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[SMF/UPF] remote GTPC/GTPU IP address and TEID not updated in rx GTPv2C Modify Bearer Request #1367

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pespin opened this issue Feb 15, 2022 · 4 comments
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[SMF/UPF] remote GTPC/GTPU IP address and TEID not updated in rx GTPv2C Modify Bearer Request #1367

pespin opened this issue Feb 15, 2022 · 4 comments
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New Feature New features to implement

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@pespin
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pespin commented Feb 15, 2022 •
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The SGW can send "Modify Bearer Request" at any time which asks the PGW to change the SGW-side GTPC and/or GTPU IP Address, as well a the local TEIC or TEID.
This is done by means of IE "Sender F-TEID for Control Plane".
IE group "Bearer Context" also seems to provide some information per bearer in the "S5/8-U SGW F-TEID", "S12 RNC F-TEID", "S4-U SGSN F-TEID" sub-IEs.

Similarly, same kind of stuff has to be done in GTPv1C when receiving an "Update PDP Context Request" containing any of the IEs "Tunnel Endpoint Identifier Data I", "Tunnel Endpoint Identifier Control Plane", "SGSN Address for Control Plane", "SGSN Address for User Traffic".
This kinf of update is used for instance when an HNBGW sets up a direct GTPU tunnel between the HNB and the GGSN.

Right now, open5gs-smfd is not updating the following fields when receiving such a message:

  • remote TEIC (sess->sgw_s5c_teid)
  • remote TEID (bearer->sgw_s5u_teid)
  • GTPC remote address (sess->sgw_s5c_ip)
  • GTPU remote address (bearer->sgw_s5u_ip)

The GTPC ones should be fairly straightforward to update in smf_s5c_handle_modify_bearer_request(). However, of the GTPU part requires some sort of signalling over PFCP to tell the UPF to update the sgw_s5u_teid and sgw_s5u_ip.

Relevant specs:

  • 3GPP TS 29.274 7.2.7 "Modify Bearer Request"
  • 3GPP TS 29.060 7.3.3 "Update PDP Context Request"
@pespin pespin mentioned this issue Feb 15, 2022
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@acetcom
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acetcom commented Feb 19, 2022

Hi @pespin

That feature is not implemented yet. I don't have plans to implement this for the time being as I have other work to do. Of course, contributions are always welcome.

Thanks a lot!
Sukchan

@laf0rge
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laf0rge commented Feb 21, 2022

just for the record: This is a very normal procedure every time the subscriber moves between SGW serving areas. at that point, the SGW changes, and hence the PGW needs to update its context.

pespin added a commit to sysmocom/open5gs that referenced this issue Feb 23, 2022
@pespin
[SMF] UpdatePDPContext: forward update of remote TEID+IPaddr to UPF
1827bbb 
Updating the remote GTP-U IP address and/or TEID on the GGSN is a common
practice, used for instance by an SGSN in a UTRAN network to connect an
HNB(GW) to exchange GTP-U directly with the GGSN. It is also used in
general when doing handovers.
When receiving a UpdatePDPContext with the new address, we need to
forward the update to the UPF so that it takes it into account when
forwarding packets.

This patch only implements updating the information towards the UPF when
GTPv1C is used. Similar approach for GTPv2C (upon receival of Modify
Bearer Request) is still unimplemented.

Related: open5gs#1367
acetcom pushed a commit that referenced this issue Feb 23, 2022
@pespin
[SMF] UpdatePDPContext: forward update of remote TEID+IPaddr to UPF (#…
5ad1b18 
…1383)

* [SMF] typo fixes in commented code

* [SMF] Fix early err return handling UpdatePDPContextRequest

* [SMF] UpdatePDPContext: forward update of remote TEID+IPaddr to UPF

Updating the remote GTP-U IP address and/or TEID on the GGSN is a common
practice, used for instance by an SGSN in a UTRAN network to connect an
HNB(GW) to exchange GTP-U directly with the GGSN. It is also used in
general when doing handovers.
When receiving a UpdatePDPContext with the new address, we need to
forward the update to the UPF so that it takes it into account when
forwarding packets.

This patch only implements updating the information towards the UPF when
GTPv1C is used. Similar approach for GTPv2C (upon receival of Modify
Bearer Request) is still unimplemented.

Related: #1367
@pespin
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pespin commented Feb 23, 2022

So after 1383 has been merged, the current status for this ticket is that:

  • GTPv1C (UpdatePDPContextRequest/Response): TEID+IPaddr are properly updated in both SMF and UPF.
  • GTPv2C (ModifyBearerRequest/Response): TEID+IPaddr are still NOT updated in SMF nor in UPF.

@pespin pespin mentioned this issue Mar 16, 2022
Closed
@acetcom acetcom mentioned this issue Mar 30, 2022
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@acetcom acetcom added the New Feature New features to implement label Apr 11, 2022
acetcom added a commit that referenced this issue May 12, 2022
@acetcom
X2 handover with SGW change (#1367, #1459)
4d2f772
@pespin pespin mentioned this issue Jun 8, 2022
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@pespin
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pespin commented Jun 13, 2022

Hi @acetcom , IIUC you already implemented what was missing for GTPv2C in 4d2f772? So, SMF is already updating the GTPv2U remote IP address on the UPF?

If that's the case, I think this ticket can be closed.

@acetcom acetcom closed this as completed Jun 13, 2022
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@laf0rge @pespin @acetcom