Architecture Discussion on SRv6 Mobile User plane
draft-kohno-dmm-srv6mob-arch-06
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| Authors | Miya Kohno , Francois Clad , Pablo Camarillo , Zafar Ali | ||
| Last updated | 2023-03-12 | ||
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draft-kohno-dmm-srv6mob-arch-06
DMM Working Group M. Kohno
Internet-Draft F. Clad
Intended status: Informational P. Camarillo
Expires: 10 September 2023 Z. Ali
Cisco Systems, Inc.
9 March 2023
Architecture Discussion on SRv6 Mobile User plane
draft-kohno-dmm-srv6mob-arch-06
Abstract
This document discusses the solution approach and its architectural
benefits of translating mobile session information into routing
information, applying segment routing capabilities, and operating in
a routing paradigm.
Status of This Memo
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This Internet-Draft will expire on 10 September 2023.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Problem Definition . . . . . . . . . . . . . . . . . . . . . 2
3. SRv6 mobile user plane and the 5G use cases . . . . . . . . . 3
3.1. Network Slicing . . . . . . . . . . . . . . . . . . . . . 3
3.2. Edge Computing . . . . . . . . . . . . . . . . . . . . . 3
3.3. URLLC (Ultra-Reliable Low-Latency Communication)
support . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Co-existence and Incremental Deployability . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The current mobile user plane is defined as an overlay tunnel session
to a mobile anchor point (UPF: User Plane Function in 5G context).
While this approach may be convenient from the standpoint of per-
session per-usage charging, it is difficult to cost-effectively and
scalably address the high traffic volumes of the 5G/Beyond 5G era and
more distributed data and computing demands of the future.
In addition, the requirements for wireless systems, such as IoT and
FWA (Fixed Wireless Access) applications, are becoming more diverse,
and there are cases where the conventional per-session per-usage
charging is not necessarily applicable.
This document discusses the solution approach and its architectural
benefits of translating mobile session information into routing
information, applying segment routing capabilities, and operating in
a routing paradigm.
2. Problem Definition
The current tunnel session based mobile user plane has the following
limitations and is getting hard to support new application
requirements.
* Non-optimal for any-to-any communication
* Non-optimal for edge/distributed computing
* Non-optimal for fixed and mobile convergence (FMC)
* No control of the underlay path
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In addition, the anchor point that terminates tunnel sessions becomes
a scaling bottleneck.
As for FMC, there is currently a coordinated standardization effort
between 3GPP WWC [TS.23316] and BBF [BBF407]. However, the idea is
to anchor even wireline traffic in the mobile packet core, which
compromises simplicity and scalability.
The IP routing paradigm naturally eliminates these tunnel session
based shortcomings. Segment Routing enables fast protection, policy,
slicing, etc. to provide reliability and SLA differentiation.
3. SRv6 mobile user plane and the 5G use cases
This section describes the advantages of applying SRv6 mobile user
plane for 5G use cases.
3.1. Network Slicing
Network slicing enables network segmentation, isolation, and SLA
differentiation in terms of latency and availability. End-to-end
slicing will be achieved by mapping and coordinating IP network
slicing, RAN and mobile packet core slicing.
But existing mobile user plane which is overlay tunnel does not have
underlying IP network awareness, which could lead to the inability in
meeting SLAs. Removing the tunnel and treating it with a routing
paradigm simplifies the problem.
Segment Routing has a comprehensive set of slice engineering
technologies. How to build network slicing using the Segment Routing
based technology is described in
[I-D.ali-spring-network-slicing-building-blocks].
Moreover, the stateless slice identifier encoding
[I-D.filsfils-spring-srv6-stateless-slice-id] can be applicable to
enable per-slice forwarding policy using the IPv6 header.
3.2. Edge Computing
Edge computing, where the computing workloads and datastores are
placed closer to users, is recognized as one of the key pillars to
meet 5G's demanding requirements, with regard to low latency,
bandwidth efficiency, and data localty and privacy.
