CCNA Day 46 - QoS (Part 1)

What does PSTN stand for?

Public Switched Telephone Network

What does POTS stand for?

Plain Old Telephone Service

When the switchport voice vlan command is applied to an interface, which traffic will be tagged? Traffic from the PC or from the IP phone?

Traffic from the IP phone

(traffic from the PC will be untagged as usual for an access port)

Configure the voice VLAN:

SW1(config-if)# [...]

switchport voice vlan vlan-number

PoE: What does PSE stand for?

Power Sourcing Equipment

Electronic devices use [AC/DC] power.

DC

PoE: [...] can be configured to prevent a PD from taking too much power.

Power policing

Power policing: Configure the switch to disable the interface and generate a Syslog message if the PD draws too much power:

SW1(config-if)# [...]

power inline police

or

power inline police action errdisable

Power policing: Configure the switch to restart the interface and generate a Syslog message if the PD draws too much power:

SW1(config-if)# [...]

power inline police action log

What does Cisco ILP stand for?

Cisco Inline Power

PoE (Type 1) is IEEE [...]

802.3af

PoE+ (Type 2) is IEEE [...]

802.3at

UPoE (Type 3) is IEEE [...]

802.3bt

UPoE+ (Type 4) is IEEE [...]

802.3bt

PoE (Type 1) offers [...] watts of power.

15

PoE+ (Type 2) offers [...] watts of power.

30

UPoE (Type 3) offers [...] watts of power.

60

UPoE+ (Type 4) offers [...] watts of power.

100

Cisco ILP offers [...] watts of power.

7

Cisco ILP uses [...] powered wire pairs.

2

PoE (Type 1) uses [...] powered wire pairs.

2

PoE+ (Type 2) uses [...] powered wire pairs.

2

UPoE (Type 3) uses [...] powered wire pairs.

4

UPoE+ (Type 4) uses [...] powered wire pairs.

4

QoS: [...] refers to the overall capacity of a link.

Bandwidth

QoS: [...] is the amount of time it takes traffic to go from source to destination.

Delay (=one-way delay)

(Two-way delay measures both ways)

QoS: [...] is the variation in one-way delay between packets sent by the same application.

Jitter

QoS: [...] is the percentage of packets that do not reach their destination.

Loss

What is considered acceptable one-way delay for interactive audio traffic?

150 ms or less

What is considered acceptable jitter for interactive audio traffic?

30 ms or less

What is considered acceptable loss for interactive audio traffic?

1% or less

QoS: By default, queued messages will be forward in a [...] manner.

FIFO

What does FIFO stand for?

First In First Out

When packets are dropped due to a full queue, it is called [...].

tail drop

Tail drop is harmful because it can lead to [...].

TCP global synchronization

QoS: What does RED stand for?

Random Early Detection

QoS: What does WRED stand for?

Weighted Random Early Detection

QoS: What features drop random packets when traffic queues pass a certain threshold?

RED / WRED