On Mon, Feb 26, 2018 at 5:33 PM, Voyer, Daniel <daniel.vo...@bell.ca> wrote: > Tom, > > In respect of this current draft, and highlighted by Pablo’s comments, is to > propose adding to this draft the use of encapsulation as default behavior for > v4/v6 traffic. > > The use of EH insertion is totally the operator’s discretion, within the > operator domain if the operator chose to. > Right, EH insertion could be at an operators discretion. But then so is deploying proprietary IP protocols, overloading standard protocol fields with proprietary info, rearranging IP headers, using IPv10, etc. Doing these sort of things are possible and actually common in closed networks, but they are not interoperable standards.
I'd also point out that the issues raised in the 6man discussion were material and raised fundamental questions if header insertion is robust even in a controlled domain. Even if the argument is that EH insertion will only ever be done in a controlled domain, these issues still need to be addressed I think. Tom > I think Pablo’s proposition make sense. Thoughts ? > > dan > > > On 2018-02-26, 3:24 PM, "Tom Herbert" <t...@quantonium.net> wrote: > > On Mon, Feb 26, 2018 at 12:05 PM, Pablo Camarillo (pcamaril) > <pcama...@cisco.com> wrote: > > Hello authors, DMM, > > > > > > > > I have reviewed your I-D on SRv6 for mobile user-plane and I would like > to > > make some proposals. I have already discussed and brainstormed the > details > > with some of the authors of the draft and they agree to this changes, > > however I would like to get the WG feedback on it. > > > > > > > > Thank you, > > > > Pablo. > > > > > > > > I believe its straightforward to support IPv4 UE traffic by doing SRv6 > with > > T.Encaps behavior. Hence, I think this should be documented in the > draft. > > > > The encapsulation behavior should be the default one, both for IPv4 and > IPv6 > > UE traffic. However, a specific provider is allowed to do SRH insertion > > within a controlled domain > [draft-voyer-6man-extension-header-insertion-02] > > for UE IPv6 traffic. > > Pablo, > > That draft received substantial pushback on 6man list. EH insertion is > not allowed by RFC8200 and a host of points were raised why it > shouldn't be allowed. The authors have not responded to this feedback > yet. Also, IMO, the argument that it's okay to do this within a > controlled domain is weak, such an argument could be used to pretty > much justify anything one might do with protocols. > > Tom > > > > > Also, in order to reduce overhead at the UPFs when using encapsulation, > I > > would replace the End.B6 function for a new End.MAP function. > > > > For example, if we consider the following topology: > > > > UE----gNB----UPF1----UPF2 > > > > > > > > Then the uplink packet flow for the basic mode would look like this: > > > > UE_out: (A, Z) > > > > gNB_out: (gNB, U1::1) (A, Z) -> T.Encaps <U1::1> > > > > UPF1_out: (gNB, U2::1) (A, Z) -> End.MAP > > > > UPF2_out: (A, Z) -> End.DT > > > > > > > > The End.MAP function is simply replacing the UPF1 SID for the UPF2 SID. > > > > > > > > Notice that using encapsulation, if you compare it with today user-plane > > using IPv6/GTP, the result is that SRv6 is just adding 40B of overhead > (IPv6 > > header), while GTP over IPv6 is using 56B (IPv6, UDP, GTP). > > > > > > > > ======= > > > > > > > > With respect to the aggregation mode, aside from using the encapsulation > > mode as described before, I would also like to add a note on the I-D on > the > > fact that we can support the aggregation mode without changes in the N2 > > interface: > > > > The current I-D for aggregation mode assumes that the gNB (uplink) has > > knowledge of an SR policy that contains all the SIDs belonging to TE, > NFV > > and so on. Even though the I-D does not describe how the gNB is > retrieving > > this information, I would like to make a statement on the fact that > there > > are two alternatives: > > > > A. The N2 interface is modified in order to signal a SID list to the > gNB. > > > > B. The N2 interface is not modified. In this case, we signal through > the N2 > > interface an SRv6 BindingSID, that the gNB is going to resolve into a > SID > > list via an SDN controller either using PCEP, reverse DNS lookup or > LISP. > > > > > > > > I’m aware that the I-D focuses on the user-plane, however