GTP Overview
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Transcript of GTP Overview
İki Teknoloji 1
LTE:Afeaturebasedintroduction
LTECoreFeatures
Annex.GTPPrimer
Irfan Ali
Video at youtube: https://www.youtube.com/watch?v=FPfExr9bEEg&list=PLgQvzsPaZX_bimBc5Wu4m6-cVD4bZDav9&index=9
Irfan Ali 2İki Teknoloji 2
WhatisGTP?
• GTP=GPRSTunneling Protocol
• WhatisTunneling intheIPWorld?Ø TunnelingintheIPworldmeansputtinganIPpacketinsideanotherIPpacket.
IP_src -> IP_dst PayloadIP_a->
IP_b
InnerIPPacket
OuterIPPacket
GPRS General Packet Radio Service
Irfan Ali 3İki Teknoloji 3
WhatisthepurposeofGTPTunneling?
• RouteanIPpacketalongapaththatisnottopologicallycorrectforthepacket.
Mehmet’s IP address46.1.78.189 ->10.40.40.12 Internet
S-GW
P-GW
eNB
Ayse
Mehmet
10.10.10.1
10.10.10.2
10.10.10.0/24
10.10.20.1
10.10.20.0/24
10.10.20.2 GTP
Tun
nel
IP_sgw -> IP_enb
UDP_dst=2152
TEID_x
IP_pgw -> IP_sgw
IP
UDP_dst=2152
UDP
TEID_k
GTP-U header
Mehmet’s IP address10.40.40.12
DHCP
GTP is IP-in-UDP Tunneling
HiIP_a -> IP_m
HiIP_a -> IP_m
HiIP_a -> IP_m
HiIP_a -> IP_m
Irfan Ali 4İki Teknoloji 4
HowdoestheGTP-UTunnelgetsetup?
• GTPProtocolhastwopartsØ SignalingpartcalledGTP-C(GTP-Control)Ø UserdatapartcalledGTP-U(GTP-User)
• GTP-CisusedtosetupGTP-Utunnel• BothGTP-CandGTP-UrunontopofUDP• IP-in-UDPtunnelingisonlyusedforGTP-U• GTP-Ccarriescontrol/signalingmessages
IP_pgw -> IP_sgw
IP_a -> IP_m
UDP_dst=2152
TEID_a IP_pgw -> IP_sgw
UDP_dst=2123
TEID_k
IP UDP GTP-U header IP UDP GTP-C
header
GTP-C message
Irfan Ali 5İki Teknoloji 5
SGW PGW
TEID
21232123
2152
TEID
IPc,sgw
2152
IPu,pgwIPu,sgw
TxRx Tx Rx
TEIDTEID
TxRx Tx Rx
TEIDas
TEIDbs
TEIDcs
IPc,pgw
SGW PGW
TEID
2123
2152
2123
2152
TEID
IPc,sgw
IPu,sgw
IPc,pgw
IPu,pgw
TxRx Tx Rx
TxRx Tx Rx
TEIDTEID
HowdoesGTP-UTunnelgetsetup:Example
TEIDas
TEIDas
0
C.S. Req (IMSIa, C: IPc,sgw,TEIDas, EBID5:IPu,sgw,TEIDas) C.S. Rsp (C:IPu,pgw,TEIDap,
EBID5:IPu,pgw, TEIDxp)
TEIDbs
TEIDcs
TEIDap
TEIDbp
TEIDcp
TEIDap
TEIDbs
TEIDcs
TEIDbp
TEIDcp
Irfan Ali 6İki Teknoloji 6
PacketTrace:CreateSessionRequest(S11);MME->SGW
MMESGW/PGW
0
212321230x1
eNBSGW/PGW
21522152
S11
S1U
Irfan Ali 7İki Teknoloji 7
PacketTrace:CreateSessionResponse(S11);SGW->MME
MMESGW/PGW
212321230x1
eNBSGW/PGW
21522152
S11
S1U
0x80..01
0xc0..1
Irfan Ali 8İki Teknoloji 8
PacketTrace:ModifyBearerRequest(S11);MME->SGW
MMESGW/PGW
212321230x1
eNBSGW/PGW
21522152
S11
S1U
0x80..01
0xc0..1
0x800..001
0x3ea
Irfan Ali 9İki Teknoloji 9
PacketTrace:GTP-U:S1-U;eNB ->SGW/PGW
eNBSGW/PGW
21522152
S1U
0x010000
UE Server10.255.1.111 10.0.0.10010.1.2.11 10.1.1.12
TxRx Tx Rx
Irfan Ali 10İki Teknoloji 10
PacketTraceGTP-U:S1-U;eNB <- SGW/PGW
eNBSGW/PGW
21522152
S1U
0x010000
UE Server10.255.1.111 10.0.0.10010.1.2.11 10.1.1.12
TxRx
Irfan Ali 11İki Teknoloji 11
GTPPathandPathManagement
• Pathisbetweentwoendpoints.EachendpointisIP_address+UDP_Port#
• TherecanbeseveralGTPtunnelsonapath(eachwithdifferentTEIDs).
