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How is traffic flow differentiated between default and dedicated bearer?

+3 votes
186 views

Lets say UE has two bearers established - default and dedicated. Each has its own APN
How is traffic differentiated between these two bearer and on what basis?

Say APN = A for default bearer
APN = B for dedicated bearer

Say APN A has default bandwidth of 200 kbps

Say UE is sending packets beyond bandwidth of 200 kbps, will it use dedicated bearer? Who decides this?

Thanks.

posted Aug 17, 2015 by Alkesh Mehta

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1 Answer

+2 votes

Each has its own APN??

This part is not clear

you query is not clear

Let me tell you how it will work.

For every dedicated bearer there will a packet-filter associated to it.

If the dedicated bearer is GBR bearer. Then it will have a Guaranteed-Bandwidth associated with it along with Maximum Bandwidth.
For Eg Ded Bearer 1 has 2 filters, 1 uplink and 1 downlink with GBR 500kbps and MBR 600kbps

So, the data flow rate should be atleast 500kbps but should not exceed 600kbps

Now, let's consider a case of Non-GBR bearer
In this case every filter will have a Max-Bandwidth associated with it.
Eg: Dedicated Bearer 2 has 2 filters, 1 uplink and 1 downlink. MBR for the fitler is 500kbps.
So that filter can use bandwidth from 1kbps to 500kbps however it cannot exceed it.

There is one more term to consider in case of non-gbr bearers. APN-AMBR
This bandwidth is shared among all filters of non-gbr bearers

Eg: APN-AMBR for a bearer is 1000kbps
now let's say you have 10 filters which are part of non-gbr bearer and each has 150kbps max bandwidth. So, now PGW has to ensure that all of them together should not consume bandwidth over 1000kbps.

Hope this helped

Regards,
Peeyush Sharma

answer Aug 17, 2015 by Peeyush Sharma
Thanks Peeyush.

For APN, i meant that APN A is used for default bearer and B for dedicated bearer.

How can core direct UE to use particular APN/bearer in this case dedicated bearer when bandwidth for non-gbr is exceeded?
Alkesh

Let me tell you one thing. You cannot have a dedicated bearer for an APN without default bearer for it.
Let's say you have 2 APN. APN A and APN B
You cannot create Dedicated bearer with APN B without a default bearer for APN B.
You before making a dedicated bearer with some APN you need to have a default bearer for that APN too.

When we say APN they have a particular role to play
Let' say to make a VoLTE call you can create a IMS based APN which will allow only IMS related traffic. In this case default bearer will allow only IMS Signalling messages through it. For Voice and Video call dedicated bearer will be used.
Based on the filters and their precedence the incoming packet will be directed to any bearer.

Let's say you have APN B, this APN is used to http traffic or say your internet browing. In this case if you do not want to differentiate any service you can allow traffic to pass through default bearer only.

Regards,
Peeyush Sharma
Good explanation !
+1
Thank you for the appreciation :)
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