3 Understanding Cisco IP Phones

Question 1

802.3af

Answer 1

Power over Ethernet; Industry-standard method of supplying power over an Ethernet cable to attached devices

Question 2

802.3at

Answer 2

A PoE standard that supports devices requiring more power (up to 25.5 W)

Question 3

Power over Ethernet (PoE)

Answer 3

The capability to send electricity over an Ethernet cable to power a connected device

Question 4

Cisco Inline Power

Answer 4

Cisco-proprietary, prestandard method of supplying power over an Ethernet cable to attached devices

Question 5

Cisco Discovery Protocol (CDP)

Answer 5

Protocol that allows Cisco devices to discover other, directly attached Cisco devices. Switches also use CDP to send voice VLAN information to attached IP phones

Question 6

Virtual LAN (VLAN)

Answer 6

A configuration used to break a switch into multiple broadcast domains

Question 7

Trunking

Answer 7

Allows VLAN information to be passed between switches

Question 8

802.1Q

Answer 8

An industry-standard trunking protocol that allows traffic for multiple VLANS to be sent between switches

Question 9

Dynamic Trunking Protocol (DTP)

Answer 9

Allows switches to dynamically negotiate trunk links

Question 10

Skinny Client Control Protocol (SCCP)

Answer 10

Cisco-proprietary voice-signaling protocol used to control Cisco IP phones

Question 11

Session Initiation Protocol (SIP)

Answer 11

Voice-signaling protocol created by the IETF as a light-weight alternative to H.323

Question 12

Network Time Protocol (NTP)

Answer 12

Synchronizes the clock of a network device to a more accurate NTP server.

Question 13

QoS

Answer 13

Quality of service is the ability of the network to provide better or special service to a set of users and applications at the expense of other users and applications.

Question 14

Link Efficiency

Answer 14

focuses on delivering network traffic in the most efficient way

Question 15

Classification

Answer 15

The first device that receives a packet identifies it using tools such as access-lists, incoming interfaces, or deep packet inspection.

Question 16

Marking

Answer 16

After a packet is identified, it is marked in Layer 2 or 3 so that switches or routers can read it. Devices then route the packet based on the marking.

Question 17

Policing

Answer 17

Limiting a class to a max bandwidth it can use, it will be dropped if it exceeds this

Question 18

queuing

Answer 18

Queuing define the rules the router should apply when congestion occurs

Question 19

LLQ

Answer 19

Combo of CB-WFQ, but adds a strict priority element.
○ So VOIP gets this and it will jump in front of everything
○ The Strict priority element is limiting this que to a certain amount so that it doesn’t completely take over the link

Question 20

WFQ

Answer 20

Low traffic senders get priority over high traffic senders as the won’t put a strain on the network.

Question 21

CBWFQ

Answer 21

Divides bandwidth among classes that you define (used for Data traffic) and gives them a limit or percentage of the link

Question 22

Link fragmentation and interleaving (LFI)

Answer 22

LFI addresses the issue of serialization delay

by chopping large packets into smaller pieces before they are sent

Question 23

DSCP

Answer 23

- DSCP EF (Expedited Forwarding) is used for VoIP payload traffic (carrying voice data), this gets the best treatment
DSCP AF (Assured Forwading) rates traffic in two ways it first has 4 different queues each ranked from best to worst and then traffic also gets a rating inside that queue rated from 1-3. Collision avoidance uses this to figure out what packets to drop if needed

Question 24

AutoQoS

Answer 24

Provides a template based QOS configuration which is run on the network devices

Question 25

Integrated Services (Intserv)

Answer 25

A RSVP is made just before the call which set the bandwidth aside. This works great until it takes up all the bandwidth

Question 26

Differentiated Services (Diffserv)

Answer 26

More common than Intserv, this does the classifying and gives them different priorities