gprs traffic management

System Training

GPRS Traffic Management

Trainer Guide

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© Nokia Oyj 1 (25)


The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Networks' customers only for the purposes of the agreement under which the document is submitted, and no part of it may be reproduced or transmitted in any form or means without the prior written permission of Nokia Networks. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation.

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Nokia Networks' liability for any errors in the document is limited to the documentary correction of errors. Nokia Networks WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of this document or the information in it.

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Copyright © Nokia Oyj 2003. All rights reserved.

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Contents

Contents

1 Course preparation..................................................................4

2 GPRS Traffic Management........................................................5

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2 Course preparation

Sessions General introduction

Materials Training slides, or

PowerPoint-presentation file

Flipchart

Training document

Equipment Whiteboard

Overhead projector (OHP), or

Video projector connected to PC

Empty transparencies

Markers

Preparation The Training Document binders:

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3 GPRS Traffic Management

Module GPRS Traffic Management

Subject To introduce the students the GPRS mobility management, charging, security, addressing and services related concepts

Objectives This module enables the participant to:

Explain the mobility management functions in GPRS:

GPRS attach / detach

Cell update

Routing area update.

Explain the session management functions in GPRS:

PDP context activation

Explain the difference between idle, ready and standby MS states and their relation to the different MM functions

Explain IP addressing in GPRS

Describe charging in GPRS

Explain the concept of security in GPRS

Describe the data flows for a roaming GPRS MS

without reference to notes.

Programme Introduction

GPRS Mobility and Session Management

Mobile-terminated SMS transfer

Roaming

Security

GPRS Services

Charging

Lawful Interception

Quality of Service

Materials PowerPoint slides

Training Document: Module: Introduction to TCP/IP

Equipment OH projector or video projector with PC

Flipchart and/or whiteboard

Preparation None

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Trainer Participant Props(equipment)

Overview

Aim

to provide a clear picture of the new mobility management concepts in GPRS and to understand data transfer, charging, security and addressing issues in GPRS.

Time

This modules gives the participant a feeling on how a connection is established and maintained. Consequently, a detailed discussion on GPRS MM and SM is recommended: 4 to 6 hours

Experience

Ask each participant about his/her experience in this topic.

Gain

Ask each participant what s/he hopes to gain by this module.

Objectives

Show objectives slide.

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Process

The trainer generates flipchart illustrations and uses slides to proceed through the material.

The participants have the training document where the slides are embedded.

The participants have the exercises.

Most of the information presented in class can also be found in the training document.

The trainer will be asking questions throughout the course.

The participants are also encouraged to pose questions.

Contents

GPRS Mobility and Session Management

Introduction to Mobility and Session Management

Mobility Management – Routing Areas

Mobility Management States

Mobility Management GPRS Attach and Detach

Session Management - PDP Context Functions

Mobility Management - Location Management

Roaming

SGSN and MSC/VLR interaction

Addressing

Security

GPRS Services

Generate a flipchart of the contents. Hang on wall for the rest of the session. It serves as a map for the students and as a reminder for you what topics to present.

outline

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Reassurance

This session provides background information to help better understand the functioning of GPRS. The session should answer questions such as “What are all the new numbers in GPRS?”, “How is the mobility handled in GPRS?”, “Is GPRS secure?”, “How does the data flow through the GPRS from the web server to the MS?” and “How is charging done in GPRS?”.

Body

2. Introduction ?- What do you remember from GSM mobility management

NOTE! If students seem to be familiar with the topic (hopefully) don’t spend too much time here (you can even pass this)

?- what information do we have (and where) for subscriber identity, subscriber location, subscriber services, authentication?

NOTE! Depending on the technical experience and the needs of the group you may optionally only note the additional information. The idea is just to get through the role of SGSN, which is much like that of the MSC for circuit switched users.

HLR role

MSC/VLR role

Location updates

Location Area

Handovers

The difference between the GPRS MS and GSM MS location management is that GPRS MS has to update location information in the SGSN.

The information for a GPRS user in the different network elements falls in to three categories: identity, location, services and authentication data.

see slide 2 to 9

Whiteboard/flipchart under identity, location, services and authentication write the different information

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Example with diplomat starts here. Try to pick a catchy character, not other than the diplomat in the book and a story about what the character is doing etc. to liven up the people. Storytelling at it’s best?

Note that it would be better if you didn’t follow the example in the book one-to-one. Make up your own. Just stay focused, and go through the things you think your group finds interesting.

Explain the meaning of GPRS attach and PDP context activation

Start with drawing GPRS attach on a high level and the meaning of that.

Draw the PDP context activation. If the students are familiar with LAN-concepts compare the actions to that.

