Comparison and Analysis of FIFO, PQ, and WFQ Disciplines in
OPNET
Comparison and analysis of FIFO, PQ, and WFQ Disciplines in
OPNETPresentation OutlineIntroduction
Background Information
OPNET Implementation
Simulation Results
Conclusion and QuestionsIntroduction Queuing methods are used to
handle network resourcesReal-time applications such as voice and
video conferencing are especially susceptible to delays and packet
lossesThe Quality of Service (QoS) network devices must employ
proper queuing methods to differentiate among arriving packets
Queuing disciplines are implemented in routers
BackgroundComparison and analysis of queuing disciplines in
OPNETFocus on: FIFO First-in, First Out PQ Priority Queuing WFQ
Weighted Fair Queuing
Apply each queuing method towards: FTP Voice Video
ConferencingBackground - FIFOFIFO : First-In, First-Out
QueuingSimplest queuing discipline First packet to arrive into
buffer is the first packet to leave bufferAll packets treated
equallyPackets dropped if buffer full, regardless of importance of
packets
Background - PQBased on FIFO queues, but use multiple
buffersArriving packets are tagged to reflect their importanceHigh
priority packets are serviced and transmitted firstPackets dropped
if they arrive at a full buffer
Real-time applications such as VoIP and video conferencing
should in theory observe less delay under this queuing
disciplineBackground - WFQArriving packets are tagged and placed in
separate queuesAllocation and sharing of bandwidth is determined by
weight factor given to each buffer WFQ scheduler serves buffers in
circular manner WFQ is work-conserving: service is provided to next
queue upon finding an empty queue
Background - WFQ
OPNET ImplementationScenarios and applications
consideredScenario1Scenario2Scenario3QueuingdisciplineFirst-in,First-outQueuingPriorityQueuingWeightedFairQueuingSimulationTime150
MS 150 MS150
MSApplicationsconsideredFTPVoIPVideoConferencingFTPVoIPVideoConferencingFTPVoIPVideoConferencing
Network Topology
Campus network 10 x 10 km
5 workstations
2 routers
1 Ethernet server
Application, Profile, and QoSDefinitions
OPNET Implementation
ApplicationDefinitionAttributesApplicationNameFTPVoIPVideoConferencingDescriptionHighLoadPCMQualitySpeechLowResolutionVideoTypeofService(ToS)BestEffort(0)InteractiveVoice(6)StreamingMultimedia(4)OPNET
ImplementationApplication Attributes Simulation Results End-to-End
Delay in Voice
Time taken for packets to be transmitted from source to
destination.
Application : Voice, Video
ETE in voice and video should be small to provide natural
conversationFIFO shows most ETE Delay (~ 2.2 sec)
PQ and WFQ have lower ETE delay. It is near from the zero Voice
Traffic ReceivedSimulation Results
VoiceTrafficreceivedinbytes/sTrafficreceivedroughlyequalinitiallyDegreeoflossincreasesovertimeFIFOqueuingresultsinfewerbytesreceivedPQandWFQresultinmoretrafficreceived
Video Traffic Received
Traffic received statistics for Video conferencing, where it can
be observed that in cases of WFQ, FIFO, PQ.
WFQ started to drop packets roughly about 2.2 seconds of network
operation while reaching a maximum of about 50.000 bytes of dataPQs
performance was found to be the worst, as it is only a simple
variation of the FIFO queuing method
FIFO reached a maximum of about 35,000 bytes and then started
losing packets
Simulation Results IP Traffic Dropped
Simulation Results
the number of IP datagrams or packets dropped per second is
found to be the highest for the FIFO queuing method, while PQ and
WFQ showed fewer drop in packets across all IP interfaces during
the simulation. The results obtained could be explained in terms of
the queue sizes of each of the queuing disciplines employed. Since
FIFO has just one queue, the number of packets dropped is expected
to rise as the queue becomes full. PQ and WFQ, on the other hand,
employ multiple queues and so the number of packets dropped will be
fewer if either of those methods is employedConclusionEnd-to-End
Delay in Voice PQ and WFQ have lower ETE delay. It is near from the
zero.Worst: FIFOVoice Traffic ReceivedPQandWFQresultin
moretrafficreceivedWorst: FIFOVideo Traffic ReceivedBest: Weighted
Fair Queues and FIFOWorst: PQIP Traffic DroppedLess IP segment drop
PQ and WFQWorst: higher IP segment drop FIFO
Thank You
