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Does core network need to implement GTP-based or PMIP S5/S8 interface if it is combined S-GW/P-GW?

+2 votes

Hi all

Because combined S-GW/P-GW is one node, so do we still need to implement the connection between them?
Is it necessary for core network to implement GTP-based or PMIP based S5/S8 interface if it is combined S-GW/P-GW?

Is there any 3GPP spec mention about combined S-GW/P-GW? what is the cons and reasons to do this?


posted Jan 16, 2017 by Jim Tan

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1 Answer

0 votes

To server small no of users, EPC Lite product can be used. EPC lite has all the necessary component of LTE network to provide LTE network services to its users. For emergency/defense services, network in a box is popular solution. Putting MME, SGW and PGW into a single box, does not mean all the interfaces such as S11, S1-U, S5/S8 have been merged. From the hardware point of view, all the nodes are packed together so that network can be deployed in fast manner.

Now coming to your question combining the SGW and PGW means, need to re-write application so that it can serve all the interfaces such as S11 towards MME and SGi towards external network. Traffic for S5/S8 interface would be mapped at the application level. It saves hardware cost and avoid data plane delay. Disadvantage what I realized is as part of mobility, # of handover messages will landed up more at the same combined node.

answer Jan 16, 2017 by Harshita
Thank you for your reply. So in this case, there is no two options in S5/S8 interface(GTP based or PMIP based)? Is there any spec talk about combined S-GW/P-GW?
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+1 vote

Hi all

I find some information on internet of this question "What pros and cons of combined S-GW/P-GW?".
However it did not write the reasons.

I find this answer in

It said that combined S-GW/P-GW have these advantages:
Reduced signaling overhead (S5 and S8 would be internal)
Fewer hops on the bearer path
Less backhaul
Reduced signaling on the S7 interface
Lower session requirement for the PGW

I cannot understand why it can reduce signaling on the S7 interface.
and although I probably know other advantages' reason, I am not sure.
Someone please tell me.


0 votes

As per LTE core network architecture, MME shares S11 interface with SGW and SGW has S5/S8 interface with PGW.
I went through Create Session Response message sent by SGW to MME and found PGW-C and PGW-U tunnel ids.
I want to know what MME does with these PGW-C and PGW-U tunnel Ids ?

0 votes

Can someone suggest me the below requirements:
1. I want to test S6a interface so what are the best possible testing tools available. Open source are highly preferable
2. I want to test S5/S8 interface so what are the best possible testing tools available. Open source are highly preferable

+2 votes

while going through 3GPP 23.401, I stopped at PGW functionality. The following statement was written.
"If a UE is accessing multiple PDNs, there may be more than one PDN GW for that UE, however a mix of S5/S8 connectivity and Gn/Gp connectivity is not supported for that UE simultaneously". I couldn't understand it. Can someone please elaborate it.

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