ADTRAN Total Access 5000 - TWAMP Active Test Session

Appendix D, TWAMP Provisioning - TWAMP Provisioning
65K510DEP08-1A D-3
Ifthesenderandreceiveraddressesaresetto0,thentheIPaddressesusedintheIPpacket
thatencapsulatestherequest‐sessioncommandshallbeusedinthetestpackets.
Thetimeoutintherequest‐sessioncommandshallbeusedbythesession‐reflectorasthe
amountoftime
thatthereflectormustwaitafterreceivingastop‐sessionsmessage.The
reflectorshallkeepreflectingpackets untilthisamountoftimepasses.Afterthis,thereflector
stopsreflectingpackets.
Thetype‐PdescriptorwasusedtosettheDSCPorPHBinthemessagefromthesender.The
reflectorshould
usethesesamevaluesinthereflectedpacket.
ThesendschedulefortestpacketsisNOTusedinTWAMP.Thesendershouldautonomously
decidethesendschedule.
TWAMP Active Test Session
Atthispoint,aswitchismadefromusingTCPtousingtheUDPprotocol.WithTWAMP,the
session‐reflectorsendsouttestpacketsinresponsetoeachtestpacketitreceives.
Thesendscheduleisnotcommunicatedtothesession‐reflector.Assuch,thereisnoneedfor
astandardized
computationofpackettiming.Thesender,though,shouldhaveitsbest
approximationofitsrealtimeplacedintothedeparturetimestampfield.
TheTWAMPsession‐reflectortimestampsthereceivedpacket,copiesthepacketsequence
numberinthecorrespondingreflectedpacketfield,transmitsthereflectedpacket,andignores
packetsreceivedaftertheʺ
stop‐sessioncommand+timeoutʺ.
TheTWAMPtestpacketfromthereflectorconsistsofthefollowingparameters:
•Sequencenumber‐isthesequencenumberofthetestpacketaccordingtoitsarrivaltime
atthesession‐reflector.Thisvalueshouldstartwithzeroandincrementbyoneforeach
subsequentpacket.This
isindependentfromthesequencenumberofthearriving
packets.
•Timestamp‐thesessionreflectorʹstransmittimestamp.Formatissameasusedin
OWAMP.
•Errorestimate‐thetimeerrorestimateinthesessionreflectorʹstransmittimestamp.
FormatisthesameasusedinOWAMP.
• Receivetimestamp‐thesessionreflectorʹsreceive
timestamp.Formatissameasusedin
OWAMP.Thedifferencebetweentimestam pandreceivetimestampistheamountof
timethepacketwasintransitionatthesession‐reflector.Theerrorestimateassociated
withtimestampalsoapplieshere.
• ʺSenderSequenceNumber‐anexactcopyofthesequencenumberfromthe
session
sendertestpacket.
•SenderTimestamp‐anexactcopyofthetimestampfromthesession‐sendertestpacket
•SenderErrorEstimate‐anexactcopyoftheerrorestimatefromthesession‐sendertest
packet
•Packetpadding‐anexactcopyof thepacketpaddingfromthesession‐sendertestpacket