Module 14

The GSM/GPRS Modem

Module Objectives

In this module we will discuss:

GSM/GPRS Theory of operation

Schneider recommendations for

configuration

Troubleshooting tips

ETG 3000 V 1.1 Evolutions

Main V 1.1 features

Provide GSM/GPRS communications on TSX ETG 3021

Euro Band (900-1800 Mhz)

Launch TSX ETG 3022 GSM/GPRS communications - US

frequency (850-1900 MHz)

Call back on ring function: on PSTN and GSM / GPRS

Implement Security features on GPRS over internet

VPN remote access, data encryption support,

IP filtering (mini firewall: filtering of IP client

addresses)

Implement transparent routing access capabilities on

GPRS

When VPN is used

TSX ETG 3021 / 3022

GSM / GPRS

Embedded modem

rlimaymantaNotaPERMITE TENER COMUNCIACION A ACCESO REMOTO A TRAVEZ DE UNA ENCRIPTACION DE DATOS

GPRS Overview (General Packet Radio Service)

Available on TSX ETG 3021 / 3022 modules (V1.1 version)

GPRS is a packet oriented Data Service based on GSM technology. (Global System for Mobile)

Provides a cost effective solution for wireless and continuous remote connection to distributed installations

Main advantages over GSM and PSTN Communications cost : Data transfer is typically

charged per amount of data exchanged (amount of megabytes per month),

while data communication via traditional circuit switching is billed per minute of connection time.

GPRS allows continuous / permanent remote connections

Higher Data rates than GSM > Theoretically

InternetInternet

GPRS

Network

GPRS

Network

rlimaymantaNotaGPRS LA EMPRESA COBRA POR CONSUMO DE DATOS Y EN GSM COBRA POR TIEMPO DE CONEXION

GPRS/VPN ETG 302X Applications

PC (Internet connected) access to Remote ETG 302x and devices

Using remote devices address

ETG 302x access to Remote ETG 302x and devices

139.158.10.24

Ethernet

Modbus 139.158.10.23

139.158.10.20

Ethernet

Modbus

85.20.65.101

85.20.65.110

InternetInternetGPRS

Network

GPRS

Network

VPN

139.158.10.24

Ethernet

Modbus

InternetInternetGPRS

Network

GPRS

Network

VPN

139.158.10.23

139.158.10.20

GPRS Communications

During a GPRS connection:

The ETG302x module connects to the GPRS network via

an Access Point Name (APN) given by the GPRS

service provider

The Access Point Name (APN) creates the gateway

between the GPRS network and the internet

The client PC or application is also connected to the

internet.

To ensure a secure remote access, ETG302x

modules also implement security services such

as:

VPN (Virtual Private Network)

IP filtering

Data encryption capabilities

InternetInternet

GPRS

Network

GPRS

Network

APN

VPN

GPRS Connection Principles

A SIM card and a specific GPRS subscription / contract provided by a GPRS service Provider is required

Connections are always established from modem to GPRS network, and never from GPRS network to modem It is not possible for a client application to directly open a

connection by dialing the ETG302x directly as in PSTN

The ETG 302x module accepts incoming GSM or PSTN calls and supports Internet Call back function in order to connect itself to the GPRS network from a remote request

ETG 302x modules provides two modes for connecting to GPRS network Permanent mode:

Automatic connection at startup or after a boot or after a connection loss

On Demand mode:

on a process or application condition. (via internal registers)

via Call back function

InternetInternet

GPRS

Network

GPRS

Network

APN

GPRS Connection Principles (Cont)

Upon a connection:

The ETG302x module receives an IP address

from the provider

either a Public IP or a private IP address

either a Static IP or a Dynamic IP address depending

on the GPRS subscription

ETG302x supports both Static or Dynamics IP

addresses.

For Dynamic IP addresses, ETG 302x provides

DynDNS support

Note =S= recommends subscriptions have:

Public APN with public IP address (reachable from

the internet)

Static IP address the service assigns the module a

static IP address. You can eliminate DynDNS

InternetInternet

GPRS

Network

GPRS

Network

APN

VPN

Private/Public APN

Private APN with private IP Address

Dedicated access within a company intranet (same as =S= VPN)

ETG and connected devices can access the internet

Nobody from the internet can reach the ETG and connected devices

Public APN with public IP address

ETG and connected devices can access internet

PC or other devices from internet can reach ETG and connected devices

Note: Requires enhanced security such as VPN. Some ports may be

blocked by provider (ports < 1024). VPN gets around this via a tunnel

Internet/IntranetInternet/Intranet

Private

APN

GPRS network Ethernet

Modbus

InternetInternet

Public

APN

GPRS network Ethernet

Modbus

More Subscription Details

GSM/GPRS service providers typically offer dedicated subscriptions well adapted to industrial applications, also called M2M (Machine to Machine) subscriptions.

