Re: [DMM] Comments to draft-hmm-dmm-5g-uplane-analysis-01

[Behcet Sarikaya <[e-mail]>]

Alex, user plane means data plane in 3GPP terminology.
Data plane versus control plane  separation to my knowledge has first been
introduced by 3GPP.

Behcet
PS. Maybe Sridhar can add some 3GPP standard quotes/references here.



On Fri, Oct 5, 2018 at 12:25 AM Alexandre Petrescu <
[e-mail]> wrote:

> Thank you very much for the clarification.
>
> I understand now that GTP is a user-plane function run in the network.
>
> - the UE (smartphone) never runs GTP.  I think this is worth putting in
>    the draft and state it as such, if we so believe.
>
> - it is strange for me to call it a User-Plane Function while the user
>    has no impact on it.  I think this abbreviation deserves
>    clarification.  We can suggest to 3GPP to change the name.
>
> (terms like data-plane/control-plane (not user-plane) are already in
> widespread use, and could be improved).
>
> Alex
>
>
>
> Le 03/10/2018 à 18:29, Sridhar Bhaskaran a écrit :
> >  >>A UPF is any function that can be executed on user traffic in mobile
> > network. Having said that however, I think the first UPFs that we will
> > see will be in the form of SGW, PGW.
> >
> > Even this is not accurate..
> >
> > A UPF is a _*5G system core network*_ entity whereas the SGW-U and PGW-U
> > are EPC core network entities. 5G core network has many differences from
> > EPC. To avoid confusion it should be noted that 5G NR radio can be
> > deployed with EPC as the core network and technically such deployments
> > can also be called as 5G deployments. But an UPF has no role in such
> > deployments.
> >
> > Some of the user plane functionalities of an UPF are completely
> > different from SGW-U or PGW-U.. Here are few differences (not exhaustive)
> >
> > 1. SGW-U and PGW-U --> one GTP-U tunnel per EPS bearer. No need of any
> > QFI marking. UPF on the other hand has one GTP-U tunnel per PDU session.
> > Different QoS flows within that PDU session are identified based on the
> > QFI marking. So a UPF has to support QFI marking.
> > 2. An UPF can support classification and encapsulation Ethernet frames
> > whereas a SGW-U/PGW-U has no requirement to support classification and
> > encapsulation of Ethernet frames.
> > 3. An UPF supporting Ethernet PDU session type may support ARP proxying
> > / IPv6 ND Proxying whereas a SGW-U/PGW-U have no such requirement..
> > 4. An UPF shall support RQI bit for reflective QoS. A PGW-U/SGW-U has no
> > such requirement.
> >
> > One may say that SGW-U / PGW-U also plays a role in user plane
> > forwarding and hence why not call it a UPF?  For the lack of a better
> > terminology, 3GPP has called the entity that performs the user plane
> > functionalities and features within a _*5G core network*_ as UPF. Those
> > functionalities are not exactly similar to EPC.
> >
> > Thanks
> > Sridhar
> >
> > On Tue, Oct 2, 2018 at 10:45 PM Arashmid Akhavain
> > <[e-mail] <mailto:[e-mail]>>
> wrote:
> >
> >     Not necessarily,____
> >
> >     __ __
> >
> >     You are correct in that PGW is a UPF, but a UPF is by no means
> >     limited to PGW. A UPF is any function that can be executed on user
> >     traffic in mobile network. Having said that however, I think the
> >     first UPFs that we will see will be in the form of SGW, PGW.____
> >
> >     __ __
> >
> >     Arashmid____
> >
> >     __ __
> >
> >     *From:*dmm [mailto:[e-mail]
> >     <mailto:[e-mail]>] *On Behalf Of *Behcet Sarikaya
> >     *Sent:* Tuesday, October 02, 2018 11:44 AM
> >     *To:* Shunsuke Homma <[e-mail]
> >     <mailto:[e-mail]>>
> >     *Cc:* dmm <[e-mail] <mailto:[e-mail]>>
> >     *Subject:* Re: [DMM] Comments to
> draft-hmm-dmm-5g-uplane-analysis-01____
> >
> >     __ __
> >
> >     UPF is virtualized PGW, folks.____
> >
> >     While PGW is fixed in location and possibly serving a large number
> >     of UE which are geographically in the area, that part of the city
> >     and that city itself, UPF can be deployed closer to the UE and thus
> >     probably serving smaller number of UEs____
> >
> >     __ __
> >
> >     Behcet____
> >
> >     __ __
> >
> >     On Mon, Oct 1, 2018 at 10:47 PM Shunsuke Homma
> >     <[e-mail] <mailto:[e-mail]>>
> >     wrote:____
> >
> >         Thanks Dark for your explaining what is UPF instead of me.
