Saturday, June 13, 2009

Bearer Aware Applications?

This is it guys. The final truth. Bearer aware applications. I honestly dont know if that term means anything other than applications running on a mobile choosing the bearers based on the network availability. Am I right? Lets consider that I am correct and move ahead with the discussion.

For past few days I was trying to understand the end to end working of LTE, though my scope is limited to EPC. The whole bearer creations, modifications etc seems very good, but it is very much required to understand how they exactly effect the communication. Everything originates from the mobile device and network has to support what mobile is asking. I want to take iPhone here as an example. Lets say we are browsing web on the iphone. With Skype integration in iphone now we can make voip calls too. So I keep browsing and find something really interesting on streaming protocols which I want to share with my cousin in Germany. So I open up skype make an voip call start discussing the streaming project with him. This is the scenario.

We need to consider few things here. FIrst is the network support, then mobile phone operating system and third is the applications. With LTE the above scenario is very much possible, so we have network support. I want to have my basic default bearer established. When I start Safari a dedicated bearer is established with HTTP TFT. When I launch skype and start making a voip call I will have another dedicated bearer established with QoS supporting voice. The network is intelligent enough to handle this.

Its quite clear to me how the network behaves. The problem I am facing is mobile phone operating system. The bearers are established based on the mobile phone, lets call it as UE, request. So the question is does the UE OS support establishing multiple bearers. That is the support has to be present in the OS? So I did some research. What I found was little annoying. Few google searches landed me into nokia developer forum where people were discussing the same thing. Do N-series of Nokia support establishment of multiple PDP contexts? (referring to 3G here). I read developers facing problems while activating secondary pdp context. A link said Symbian v0.9.3 has support for establishing multiple PDP context to multiple APN;s and multiple secondary PDP contexts support. This mean the UE OS should have the support for establishing the multiple bearers. This support can be used by applications to establish individual bearer for each of them to run. The question here is how the network will be evaluated? Meaning how will application understand when to create a new bearer? Will mobile OS talk to the application here? How is the design?

This is where I am stuck.

Moving further. I am part of corporate network. Say my company decided to have its own APN and run an email server. So mobile phones can connect to that APN and have a dedicated bearer with a QoS established to retrieve emails. How is this done? If we buy a mobile phone the APN settings are pre-configured. Which means when ever you connect to the network a connection to mentioned APN is established. If my company has to have its own APN, where is that APN to be placed. When I was configuring Cisco 7200 I had a option to configure multiple APN's with a single GGSN IP address. This mean if organizations want to have a APN they need to talk to the service providers? Is there a way to have an APN outside the service provider network? The big question is am I asking the right questions here or missing something?

Folks, any ideas? Search is on to find answers to above.

This actually makes me think of changing my career line for while. May be I should go work for a service provider for a while, understand things better and get back to software. Anybody offering :-D


Anonymous said...


First, yes, u got it right here :-) It's the MS/UE currently to evaluate the application (L7) requirements and ask for a secondary PDP, mapping bearer QoS with the User IP L3 QoS. And guess, it's not there at all :-) Or let's say I've never seen this in practice even I have some experience with QoS in mobile networks... So yes, unfortunately so far there is no Bearer to User QoS mapping in the MS/UE afaik... It should be available with an IMS device, never seen such... So the only way for an operator to handle somehow the QoS is having different APNs with different QoS... But diff. IPs, which is not a problem, for IMS could be :) Well, with PCRF you could manage QoS, I think even network-initiated secondary PDPs should be working...

For the other part with the APNs I'm afraid there is some misunderstanding... It's OK, the APNs are configurable in the MS/UE if this is what you are asking... But at the other end (the network) the APNs are configured only by the operator. Even it's a corporate APN, corporate means it will be there in the GGSN, but there will be a separate VPN connection on Gi to the corporate network. So, yes, every company has a contract with the network operator for handling this. Well, your own RADIUS could be used if you wish for AAA :) But the APN is in the GGSN of your operator. And one GGSN IP is OK, this has nothing to do with the APNs.


Santosh said...

Thanks a ton for the detailed explanation. Appreciate it a lot.