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User's Manual - 41

QoS (Quality of Service)

Advanced Mode

Quality of Service refers to a resource reservation control mechanism, which guarantees a certain quality

to different services on the network. Quality of service guarantees are important if the network capacity

isinsufcient,especiallyforrealtimestreamingmultimediaapplications.Qualitycanbedenedas,for

instance, a maintained level of bit rate, low latency, no packet dropping, etc.

ThefollowingarethemainbenetsofaQoSawarenetwork:

■

Theabilitytoprioritizetrafcandguaranteeacertainlevelofperformancetothedataow.

■

The ability to control the amount of bandwidth each application may use, and thus provide higher

reliability and stability on the network.

Requirements for QoS

To utilize QoS in a network environment, the following requirements must be met:

■

All network switches and routers in the network must include support for QoS.

■

The network video devices used in the network must be QoS-enabled.

QoS models

CoS (the VLAN 802.1p model)

IEEE802.1p defines a QoS model at OSI Layer 2 (Data Link Layer), which is called CoS, Class of

Service. It adds a 3-bit value to the VLAN MAC header, which indicates prioritization from 0~7 (Eight

different classes of service are available). The priority is set up on the network switches, which then use

different queuing disciplines to forward the packets.

Below is the setting column for CoS. Enter the VLAN ID of your switch (0~4095) and choose the priority

for each application (0~7).

IfyouassignVideothehighestlevel,theswitchwillhandlevideopacketsrst.

NOTE

►TheVLANSwitch(802.1p)isrequired.ThewebbrowsingmayfailiftheCoSsettingisincorrect.

►ClassofServicetechnologiesdonotguaranteealevelofserviceintermsofbandwidthanddelivery

timetheyoffera"besteffort."UserscanthinkofCoSas"coarselygrained"trafccontrolandQoSas

"nelygrained"trafccontrol.

►ThoughCoSissimpletomanage,itlacksscalabilityanddoesnotofferendtoendguaranteessinceit

is based on L2 protocol.

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Vivotek 3GPP Manual de usuario Pagina 41