> >
> >         Alex, brief definitions of UPF are described in the section
> >         4.1.1.1 of
> >         this draft. Also, you can find more details in 3GPP TS23.501.
> >
> >         Regards,
> >
> >         Shunsuke
> >
> >         On 2018/10/01 20:32, [e-mail]
> >         <mailto:[e-mail]> wrote:
> >          > Hi Alex,
> >          > and sorry for jumping into the discussion...
> >          >  From my and (AFAIK) 3GPPs understanding your smartphone is a
> >         UE - sitting on the other side of RAN (gNB) - whereas a UPF
> >         normally is seen as UP entry (and exit) of the 5G core (i.e.
> >         handling all UP traffic in a true CP/UP split fashion).
> >          > Any other ideas on this? Can someone imagine any scenario
> >         where UE implements UPF?
> >          > Thanks!
> >          > Best Regards
> >          > Dirk
> >          >
> >          > -----Original Message-----
> >          > From: dmm [mailto:[e-mail]
> >         <mailto:[e-mail]>] On Behalf Of Alexandre Petrescu
> >          > Sent: Montag, 1. Oktober 2018 13:22
> >          > To: [e-mail] <mailto:[e-mail]>
> >          > Subject: Re: [DMM] Comments to
> >         draft-hmm-dmm-5g-uplane-analysis-01
> >          >
> >          >
> >          >
> >          > Le 01/10/2018 à 05:50, Shunsuke Homma a écrit :
> >          >> Hi all,
> >          >> # Sorry for my late response...
> >          >>
> >          >> Thank you for your lively discussion. It is very helpful for
> >          >> understanding points which need supplemental explanation and
> >         more
> >          >> consideration.
> >          >>
> >          >> Following the discussion, we're planning to update the I-D
> for
> >          >> covering the points below:
> >          >>
> >          >> - termination points of GTP-U
> >          >>     (RANs and UPFs terminate GTP-U in 5GS.)
> >          >
> >          > What is UPF?
> >          >
> >          > I understand UPF stands for User-Plane Function.
> >          >
> >          > Is my smartphone supposed to implement UPF?
> >          >
> >          > Alex
> >          >
> >          >> - setting QoS parameter of outer IP header
> >          >>     (Note that it's not just copy of inner to outer.)
> >          >> - problems related to IP connectivity (e.g., MTU in IPv6
> >         networks,
> >          >> IPv4 address duplication)
> >          >> - summary of network slicing in 5GS
> >          >>     (E.g., "slice is composed of SMF and UPFs. AMF selects
> SMF
> >          >> depending on NSSAI sent from UE, and SMF indicates to the UE
> >         the UPF
> >          >> that it is
> >          >> allocated.")
> >          >> - case studies on UPF selection
> >          >>     (E.g., parameters used for deciding destination UPF) #
> >         Optimizing
> >          >> forwarding paths solution might be realized with UPF
> selection
> >          >> mechanism in 3GPP architecture. (ID-LOC may be applied as
> such
> >          >> mechanism.)
> >          >>
> >          >>
> >          >> If you have any request for us on this updating, please let
> >         us know.
> >          >>
> >          >> Best regards,
> >          >>
> >          >> Shunsuke
> >          >>
> >          >> On 2018/09/08 3:28, Dino Farinacci wrote:
> >          >>>> I understand your point, but there is no guarantee for a
> >         precise QoS
> >          >>>> without using some sort of encapsulation being it GTP,
> >         RSVP, etc.
