GPRS attach and PDP context activation sequence diagrams

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

GSM GSM GPRS Network
Coverage
EventHelix.com/EventStudio 2.5
Cell BSS Core Network Old Core Network GGSN Site GSM Databases 01-Feb-05 07:06 (Page 1)
EIR HLR
UT BSC SGSN DNS Server MSC VLR Old SGSN Old MSC GGSN Radius DHCP
VLR Server Server

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 covered
here.

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

GPRS Attach The terminal initiates the attach
procedure after power on. The
GMM Attach Request message contains the previously
used TMSI (Temporary Mobile
TMSI, MNC, MCC, LAC, RAC Subscriber Id). The mobile
network identity, the location area
Search for the TMSI and routing area information is
also included in the message.
Identity Request
The SGSN (Serving GPRS
TMSI Support Node) searches for TMSI
in its database.
Identity Response
No entry is found for the TMSI, so
IMSI the SGSN uses the old location
area information to identify the
Identity Request old SGSN where this terminal was
being served.
Identity Response
Authentication Request The old SGSN responds with the
GPRS mobile's IMSI
RAND (International Mobile Subscriber
Identity) to the SGSN.
Pass the RAND value
to the SIM and obtain The SGSN asks the terminal to
identify itself.
the Kc and SRES
values The terminal responds back.

Authentication Response The SGSN authenticates the GPRS
mobile by sending a RAND value
SRES (a random value).

Identity Check Request The SIM applies secret GSM
algorithms on the RAND and the
secret key Ki to obtain the session
key Kc and SRES.

The computed SRES value is
passed to the SGSN.

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

GSM GSM GPRS Network
Coverage
EventHelix.com/EventStudio 2.5
Cell BSS Core Network Old Core Network GGSN Site GSM Databases 01-Feb-05 07:06 (Page 2)
EIR HLR
UT BSC SGSN DNS Server MSC VLR Old SGSN Old MSC GGSN Radius DHCP
VLR Server Server

Identity Check Response The SGSN then requests the
identity of the GPRS mobile.
IMEI Check Request
GPRS mobile responds back with
Location Updating Request IMEI Check Response the identity.
Update Location
Cancel Location Verify that that GPRS mobile
Cancel Location Ack being used by the user is not a
stolen one. The IMEI (Internaional
Insert Subscriber Data Mobile Equipment Identity)
Insert Subscriber Data Ack obtained from the GPRS mobile is
sent to the Equipment
Update Location Ack Identification Register (EIR).

Update Location The EIR clears the subscriber and
responds back to the SGSN with
Cancel Location the status.
Cancel Location Ack
The SGSN now informs the Home
Location Register (HLR) about the
new location of the GPRS mobile.

The HLR informs the old SGSN
that the GPRS mobile has moved
to a new location.

The old SGSN acknowledges
back.

The HLR updates the new SGSN
with all the subscriber
information.

The SGSN responds back to the
HLR.

The HLR now responds back to
the SGSN's "Update Location"
message.

The mobile had initiated a
combined attach, so the SGSN
also updates the location
information at the MSC-VLR that
will handle the voice calls.

The MSC also initiates an update
at the HLR. The sequence of
actions here is identical to that of
the SGSN's HLR update.

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

GSM GSM GPRS Network
Coverage
EventHelix.com/EventStudio 2.5
Cell BSS Core Network Old Core Network GGSN Site GSM Databases 01-Feb-05 07:06 (Page 3)
EIR HLR
UT BSC SGSN DNS Server MSC VLR Old SGSN Old MSC GGSN Radius DHCP
VLR Server Server

Insert Subscriber Data

Insert Subscriber Data Ack

Update Location Ack

Location Updating Accept The MSC informs the SGSN that it
has finished the location update.
GMM Attach Accept
The SGSN responds back to the
GMM Attach Complete original GRPS combined attach
TMSI Reallocation Complete request from the mobile.

PDP Context Activation The GPRS mobile acknowledges
the receipt of "Attach Accept".
Activate PDP Context
The Attach Complete signals the
APN completion of the attach
procedure. This is passed to the
DNS Query MSC-VLR as "TMSI Reallocation
Complete".
APN
The GPRS mobile now initiates
DNS Response the PDP context activation
procedure to obtain the IP
GGSN IP Address address for the device. The
Access Point Name (APN)
Create PDP Context Request specified by the service provider
is passed as a parameter.
PAP, CHAP, PDP Request
The SGSN initiates a DNS query to
Radius Authentication Request find the GGSN corresponding to
the APN specified by the mobile.
PAP, CHAP (GGSN - Global GPRS Support
Node.)
Radius Authentication Response
The DNS provides the GGSN IP
DHCP Address Request address.

The SGSN routes the PDP context
activation request to the GGSN
corresponding to the APN.

The GGSN authenticates the
GPRS subscription at the RADIUS
server.

The RADIUS server successfully
authenticates the subscriber and
replies back to the GGSN.

The GGSN now requests a DHCP
server for an dynamic IP address

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

GSM GSM GPRS Network
Coverage
EventHelix.com/EventStudio 2.5
Cell BSS Core Network Old Core Network GGSN Site GSM Databases 01-Feb-05 07:06 (Page 4)
EIR HLR
UT BSC SGSN DNS Server MSC VLR Old SGSN Old MSC GGSN Radius DHCP
VLR Server Server

DHCP Address Response for the GPRS mobile.

Create PDP Context Response The DNS server provides the IP
address.
Activate PDP Context Accept
The GGSN responds back to the
SGSN, indicating completion of
the PDP context activation
procedure.

The SGSN replies back to the
GPRS mobile. This signals
completion of the PDP context
activation.