Connection to the GSM network (GPRS Attach) When the GPRS terminal is switched on, it sends an ‘attach’ message to the network. The SGSN collects the user data from the HLR and authenticates the user before attaching the terminal.

Connection to the IP network (PDP context)

Once the GPRS terminal is attached, it

You can use an empty slide and a projector but a BIG whiteboard is better. Remember SYSTRA?

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can request an IP address (e.g. 155.131.33.55) from the network. This address is used to route data to the terminal. A user can have a:

Static IP address – the user always has the same IP address, or a,

Dynamic IP address – the network allocates the user a different IP address for each connection.

3. Mobility Management

Mobility Management - Routing Areas

Explain the concept of routing areas

? How can we put the routing areas (rules)?

Explain RAI

One or more cells form a routing area.

Routing area cannot be served by two different SGSNs

Routing area must be contained in one location area.

A routing area is identified by a Routing Area Identity, RAI.

RAI = MCC + MNC + LAC + RAC

Continue drawing on the whiteboard or slide. There are also slides for this in the trainer slides.

Write on flipchart. Hang on wall for the rest of the course

Mobility Management States

Explain the mobility management states (continue example)

first mention the state names and

The IDLE state is used when the MS is passive (not GPRS attached).

An MS is in READY state an active

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functions briefly

then continue with the example

fill in the picture the most important pieces of subs. Information: what is known at what stage

mention what the MS/network does to change state

you can briefly mention what functions the network and the MS can do in each stage

EMPHASIZE that the PDP context activation is the key to PDP data transfer

phase when it is transmitting or has just been transmitting.

The STANDBY state is used when the subscriber has ended an active phase.

In READY state:

The MS is attached to the mobility management and the location of the MS is known on cell level.

The MS is capable of receiving and sending data. To be able to send data to an external IP network, the MS must also have an active PDP context. The SGSN can send data to the MS without paging at any time and the MS can send data to the SGSN at any time.

The network does not have to page a subscriber.

The MS may activate and deactivate PDP contexts.

The network holds a valid mobility management context for the subscriber.

In STANDBY state:

The MS is attached to the mobility management and the location of an MS is known on routing area level.

If the MS sends data, the MS moves to READY state.

There is a valid mobility management context for the MS in the SGSN and the MS.

The MS can receive pages for circuit switched services via the SGSN.

Packet data transmission is not possible in this state.

Whiteboard, Slide

Mobility Management -GPRS Attach and Detach

Explain GPRS attach in message levelWith GPRS Attach and GPRS Detach connections to the GPRS network can be established and terminated. The MS Use whiteboard

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the example used in the book is attach for the first time in PLMN

you may also present attach when the subscriber is already known in the network

Emphasise result: MM context is established in SGSN and MM

sends a request to attach or detach from the GPRS network. SGSN receives the requests and processes them.

The result of GPRS Attach is that the mobile moves to READY state and what is called a mobility management context is established in the SGSN.

or trainer slides (4) “GPRS attach x”

Mobility Management -Location Management

? why do we need location management

? what kind should we have for GPRS

continue example, now the characters MS moving about

what if in standby

what if ready

Explain cell update

Explain routing area update

Explain Intra-SGSN routing area update step by step

Cell Update when MS changes cell within a routing area in READY mode

When the MS changes cell between the different routing areas, it performs a Routing Area Update.

There are two types of routing area updates, the Intra-SGSN Routing Area Update and the Inter-SGSN Routing Area Update.

Draw the cases on whiteboard or

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*Note that the people having a strong GSM background most likely will find very little new stuff in this, It’s just Inter-MSC LU.

**Note that a little bit more interesting (new stuff) and overlapping with Inter-SGSN RA is the Combined RA/LA Inter-SGSN routing Area Update. The flow of messages is in the appendix.

? What if an MS is in Standby state and not moving (or transferring data)

All the MSs attached to the GPRS will perform a periodic Routing Area Update.

Broadcast by network

A shorter time than the MS reachable timer (which if expires results in MS to IDLE state in SGSN)

For the trainer:

If implicit detach is enabled it will also result in the MS to be erased from the

show slides “Intra-SGSN Routing Area Update” and “Inter-SGSN routing area Update”

draw Intra-SGSN routing area update on whiteboard message by message or use slides “Intra-SGSN Routing area update”

This can be explained quite quickly using the trainer slides “Inter-SGSN routing Area Update” and almost as fast with whiteboard. Again a choice based on breaking the rhythm.

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SGSN (mobility management context removed

A flag called the Paging Proceed Flag is always removed (set to 0) when the MS reachable timer expires. The SGSN checks the PPF before paging the MS. If the flag is not set then the MS is not paged.

