Modul 7 gprs operation

GSM-GPRS Operation
GPRS Procedures And
Operations
Modul 7

2
Agenda
1. Introduction to GPRS
• Apakah itu GPRS ?
• Pengkodean di GPRS
• Kelas-kelas MS pada GPRS
• Aplikasi-aplikasi GPRS
2. Bagaimana GPRS bekerja?
3. Karakteristik GPRS
4. Aplikasi-Aplikasi GPRS
5. Keterbatasan GPRS
6. Arsitektur GPRS
7. Fungsi Elemen
kris.sujatmoko@gmail.com

3
MSC
Local
Area
Network
Server
Route
r
Corporate 1
Local
Area
Network
Server
Route
r
Corporate 2
GPRS
INFRASTRUCTURE
Border
Gateway
(BG)
Serving
GPRS
Support
Node
(SGSN)
HLR/Au
C
EIR
BS
C
BT
S
U
m
SMSC
Firewall
Firewal
l
Gateway
GPRS
Support Node
(GGSN)
GPRS Logical Architecture
Legal Interception
Gateway (LIG)
Firewall
Inter-
PLMN
network
Data
network
(Internet)
Data
network
(Internet
)
PSTN
Network
SS7
Network
GPRS
backbone
network
(IP based)
Billing System
Charging
Gateway (CG)
Domain Name
Server (DNS)

4
Logical architecture: Interfaces
other PLMN
MSC/VLR HLR
EIR
SGSN
GGSN
GGSN
SGSN
PDN TE
SMS-GMSC
SMS-IWMSC
MS BSS
GiGn
Gn Gp
Gb
Gd
Um
GcGr
Gs
Gf
CE
D
A
Signalling &
Data Transfer
Signalling
GPRS Interfaces

5
Functional view of GPRS
Local
area
network
Server
Router
Local
area
network
Server
Router
Corporate 2
Corporate 1
Intra-PLMN
backbone
network
(IP based)
Serving GPRS
Support Node
(SGSN)
Point-To-
Multipoint
Service
Center
(PTM SC)
Gateway GPRS
Support Node
(GGSN)
GPRS
INFRASTRUCTURE
HLR/AuC
MSC
BSCBTS Packet
networkPSTN
Packet
networkSS7
Network
Packet
network
Data
network
(Internet)
Packet
network
Data
network
(X.25)
Packet
network
Inter-PLMN
Backbone
network
Border
Gateway (BG)
Gb
Gr Gd
Gi.IP
Gi.X.25
Firewall
Firewall
Firewall
Um
R/S
SMS-GMSC
Gr Gd
Gs
Gs
Gp
Gn
Gn
EIR
MAP-F
SGSN = Serving GPRS Support Node
GGSN = Gateway GPRS Support Node
NMS = Network Management System
BG = Border Gateway
CG = Charging Gateway
FW = Firewall
LIG = Legal Interception Gateway

6
GPRS network seen by an other data network
L o c a l
a r e a
n e tw o r k
R o u t e r
C o r p o r a t e 2
L o c a l
a r e a
n e tw o r k
R o u te r
C o r p o r a t e 1
P a c k e t
n e tw o r k
D a ta
n e tw o r k
(In te r n e t)
G P R S
S U B N E T W O R K
S U B N E T W O R K
1 5 5 .2 2 2 .3 3 .X X X
S U B N E T W O R K
1 3 1 . 4 4 .1 5 . X X X
S U B N E T W O R K
1 9 1 . 2 0 0 . 4 4 . X X X
H O S T
1 9 1 .2 0 0 .4 4 .2 1
H O S T
1 3 1 .4 4 .1 5 .3
H O S T
1 5 5 .2 2 2 .3 3 .5 5
" R o u te r "

7
Data transfer
Local
area
network
Server
Router
SGSN
GGSN
IP
ROUTER
BSCBTS
GPRS
backbone
network
(IP based)
SGSN
GGSN
IP
ROUTER
BSC BTS
GPRS
backbone
network
(IP based)
Packet
network
Inter-operator
backbone
network
Packet
network
Data
network
(Internet)
Corporate
HOME GPRS
NETWORK
VISITED
GPRS
NETWORK
case 1
case 2
case 3

