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How MME selects P-GW?

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How MME selects P-GW?
posted Oct 2, 2016 by Bhagyashree R

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2 Answers

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During the attach procedure, MME fetches the subscription profile the HSS. For this purpose it sends Update-Location-Request message to HSS and get back the "Update Location Answer" in response from HSS. Update Location Answer message carries " MIP6-Agent-Info " AVP within the APN-Configuration AVP.

MIP6-Agent-Info AVP contains PGW identity as an IP address (MIP-Home-Agent-Address) or FDQN (MIP-Home-Agent-Host).
Based on that MME builds and sends Create Session Request message to SGW and in turn SGW builds and sends Create Session Request message to the PGW.

Along with MIP6-Agent-Info AVP, PDN-GW-Allocation-Type AVP would be present which actually tells IP address presents within the MIP6-Agent-Info AVP is either statically configured or dynamically.

Hope this level of information would help you.

answer Oct 2, 2016 by Harshita
Thank you Harshita for your detailed explanation.
0 votes

As additional, MME will query the PGW information to DNS core based on FQDN APN. DNS will send back the IP address of PGW to MME for create session request.

answer May 7, 2017 by Hana Pamora
Similar Questions
+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 http://www.cisco.com/c/dam/en/us/solutions/service-provider/mobile-internet/whitepaper_c11-577763_v1.pdf

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.

thanks

+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?

thanks

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