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Testing General PacketRadio ServiceGPRS

Harshawardhan Lele

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Todays Switching Network

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Todays Mobile Network 2G

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DTAP

SCCP

PCM30

MTP

BSSMAP

PCM30

LAPD

RSL

DTAPL

2

M

O

&

M

PCM30

MTP

TCAP

SCCP

MAP

I SUP

TCAP

SCCP

PCM30

MTP

MAP

Todays Mobile Network 2G

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Mobile Network

Iu-CS

Iu-CS Iu-PS

Iu-PS

IubRNC

Node BNode B

RNS

IurIub

RNC

Node BNode B

RNS

VLR

MSC

VLR

MSC

AE

GMSC

AbisBSC

BTSBTS

BSS

PSTN

PSTN

G EIRF

HLR

AUC

D

C

H

Gs

SGSN

AbisBSC

BTSBTS

BSS

Gb

GGSN

GnGp

PDN

other PLMN

Gi

Gf

Gr

Gc

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System Overview

Existing GSM Networkcontaining BSS (BTS; BSC); MSC; VLR; HLR; EIR

circuit switched (CS)

connected to SS#7 Network

Additional Networkcontaining BSS with PCU; SGSN; GGSN

packet switched (PS)

connected to Packet Data Networks (PDN)

Shared ResourcesBSS (BTS)

VLR; HLR; EIR

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Test Areas

Physical Layer TestingCS Testingsignalling protocols (e.g.: MTP; SCCP; TCAP; MAP)

switched circuits

user level

PS Testingnetwork layers

user layers

user level (applications)

Interworking

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SMS-GMSCSMS-IWMSC

SGSNBSSMT

TE GGSN

PDN

TE

GGSN

Other PLMN

SM-SC

HLRMSC/VLR

EIR

E C

Gd

D

Gr

GcGsA

Gn

Gb

UmR GiGp Gf

Signalling Interface

Signalling and Data Transfer Interface

SGSN

Gn

GPRS Reference Model

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U

m

Gb GiGn

GSM RF

MAC

RLC

LLC

SNDCP

IP / X.25

Appli

-

catio

n

LLC Relay

GSM RF

MAC

RLC

L1bis

BSSGP

Network

Service

L1bis

Network

Service

BSSGP

LLC

SNDCP

L1

IP

GTP

L1

Frame

Relay

IP

GTP

IP / X.25

M

SBSS SGSN GGSN

RLCMAC

UDP [TCP] UDP [TCP]

Frame

Relay

IP / X.25

L1

L2

Transmissions Plan (Data)

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Data Interfaces

UmRF; MAC; RLC; LLC; SNDCP; IP

GPRS Abisproprietary protocol; MAC; RLC; LLC; SNDCP; IP

GbFR (/ ATM); NS; BSSGP; LLC; SNDCP; GMM, IP

Gn (Gp)FR / Ethernet (/ ATM); IP; UDP (/ TCP); GTP; IP

GiFR / Ethernet (/ ATM); IP

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GSM RF

MAC

RLC

LLC

GMM/SM

LLC Relay

GSM RF

MAC

RLC

L1bis

BSSGP

Network

Service

L1bis

Network

Service

BSSGP

LLC

GMM/SM

Um Gb

MS BSS SGSN

RLC

MAC

Transmissions Plan (Signalling)

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Signalling Interfaces

Um ( / GPRS Abis)RF (/ proprietary); MAC; RLC; LLC; GMM/SM (SMS)

GbFR; NS; LLC; GMM/SM (SMS)

Gr (SGSN / HLR), Gc (SGSN / EIR), Gf (GGSN / HLR)MTP; SCCP; TCAP; MAP

Gs (SGSN / VLR)MTP; SCCP; BSSAP+

Gd (SGSN / SMS-IW/GMSC)MTP; SCCP; TCAP; MAP (SMS)

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Physical Interfaces and Layer 2

E1 / T1Frame Relay ( ITU / ANSI)

channelized, unchannelized, fractional mode

Ethernet10BaseT, 100BaseTx

Router to Frame Relay / E1

ATM (future use/UMTS)STM-1, STM-4, DS1,DS3, E1, E3

AAL5, AAL2

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Interactions with other Services

SMSIMSI attached - via MSC

GPRS attached - via SGSN

both - via MSC or SGSN

circuit switched servicesMS class-A/B/C mode

limited RF resources - GPRS suspend / resume

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Common Entities and Procedures

entitiesHLR (e.g. G/SGSN IP address; PDP contexts)

VLR (e.g. currently serving SGSN IP address)

EIR (standard IMEI)

procedurescombined IMSI and GPRS attach

combined routeing area / location area update

cell update

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Monitoring

complex behaviour - view of all interfaces needednew statisticsmean packet delay; Kbyte / s; mean packet size; Kbyte / user ...

new call traces

GPRS attach - data transmissions - GPRS detachPDP context activation - data transmission - PDP context

deavtivation

BillingRadius

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Packet transfer

TCP timing problemsPacket Generation / verificationemulation of all lower layers up to IP

on Abis, Gb, Gn, Gi

timestamp, checksum, interfaces

IP routing to standard interfacesgeneration and checking of user layers

GPRS and PDN interworking

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Performance Measurement

Erlang and BHCA not applicableKbyte per second

packets per second

maximum and mean packet delay

QOS

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Monitoring 1/2

Signaling

Point ASignaling

Point B

K1205

Protocol Tester is a passive monitor

Decodes protocol messages between two network elements

Checks for errors in protocol messages or procedures

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Monitor all Interfaces simultaneously

BSS SGSN GGSNPDN

K1205

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Monitoring Gb Interface

Gn Interface

Gi Interface

Gd Interface

Gr Interface

Gs Interface

Gc Interface

Gf Interface

GPRS Abis for Nortel, Siemens, Ericsson, Alacatel,

Nokia, Motorola & Lucent

Tektronix K1205 offers

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GPRS Applications on K12xx

GPRS Gb Analyser

GPRS Statistics

GPRS CDR Viewer

GPRS Service Profiles

GPRS MM/SM statistics

GPRS Deciphering Application

GPRS Call Trace

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GPRS Gb Analyzer

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GPRS Gb Analyzer - What for?

