Hi Pablo,
The IP adjacency to the UE is from the UPF, not from the gNB.
While gNB is an IP router, it is at the underlay. This is similar to the
following situation:
Host1 ---- EVPN PE1 --------- EVPN PE2 ---- Host2
Host1 and Host2 have IP adjacency, even though EVPN PE1 and PE2 are IP routers.
Host1 and EVPN PE1 are not IP adjacent.
Jeffrey
-----Original Message-----
From: Pablo Camarillo (pcamaril) <[email protected]>
Sent: Friday, June 4, 2021 12:52 PM
To: Jeffrey (Zhaohui) Zhang <[email protected]>
Cc: [email protected]
Subject: RE: [DMM] [spring] note: WGLC on draft-ietf-dmm-srv6-mobile-uplane-11
[External Email. Be cautious of content]
Hi Jeffrey,
Why do you say there is no IP adjacency from gNB to UE?
In the downlink, the gNB receives an IP packet from the UPF destined to itself.
The gNB decapsulates such packet, and forwards the inner-exposed packet to the
UE. Assuming the inner-exposed packet is IPv4, in such case the IPv4
Destination Address is the one of the UE.
RFC1812: "Adjacent - reachable without going through any IP routers"
As far as I know, there is no IP router in between the gNB and the UE. Can you
please clarify?
Cheers,
Pablo.
-----Original Message-----
From: Jeffrey (Zhaohui) Zhang <[email protected]>
Sent: martes, 1 de junio de 2021 16:04
To: Pablo Camarillo (pcamaril) <[email protected]>; [email protected]
Subject: RE: [DMM] [spring] note: WGLC on draft-ietf-dmm-srv6-mobile-uplane-11
Hi Pablo,
Let me pull this up:
-----------
Zzh4> gNB is certainly an IP device but its IP adjacency is in the "underlay"
(transport network) not at the "overlay" (towards the UE).
[PC5] The End.DX4 behavior (or the others) are not limited or restricted by
"underlay" vs "overlay" IP adjacencies. The behavior is the same: remove the
encaps, forward on a particular IP adjacency (regardless of its type).
Zzh4> In the wireline/IETF VPN case, there is PE-CE IP adjacency. Traffic from
CE is forwarded based on IP lookup in the VRF, whether the traffic to the CE
requires IP lookup or not (i.e. whether per-CE or per-VPN label is used, or
whether END.DT4/6/X is used).
Zzh4> In case of gNB, UE-gNB is not IP adjacency and traffic to/from a UE does
not have IP lookup (based on the inner IP header) at the gNB.
---------
As I pointed out in zzh4>, the point is that there is *no IP adjacency* between
UE and gNB.
Practically, a device can implement the END.DX4/6 behavior to forward IP
traffic over non-IP adjacencies. It's just that RFC8986 specifically calls out
IP adjacencies. You may want to point it out and see if SR folks have any
concerns.
Jeffrey
Juniper Business Use Only
Juniper Business Use Only
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