8
Data Transfer Between GSNs
User
packet
User
packet
Userpacket Userpacket
SGSN GGSN
The stream of containers
forming a tunnel.
User
packet

9
GTP Container
User packet
Tunnel ID:
IMSI…
THE GTP PACKET
IP (+TCP/UDP)
Who is the user?
To which GSN?
GSN IP-
address
E.g. a TCP/IP packet
carrying e-mail

10
Protokol Di GPRS
 Pada Jaringan GPRS,
data harus dilewatkan
ke stack protokol yg
berbeda sebelum
diterima oleh alamat
tujuan
 Protokol ini sudah
integrated dielemen
GPRS yg sifatnya
sudah terproteksi dan
pengirimannya
terjamin

11
Protokol Pada MS
 Internet Protocol dan X.25  monitor
routing informasi pelanggan di jar backbone
GPRS
 Subnetwork Dependent Convergence
Protocol (SNDCP)  bertanggung jawab
dlm kompresi dan segmentasi data ke unit2
kecil
 Logical Link Control Protocol (LLC) 
menjamin koneksi aman (reliable and
ciphered connection) ke SGSN
 Radio Link Control Protocol (RLC) 
memberikoneksi air interface utk transmisi
data. Jika ada error transmisi dpt diketahui
pd saat data sampai direceiver
 Medium Access Control Protocol (MAC)
 mengontrol terjadinya koneksi di air
interface mulai dari assignment dan
acknowledgment
 GSM Radio Frequency protocol layer 
bertanggung jawab utk memberikan saluran
fisik berupa air interface

12
Protokol di BSS
 Base Station Subsystem GPRS Protocol (BSSGP)  bertanggung jawab
utk routing ke SGSN
 SGSN mempunyai kemampuan utk memilih rute data alternatif
 Network Service Protocol (NS) BSSGP Packet Data Units dibawa ke
Service Access Point pada layer jaringan
 Protokol ketiga dan terakhir di BSS : L1 bis Protocol

13
Protocol Di SGSN
 GPRS Tunneling Protocol (GTP) IP address GPRS
backbone network, bertanggung jawab thd semua pesan GPRS,
signaling dan data pelanggan melalui tunneled transmission
antar GPRS Support Nodes. Transmisinya tdk bisa diinterferensi
oleh user lain
 User Datagram Protocol (UDP)  digunakan dlm transmisi
tunneled PDU ketika aplikasi tdk aktif di sisi receiver
 Transmission Control Protocol (TCP)  reliable transmission.

14
BTS BSC
SGSN
GGSN Intranet
GGSN
Internet
CG
Billing
System
Router
Server
Local
Area
NW
Corporate
GPRS
Core
Network
BG
InterPLMN
Network LIG
GPRS Core Network
Logical Network Elements
SGSN = Serving GPRS Support Node
GGSN = Gateway GPRS Support Node
NMS = Network Management System
BG = Border Gateway
CG = Charging Gateway
FW = Firewall
LIG = Lawful Interception Gateway
FW
FW
NMS
DNS

15
GPRS Mobility Management (GMM)
 Procedures that take care of the mobility of the user are
called GPRS Mobility Management (GMM). The GMM
procedures are similar to the mobility management for
circuit switched users.
 One of a GMM procedure is the GPRS attach
procedure. When a GPRS terminal is powered on, it
sends an 'attach' message to the network.
 The SGSN authenticates the user before attaching the
terminal to the GPRS network. Once a subscriber has
attached to the network, logical connection is established
between the MS, the SGSN, and the HLR.

16
Session Management (SM)
 Procedures that handle the user connection to the
external data networks are called Session Management
(SM)
 The procedure to establish a connection to an external
data network is called “PDP context activation”
procedure. Hereby, a connection is established between
the MS and GGSN via the SGSN.
 The GPRS MS has to register with the PLMN for the first
time, much in the same way as a normal GSM MS. The
difference between the GPRS and GSM MS phone is
that it has to update location information in the SGSN as
well.