Monitoring and analysis of actual subscriberactivities and crucial QoS parameters at the Gb-

interface

Obtaining valuable information on GMM, SM

procedures, QoS parameters and service usage

Troubleshooting at the Gb-interface

(e.g. based on detected failed GMM, SM procedures)

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GPRS Gb Analyzer - Features (1)

Displays important information for thousands ofGPRS sessions

(e.g. IMSI, P-TMSI, current state, Attach type, )

Displays and stores statistical output in tabulated

formatMeasures signaling performance

Monitors and analyzes important QoS parameter

(e.g. requested vs. negotiated vs. actual)

Evaluates service usage and their durationOperates Online and Offline

Is part of K12 basic SW

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GPRS Gb Analyzer - Features (2)

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GPRS Gb Statistics

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K12xx GPRS Statistics

GPRS procedures

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GPRS Applications on K12xx (3)

CDR Viewer

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GPRS Applications on K12xx (4)

GPRS Service Profiles

http://localhost/var/www/apps/USERS/Jense/Tektronix/programs/Medusa/0_Technical/QoS/QoS.ppt

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GPRS Applications on K12xx (5)

Extension of GPRS MM/SM statistics

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GPRS Applications on (5)

Extension of GPRS MM/SM statistics

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is intended as a secure transmission of data overthe

air interface

is performed between SGSN and MS through the

GPRS encryption algorithm (GEA/x). As ofRelease 98 only GEA/1 is available.

is applied to signaling data and payload.

is one task of protocol layer LLC

(GSM 04.64) is mandatory for GPRS terminals

Ciphering in GPRS networks ...

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GEA/xGEA/x

GPRS Ciphering - Methodology

Kc

Input Direction

Unciphered

Frame

Deciphered

FrameCiphered

Frame

Kc

Input Direction

MS or SGSN SGSN or MS

GPRS Encryption Algorithm (GEA/x) has three input parameters:Ciphering Key Kc

Transfer direction

Frame dependent input variable

OutputOutput

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Deciphering in GPRS networks

Data FieldFCS HeadEncrypted Bits Head

Cipher Sequence

Kc

Direction Bit (0/1)

For I- and S- Frames

F{ IOV and N(S)}

For UI-Frame

F{IOV and N(u)}

GEAx

Data Flow

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K12 Gb deciphering solution* Optional

E i h i ith t d i h i

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If deciphering is not supported by means of amonitoring tool all enciphered signalling and payload

data are invisible up to the Gb interface

Consequently, important informations are denied to

the technician or engineer attempting to observe the

transmissions behavior under normal (enciphered)

conditions.

Of course, enciphering could be disabled temporarilyduring monitoring and analysis, but

Enciphering without decipheringcapability (within a monitoring tool)

If deciphering is not supported by means of amonitoring tool all enciphered signaling and payload

data are invisible up to the Gb interface

Consequently, important information are denied to

the technician or engineer attempting to observe the

transmissions behavior under normal (enciphered)

conditions.

Of course, enciphering could be disabled temporarilyduring monitoring and analysis, but

this seems to be no suitable way out !

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K12 Gb Deciphering - What for?

The K12 Gb deciphering solution deciphers GPRStransmissions at the Gb interface automatically,

providing unhampered access to all messages above

the protocol layer Logical Link Control (LLC).

It allows enciphering to remain on during

monitoring and analysis

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K12 Gb Deciphering - So what?

Enciphering is allowed to remain on duringmonitoring and analysis

Subscribers receive the uninterrupted security and

privacy they expect

Troubleshooting, optimization, statistics can beperformed in usual way

Tektronix outstanding position for non-intrusive

GPRS testing can be strengthened

Gunnar Heine (Accepted expert in mobile network technologies): even skeptic colleagues and customers who barely apply newfeatures of the K1205 are nowadays persuaded of the value of the

deciphering application and use it on a regular base

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K12 Gb Deciphering - Features (1)

Three operation modesFull Automatic Mode

Automatic recognition up to 25000 subscribers (over the IMSI) and their

corresponding Kc values

Half Automatic ModeAutomatic recognition of Kc values for up to 25000 manually entered

IMSIs

Manual ModeProcessingup to 25000 manually-entered IMSI and Kc values

GEA1 and GEA2 support

Real-time mode and post-capture modeCapability to delete inactive or detached subscribers

GPRS D i h i S l ti K1205

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GPRS Deciphering - Solution on K1205(2)

Gb

Gr

SGSN

HLR

BSS/

PCU

Encryption

K1205

Enciphered messages on Gb

GPRS D i h i S l ti K1205

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Enciphered messages on GbDeciphered messages on Gb Gb

Gr

SGSN

HLR

BSS/

PCU

Encryption

K1205

Decipher

GPRS Deciphering - Solution on K1205(3)