3 Understanding Cisco IP Phones Flashcards
802.3af
Power over Ethernet; Industry-standard method of supplying power over an Ethernet cable to attached devices
802.3at
A PoE standard that supports devices requiring more power (up to 25.5 W)
Power over Ethernet (PoE)
The capability to send electricity over an Ethernet cable to power a connected device
Cisco Inline Power
Cisco-proprietary, prestandard method of supplying power over an Ethernet cable to attached devices
Cisco Discovery Protocol (CDP)
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
Virtual LAN (VLAN)
A configuration used to break a switch into multiple broadcast domains
Trunking
Allows VLAN information to be passed between switches
802.1Q
An industry-standard trunking protocol that allows traffic for multiple VLANS to be sent between switches
Dynamic Trunking Protocol (DTP)
Allows switches to dynamically negotiate trunk links
Skinny Client Control Protocol (SCCP)
Cisco-proprietary voice-signaling protocol used to control Cisco IP phones
Session Initiation Protocol (SIP)
Voice-signaling protocol created by the IETF as a light-weight alternative to H.323
Network Time Protocol (NTP)
Synchronizes the clock of a network device to a more accurate NTP server.
QoS
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.
Link Efficiency
focuses on delivering network traffic in the most efficient way
Classification
The first device that receives a packet identifies it using tools such as access-lists, incoming interfaces, or deep packet inspection.
Marking
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.
Policing
Limiting a class to a max bandwidth it can use, it will be dropped if it exceeds this
queuing
Queuing define the rules the router should apply when congestion occurs
LLQ
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
WFQ
Low traffic senders get priority over high traffic senders as the won’t put a strain on the network.
CBWFQ
Divides bandwidth among classes that you define (used for Data traffic) and gives them a limit or percentage of the link
Link fragmentation and interleaving (LFI)
LFI addresses the issue of serialization delay
by chopping large packets into smaller pieces before they are sent
DSCP
- 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
AutoQoS
Provides a template based QOS configuration which is run on the network devices
Integrated Services (Intserv)
A RSVP is made just before the call which set the bandwidth aside. This works great until it takes up all the bandwidth
Differentiated Services (Diffserv)
More common than Intserv, this does the classifying and gives them different priorities