> >          >>>> Even with tunnels, there is no guarantee that all nodes
> >         along the
> >          >>>> path have the same hardware capability and can provide the
> >         same QoS
> >          >>>> treatment.
> >          >>>
> >          >>> There is existing hardware where the encapsulator copies
> >         inner QoS to
> >          >>> outer QoS. All routers along the path just process the
> >         outer QoS, no
> >          >>> changes to or new processing requirements for them.
> >          >>>
> >          >>>> For example, the code points in routers need to be
> >         configured to
> >          >>>> correctly handle the EXP bits in MPLS labels. But there is
> no
> >          >>>> guarantee that all routers can support all values. The EXP
> >         values
> >          >>>> get mapped to code points but the mapping is not always
> >         one to one.
> >          >>>> 3-bit EXPs can map to 4 code points on those routers with
> less
> >          >>>> capable H/W.
> >          >>>
> >          >>> That is a completely different matter. The discussion is
> about
> >          >>> remarking. And if one remarks to what the path cannot
> >         support, well
> >          >>> things don’t work as expected.
> >          >>>
> >          >>>> Slicing is almost the same. It allows user traffic to be
> >         mapped to
> >          >>>> what the operator provides.
> >          >>>> I agree with you that network should not touch/change
> original
> >          >>>> header bits. GTP or any other encapsulation easily allow
> >         for this.
> >          >>>> The question is whether we can provide for this without
> using
> >          >>>> encapsulation. IPv6 might be the answer. But as Tom
> >         pointed out,
> >          >>>> flow labels can still change in the middle. Is there any
> >         room for
> >          >>>> improvement. SIDs might present an opportunity.
> >          >>>
> >          >>> Not if they are encapsulated and routers don’t touch
> >         packets inside.
> >          >>>
> >          >>> Dino
> >          >>>
> >          >>>>
> >          >>>>
> >          >>>>
> >          >>>>
> >          >>>>
> >          >>>>> -----Original Message-----
> >          >>>>> From: Dino Farinacci [mailto:[e-mail]
> >         <mailto:[e-mail]>]
> >          >>>>> Sent: 07 September 2018 13:08
> >          >>>>> To: Arashmid Akhavain <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>> Cc: Tom Herbert <[e-mail]
> >         <mailto:[e-mail]>>; [e-mail]
> >         <mailto:[e-mail]>;
> >          >>>>> dmm <[e-mail] <mailto:[e-mail]>>
> >          >>>>> Subject: Re: [DMM] Comments to
> >         draft-hmm-dmm-5g-uplane-analysis-01
> >          >>>>>
> >          >>>>> I think you’ll still have the PHB re-marking issues I
> >         mentioned in
> >          >>>>> previous emails. The question is, should the network
> >         touch/change
> >          >>>>> any header bits of the packet the source has built. The
> >         answer
> >          >>>>> should probably be no.
> >          >>>>>
> >          >>>>> Having said that, GTP did it the right way, even though
> >         it cost in
> >          >>>>> header length.
> >          >>>>>
> >          >>>>> Dino
> >          >>>>>
> >          >>>>>> On Sep 7, 2018, at 8:26 AM, Arashmid Akhavain
> >          >>>>> <[e-mail]
> >         <mailto:[e-mail]>> wrote:
> >          >>>>>>
> >          >>>>>> Correct, flow labels can change along the path. That's
> >         why I like
> >          >>>>>> the slicing
> >          >>>>> concept.
> >          >>>>>> UEs can request services with different attributes,
> >         operators
> >          >>>>>> control how
> >          >>>>> service request are mapped into slices. I should look
> >         into the air
> >          >>>>> side of the business and see what happens there.