• Thereistypicallya“softwareprocess”thatbindstoeachend-point.
• PathManagementmessages:Toensurethatapathisalive(boththephysicallinkandprocessattheendpoint),periodicecho-request andecho-response aresent.
• Failure-detectionanderror-recoverymechanismsaredefined.
SGW PGW
TEID
2123
2152
2123
2152
TEIDas
TEIDbs
TEIDcs
TEIDxs
TEIDys
TEIDzs
TEID
IPc,sgw
IPu,sgw
IPc,pgw
IPu,pgw
TxRx Tx Rx
Path
Path
Irfan Ali 12İki Teknoloji 12
PacketTraces:GTP-UEcho-request&EchoResponse
In GTP-Cv2 Echo request/response messages
do not contain TEID field
In GTP-Cv2 Echo request/response messages
do not contain TEID field
Irfan Ali 13İki Teknoloji 13
InterfacesonwhichGTPisused
• GTP-Cv2isusednotonly formobilitymanagement,butalsoforgeneralsignalingpurposes, eg providing UE’scellinformation tothePGWandfromtheretooperator’sservicenetwork.
Internet
MME
S-GW
P-GWHSS
eNB
UE’s IP address
S1-MME
S11
S6a
S5
S1-UMME
S10
S1AP
GTP C
GTP C
Irfan Ali 14İki Teknoloji 14
Specifications
• GTPCv2 TS29.274• GTPUv1 TS29.281
• GTPCv1 TS29.060
• Historically(beforeRel-8,i.e.before2009Q1),TS29.060usedtobethekeyGTPspecification(bothGTPCv1andGTPUv1).ButsinceRel-8,TS29.060isonlyapplicableto3Ginterfaces(Gn/Gp,betweenSGSN<->GGSNandbetweenSGSNs)andnottoEPCinterfaces.ItsspecificationonlyappliestoGTPCv1Ø Ignoreanythingthat29.060saysaboutGTPU.
İki Teknoloji 15
Annex
Irfan Ali 16İki Teknoloji 16
RulesforGTP-CIPaddressandportnumbers• Threetypesofmessages
• RulesforPort#andIPaddresses
Ø InitialMessage:1. TheUDPDestination PortnumberforGTPv2Initial messagesshallbe21232. TheUDPSourcePort foraGTPv2Initialmessageisalocallyallocatedport number.3. Duringtheestablishment oftheGTPtunnel, theGTPv2entityselectsandcommunicates tothepeerGTPv2entitytheIPDestination Addressat
whichitexpects toreceivesubsequent control planeInitialmessagesrelatedtothatGTPtunnel viathe "SenderF-TEIDforControl Plane"IE
Ø Triggeredmessage1. TheIPSourceAddressofaGTPv2TriggeredmessageandforaTriggeredReplymessageshallbecopied fromtheIPdestination addressofthe
messagetowhich thisGTPv2entityisreplying2. TheIPDestination AddressofaGTPv2TriggeredmessageandforaTriggeredReplymessageshallbecopied fromtheIPSourceAddressofthe
messagetowhich thisGTPv2entityisreplying3. TheUDPSourcePort ofaGTPv2TriggeredmessageshallbethevaluefromtheUDPDestination Portofthecorresponding messagetowhich
thisGTPv2entityisreplying4. TheUDPDestination Port valueofaGTPv2Triggered messageshallbethevalueoftheUDPSourcePort ofthecorresponding messagetowhich
thisGTPv2entityisreplying
Ø TriggeredReplymessage1. Samerulesastriggeredmessage.
• RulesforTEID#Ø Thefirst CreateSession RequestmessageonS11foraUEshallhaveTEID=0x0Ø The(firstandsubsequent) CreateSession RequestmessageonS5foraUEshallhaveTEID=0x0
GTP-C Peer A
GTP-C Peer B
Initial Message
Triggered Message
Triggered Reply Message