QoS

Question 1

VOIP

Answer 1

Voice over IP, allows for phone calls over an IP network by connecting to a switch

Question 2

Internal 3-port switch

Answer 2

interface on a IP phone, “uplink” connects to switch, “downlink” connects to PC, last port connects internally to the phone

Question 3

voice vlan

Answer 3

Used to put traffic from IP phones into a special vlan with higher priority

Question 4

Power policing

Answer 4

PoE supplies device with just enough power that it needs

Question 5

Bandwidth

Answer 5

Overall capacity of a link

Question 6

one-way delay

Answer 6

time traffic takes from source to destination

Question 7

Jitter

Answer 7

Variation in delay between packets sent by the same application

Question 8

Loss

Answer 8

The # of packets sent not reaching destination

Question 9

Standard quality

Answer 9

One-way delay: 150ms or less
Jitter: 30 ms or less
loss: 1% or less

Question 10

Classification/marking

Answer 10

Organizes traffic/packets into traffic classes (categories) to give priority

Question 11

What is the PCP for in dot1q

Answer 11

Priority Code Point, used to prioritize traffic when using dot1q

Question 12

DSCP

Answer 12

Differentiated Services Code Point, field in the IP header that can be used to identify high/low traffic

Question 13

Default forwarding

Answer 13

Best effort traffic

Question 14

Expedited Forwarding

Answer 14

Low loss/latency/jitter traffic (usually voice) (DSCP mark 46)

Question 15

Assured Forwarding

Answer 15

set of 12 standard values

contains traffic classes (high = more priority)
Drop precedence (priority within classes)

Question 16

Class Selector (CS)

Answer 16

set of 8 standard values, provides backward compatibility with IPP

Question 17

Mark

Answer 17

When the PCP/DSCP value is checked for priority

Question 18

Trust boundary

Answer 18

Defines where devices choose to trust QoS markings in received messages.

Question 19

Queuing

Answer 19

When more traffic than a router can handle arrives, it is placed into queue and packets go FIFO.

Question 20

tail drop

Answer 20

packets are dropped by the Router if the queue is full

Question 21

TCP global synch

Answer 21

Can be triggered by tail drops, TCP windows shorten in order to get through the queue but all of them will slow down

Question 22

Random Early Detection

Answer 22

Router drops certain TCP packets early in the queue to prevent global sync

Question 23

Weighted Random Early Detection

Answer 23

Similar to RED but allows you to control which packets get dropped first

Question 24

Scheduler

Answer 24

With multiple queues, scheduler decides which queue gets to go next

Question 25

Class Based Weighted Fair Queuing

Answer 25

similar to weighted round robin but queues are guaranteed

Question 26

LLQ

Answer 26

Low latency Queuing, One queue is given priority at all times

Question 27

What are the two ways of controlling the rate of the traffic through the router?

Answer 27

Shaping and Policing

Question 28

Shaping

Answer 28

Buffers traffic in the queue if traffic goes over set rate

Question 29

Policing

Answer 29

Drops traffic if traffic goes over the configured rate