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Rank 1: Guest
Posts: 13
Registered: ‎17-08-2009

Vodafone Mobile Broadband - PDP Data And Header Compression?

Hello

After installing Vodafone mobile connect, i checked up my modem settings.

at+cgdcont? command brings up two different internet CID profiles:

+CGDCONT: 2,"IP","internet","0.0.0.0",0,0
+CGDCONT: 4,"IP","internet","0.0.0.0",0,1

I've found out the last two flags mean PDP Data compresion, and PDP Header compression.

Can you elaborate more in this subject, and explain what they actually do?
For some reason the other profile has PDP Header compression on, why is this useful?

BR,
Poppe
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Moderator (Retired)
Posts: 5,931
Registered: ‎04-08-2008

Vodafone Mobile Broadband - PDP Data And Header Compression?

Hey Poppe, and welcome B-)

I'll be honest... this is a little beyond my understanding. Is there something wrong with your modem?

If there is a problem, please let us know, and I'm confident we can find a resolution - it's not really part of our support role to elaborate on the technical in's and out's of a type of technology I'm afraid, but maybe one of the forum members is willing to help you better understand this topic?


Daz

eForum Team


PS... why not check out our Online Services today for a look at Online Billing? It's a great way to manage your account with us, and so simple :P
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Rank 1: Guest
Posts: 13
Registered: ‎17-08-2009

Vodafone Mobile Broadband - PDP Data And Header Compression?

Hello

Both of the profiles work, but i'd like to know what they do.
What's the use of PDP Data compresion and PDP Header compression?

Is the connection supposedly faster if i use the profile that has compression turned on?

After a search on the internet, i can find lots of pages tell you can use these features. But none of them explain what they actually do.

It's like a big button in a computer, that nobody knows what it does. I think it's weird.

1 = turned on
0 = turned off
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Rank 6: Frequent Poster
Posts: 103
Registered: ‎04-04-2009

Vodafone Mobile Broadband - PDP Data And Header Compression?

Both of the profiles work, but i'd like to know what they do.
What's the use of PDP Data compression and PDP Header compression?

Simplified so not entirely accurate... PDP (Packet Data Protocol) is a protocol similar in design to the Internet's PPP (Point to Point Protocol). PDP's job is to identify the data streams (PDP contexts) of the various uses, provide some control to these streams, provide parameters to the end device and isolate the traffic plane from the control plane (i.e. hide the underlying network from the users).

Like all packet based transports - there is a header section containing the user identifying information, as well as some control information - and a data section containing the user data. There is also a concept where the percentage of header to data provides the protocol's overhead value. Overhead is effectively bits that must be sent for correct operation - but the operator (Vodafone) won't necessarily see any direct revenue from those bits. So compression is sometimes used to try and improve this overhead value.

Therefore, Header compression - compresses items in the header that do not have to be processed every hop; Data compression - compresses the users data.

So therefore; very similar to the PPP header & data compression which you will find lots of information about.
Is the connection supposedly faster if i use the profile that has compression turned on?

Theoretically - yes. But I doubt you will notice it in practice - especially on 3G (UMTS). You might notice some improvement when using GSM.
After a search on the internet, i can find lots of pages tell you can use these features. But none of them explain what they actually do.

It's like a big button in a computer, that nobody knows what it does. I think it's weird.

All the standards for the European mobile networks are developed/written by the 3GPP (3rd Generation Partnership Project). So the exact information you are looking for can be found at the site: (http://www.3gpp.org/specifications). The ratified standards are free for the public to read.

Knock yourself out - there are massive amounts of documentation on that site.

I once heard a quote that - for the Apollo space program if you put all the documentation generated end-to-end - it would reach from Houston to London. If you put all the documentation generated by the GSM project (now 3GPP) end to end it would reach around the earth. And since I heard that quote - some 10 years ago - the 3GPP project has continued to generate documentation. The latest new architecture was ratified late last year - with ongoing updates still being produced. That is not counting the updates to all the previous architectures and associated standards.
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Community Manager (Retired)
Community Manager (Retired)
Posts: 8,790
Registered: ‎30-11-2007

Vodafone Mobile Broadband - PDP Data And Header Compression?

Hi poppe,

Well Heady has beaten us there!

I'll be honest, with us being a technical help forum, we have a mass of knowledge on how to fix things, but can sometimes be a little weaker on topics such as how things work. Still, I think Heady's covered that off there, thanks Heady!

Tom

eForum Team
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