15 Replies Latest reply: Feb 19, 2014 8:09 PM by jack chan RSS

IP address assignment in GPRS

Cryptoman Novice

I have been trying to get some information on how a GPRS module can communicate bidirectionally with a PC that is connected to the Internet via a static IP address. I have reviewed the available posts on this forum as well as a few others and have read a few tutorials on this topic. Following is what I managed to gather so far and would like to get the expert opinion of fellow members on this topic.

 

Please feel free to add your own suggestions and notes as you see fit.

 

1 - The PC cannot directly initiate a connection with the GPRS module. A data session ALWAYS has to be initiated by the GPRS module first before the PC can talk to it.

 

2 - The PC is able to talk to the GPRS module only via the dynamic IP address that is assigned by the GGSN on the network. The PC is able to access this IP address ONLY AFTER the GPRS module initiates a data session. This IP address can change if the GPRS connection is terminated for whatever reason (i.e. bythe user or the network or due to an unexpected link failure). In case of such terminations, the GPRS module has to re-initiate a new PDP session for the PC to talk to the module again. Otherwise, the PC will not be able to send data to the GPRS module because it does not know the renewed IP address  assigned to the module after a reconnection to the GSM network.

 

3 - As discussed in M2M.com's various posts, the only way for the PC to initiate a data session with the GPRS module is to send an SMS with a content equivalent to "call home" that prompts the GPRS module to start a data session to receive the pending data from the PC.

 

4 - There is no method to predefine a table of fixed IP addresses on a GPRS module to use during data sessions. The IP address assignments are ALWAYS done by the GSM network that the GPRS module is registered to and they cannot be known or fixed in advance. No assumptions can be made on the pool of IP addresses that can be assigned to the GPRS module.

 

Thank you for all your input and interest in this discussion.

 

Regards...

  • Re: IP address assignment in GPRS
    falewis68 Novice

    Some operators do offer a Fixed IP address for your mobile devices. You will still need to initiate the GPRS session to establish communication with the device; however, the IP address would be the same for every session. Please note that this is not necessarily a Public addressable IP address  but a Private IP address that is accessible via your VPN connectivity to the device.

    • Re: IP address assignment in GPRS
      Cryptoman Novice

      Thanks for your response.

       

      My understanding is although there may be a VPN between a GPRS device (with a static IP) and a PC, it is not possible for the PC to start a communication with the GPRS device. Is that the case?

       

      thanks...

  • Re: IP address assignment in GPRS
    Tony Yang Apprentice

    GSM operator can offer you a SIM card with Static IP address. VPN is also a good choice.

    • Re: IP address assignment in GPRS
      Cryptoman Novice

      Hi Tony,

       

      Thanks for your response.

       

      Having a SIM with a static IP address sounds like a good option. Can you recommend a reference or an information source where I can find out a bit more about SIM with a fixed IP address and using a VPN for GPRS devices?

       

      Regards...

      • Re: IP address assignment in GPRS
        Newbie

        Hi,

        You may just simply ask your local mobile operator. The solution will be as follow:

         

        For m2m, I assume your device with mobile operator SIM cards and communicate with your server in your site.

        Mobile operators can offer fixed private IP for each SIM which is done by operator, you have nothing to do on it. After that, you need to set up a VPN on internet (Low cost solution), or a leased line (Higher cost but more security and commited performance) between your server site to mobile operator data center. If VPN is used, normally this will be IPSec VPN by routers and firewall setup.

         

        Usually, mobile operators can offer you this end to end solution.

        Ray

        • Re: IP address assignment in GPRS
          Cryptoman Novice

          Hi Ray,

           

          Thanks for these valuable pointers. So the VPN is going to be established between my servers and the mobile operator's data centre. That is a good starting point for me. I guess I will need to check that with the operator too to see if they are OK with the VPN setup and there are no problems as far as they are concerned.

          From a security perspective, once I establish my VPN, does the mobile operator have access to the raw data during its transit at all or is it end-to-end secure?

           

          Regards...

          • Re: IP address assignment in GPRS
            Newbie

            I believe this is not end-to-end secure. The VPN is just setup in internet between operator data and your server site. This is very complex solution for end-to-end data security. May be you can consider in application layer (SSL VPN).

            • Re: IP address assignment in GPRS
              Cryptoman Novice

              Yes Ray. That's what I was thinking as well. Once data is in the operator's network, it is visible to them at will. Therefore, encapsulating the application data into a secure packet that appears as random data to the operator will be the safest option.

               

              Regards...

      • Re: IP address assignment in GPRS
        jack chan Novice

        Hi crytoman

        I recommend some sources and devices for you!

        www.e-lins.com/EN/

  • Re: IP address assignment in GPRS
    Newbie

    The problem you have, most if not all mobile networks only support Mobile Originate (MO) PDP contexts. So you will only ever be able to intiate PDP context from the mobile end.

  • Re: IP address assignment in GPRS
    Newbie

    Although I don't yet access to the API, doesn't it have a way to retrieve the SIM's IP address from its ICCID or IMSI?

     

     

    I believe Vodafone's GDSP (their M2M solution) does this.

  • Re: IP address assignment in GPRS
    Newbie

    The usual way of doing this (in my experience) is requesting a private APN from your service provider. You then set up a RADIUS server on your side and connect this to the GGSN through an IPSEC tunnel. Once you have the RADIUS server up and running you can either assign your devices static IPs or (if you have many devices which is not online all the time) set up a link between the RADIUS server and the PC program/server where you are able to retrieve, based on the IMSI or ICCID, the current dynamically assigned IP address given to a device