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Chapter6—UsingtheSoftware
MultiVOIP®Voice/FaxoverIPGateways 115
IPStatistics
UDPversusTCP.(UserDatagramProtocolversusTransmissionControlProtocol).UDPprovidesunguaranteed,
connectionlesstransmissionofdataacrossanIPnetwork.Bycontrast,TCPprovidesreliable,connection‐
orientedtransmissionofdata.
BothTCPandUDPsplitdataintopacketscalled“datagrams.”However,TCPincludesextraheadersinthe
datagramto
enableretransmissionoflostpacketsandreassemblyofpacketsintotheircorrectorder ifthey
arriveoutoforder.UDPdoesnotprovidethis.LostUDPpacketsareirretrievable;thatis,out‐of‐orderUDP
packetscannotbereconstitutedintheirproperorder.
Despitethesedisadvantages,UDPpacketscanbe
transmittedfasterthanTCPpackets—asmuchasthreetimes
faster.Incertainapplications,likeaudioandvideodatatransmission,theneedforhighspeedoutweighsthe
needforverifieddataintegrity.Soundorpicturesoftenremainintelligibledespiteacertainamountoflostor
disordereddatapackets(whichcomesthrough as
static).