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Network Programming > QOS > Flashcards

QOS Flashcards

1
Q

QOS

A

To end user applications are performing properly (no drop calls, videos are smooth)

To network managers: Maximize utilization of the network bandwidth while meeting performance expectation

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2
Q

Jitter

A

Change in the amount of time it takes a packet to move from A to B

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3
Q

What is QoS mechanism for IP network

A

QoS is a mean to distinguish the packets and treat them differently

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4
Q

There are two QoS mechanisms for IP networks

A

IntServ (Integrated services)

DiffServ (Differentiated Services)

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5
Q

IntServ - Integrated Services

A

Individual flows are distinguished on end-to-end basis

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6
Q

DiffServ

A

Individual flows are aggregated into smaller number of classes given differential treatment on a per hop basis

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7
Q

In integrated Services (IntServ) each device in the network will reserve bandwidth for the flow

A

True

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8
Q

In Differentiated Services (Diff Serv) the flow is assigned to a class and each device garauntee bandwidth for the class

A

True

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9
Q

RSVP is a protocol that requests …………. …………. from every …………. in the path of the flow

A

bandwiidth reservation node

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10
Q

RSVP T or F

It is not a protocol to signal QoS information for bandwidth reservation

A

F , It is a protocol

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11
Q

RSVP T or F

It can make resource reservation for only unicast application

A

F , it can make resorce reservation for unicast and multicast applications

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12
Q

RSVP T or F

It is sender oriented ( the sender of data flow initiates and maintains resource reservation )

A

F

It is receiver oriented (meaning receiver of data flow initiates and maintains the resource reservation used for that flow)

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13
Q

RSVP T or F

RSVP does not maintain states in router and hosts

A

F RSVP do maintain states in router and hosts

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14
Q

RSVP T or F

RSVP is routing protocol

A

F

RSVP is not a routing protocol but it depends on routing protocols to determine path of the flow

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15
Q

RSVP T or F

RSVP supports only IPv4

A

RSVP supports both IPv4 and IPv6

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16
Q

QoS applicable when we have transient congestion

A

True

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17
Q

QoS has three operations

A

1-Classification and marking
2-Policing
3-Scheduling (queuing and dropping)

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18
Q

Classification and marking

A

Classify thhe traffic that should be treated differently

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19
Q

Policing

A

Check if packets ar confronting to administrively defined traffic rates and take actions (marking, remarking and dropping)

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20
Q

Scheduling

A

How packets exists and queued
Post queueing mechanisms
Network tool to optimize link utlization

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21
Q

T or F

Classification of packets can happen without marking

A

True

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22
Q

How the classification of packet is done

A

Classification of packets is done at each node of the network but not required to be done everywhere where packets are sorted into different types which different policies can be applied

23
Q

Marking is the process of setting of the Differential Setting field (DS value field) so that traffic can be easily identified later

A

True

24
Q

There are different types of classification, we may consider for example Etherenet classification according to

A
  • Physical interface (layer 1)
  • MAC address (layer 2)
  • Source/destination IP (layer 3)
  • Transport protocol (layer 4)
  • Application signeture (layer 5)
25
Q

Many ways of marking field

A

Layer 2 marking (add 32 bit field betrween source MAC address and the type of field in the original frame

26
Q

Layer 3 marking field

A

Type of Service (TOS Byte)

27
Q

Policies are not applied directly

A

True,
1- Packets are identified according to their classification
2- Packets are marketed according to rules
3- A decision is taken according to available rules

28
Q

Policing - Leaky bucket

A

Smooth out traffic by passing out traffic at a specific rate

If the bucket is full - packets are discarded

Used to enforce very strict policy on the traffic

29
Q

Token bucket

A

Allow burst but in a controlled way , it smoothes traffic too but permits burstiness quivilant to the number of tokens accumulated in the bucket

Duration of Burst= Duration of empty bucket

30
Q

Duration of a burst = (bucket capacity in bytes)/ (Maximuum transmision rate in bytes/s - token arrival rate in bytes/s)

A

True

31
Q

CIR : Commited information rate

A

Long term average rate that the network provider is committed to honor by an agreement with thecustomer

32
Q

CIR is measured in bytes per second

A

True

33
Q

Only the IP layer is considerd in countin the CIR

A

True

34
Q

In general packet transmission is a series of bursts intervened by quiet intervals

A

True

35
Q

PIR Peak information Rate

A

Maximum rate the traffic is allowed

36
Q

Max transmission is limited by PIR

A

TRUE

37
Q

Excess burst are permitted above CIR ( committed information rate) but only until PIR is reached

A

TRUE

38
Q

Long term average should remain below CIR , Traffic above PIR is not permitted

A

true

39
Q

There are three types of trafic metering and coloring mechanisms:

A

Simple one tate two color marker
Single rate three color marker
two rate three color marker

40
Q

Buffer

A

Physical memory to store packets

41
Q

Queue

A

Holding an ordered identifiers to packets

42
Q

One queue means no scheduler implies no QoS

A

True

43
Q

Multiple queues needs a scheduler

A

True, the scheduler determine which queue to serve nxt

44
Q

Schedluer: FIFO First input first output

A

True

45
Q

Priority scheduling:
If prioiruy queue is active it is served after any non-priority queue currently ebing served
Head packet in prioiruty queue waits at most the serving time of non prioirity packet

A

true

46
Q 
Weighted bandwidth schedluing
It contains many algorithms:
1-WRR weighted Round Robin
2-WFQ weighted fair queuing
3-Deficit Round Robin
A

TRUE

47
Q

Weighted Round Robin Scheduler
In a round of scheduler , the scheduler visits each queue and serves an amount of traffic from that queue determinde by the queue weights

A

TRUE

48
Q

Weighted Fair queuing : Each Flow i is given a weight wi

A

True

49
Q

Queue cannot drom to an infinite length because memory space is not infininte

A

True

50
Q

Dropping algorithms used to drop packets are as queues grom in length

A

true

51
Q

Two types of dropping algoritms

A

1- Tail drop (default behavior)

2-RED (random early detection)

52
Q

Tail drop

A

If queue depth > = queue limit drop packet else addd packet to queue

53
Q

Weighted tail drop we have different thresholds

A

true

54
Q

Random early detection

RED is a congestion avoidance technique
• RED distributes drops over various sessions to desynchronize TCP sessions

A 
Average queue depth < qmin → enqueue packet
Average queue depth > qmax → drop packet
Average queue depth between min and max
→ drop packet with a random
→ but increasing probability

Network Programming (2 decks)

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