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Computer Networks > Network Layer > Flashcards

Network Layer Flashcards

1
Q

Network layer addresses _____ into _____

A

Logical addresses into physical addresses

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2
Q

Network layer determines route from ___ to ___, and manages tasks like ___ and ___

A

source, destination, switching, routing

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3
Q

Network layer transports ____

A

segments from sending to receiving host

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4
Q

On sending side, Segments are encapsulated into ___

A

datagrams

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5
Q

On receiving side, deliver…

A

Segments into transport layer

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6
Q

In network layer, router finds out the info on routing from

A

extracting the header field

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7
Q

Describe each of the network layer functions

A

Forwarding: move packets from router input to appropriate router output
Routing: determine route taken by packets from source to destination

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8
Q

Data Plane refers to

A

all the router local functions and processes that forward datagram from one interface to another

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9
Q

Control Plane refers to

A

All the network-wide functions and processes that determine which path to use for routing datagrams

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10
Q

Routing protocol examples

A

OSPF, BCP, Spanning Tree etc.

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11
Q

Traditional routing algorithms are implemented in

A

routers

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12
Q

Software Defined Networking is implemented in

A

remote servers

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13
Q

SDN is a

A

method for managing and configuring networks using software.

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14
Q

SDN has been made possible

A

by separating Control Plane from Data Plane

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15
Q

What is the advantage of SDN?

A

Enables IT administrators to fix networks using software application, instead of changing configuration of Physical equipment.

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16
Q

Routing algorithms communicate the routing components in other routers to compute… ?

A

Values of Forwarding Table

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17
Q

In a Logically centralized control plane…

A

A distinct(typically remote) controller interacts with local control agents

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18
Q

In Logically centralized control plane, distinct controller belongs to what plane?

A

Control Plane

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19
Q

In Logically centralized control plane, control agents belong to what plane?

A

Data Plane

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20
Q

In a Logically centralized control plane control agents can directly communicate with each other. True or False?

A

False

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21
Q

In a Logically centralized control plane control agents can take part in calculating the forward table. True or False?

A

True

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22
Q

Service model possible questions?

A
  1. Guaranteed Delivery? Can transport layer trust networrk layer?
  2. Is the order kept?
  3. Is the time of transmission same as reception
  4. Is there any feedback on congestion or bottleneck?
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23
Q

Network Service Model defines

A

Characteristics of NxN transport of data between one edge of the network and the other

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24
Q

Provide example services of NSM to individual datagrams?

A
  1. Guaranteed delivery

2. Guaranteed delivery in a certain time limit

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25
Q

Give example of two network architectures

A

Network, ATM

26
Q

What is the internet’s service model? Does it have bandwidth? Does it have no-loss? Does it have order? does it have timing? Does it give feedback on congestion?

A

best effort; no; no; no; no; no

27
Q

What kind of ATM service model’s exist?

A

CBR, VBR, ABR, UBR

28
Q

Describe the properties of CBR? Does it have bandwidth? Does it have no-loss? Does it have order? does it have timing? Does it give feedback on congestion?

A

Bandwidth: constant, no-loss: yes, order: yes, timing: yes, no congestion at all

29
Q

Describe the properties of VBR? Does it have bandwidth? Does it have no-loss? Does it have order? does it have timing? Does it give feedback on congestion?

A

Bandwidth: guaranteed rate, no-loss: yes, order: yes, timing: yes, no congestion at all

30
Q

Describe the properties of ABR? Does it have bandwidth? Does it have no-loss? Does it have order? does it have timing? Does it give feedback on congestion?

A

Bandwidth: guaranteed minimum, no-loss: no, order: yes, timing: no, congestion feedback: yes

31
Q

Describe the properties of UBR? Does it have bandwidth? Does it have no-loss? Does it have order? does it have timing? Does it give feedback on congestion?

A

Bandwidth: none, no-loss: no, order: yes, timing: no, congestion feedback: no

32
Q

Best effort is the metaphore for

A

no service at all

33
Q

What are the four components of a router?

A

Router input ports, router output ports, routing processor, high-speed watching fabric

34
Q

Which of the router’s components belong to forwarding data plane?

A

Router input ports, router output ports, high-speed switching fabric

35
Q

Which of the components belong to management control plane?

A

routing processor

36
Q

What functions does input port make? Explain each of the functions?

A

Lookup function - when packet arrives, the forwarding table is consulted to determine the output port to which the packet will be forwarded via the switching fabric

37
Q

Packets carrying routing protocol information are forwarded from ___ to ___

A

input port, routing processor

38
Q

Switching fabrics main function?

A

Connects the routers input ports to suitable output ports.

39
Q

Which of the component forms a network inside a network router?

A

Switching fabric

40
Q

Output ports main function?

A

stores packets received from switching fabric and transmits the packet on the ongoing link

41
Q

Routing processor main function?

A

Execute routing protocols, maintains routing tables, attach link state information, computes for forwarding table, performs the network management functions

42
Q

Which algorithm is used in the forwarding table?

A

Longest prefix matching

43
Q

what is the Switching rate?

A

switching rate: rate at which packets can be transfer from inputs to outputs

44
Q

What are the three ways in which switching can be done?

A

Memory, bus, crossbar

45
Q

Switching via memory is used in

A

First generation routers

46
Q

How does switching via memory work?

A

Switching between input and output ports is done under control of CPU

47
Q

In switching via memory, speed is limited by

A

memory bandwidth

48
Q

How does switching via bus work?

A

Switching between input and output ports is done over a shared bus

49
Q

Maximum how many packets can be transferred over the bus?

A

1

50
Q

In switching via bus, speed is limited by

A

bus bandwidth

51
Q

To overcome bus bandwidth limitations, ___ has been created

A

switching via interconnection network(crossbar)

52
Q

Why does the input buffer overflow occur?

A

fabric slower than input ports combined

53
Q

Describe Head-of-the-Line (HOL) blocking

A

queued datagram at front of queue prevents others in queue from moving forward

54
Q

Why is buffering needed in output ports?

A

buffering required when datagrams arrive from fabric faster than the transmission rate

55
Q

What is scheduling discipline?

A

scheduling discipline chooses among queued datagrams for transmission

56
Q

output port buffer overflow might cause

A

queuing delay and loss

57
Q

What is the formula for calculating the buffer?

A

RTT * C / sqrt(N), where C is the capacity and N is the number of flows

58
Q

Give examples of discarding policies

A

Tail drop, priority, random

59
Q

Describe priority scheduling

A

Schedule according to priority. Priority is selected via dividing the classes into the categories. To make such a division, header is consulted

60
Q

If a higher priority class arrives, when the smaller class is being executed, will it be interrupted?

A

No

61
Q

Name four scheduling policies

A

Priority, Round Robin, Weighted Fair Queuing, FIFO

62
Q

What do frag flag bit value means?

A

To find out if the fragmentation is last or not

Computer Networks (6 decks)

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