test 6

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.

False

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.

False

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

Finds a least cost path from source to destination. Floods link state control information. Is an intra-domain routing protocol.

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

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.

How does router 2c learn of the path AS3, X to destination network X?

From 3a via eBGP.

Which of the functions below belong in the controller layer labeled "Network-wide distributed, robust state management"? Check all below that apply.

Host information Switch information Statistics Flow tables Link-state information

Per-router control plane.

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.

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

Network graph Intent

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?

None of these other networks

Which of the functions below belong in the controller layer labeled "Communication to/from controlled device"? Check all below that apply.

OpenFlow protocol

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

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

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.)

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.

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?

W

Network-control applications

(a)

SDN Controller (network operating system)

(b)

SDN-controlled switches

(c)

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

False

OSPF uses BGP for routing among areas.

False

Static routing.

Routes change slowly over time.

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

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

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

policy

Software-defined networking (SDN).

A (typically) remote controller gathers information from routers, and then computes and installs the forwarding tables in routers.

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

Chooses the gateway that has the smallest cost.

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).

4

Centralized, global routing.

All routers have complete topology, and link cost information.

Decentralized routing.

An iterative process of computation, exchange of informatoin with neighbors. Routers may initially only know link costs to directly-attached neighbors.

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?

B X A

How does router 2d learn of the path AS3, X to destination network X?

From 2c via iBGP.

Which of the statements below about ICMP are true?

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

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

OSPF implements hierarchical routing OSFP uses a Dijkstra-like algorithm to implement least cost path routing. OSPF is an intra-domain routing protocol.

Interdomain routing.

Routing among different ASes ("networks").

Intradomain routing.

Routing among routers within same AS ("network")

Dynamic routing.

Routing changes quickly over time.

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

all of the above

The ICMP protocol

runs directly on top of IP

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).

e

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)."

intra-AS routing OSPF Driven more by performance than by routing policy intra-domain routing