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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
Give example of two network architectures
Network, ATM
26
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?
best effort; no; no; no; no; no
27
What kind of ATM service model's exist?
CBR, VBR, ABR, UBR
28
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?
Bandwidth: constant, no-loss: yes, order: yes, timing: yes, no congestion at all
29
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?
Bandwidth: guaranteed rate, no-loss: yes, order: yes, timing: yes, no congestion at all
30
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?
Bandwidth: guaranteed minimum, no-loss: no, order: yes, timing: no, congestion feedback: yes
31
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?
Bandwidth: none, no-loss: no, order: yes, timing: no, congestion feedback: no
32
Best effort is the metaphore for
no service at all
33
What are the four components of a router?
Router input ports, router output ports, routing processor, high-speed watching fabric
34
Which of the router's components belong to forwarding data plane?
Router input ports, router output ports, high-speed switching fabric
35
Which of the components belong to management control plane?
routing processor
36
What functions does input port make? Explain each of the functions?
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
Packets carrying routing protocol information are forwarded from ___ to ___
input port, routing processor
38
Switching fabrics main function?
Connects the routers input ports to suitable output ports.
39
Which of the component forms a network inside a network router?
Switching fabric
40
Output ports main function?
stores packets received from switching fabric and transmits the packet on the ongoing link
41
Routing processor main function?
Execute routing protocols, maintains routing tables, attach link state information, computes for forwarding table, performs the network management functions
42
Which algorithm is used in the forwarding table?
Longest prefix matching
43
what is the Switching rate?
switching rate: rate at which packets can be transfer from inputs to outputs
44
What are the three ways in which switching can be done?
Memory, bus, crossbar
45
Switching via memory is used in
First generation routers
46
How does switching via memory work?
Switching between input and output ports is done under control of CPU
47
In switching via memory, speed is limited by
memory bandwidth
48
How does switching via bus work?
Switching between input and output ports is done over a shared bus
49
Maximum how many packets can be transferred over the bus?
1
50
In switching via bus, speed is limited by
bus bandwidth
51
To overcome bus bandwidth limitations, ___ has been created
switching via interconnection network(crossbar)
52
Why does the input buffer overflow occur?
fabric slower than input ports combined
53
Describe Head-of-the-Line (HOL) blocking
queued datagram at front of queue prevents others in queue from moving forward
54
Why is buffering needed in output ports?
buffering required when datagrams arrive from fabric faster than the transmission rate
55
What is scheduling discipline?
scheduling discipline chooses among queued datagrams for transmission
56
output port buffer overflow might cause
queuing delay and loss
57
What is the formula for calculating the buffer?
RTT * C / sqrt(N), where C is the capacity and N is the number of flows
58
Give examples of discarding policies
Tail drop, priority, random
59
Describe priority scheduling
Schedule according to priority. Priority is selected via dividing the classes into the categories. To make such a division, header is consulted
60
If a higher priority class arrives, when the smaller class is being executed, will it be interrupted?
No
61
Name four scheduling policies
Priority, Round Robin, Weighted Fair Queuing, FIFO
62
What do frag flag bit value means?
To find out if the fragmentation is last or not

Computer Networks (6 decks)

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