Dear Dino, Some clarifications on your comments
>>> It was never clear to me and no one could ever explain exactly why a TEID is needed. I presumed for accounting reasons. But if there was a one-to-one mapping between tunnel and user, why couldn’t the inner addresses be used for accounting? [Sridhar] In EPC, each bearer has a GTPU tunnel. TEID identifies a tunnel and hence consequently a bearer. Once the bearer context is identified the QoS and charging policy applicable to the bearer is applied. So the purpose of TEID is not just for accounting. Its for QoS treatment, charging and bearer context identification. In 5G, each PDU session has a GTPU tunnel. So TEID identifies the PDU session whereas the QFI carried in GTPU extension header identifies the flow. So in 5G TEID + QFI is used for QoS treatment and charging. >>> How can packets be sent if the session is not setup. If the session is not setup, the encapsulator should have no state. And packets should be dropped locally and not go far to get an error back. This sounds architecturally broken. [Sridhar] The purpose of GTP-U error indication is to signal in band to the sender that a GTP-U tunnel endpoint (TEID) at the receiving side is lost for any reason. "No session exist" does not mean Session is not setup. "No session exist" scenario after a session setup can happen due to local error conditions, bearers released for administrative reasons etc. >>> You should explain in summary form the model the control-plane uses. Does it use TCP for reliability, does it use multicast, is it like a routing protocol, is it like a management protocol. What are the failure modes, the state/bandwidth tradeoffs. [Sridhar] Explaining all these in IETF draft is simply reproducing what is already there in TS 29.244. A reference to TS 29.244 should be enough. See section 6.4 of TS 29.244 for reliable delivery of PFCP messages. Thanks Sridhar 3GPP CT4 Delegate
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