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
<[email protected] <mailto:[email protected]>> 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:[email protected]
<mailto:[email protected]>] *On Behalf Of *Behcet Sarikaya
*Sent:* Tuesday, October 02, 2018 11:44 AM
*To:* Shunsuke Homma <[email protected]
<mailto:[email protected]>>
*Cc:* dmm <[email protected] <mailto:[email protected]>>
*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
<[email protected] <mailto:[email protected]>>
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, [email protected]
<mailto:[email protected]> 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:[email protected]
<mailto:[email protected]>] On Behalf Of Alexandre Petrescu
> Sent: Montag, 1. Oktober 2018 13:22
> To: [email protected] <mailto:[email protected]>
> 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:[email protected]
<mailto:[email protected]>]
>>>>> Sent: 07 September 2018 13:08
>>>>> To: Arashmid Akhavain <[email protected]
<mailto:[email protected]>>
>>>>> Cc: Tom Herbert <[email protected]
<mailto:[email protected]>>; [email protected]
<mailto:[email protected]>;
>>>>> dmm <[email protected] <mailto:[email protected]>>
>>>>> 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
>>>>> <[email protected]
<mailto:[email protected]>> 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:[email protected]
<mailto:[email protected]>]
>>>>>>> Sent: 07 September 2018 11:13
>>>>>>> To: Arashmid Akhavain <[email protected]
<mailto:[email protected]>>
>>>>>>> Cc: Dino Farinacci <[email protected]
<mailto:[email protected]>>;
>>>>>>> [email protected]
<mailto:[email protected]>; dmm <[email protected]
<mailto:[email protected]>>
>>>>>>> Subject: Re: [DMM] Comments to
>>>>>>> draft-hmm-dmm-5g-uplane-analysis-01
>>>>>>>
>>>>>>> On Fri, Sep 7, 2018 at 8:01 AM, Arashmid Akhavain
>>>>>>> <[email protected]
<mailto:[email protected]>> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: Dino Farinacci [mailto:[email protected]
<mailto:[email protected]>]
>>>>>>>>> Sent: 06 September 2018 18:59
>>>>>>>>> To: Arashmid Akhavain <[email protected]
<mailto:[email protected]>>
>>>>>>>>> Cc: Tom Herbert <[email protected]
<mailto:[email protected]>>; ta-miyasaka@kddi-
>>>>> research.jp <http://research.jp>;
>>>>>>>>> dmm <[email protected] <mailto:[email protected]>>
>>>>>>>>> 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:[email protected]
<mailto:[email protected]>] On Behalf Of Dino
>>>>>>>>>>> Farinacci
>>>>>>>>>>> Sent: 06 September 2018 12:45
>>>>>>>>>>> To: Tom Herbert <[email protected]
<mailto:[email protected]>>
>>>>>>>>>>> Cc: [email protected]
<mailto:[email protected]>; dmm <[email protected]
<mailto:[email protected]>>
>>>>>>>>>>> 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
>>>>>>>>>>> [email protected] <mailto:[email protected]>
>>>>>>>>>>> https://www.ietf.org/mailman/listinfo/dmm
>>>>>>>>
>>>>
>>>
>>> _______________________________________________
>>> dmm mailing list
>>> [email protected] <mailto:[email protected]>
>>> https://www.ietf.org/mailman/listinfo/dmm
>>>
>>
>>
>
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--
----------------------------------
Shunsuke Homma
<[email protected]
<mailto:[email protected]>>
TEL: +81 422 59 3486
FAX: +81 422 60 7460
NTT Network Service Systems Labs.
Musashino city, Tokyo, Japan
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_> /__
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