> >          >>>>>>
> >          >>>>>>
> >          >>>>>>
> >          >>>>>>> -----Original Message-----
> >          >>>>>>> From: Tom Herbert [mailto:[e-mail]
> >         <mailto:[e-mail]>]
> >          >>>>>>> Sent: 07 September 2018 11:13
> >          >>>>>>> To: Arashmid Akhavain <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>>>> Cc: Dino Farinacci <[e-mail]
> >         <mailto:[e-mail]>>;
> >          >>>>>>> [e-mail]
> >         <mailto:[e-mail]>; dmm <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>>>> Subject: Re: [DMM] Comments to
> >          >>>>>>> draft-hmm-dmm-5g-uplane-analysis-01
> >          >>>>>>>
> >          >>>>>>> On Fri, Sep 7, 2018 at 8:01 AM, Arashmid Akhavain
> >          >>>>>>> <[e-mail]
> >         <mailto:arashmid.akhavain@huawei...com>> wrote:
> >          >>>>>>>>
> >          >>>>>>>>
> >          >>>>>>>>> -----Original Message-----
> >          >>>>>>>>> From: Dino Farinacci [mailto:[e-mail]
> >         <mailto:[e-mail]>]
> >          >>>>>>>>> Sent: 06 September 2018 18:59
> >          >>>>>>>>> To: Arashmid Akhavain <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>>>>>> Cc: Tom Herbert <[e-mail]
> >         <mailto:[e-mail]>>; ta-miyasaka@kddi-
> >          >>>>> research.jp <http://research.jp>;
> >          >>>>>>>>> dmm <[e-mail] <mailto:[e-mail]>>
> >          >>>>>>>>> Subject: Re: [DMM] Comments to
> >          >>>>>>>>> draft-hmm-dmm-5g-uplane-analysis-
> >          >>>>> 01
> >          >>>>>>>>>
> >          >>>>>>>>>> Dino brought up a good point. Here is my two cents
> >         worth:
> >          >>>>>>>>>
> >          >>>>>>>>> Not sure which point.
> >          >>>>>>>>>
> >          >>>>>>>>>> As it was explained by Sridhar,  each UE can have
> >         multiple
> >          >>>>>>>>>> contexts. For
> >          >>>>>>>>> example, today some operators provide Data and VoLTE
> >         service to
> >          >>>>>>>>> their customers. These two services are represented
> >         by separate
> >          >>>>>>>>> GTP tunnels in the core with each tunnel tied up to a
> >         particular QoS.
> >          >>>>>>>>>>
> >          >>>>>>>>>> IPv4 didn't fit the bill when GTP work was under way
> >         as it
> >          >>>>>>>>>> couldn't uniquely identify multiple UE
> >          >>>>>>>>>
> >          >>>>>>>>> There is no reason why it shouldn’t. And IPv6, for
> this
> >          >>>>>>>>> use-case doesn’t add anything new other than a 28 bit
> >          >>>>>>>>> traffic-class/flow-label that can provide more bits
> >         for “new
> >          >>>>> functionality”.
> >          >>>>>>>>
> >          >>>>>>>>
> >          >>>>>>>> [Arashmid]  And that's what I meant. Having a flow
> >         label is handy.
> >          >>>>>>>> We can perhaps use it to identify different UE
> sessions.
> >          >>>>>>>>
> >          >>>>>>> Careful if you use the flow label to identify flows. It
> >         should be
> >          >>>>>>> considered "soft identification" since it might not
> >         always be
> >          >>>>>>> correct (it can be changed en route, isn't protected by
> any
> >          >>>>>>> checksum, anyone can set it however they want, etc.).
> >         It's useful
> >          >>>>>>> for things like ECMP that don't require 100% accuracy in
> >          >>>>>>> identifying flow. The flow label was briefly considered
> for
> >          >>>>>>> holding VNIs in network virtualization, but we
> >          >>>>> talked them out of that.
> >          >>>>>>>
> >          >>>>>>> Tom
> >          >>>>>>>
> >          >>>>>>>>>
> >          >>>>>>>>>> sessions/context/bearer. So, GTP and TEID did the
> >         job. But I
> >          >>>>>>>>>> agree with
> >          >>>>>>>>> Dino that IPv6 is much more versatile and is
> >         definitely worth
> >          >>>>>>>>> looking at as an alternative.