17
Subcriber information, Information
Elements and Location
Type of info What info Where
Identity IMSI
TMSI
IP address
SIM, HLR, VLR, SGSN
SGSN, MS
MS, SGSN, GGSN
Location VLR address
Location area
Serving SGSN
Routing area
HLR
SGSN, VLR
HLR, VLR
SGSN
Services Basic services, supplementary services, circuit
switched bearer services, GPRS service
information
Basic services, supplementary services, CS
bearer services
GPRS service information
HLR
VLR
SGSN
Authentication data Ki, algorithms
Triplets
SIM, AC
VLR, SGSN

18
Routing Area
 A routing area is defined as one or more cells with a
maximum size of number of cells in one location
area that is used for paging GPRS subscribers.
SGSN-1
BSC-1
RA-1 RA-3
SGSN-2
BSC-2
RA-2
LA-1 LA-3
Cell ⊂ Routing area ⊂ Location area ⊂ MSC coverage area
Cell ⊂ Routing area ⊂ SGSN coverage area

19
Routing Area Identity (RAI)
 The RAI is defined by the operator and is broadcast by the system.
The GPRS MS monitors the RAI when changing cells to see if a RA
border has been crossed. If the RA changes, it is the responsibility
of the MS to initiate the RA update procedure. The structure of the
RAI is:
 Where RAC is Routing Area Code
 The RAI is LAI + RAC. The RAI is of fixed length - 15 digits.
RAI = MCC + MNC + LAC + RAC

20
Mobility Management States
 A GPRS MS has one of three mobility
management states:
 The Idle state is used when the MS is passive
(not GPRS attached).
 A MS is in Ready state and in the active phase
when it is transmitting or has just been
transmitting data.
 The Standby state is entered when the
subscriber has ended an active phase but is still
attached to the network.

21
MS In Idle State
RA-1
VLR-1
HLR
SGSN-1BSC
IMSI 244...
VLR
SGSN
IMSI
LAI
SGSN ?
IMSI ?
RA ?
Cell ?
LA-1

22
MS In Ready State
RA-1
VLR-1
HLR
SGSN-1BSC
IMSI 244...
VLR VLR-1
SGSN SGSN-1
IMSI 244...
LAI LA-1
SGSN SGSN-1
IMSI 244...
RAI RA-1
CellCell cellcell--11
LA-1

23
MS In Standby State
RA-1
VLR-1
HLR
SGSN-1BSC
IMSI 244...
VLR VLR-1
SGSN SGSN-1
IMSI 244...
LAI LA-1
SGSN SGSN-1
IMSI 244...
RAI RA-1
CellCell ??????????
LA-1

24
GMM Procedure : GPRS Attach
RA-1
HLR
SGSN-1
BSC
LA-1
1
2a 2b

25
GPRS Attach….
RA-1
HLR/AC
SGSN-1
BSC
LA-1
3a
3b
3f
3c

26
GPRS Attach…With IMEI Checking
(optional)
RA-1
EIR
SGSN-1
BSC
LA-1
4c
4d
4a
4b

27
GPRS Attach…
RA-1
HLR
SGSN-1
BSC
LA-1
5a
5b
5c
5d
6a
6b

28
Location Management
 The location management procedures are
a group of mobility management procedures
that we use to handle the changing of a cell
or a routing area or a SGSN coverage area.
Information in the databases has to be
modified during these procedures.
 Periodic routing area update is used for
checking that a MS that has not done any
routing area updates for some period of time
is still reachable.

29
Routing Area Update
Two types of routing area updates:
 Inter-SGSN routing area update:
If the old and new routing areas are managed by
different SGSNs, an inter-SGSN routing area update is
performed. The old SGSN forwards user packets to the
new SGSN.
 Intra-SGSN routing area update:
If the old and the new routing area belong to the same
SGSN, an intra-SGSN routing area update is performed

