D-Link DWC-1000 [174/368] Qos configuration

D-Link DWC-1000 User Manual 174

Section 5 - Advanced Network Conguration

Qos Conguration

In a typical controller, each physical port consists of one or more queues for transmitting packets on the attached

network.Multiplequeuesperportareoftenprovidedtogivepreferencetocertainpacketsoverothersbasedon

user‐denedcriteria.Whenapacketisqueuedfortransmissioninaport,therateatwhichitisserviceddepends

onhowthequeueisconguredandpossiblytheamountoftracpresentintheotherqueuesoftheport.Ifa

delay is necessary, packets get held in the queue until the scheduler authorizes the queue for transmission. As

queues become full, packets have no place to be held for transmission and get dropped by the controller.

QoSisameansofprovidingconsistent,predictabledatadeliverybydistinguishingbetweenpacketsthathave

stricttimingrequirementsfromthosethataremoretolerantofdelay.Packetswithstricttimingrequirements

aregiven“specialtreatment”inaQoScapablenetwork.Withthisinmind,allelementsofthenetworkmustbe

QoS‐capable.ThepresenceofatleastonenodewhichisnotQoS‐capablecreatesadeciencyinthenetwork

path and the performance of the entire packet ow is compromised.

Qos Priority

ConguringQoSPrioritysettingsisa3-stepprocess:

1. EnableQoSmode(nextpage),and

2. DenetheTrustModeoneachport(referto“DeningDSCPandCoSoneachport”onpage177)

3. Denethe DHCPorCOSsettings(referto“ConguringDSCPPriority”onpage179or“Conguring

802.1pPriority”onpage178).