> >          >>>>>>>>>
> >          >>>>>>>>> That is not what I said. I said “IP could have solved
> >         this
> >          >>>>>>>>> problem”. And
> >          >>>>> “IP”
> >          >>>>>>>>> means either IPv4 or IPv6, or both at the same time.
> >          >>>>>>>>
> >          >>>>>>>>
> >          >>>>>>>> [Arashmid]
> >          >>>>>>>> How would we employ IPv4 to distinguish between
> >         different UE
> >          >>>>>>>> sessions.
> >          >>>>>>> TOS?
> >          >>>>>>>> Or you mean using encapsulation?
> >          >>>>>>>>
> >          >>>>>>>>>
> >          >>>>>>>>>> A factor worth considering though is that the use of
> >         GTP and
> >          >>>>>>>>>> TEID in mobile
> >          >>>>>>>>> core allows operators to deal with QoS on their own
> >         terms. The
> >          >>>>>>>>> tunnels with specific operator-controlled QoS are
> >         established
> >          >>>>>>>>> by the control plane between eNB, SGW, and PGW. UEs or
> >          >>>>>>>>> applications sitting in the UEs have no say in this.
> >         Well at
> >          >>>>>>>>> least till the packet exits operator's
> >          >>>>>>> network.
> >          >>>>>>>>>
> >          >>>>>>>>> The problem with one header, is that if you re-mark
> >         (known as
> >          >>>>>>>>> PHB markign in the ole days) you lose the original
> value.
> >          >>>>>>>>> Encapsulation is useful here because you can map the
> >         inner to
> >          >>>>>>>>> outer and anywhere along the path you can PHB remark
> >         on the
> >          >>>>>>>>> outer header. And then the destination can see the
> >         orignal
> >          >>>>>>>>> source’s ToS/QoS/TC/flow-label
> >          >>>>> whatever.
> >          >>>>>>>>
> >          >>>>>>>>
> >          >>>>>>>> [Arashmid] Yes, I agree. The original value is lost
> >         with PHB.
> >          >>>>>>>> Encapsulation certainly makes things easier and the
> >         inner to
> >          >>>>>>>> outer mapping trick has been widely used in IP and
> >         MPLS(multiple
> >          >>>>>>>> labels like service and transport)
> >          >>>>>>>>
> >          >>>>>>>>>
> >          >>>>>>>>>> Using the information in UE's IP packet header can
> >         jeopardise
> >          >>>>>>>>>> the above tight QoS control. I think going
> >          >>>>>>>>>
> >          >>>>>>>>> Not if you encapsulate. But note with SRv6, you can
> >         possibly
> >          >>>>>>>>> retain the original flow-label if the SID can retain
> >         those bits
> >          >>>>>>>>> before overwriting the destination address from the
> >         option’s value.
> >          >>>>>>>>
> >          >>>>>>>> [Arashmid] Agree. Encapsulation does the trick again.
> >         That's why
> >          >>>>>>>> GTP has worked well and served the purpos in the mobile
> >          >>>>>>>> back-haul so far.
> >          >>>>>>>>
> >          >>>>>>>>>
> >          >>>>>>>>> Dino
> >          >>>>>>>>>
> >          >>>>>>>>>> down this path, operators need proof that they will
> >         be still
> >          >>>>>>>>>> in the driving
> >          >>>>>>>>> seat and QoS cannot be dictated/tampered by the UE or
> any
> >          >>>>>>>>> application running in it.
> >          >>>>>>>>>>
> >          >>>>>>>>>> Now, here is an interesting question for the
> >         operators. Would
> >          >>>>>>>>>> any operator
> >          >>>>>>>>> be interested in allowing QoS  to be set by the UE or
> by
> >          >>>>>>>>> applications running in the UE and charged for by the
> >         network?
> >          >>>>>>>>> "Yes" could potentially imply impacts on the air
> >         interface, UE
> >          >>>>>>>>> resource block allocation and can make scheduling on
> >         the RAN
> >          >>>>>>>>> side
> >          >>>>> much more complex.
