Here in this chapter I have tried to depict how a MS establishes PDP connection with CoreNetwork in order to use PacketServices of the 3G network.
Courtesy :- 3G specifications and past experience.
For PDP connection to be established a MS has to first get attached to the network. Refer Attach Procedure for more details.
MS sends Activate PDP context request to the SGSN. On receiving this request SGSN checks subscriber information (via ISD from HLR) stored in MM context( created during attachProcedure). After passing subscription checking SGSN initiates DNS query to resolves the APN ( Access point name ) received in APCR. This resolved IP is nothing but address of GGSN or PGW(LTE).
Every APCR has QOS parameter which indicates BitRate for uplink and downlink connections. SGSN checks these parameters with the SusbcriberInfo QOS and comes to negotiable value for QOS.
After these checks and getting the address of GGSN, SGSN constructs a GTP-C messages of createPDPcotextRequest and sends it to the GGSN.
Some main parameters in this request are
Refer 23.060 page 187-189
SGSN now initiates RABAssigment procedure and instructs RNS to allocate a radioresource for this UE. This response contains UTEID, DTEID, RAB ID etc.
After successful allocation of RAB, SGSN sends ActivatePDPContextAccept message with NSAPI, PDPAddress, GGSN address, QOS Negotiated to the MS over RANAP DirectTransfer Message
Following diagram depicts the APCR ( acticatePdpContextRequest) procedure..
Courtesy :- 3G specifications and past experience.
For PDP connection to be established a MS has to first get attached to the network. Refer Attach Procedure for more details.
MS sends Activate PDP context request to the SGSN. On receiving this request SGSN checks subscriber information (via ISD from HLR) stored in MM context( created during attachProcedure). After passing subscription checking SGSN initiates DNS query to resolves the APN ( Access point name ) received in APCR. This resolved IP is nothing but address of GGSN or PGW(LTE).
Every APCR has QOS parameter which indicates BitRate for uplink and downlink connections. SGSN checks these parameters with the SusbcriberInfo QOS and comes to negotiable value for QOS.
After these checks and getting the address of GGSN, SGSN constructs a GTP-C messages of createPDPcotextRequest and sends it to the GGSN.
Some main parameters in this request are
- TEID:
- QOS Negotiated
- APN:
- MSISDN:
- NSAPI:
- And other charging information
Refer 23.060 page 187-189
SGSN now initiates RABAssigment procedure and instructs RNS to allocate a radioresource for this UE. This response contains UTEID, DTEID, RAB ID etc.
After successful allocation of RAB, SGSN sends ActivatePDPContextAccept message with NSAPI, PDPAddress, GGSN address, QOS Negotiated to the MS over RANAP DirectTransfer Message
Following diagram depicts the APCR ( acticatePdpContextRequest) procedure..
- NAS : Non-Access-Stratum
- DT1 : SCCP’s DataForm1 message
- DT : RANAP’s Direct Transfer message
- APCR: ActicatePdpContextRequest
- APCA: ActivatePdpContextAccept
- NSAPI : Network Service Access Point Identifier
- NSAPI in MS is PDP Sap. MS uses RAB-ID and NSAPI to uniquely identify a PDPContext.
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