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ACO 330 > Module 6 > Flashcards

Module 6 Flashcards

1
Q

The link-state algorithm in Section 4.5 has the following properties:

A

all of the above

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2
Q

Suppose that c(E,F) = 6 instead of 2 in Figure 4.27. Then the link state algorithm finds the shortest path to F in

A

step 5

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3
Q

In routing among ASs, which of the following issues dominants:

A

policy

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4
Q

The ICMP protocol

A

runs directly on top of IP

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5
Q

As part of hierarchical routing, hot-potato routing does the following:

A

Chooses the gateway that has the smallest cost.

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6
Q

Which of the following statements best describes the purpose of the SNMP protocol:

A

The SNMP protocol is a tool for gathering data about network conditions and executing remote actions at remote managed devices

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7
Q

What is the purpose of the SNMP SetRequest message?

A

To allow a managing entity to set the value of one or more MIB objects in a managed device.

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8
Q

Suppose a network manager wanted to query the value of the number of TCP segments received by a host running the Microsoft Windows 2000 operating system in a US-based company. What would be the prefix (leading digits) of the MIB variable that should be queried:

A

1.3.6.1.2.1.1

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9
Q

What is the maximum number of received UDP datagrams that can be counted (without overflow) in the MIB-2 UDP module?

A

2**32 - 1

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10
Q

TF:
In a distance-vector routing algorithm, each node has a map of the entire network and determines the shortest path from itself to all other nodes in the network.

A

False

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11
Q

TF:
In the BGP routing algorithm, each AS advertises to its neighbors its estimates of the shortest distances from the AS to all possible destination ASs.

A

False

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12
Q

TF:
OSPF uses BGP for routing among areas.

A

False

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13
Q

TF:
Every autonomous system must use the same intra-autonomous system routing algorithm.

A

False

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14
Q

TF:
The management information base (MIB) is a repository of data maintained at a managing entity site, providing the network manager with a centralized, quick-to-query database regarding current network status.

A

False

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15
Q

TF:
The SNMP
Trap
message is sent by a managed entity to inform a managing entity of an exceptional event, and requires that the managing entity respond to the event via a
SetRequest
message.

A

False

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16
Q

Which of the following statements correctly identify the differences between routing and forwarding. Select one or more statements.

A

Forwarding refers to moving packets from a router’s input to appropriate router output, and is implemented in the data plane.

Routing refers to determining the route taken by packets from source to destination, and is implemented in the control plane.

17
Q

Match the name of the approach towards implementing a control plane with a description of how this approach works.

  1. Per-router control plane
  2. Software-defined networking (SDN)
A
  1. Individual routing algorithm components - with a component operating in each and every router - interact with each other in the control plane. The individual routing algorithm component executing in a given router computes the local fowarding table fir that router.
  2. A (typically) remote controller gathers information from routers, and then computes and installs the forwarding tables in routers.
18
Q

What is the definition of a “good” path for a routing protocol? Chose the best single answer.

A

Routing algorithms typically work with abstract link weights that could represent any of, or combinations of, all of the other answers.

19
Q

Consider Dijkstra’s link-state routing algorithm that is computing a least-cost path from node a to other nodes b, c, d, e, f. Which of the following statements is true. (Refer to Section 5.2 in the text for notation.)

A

The values computed in the vector D(v), the currently known least cost of a path from a to any node v, will never increase following an iteration.

Suppose nodes b, c, and d are in the set N’. These nodes will remain in N’ for the rest of the algorithm, since the least-cost paths from a to b, c, and d are known.

In the initialization step, the initial cost from a to each of these destinations is initialized to either the cost of a link directly connecting a to a direct neighbor, or infinity otherwise.

20
Q

Match the name of a general approach to routing with characteristics of that approach.

  1. Centralized, global routing.
  2. Decentralized Routing.
  3. Static routing.
  4. Dynamic routing.
A
  1. All routers have complete topology, and link cost information.
  2. An iterative process of computation, exchange of informatoin with neighbors. Routers may initially only know link costs to directly-attached neighbors.
  3. Routes change slowly over time.
  4. Routing changes quickly over time.
21
Q

Consider the graph shown below and the use of Dijkstra’s algorithm to compute a least cost path from a to all destinations. Suppose that nodes b and d have already been added to N’. What is the next node to be added to N’ (refer to the text for an explanation of notation).

(letter)

A

e

22
Q

Consider the graph shown below and the use of Dijkstra’s algorithm to compute a least cost path from a to all destinations. Suppose that nodes b and d have already been added to N’. What is the path cost to the next node to be added to N’ (refer to the text for an explanation of notation).

(number)

A

4

23
Q

Match the terms “interdomain routing” and intradomain routing” with their definitions. Recall that in Internet parlance, an “AS” refers to “Autonomous System” – a network under the control of a single organization.

  1. Interdomain routing.
  2. Intradomain routing.
A
  1. Routing among different ASes (“networks”).
  2. Routing among routers within same AS (“network”).
24
Q

Check the one or more of the following statements about the OSPF protocol that are true.

A

OSPF is an intra-domain routing protocol.

OSPF implements hierarchical routing

OSFP uses a Dijkstra-like algorithm to implement least cost path routing.

25
Q

Consider the OSPF routing protocol. Which of the following characteristics are associated with OSPF (as opposed to BGP)?

A

Finds a least cost path from source to destination.

Floods link state control information.

Is an intra-domain routing protocol.

26
Q

Among the following protocols, terminology or considerations, indicate those that are associated with “routing within a single network (typically owned and operated by one organization).”

A

intra-AS routing

Driven more by performance than by routing policy

intra-domain routing

OSPF

27
Q

Suppose a provider network only wants to carry traffic to/from its customer networks (i.e., to provide no transit service), and customer networks only want to carry traffic to/from itself. Consider the figure below. To implement this policy, to which of the following networks would network C advertise the path Cy?

A

A, x, B

28
Q

Again, suppose a provider network only wants to carry traffic to/from its customer networks (i.e., to provide no transit service), and customer networks only want to carry traffic to/from itself. Suppose C has advertised path Cy to A. To implement this policy, to which of the following networks would network A advertise the path ACy?

A

w

29
Q

Again, suppose a provider network only wants to carry traffic to/from its customer networks (i.e., to provide no transit service), and customer networks only want to carry traffic to/from itself. Suppose C has advertised path Cy to x. To implement this policy, to which of the following networks would network x advertise the path xCy?

A

None of these other networks

30
Q

Consider routers 2c and 2d in Autonomous System AS2 in the figure below. Indicate the flavor of BGP and the router from which each of 2c and 2d learns about the path to destination x.

  1. How does router 2c learn of the path AS3, X to destination network X?
  2. How does router 2d learn of the path AS3, X to destination network X?
A
  1. From 3a via eBGP.
  2. From 2c via iBGP.
31
Q

Consider the SDN layering shown below. Match each layer name below with a layer label (a), (b) or (c) as shown in the diagram.

  1. SDN Controller (network operating system)
  2. SDN-controlled switches
  3. Network-control-applications
A
  1. (b)
  2. (c)
  3. (a)
32
Q

Which of the functions below belong in the controller layer labeled “Interface, abstractions for network control apps”? Check all below that apply.

A

Intent

Network graph

33
Q

Which of the statements below about ICMP are true?

A

ICMP messages are carried directly in IP datagrams rather than as payload in UDP or TCP segments.

ICMP is used by hosts and routers to communicate network-level information.

The TTL-expired message type in ICMP is used by the traceroute program.

ACO 330 (2 decks)

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