30
Intra SGSN Routing Area Update
SGSN-1
BSC-1
RA-1
Old cell New cell
RA-2

31
Intra SGSN RA Update Procedure
HLR
SGSN
BSC
LA-1
GGSN
1
New RA
(1)The MS requests a routing area update

32
HLR
SGSN
BSC
LA-1
GGSN
2b
22a
New RA
Step 2 authentication

33
HLR
SGSN
BSC
LA-1
GGSN
4
23
New RA

34
Session Management
 Session management collectively refers to a set of procedures
for the activation, deactivation, and modification of a data
session between a MS and an external network
 In order to set up data sessions, the GPRS system provides a
group of functions for associating a MS with an address (typically
the IP address) and for releasing this association.
 These are called PDP context functions. The resulting PDP
context can also be modified. The MS can use the PDP context
functions only when in Standby or Ready state.
 The MS can use various kinds of IP addresses. The home
network operator may assign a static IP address to a MS
permanently. Another option for the operators is to assign a
dynamic IP address to a MS during PDP context activation

35
PDP Context Activation
MS SGSN GGSN
2. Security
Functions
1. Activate PDP
Context Request
DNS
Server
DNS
inquiry
3. Create PDP
Context Request
4. Create PDP
Context Response
Connection
establishment
with PDN
5. Activate PDP
Context Accept

36
 PDP Context Include :
 PDP type, that is, IP connection or X25
connection.
 Access point name (APN): a symbolic name for
a network interface to an external network in the
GGSN. One GGSN could have several different
access points to access different networks.
 IP address (empty = dynamic), which is also
referred to as PDP address.
 QoS parameters

37
Charging In GPRS
Charging data is collected from
SGSN and GGSN
Collected charging information:
- Mobility management data
- Duration of PDP context
- Data volume uplink/downlink
- Usage of external networks
(= Access Point)
- SGSN & GGSN address
BTS BSC
SGSN
GPRS
Backbone
IP Network
GGSN
Internet
Service
CG
Charging
Gateway
BC
Billing Center
Specific GTP' protocol used to carry CDRs
from SGSN/GGSN to Charging Gateway

38
Charging….
 CDRs produced by
GGSN
 CDRs produced by
SGSN
CG
S-CDRs
M-CDRs
SMS-CDRs
Internet
GGSN
Operator
IP backbone
SGSN
CG
Internet
GGSN
Operator
IP backbone
SGSN
G-CDRs

39
Security In GPRS
 The GPRS system has inherited the GSM Phase 2
security functions:
 Authentication of the subscribers
 IMEI checking
 User identity confidentiality (TMSI, now P-TMSI in GPRS)
 Ciphering of the data traffic between the MS and the
SGSN.
 The additional GPRS security features are:
 Private IP addressing in the GPRS backbone
 Ciphered links and authentication between nodes in the
GPRS backbone
 Screening of packets coming from the external networks.

40
Authentication…
 MS is authenticated
 Ciphering key selected
 Equipment identity is
optionally checked
 Location updated to HLR
and VLR
SGSN interfaces HLR for GPRS attachBTS BSC
SGSN
GGSN
GPRS
Backbone
IP Network
SS7
HLR
MSC/
VLR
Intranet
Internet

41
Security….
 Addressing in the backbone, external networks
(access point), and the MS
SGSN GGSN
DNS
Internet
BTS BSC
10.1.1.1
10.1.1.2
10.1.1.3
10.1.1.4
GPRS BackboneGPRS Backbone
FW
123.45.67.88
123.45.0.0/16

42
Security….
 Interconnecting GPRS networks of different
PLMNs with link physically secure
SGSN SGSN GGSN
Internet
Toward other
sites
site 1
Security Router
SGSN SGSN SGSN
site 2
Operator
Private IP
network
Secure
Links
Security Router
Link
physically
secure
GGSN site
Router

43
Security….
 Subscription- and network-controlled
screening
Internet
Operator
screening
Subscription
controlled
screening
Address:
From
172.60.10
to
172.60.20
Address:
From
172.60.21
to
172.60.50
Address:
From
172.60.10
to
172.60.50
FirewallFirewall
Firewall
Business
screening
basic
screening
GGSN
GGSN
APN=Business
APN=Basic

44
GPRS Quality Of Service

45
 Precedence class (priority)
The service precedence indicates the priority of maintaining a
service under abnormal conditions such as network congestion.
Packets may be discarded according to precedence level. The
following precedence levels are :
 Precedence Class 1 (High precedence):
Service commitments will be maintained ahead of all other
precedence levels.
 Precedence Class 2 (Normal precedence):
Service commitments will be maintained ahead of low priority
users.
 Precedence Class 3 (Low precedence):
Service commitments will be maintained after the high and
normal priority commitments have been fulfilled.