> >          >>>>>>>>>>
> >          >>>>>>>>>> Arashmid
> >          >>>>>>>>>>
> >          >>>>>>>>>>
> >          >>>>>>>>>>> -----Original Message-----
> >          >>>>>>>>>>> From: dmm [mailto:[e-mail]
> >         <mailto:[e-mail]>] On Behalf Of Dino
> >          >>>>>>>>>>> Farinacci
> >          >>>>>>>>>>> Sent: 06 September 2018 12:45
> >          >>>>>>>>>>> To: Tom Herbert <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>>>>>>>> Cc: [e-mail]
> >         <mailto:[e-mail]>; dmm <[e-mail]
> >         <mailto:[e-mail]>>
> >          >>>>>>>>>>> Subject: Re: [DMM] Comments to
> draft-hmm-dmm-5g-uplane-
> >          >>>>> analysis-
> >          >>>>>>> 01
> >          >>>>>>>>>>>
> >          >>>>>>>>>>>> Behcet,
> >          >>>>>>>>>>>>
> >          >>>>>>>>>>>> I was thinking if TEID is need then that can be
> >         encoded in a
> >          >>>>>>>>>>>> locator easily enough.
> >          >>>>>>>>>>>>
> >          >>>>>>>>>>>> Tom
> >          >>>>>>>>>>>
> >          >>>>>>>>>>> Not if a locator is a PGW that is shared by many
> UEs.
> >          >>>>>>>>>>>
> >          >>>>>>>>>>> 3GPP wants per bearer awareness so they need a
> >         specific ID,
> >          >>>>>>>>>>> that could have been the UE’s IP address. And with
> >         IPv6 it
> >          >>>>>>>>>>> can be unique and not the issue that Sridhar
> >         brought up.
> >          >>>>>>>>>>>
> >          >>>>>>>>>>> If ILA was in use, just use the ILA-ID for this
> >         purpose.
> >          >>>>>>>>>>>
> >          >>>>>>>>>>> Dino
> >          >>>>>>>>>>>
> >          >>>>>>>>>>> _______________________________________________
> >          >>>>>>>>>>> dmm mailing list
> >          >>>>>>>>>>> [e-mail] <mailto:[e-mail]>
> >          >>>>>>>>>>> https://www.ietf.org/mailman/listinfo/dmm
> >          >>>>>>>>
> >          >>>>
> >          >>>
> >          >>> _______________________________________________
> >          >>> dmm mailing list
> >          >>> [e-mail] <mailto:[e-mail]>
> >          >>> https://www.ietf.org/mailman/listinfo/dmm
> >          >>>
> >          >>
> >          >>
> >          >
> >          > _______________________________________________
> >          > dmm mailing list
> >          > [e-mail] <mailto:[e-mail]>
> >          > https://www.ietf.org/mailman/listinfo/dmm
> >          > _______________________________________________
> >          > dmm mailing list
> >          > [e-mail] <mailto:[e-mail]>
> >          > https://www.ietf.org/mailman/listinfo/dmm
> >          >
> >
> >
> >         --
> >         ----------------------------------
> >         Shunsuke Homma
> >         <[e-mail]
> >         <mailto:[e-mail]>>
> >         TEL: [phone]
> >         FAX: [phone]
> >
> >         NTT Network Service Systems Labs.
> >         Musashino city, Tokyo, Japan
> >         ----------------------------------
> >
> >         _______________________________________________
> >         dmm mailing list
> >         [e-mail] <mailto:[e-mail]>
> >         https://www.ietf.org/mailman/listinfo/dmm____
> >
> >     _______________________________________________
> >     dmm mailing list
> >     [e-mail] <mailto:[e-mail]>
> >     https://www.ietf.org/mailman/listinfo/dmm
> >
> >
> >
> > --
> >   o__
> >   _>  /__
> > (_) \(_)... Burn fat not fuel - Bike along to a healthier life and
> cleaner
> > world! :)
> >
> > Sridhar Bhaskaran
> >
> >
> >
> > _______________________________________________
> > dmm mailing list
> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/dmm
> >
>
> _______________________________________________
> dmm mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/dmm
>