3 so that s3 acts only as a relay for traffic between 137.220/16 and 67.56/16. In particular s3 should not accept/forward and traffic to/from 128.119/16. From the list of match+action rules below, select the rules to include in s3's flow table to implement this forwarding behavior. Assume that if a packet arrives and finds no ddmatch rule, it is dropped.

4.4.5.jpg

4.5-1 WHAT'S A "MIDDLEBOX"?

Which of the following network devices can be thought of as a "middlebox"? Check all that apply.

4.5-2 THE "THIN WAIST" OF THE INTERNET.

What protocol (or protocols) constitutes the "thin waist" of the Internet protocol stack? Check all that apply.

4.5-3 THE END-TO-END PRINCIPLE.

Which of the statements below are true statements regarding the "end-to-end principle"? Check all that apply.