46
 Delay Class
 The delay parameter defines the maximum values for the
mean delay and 95% delay to be incurred by data passing
through the GPRS network. The delay parameter defines
the delay incurred by data packets within the GPRS
network.
Size 120 octets 1024 octets
Class Mean Delay 95% Mean Delay 95%
1 (Predictive) 0.5 s 1.5 s 2 s 7 s
2 (Predictive) 5 s 25 s 15 s 75 s
3 (Predictive) 50 s 250 s 75 s 375 s
4 (Best Effort) Not specified

47
 Reliability Class define the probability of:
 Lost data
 Duplication of data
 Data arriving out of sequence
 Corruption of data.
 The reliability class specifies the requirements of
the various network protocol layers. The
combinations of the GTP, LLC, and RLC
transmission modes support the reliability class
performance requirements.

48
 The throughput class indicates the data throughput
requested by the user. Throughput is defined by two
negotiable parameters:
 Maximum bit rate
 Mean bit rate. This includes, for example for "bursty"
transmissions, the periods in which no data is transmitted.
 The maximum and mean bit rates can be represented by a
parameter known as the Information Transfer Rate.

49
 The maximum bit rate is measured in octets per
second at the Gi and R reference points. It specifies the
maximum rate at which data is expected to be
transferred across the network for an individual PDP
context. There is no guarantee that this maximum rate
will be achieved or sustained for any time period as this
depends upon the MS capability and available radio
resources.

50
 The mean bit rate (throughput) is measured at the Gi
and R reference points in units of octets per hour. It
specifies the average rate at which data is expected to
be transferred across the GPRS network during the
remaining lifetime of an activated PDP context. The
network may limit the subscriber to the negotiated mean
bit rate (for example, for flat rate charging), even if
additional transmission capacity is available.

51
Conclusion
1. The messages that are sent between various
components of the GPRS network are collectively
referred to as GPRS traffic. To manage this traffic
in an orderly manner, one needs a set of traffic
management procedures.
2. Procedures that handle mobility of user are called
GPRS Mobility Management (GMM). Procedures
that handle the user connection to the external
networks are called Session Management (SM).
3. There are two phases in connecting a GPRS
terminal to the network:
 Connection to the GPRS(SGSN) network or GPRS attach
 Connection to the external network: PDP context
activation

52
4. A routing area is defined as one or more
cells with a maximum size of one location
area that is used for paging GPRS
subscribers. An SGSN can have a number
of RA associated with it.
5. An MS can have:
 Static IP address: the user always has the same
IP address, or
 Dynamic IP address: the network allocates the
user a different IP address for each session.

53
6. In Idle state the MS is not attached to the GPRS.
No information about the subscriber is known.
7. A MS is in Ready state and in the active phase
when it is transmitting or has just been transmitting.
8. The MS enters Standby state when it has ended an
active phase. MS is not transmitting anything.
9. The MS performs a cell update when it changes
cell within a routing area in Ready mode.

54
10. When the MS changes cell between the different routing areas,
it performs a routing area update.
11. The GPRS core network uses private, unregistered IP
addresses. The GGSN maps (or translates) the private
addresses into one (or more) registered public IP addresses and
port pairs. The MS uses one of the public IP addresses.
12. GGSN and SGSN generate CDRs. The CDRs are transferred to
the charging gateway. The charging gateway interfaces to the
Billing Centre.
13. GPRS has inherited the GSM Phase 2 security features.
Additional GPRS specific security features are implemented:
private IP addressing in the GPRS backbone, ciphered links and
authentication between nodes in the GPRS backbone, screening
of packets coming, etc.

GSM-GPRS Operation
End of Section 7
GPRS Procedures And
Operations

Modul 7 gprs operation

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