Hi Pablo,
I have not got a chance to go through -16 closely to correlate to our email
discussions, but I have the following comments.
Previously:
-------------
In 5.3, for uplink traffic, the GW has End.M.GTP6.D for the UPF address B and
the gNB does not need to know the existence of GW. For downlink traffic, the
UPF knows there is a GW and put the GW::TEID in the SRH. Why not make GW
invisible to UPF as well and just use gNB::TEID, and then have gNB/96 as
End.M.GTP6.E on the SRGW? You can still put GW in the SRH to steer traffic
through the GW.
[PC] That is a valid point. I'll think about it and get back to you.
-------------
I think we should get a conclusion on this.
Similarly, even for the drop-in mode, SGA can use (U::TEID, C1; SL=3) for
uplink traffic instead of using (U::1, SGB::TEID, C1; SL=3). Then, on SGB, U/96
can be a End.M.GTP6.E. With that, we don't need End.M.GTP6.D.Di anymore, and
End.M.GTP6.E will be like others - checking for "Segments Left != 0" instead of
" Segments Left != 1" (no need to use SRH[0] as destination address of the GTP
packet).
BTW - 5.4 drop-in mode only talks about uplink traffic. I suppose downlink
traffic is the same - either use End.M.GTP6.D.Di or just use End.M.GTP6.D with
(gNB::TEID, ...).
In fact, drop-in mode is not thing special any more - it's just that there is
an SGB attached to the UPF as well as an SGA attached to the gNB like in 5.3.1.
Please see the following additional comments (more may come when I get a chance
to comb through).
(Z,A) or (Z,A) is used to denote the source/destination address of PDU packet.
Then, for End.M.xxx behaviors, A is used to denote something different. Better
change the A to a different letter in either the PDU packets or in the
End.M.xxx behaviors to avoid confusion.
End.M.GTP6.D has the following operation:
S02. Copy the GTP TEID to buffer memory
...
S08. Write in the last SID of the SRH the Args.Mob.Session
based on the information of buffer memory
With that, the U2::1 should be changed to U2::TEID in the following:
5.3.1.1. Packet flow - Uplink
The uplink packet flow is as follows:
UE_out : (A,Z)
gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 unmodified
(IPv6/GTP)
SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> B is an End.M.GTP6.D
SID at the SRGW
S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z)
C1_out : (SRGW, U2::1)(A,Z) -> End with PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6
Thanks.
Jeffrey
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