I believe it’s > > important to state this alternatives since it simplifies the adoption > and > > reduces impact in the existing mobile architectures (without going into > the > > details on the mechanisms for each one of the alternatives of LISP, > PCEP, > > reverse DNS-lookup). > > > > > > > > ======= > > > > > > > > On the other hand, the current I-D proposes a mechanism for stateless > > interworking with legacy access networks that doesn’t support SRv6 (SGW > > and/or eNB). This mechanism presented in the I-D is limited to IPv4/GTP > > legacy networks. I would like to propose a mechanism to support > interworking > > with legacy gNBs that does not support SRv6 but do support IPv6/GTP. > > > > The main benefit comes from the fact that we can leverage an SRv6 > BindingSID > > to have remote classification and steering of the UE traffic over an SR > > policy [draft-filsfils-spring-segment-routing-policy]. > > > > > > > > In this scenario, I propose that we add the notion of an SR GW -as the > > current stateless interworking node in the I-D-. This SR GW can be > either a > > software based platform -e.g. VPP- or any existing router -the > mechanism is > > simple and can be supported in existing HW-. This SR GW receives > through the > > control plane the SR policies and installs the required Binding SIDs. > > > > > > > > Then, for any UE connecting to a gNB, the N2 interface is going to > signal an > > IPv6 address and a TEID. However, the difference is that with this new > > mechanism the IPv6 address that we are going to signal is going to be an > > SRv6 BindingSID instantiated at the SR GW. > > > > > > > > The overall workflow is the following: > > > > > > > > Uplink > > > > Note: S1, S2 represent service functions and C1 represents a node for TE > > purposes > > > > UE sends its packet (A, Z) on a specific wireless bearer to its gNB > > > > gNB’s CP associates the session from the UE (A) with IPv6 address B and > TEID > > T (N2 interface unchanged) > > > > gNB_out: (gNB, B) (GTP: TEID T) (A, Z) ;; > Interface N3 > > is unchanged > > > > SR_GW_out: (SRGW, S1) (U2::1, C1; SL=2)(A, Z) ;; new End.GTP.UP > > > > S1_out: (SRGW, C1) (U2::1, C1; SL=1)(A, Z) > > > > C1_out: (SRGW, U2::1) (A, Z) ;; > > assuming PSP > > > > UPF2_out: (A, Z) > ;; > > End.DT > > > > > > > > Downlink > > > > UPF2_in: (Z, A) > > ;; UPF2 maps the flow with SID list <C1, S1, SRGW::TEID, gNB> > > > > UPF2_out: (U2::1, C1) (gNB, SRGW::TEID, S1, SL=3) (Z, A) ;; T.Encaps > > > > C1_out: (U2::1, S1) (gNB, SRGW::T, S1, SL=2) (Z, A) > > > > S1_out: (U2::1, SRGW::TEID) (gNB, SRGW::T, S1, SL=1) (Z, A) > > > > SR_GW: (SRGW, gNB)(GTP: TEID=T)(Z, A) ;; > > End.GTP.DN > > > > gNB_out: (Z, A) > > > > > > > > The key points are: > > > > - gNB is unchanged and encaps into GTP (N3 interface is not modified). > gNB > > only needs to support IPv6 which is currently common in existing > > deployments. > > > > - 5G Control-Plane (N2 interface) is unchanged: 1! IPv6 address (i.e. a > BSID > > at the SR GW) > > > > - SR GW removes GTP, finds SID list related to IPv6 DA (BSID), add SRH > with > > SID list > > > > - Same TE, NFV and scale properties as Aggregation mode > > > > - There is NO state for the downlink at the SR gateway > > > > - There is simple state in the uplink at the SR gateway (notice that > since > > we are leveraging the aggregation mode, we expect few SR policies on > this > > node. SR policies are shared across UEs) > > > > - As soon as the packet leaves the gNB (uplink), the traffic is > SR-routed. > > This simplifies considerably network slicing. > > [draft-hegdeppsenak-isis-sr-flex-algo]. > > > > - Traffic is already classified and steered into an SR policy when it > > arrives to the SR GW. > > > > > > > > Finally, I believe that this mechanism is so simple, that it would be > > trivial to implement it in VPP > [https://wiki.fd.io/view/VPP/What_is_VPP%3F] > > . Hence if the working group believes that this is interesting work and > we > > add it to the I-D, I will analyse how to implement it in this platform. > > > > > > _______________________________________________ > > dmm mailing list > > dmm@ietf.org > > https://www.ietf.org/mailman/listinfo/dmm > > > > _______________________________________________ dmm mailing list dmm@ietf.org https://www.ietf.org/mailman/listinfo/dmm
