gprs attach pdp new sgsn interface sequence diagram

SGSN Interfaces (GPRS Attach and PDP Context Activation for a Class B Terminal)GSM

CoverageGSM GPRS Network

Cell BSS Core Network Old Core Network GGSN Site GSM DatabasesUT BSC SGSN DNS Server MSC VLR Old SGSN Old MSC

VLRGGSN Radius

ServerDHCPServer

EIR HLR

EventHelix.com/EventStudio 2.5

01-Mar-05 06:07 ()

This sequence diagram was generated with EventStudio 2.5 (http://www.EventHelix.com/EventStudio).

We explore the sequence of interactions involved in a GPRS terminal attaching to the network. The combined attach and PDP context activation of a Class B GPRS terminal will be coveredhere.

Copyright © 2005 EventHelix.com Inc. All Rights Reserved.

GPRS Attach

GMM Attach RequestTMSI, MNC, MCC, LAC, RAC

The terminal initiates the attachprocedure after power on. Themessage contains the previouslyused TMSI (Temporary MobileSubscriber Id). The mobilenetwork identity, the location areaand routing area information isalso included in the message.

Search for the TMSI The SGSN (Serving GPRSSupport Node) searches for TMSIin its database.

Identity RequestTMSI

No entry is found for the TMSI, sothe SGSN uses the old locationarea information to identify theold SGSN where this terminal wasbeing served.

Identity ResponseIMSI

The old SGSN responds with theGPRS mobile's IMSI(International Mobile SubscriberIdentity) to the SGSN.

Identity Request The SGSN asks the terminal toidentify itself.

Identity Response The terminal responds back.

Authentication RequestRAND

The SGSN authenticates the GPRSmobile by sending a RAND value(a random value).

Authentication ResponseSRES

The computed SRES value ispassed to the SGSN.

Identity Check Request The SGSN then requests theidentity of the GPRS mobile.

Identity Check Response GPRS mobile responds back withthe identity.




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IMEI Check Request Verify that that GPRS mobilebeing used by the user is not astolen one. The IMEI (InternaionalMobile Equipment Identity)obtained from the GPRS mobile issent to the EquipmentIdentification Register (EIR).

IMEI Check Response The EIR clears the subscriber andresponds back to the SGSN withthe status.

Update Location The SGSN now informs the HomeLocation Register (HLR) about thenew location of the GPRS mobile.

Insert Subscriber Data The HLR updates the new SGSNwith all the subscriberinformation.

Insert Subscriber Data Ack The SGSN responds back to theHLR.

Update Location Ack The HLR now responds back tothe SGSN's "Update Location"message.

Location Updating Request The mobile had initiated acombined attach, so the SGSNalso updates the locationinformation at the MSC-VLR thatwill handle the voice calls.

Location Updating Accept The MSC informs the SGSN that ithas finished the location update.

GMM Attach Accept The SGSN responds back to theoriginal GRPS combined attachrequest from the mobile.

GMM Attach Complete The GPRS mobile acknowledgesthe receipt of "Attach Accept".

TMSI Reallocation Complete The Attach Complete signals thecompletion of the attachprocedure. This is passed to theMSC-VLR as "TMSI ReallocationComplete".

PDP Context Activation

Activate PDP ContextAPN

The GPRS mobile now initiatesthe PDP context activationprocedure to obtain the IP




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address for the device. TheAccess Point Name (APN)specified by the service provideris passed as a parameter.

DNS QueryAPN

The SGSN initiates a DNS query tofind the GGSN corresponding tothe APN specified by the mobile.(GGSN - Global GPRS SupportNode.)

DNS ResponseGGSN IP Address

The DNS provides the GGSN IPaddress.

Create PDP Context RequestPAP, CHAP, PDP Request

The SGSN routes the PDP contextactivation request to the GGSNcorresponding to the APN.

Create PDP Context Response The GGSN responds back to theSGSN, indicating completion ofthe PDP context activationprocedure.

Activate PDP Context Accept The SGSN replies back to theGPRS mobile. This signalscompletion of the PDP contextactivation.

gprs attach pdp new sgsn interface sequence diagram

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