Various GPRS subscriptions are available with different options: various different Data exchange rates (billing on data amount in Megabytes per

month)

option for Static IP or Dynamic IP address

Incoming TCP ports blocked or not : some providers are offering only subscriptions with TCP ports, blocked for security reasons, for instance lower than port 1024

Note: =S= recommends that you choose subscriptions with: Public APN with public IP address (visible from internet

a Static IP address

and no TCP ports blocked thus lowering remote connection constraints. It also allows connections to devices connected to the ETG

You must have the right features in you service or the module will not be able to do everything it is capable of doing

InternetInternetGPRS

Network

GPRS

Network

Dynamic IP Addressing 2 Solutions

If your GPRS subscription came with a Dynamic GPRS IP

address, it is changed / renewed frequently by your service

provider.

There are two solutions for Dynamic GPRS IP addresses: DynDNS service for working with the IP address Publication:

DNS Inc. (DynDns.com) is a free DNS service that allows you to create your own domain name.

There are limits on how many domain names you can have under the free service

Email module emails you its address when connected

What is the ETGs address?IP = 123,1,2,45

YourETG.DYNDNS.ORG

VPN Overview

VPN service provides:

Secured connections between PC connected to

Internet and remote ETG302x gateways bringing remote devices 'virtually' into your own LAN. Once

the tunnel mode is established, your programming software

and monitoring tools access the remote device transparently,

as if it are in the same local network.

Secured Site-to-Site Connections via VPN tunnels

between two remote ETG302x gateways. any device from one site can access any other device in the

remote site. This capability can also be useful for instance

as alternative solution for replacing leased lines between

sites

VPN

VPN

VPN technology allows an ETG302x to establish secure, private, bi-directional,

encrypted tunneled connections over the Internet between your central sites and

your remote equipment

Getting Ready - GSM Physical Setup - Step 1

Attach the antenna (1)

Insert the SIM chip in the rear of the ETG (2)

1

2

Module Configuration IP Address Step 2

Connect to the module with an Internet Browser

Select Setup then Modem (1)

Enter the SIM PIN code (if one exists) Many providers dont have one, it

depends on your account

Power up and go to the Modem Diagnostics area (3) operator from connection

signal strength good connection shown

12

3

GPRS Configuration Step 3

Select GPRS enable check box and enter the GPRS parameters:

Connection mode: =S= recommends start with On Demand option Access Point Name ( APN ) : Enter the APN according to your GPRS

provider and contract

Username/Password of the APN

DynDNS optional, if dynamic IP, posts IP to DynDNS account Helps you connect to module using your custom URL

Apply settings and reboot

rlimaymantaNotaUN APN TE PERMITE INGRESAR A LA RED DE UNA EMPRESA TELEFONICACOMANDO PARA VER LOS PUERTOS HABILITADOS:

netstat -n

Is it Working? Step 4

If you have trouble establishing a connection, check the log file (1)

Good connection have frames sent/received counters

1

2

PC to ETG Connection (no VPN) Step 6

Do this to verify that you can connect to the ETG before VPN

Connect ETG to Internet/Intranet

Connect PC to internet, verify that it can connect to ETG

Firewall issues

No bridging to Ethernet devices inside gateway is possible

Ethernet

VPN Client Overview

When connecting a PC to a remote ETG 302x the ETG302x acts as a VPN server. You must run a

VPN client interface on the PC

VPN required for bridging to Ethernet devices connected to ETG

When connecting an ETG302x client to a remote ETG 302x the ETG302x client can act as a VPN client.

ETG302x VPN setup includes this client configuration.

Various VPN clients can be used: thegreenbow.com VPN client software

(recommended)

Trail version is available

VPN client service provided by Windows operating

systems XP, 2000, Vista (=S= provides a sample batch file to run this service)

VPN server

VPN

VPN

VPN server

VPN Client Configuration

Remote Gateway address from either DYNdns or IP address

Preshared key must match key setup in module. Used to authenticate the connection

IKE encryption used for key authentication

VPN Configuration

Module Remote Address = PC or

different ETG

Preshared key = same in both VPN

Client & Module

Tunnel Mode - use if you wish to

connect to devices on inside of gateway

Remote LAN virtual LAN must match

in Thegreenbow and in the module (1)

Module Setup

1

1

PC connects to internet Firewall issues

Launch tunnel connection Authentication, tunnel created

When tunnel is established, communication to ETG and attached devices is possiple

No VPN tunnel necessary for serial out of ETG Most likely want to use VPN for security access

PC to ETG

tunnel Ethernet

Etg1 calls Etg2

Etg2 calls back network

On first data exchange attempt, tunnel is created

Data exchange takes place

ETG to ETG

tunnelEthernetEthernet

ETG1 ETG2

Etg1 calls Etg2

Etg2 calls back network

On first data exchange attempt, tunnel is created

PC could also be added and can connect to either ETG and to

connected PLCs

ETG to ETG, PC to ETG

tunnelEthernetEthernet

tunnel

ETG1 ETG2

Exercise 1Module 14 DemoConfiguring an ETG for ESM Modem Operation