On Wed, Sep 5, 2018 at 3:56 AM Sridhar Bhaskaran < [email protected]> wrote:
> 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. > > I checked in IETF IANA UDP assignments, pfcp 8805 udp Destination Port number for PFCP [Kimmo_Kymalainen <https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?&page=112#Kimmo_Kymalainen> ] [Kimmo_Kymalainen <https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?&page=112#Kimmo_Kymalainen> ] 2017-05-08 for packet forwarding control protocol. What is PFCP, is it GTP-U? Behcet > Thanks > Sridhar > 3GPP CT4 Delegate > _______________________________________________ > dmm mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/dmm >
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