SGSN and MSC/VLR Interaction

Explain why interaction

Explain the concept of Gs-interface

Shortly describe the combined actions

Optional topic: combined Inter-SGSN RA/LA update.

Two separate MM for Class A/B phones

More efficient (saves battery life, RR resources..) if combined/streamlined MM actions

Gs between SGSN and MSC/VLR

SGSN can talk MAP phase 2

Optional interface, implemented in Nokia solution

Combined GPRS/IMSI Attach and Detach.

Combined RA/LA update.

Circuit switched services paging via GPRS network.

Non-GPRS alerts. Identification procedure.

MM information procedure.

4. Session ManagementSession Management – PDP Context Functions

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? why do we need context activation (mentioned in intro)

Continue example. Now the MS does PDP context activation and load data.

explain the general idea, the goal

present PDP context activation with four steps

? what information about the context should we have

Explain Access Point concept

Explain PDP context deactivation

The four basic steps of PDP context activation are:

MS sends an (1)Activate PDP Context Request,

The MS can be (2) authenticated and the IMEI checked,

The SGSN checks that the request is valid and sends a (3a) Create PDP Context message to the GGSN, The GGSN returns a (3b) Create PDP Context Response. The response message includes e.g., the tunnel ID (TID), IP address, BB Protocol, Charging ID, is reordering required, QoS negotiated, PDP configuration options and cause. The IP address is included if the GGSN allocated an IP address.

The SGSN returns (4) Activate PDP Context Accept message. This message includes important details, e.g. IP address the MS should use.

Every address can be deactivated separately

GPRS detach will automatically remove all PDP contexts

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No GPRS attach (no mobility management context)

Only ready state and idle (no standby)

Roaming

Continue story with an example where your character goes abroad, switches the MS on and step by step go through:

GPRS Attach (if necessary as a review)

PDP context activation, with an APN of home network

1. Visiting user selects to use Home APN

2. MS sends "Activate PDP Context"

3. SGSN asks for GGSN IP address (using APN as the key) from Visited DNS

4. Visited DNS asks Root DNS "who knows the IP address for this name ?"

5. Root DNS replies the Home DNS address to Visited DNS

6. Visited DNS asks Home DNS for GGSN address

7. Home DNS replies the GGSN IP address

8. Visited DNS replies SGSN

9. visited SGSN sends Create PDP Context to Home GGSN

10.Home GGSN creates PDP context (possibly requests an IP address from DHCP or RADIUS server)

11.Home GGSN sends response to

Use whiteboard or draw on slide

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Explain the path of the packets from a web server/e-mail server to the MS

Optional: explain the two ways of connecting GPRS backbones of PLMNs

SGSN

12.SGSN sends PDP context accept to MS

For trainer’s info:

Anonymous Access

With anonymous access no mobility management context (no GPRS Attach) in the SGSN is required. The MS can anonymously initiate a PDP context activation.

The anonymous access context activation always uses dynamic addressing and has to have a pre-defined server where to connect.

A subscriber can use an anonymous access context only with certain pre-defined anonymous access service providers.

The idea of anonymous access could be for example that a user can access some service free of GPRS access/transfer charges. The service provider would pay the access fees (but maybe charge for some service). Buy airline tickets on-line: access free, tickets cost something.

Use whiteboard or draw on slide

Show slide Interconnection of PLMNs

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Addressing

? what is the difference between a static address and a dynamic IP address?

Explain the difference in connections for a roaming user

With static address

Dynamic address

Dynamic address, but always home network AP

Explain the difference between a non-transparent and transparent access to external networks

Explain number translation

5. SMSGPRS enables SMS transfer. The main idea of this chapter is to outline the individual ways how to transmit an SMS message to a class A and B MS.

You have to answer the question, where the decision is made whether to use cs or ps GSM for SMS transfer.

6. ChargingCharging

? How was charging done for circuit switched services?

? Do you see any problem with charging “just like before”?

? How would you charge for packet switched services / what kind of

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information do we have to collect?

all of this info in CDR

Explain CDR generation and collection to the charging gateway and transfer to the BS

? Why the charging gateway (what are the functions of charging gateway)?

Charging could be based on time: the active PDP context time, but not time used to transfer a group of packets. Instead maybe amount of data transferred.

Almost all BC different in how and in what format they want the CDRs. Interface always different

The GSNs don’t have to interface to the BC directly

GSNs simple

Generate flipchart with the necessary information.

Whiteboard / draw on slide

Generate flipchart as you go along.

7. SecuritySecurity

NOTE! This is a very interesting topic for everyone, but try to keep things under control and don’t go too deep.

? How do you feel about GSM security?

?How do you feel about Internet

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security

?How do you feel about the security when we combine the two into GPRS

? What security fuctions did we have in GSM

- when pumping the answers note also the small differences in details of the

security

Explain GPRS specific security features

Explain the types of screening we have

The GPRS system has inherited the GSM Phase2 security functions:

The authentication of the subscriber,

IMEI checking,

The user identity confidentiality (TMSI, now P-TMSI),

Ciphering of the data traffic between the MS and the SGSN.

The GPRS additional 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

There are two types of screening available in the GGSN: network- and subscription- controlled Network-controlled screening is used to protect the GPRS network from known security problems. The same screening applies for all users.

Subscription controlled screening could

Flipchart, make a list

Generate list on flipchart and explain then the details of every point.

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For the trainer’s info:

An additional type of screening would be user controlled. It is not a part of standard part of GPRS-phase1. With it the user could create and modify his or her own screening rules.

for example allow some certain user to only access the company Intranet

8: Lawful InterceptionLawful Interception

Explain lawful interception –term

? what kind of information do you think the police would be interested in (what kind of things need to be collected)

Explain LI functioning and the role of the Lawful Interception Gateway: LIG

Lawful interception is an action based on the law, which is performed by the GPRS network. Lawful interception provides information for a Law Enforcement Agency (LEA) about some pre-defined target subscriber.

data sent and received by the interception target, location information, subscriber information, etc

the GPRS network has to be able to collect this information

ADMF is the database where the "targets" (identities to be intercepted) are stored. Each SGSN/GGSN contains a duplicated ADMF database. Access to the database is restricted.

The Lawful Interception Gateway converts GPRS format to LEA (Law Enforcement Agency) equipment format

avoids that each GSN would have to be made compatible with every LEA equipment. The delivery function helps in keeping the GSN(s) simple.

Via the LIG delivery but user data and signalling can be transferred to the LEA equipment. Use whiteboard

or slide Lawful

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Interception

9. GPRS ServicesGPRS Services

Not very much here and there is a reason: current systems only support IP as PDP PTP as a service. So technology wise it’s simple.

You could expand the topic by talking about things like SMS transfer via GPRS, WAP over GPRS not to mention all the exciting things supported by “just best-effort IP”.

You could also mention the limitations now and the future possibilities with GPRS supporting real-time multimedia (GPRS with 3G access).

Advice: raise discussion.

Quality of Service

(OPTIONAL TOPIC)

This topic short today: “only” Best-effort QoS supported in current implementations. So we work like the Internet. When the air interface supports higher bandwidth the QoS makes more sense.

But in the future there will be a lot of talk about the different quality of service parameters so it makes sense to introduce them.

? What kind of things or parameters do

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you think could be used to define QoS

Explain GPRS QoS profiles

Explain precedence levels

Explain delay classes

Packet transfer delay, throughput (mean, peak), error rate (reliability)

GPRS system has one QoS profile with multiple attributes

Attributes are precedence class, delay class, reliability class, peak throughput class, and mean throughput class.

Service precedence describes how the network will handle abnormal conditions.

The other QoS parameters assume normal GSM/GPRS coverage/capacity.

There are three different service precedence levels

indicate the priority of maintaining the service.

High precedence level guarantees service ahead of all other precedence levels.

Normal precedence level guarantees service ahead of low priority users.

Low precedence level receives service after the high and normal priority commitments have been fulfilled.

Delay attribute refers to end-to-end transfer delay through the GPRS system.

There are three predictive delay classes and one best effort class.

There are five different reliability classes.

Generate an overview table of the different parameters on the whiteboard and draw a picture of MS to web server data transfer and illustrate the functioning of some of the most important parameters.

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Explain reliability classes

Explain user data throughput classes

Data reliability is defined in terms of residual error rates for the following cases:

Probability of data loss

Probability of data delivered out of sequence

Probability of duplicate data delivery, and

Probability of corrupted data

User data throughput specified in a set of throughput classes

Characterise the expected bandwidth required for a PDP context.

throughput is defined by both peak and mean classes.

peak throughput measured Gi and R reference points in octets per second.

specifies the maximum rate at which data is expected to be transferred across the network for an individual PDP context.

no guarantee, depends upon the MS capability and available radio resources.

The peak throughput is independent of the delay class

The mean throughput measured at the Gi and R reference points in octets per hour.

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.

A best effort mean throughput class may be negotiated, and means that throughput shall be made available to the MS on a per need and availability basis.

The current Nokia GPRS implementation only supports Internet

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type best-effort quality for an individual PDP context. The QoS support is under consideration for future releases.

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