Edge computing is more important than ever. This is because no
matter how much 5G improves access speeds, it won't improve end-to-
end throughput because it's largely bound to round trip delay.
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Even with existing mobile architectures, it is possible to place UPFs
in a multi-tier, or to distribute UPFs, to achieve Edge Computing.
However, complicated mechanisms are required to branch traffic or
properly use different UPFs. Also, seamless handover needs to be
compromised when UPFs are distributed.
Routing paradigm simply supports ubiquitous computing.
3.3. URLLC (Ultra-Reliable Low-Latency Communication) support
3GPP [TR.23725] investigates the key issues for meeting the URLLC
requirements on latency, jitter and reliability in the 5G System.
The solutions provided in the document are focused at improving the
overlay protocol (GTP-U) and limits to provide a few hints into how
to map such tight-SLA into the transport network. These hints are
based on static configuration or static mapping for steering the
overlay packet into the right transport SLA. Such solutions do not
scale and hinder network economics.
Another issue that deserves special mention is the ultra-reliability
issue. In order to support ultra-reliability with the tunnel session
paradigm, redundant user planes paths based on dual connectivity has
been proposed. The proposal has two main options.
* Dual Connectivity based end-to-end Redundant User Plane Paths
* Support of redundant transmission on N3/N9 interfaces
In the case of the former, UE and hosts have RHF(Redundancy Handling
Function). In sending, RFH is to replicate the traffic onto two
GTP-U tunnels, and in receiving, RHF is to merge the traffic.
In the case of the latter, traffic are to be replicated and merged
with the same sequence for specific QoS flow, which requires further
enhancements.
And in either cases, the bigger problem is the lack of a reliable way
for the redundant sessions to get through the disjoint path: even
with the redundant sessions, if it ends up using the same
infrastructure at some points, the redundancy is meaningless.
These issues can be solved more simply without GTP-U tunnel.
In addition, Segment routing has some advantages for URLLC traffic.
First, traffic can be mapped to a disjoint path or low latency path
as needed. Second, Segment routing provides an automated reliability
protection mechanism known as TI-LFA, which is a sub-50ms FRR
mechanism that provides protection regardless of the topology through
the optimal backup path. It can be provisioned slice-aware.
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4. Co-existence and Incremental Deployability
The mobile domain is a compound domain that includes Radio Access,
and it is difficult to implement a completely new architecture, so
co-existence and incremental deployability is required.
[I-D.ietf-dmm-srv6-mobile-uplane] defines the data plane convergence
between GTP-U and SRv6 between GTP-U and SRv6, so that it can co-
exist with the current mobile architecture as needed.
Further, [I-D.mhkk-dmm-srv6mup-architecture] defines the MUP
architecture for Distributed Mobility Management, which can be
plugged to the existing mobile service architecture.
5. Security Considerations
The deployment of this architecture is targeted in a trusted domain.
6. IANA Considerations
NA
7. Acknowledgements
Authors would like to thank Satoru Matsushima, Shunsuke Homma,Yuji
Tochio and Jeffrey Zhang, for their insights and comments.
8. References
8.1. Normative References
[I-D.hegdeppsenak-isis-sr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., and A. Gulko, "ISIS
Segment Routing Flexible Algorithm", Work in Progress,
Internet-Draft, draft-hegdeppsenak-isis-sr-flex-algo-02,
16 February 2018, <https://datatracker.ietf.org/doc/html/
draft-hegdeppsenak-isis-sr-flex-algo-02>.
[I-D.ietf-dmm-srv6-mobile-uplane]
Matsushima, S., Filsfils, C., Kohno, M., Camarillo, P.,
and D. Voyer, "Segment Routing IPv6 for Mobile User
Plane", Work in Progress, Internet-Draft, draft-ietf-dmm-
srv6-mobile-uplane-24, 17 January 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-dmm-
srv6-mobile-uplane-24>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
8.2. Informative References
[BBF407] BBF, "5G Wireless Wireline Convergence Architecture", BBF
TR-407 Issue:1, August 2020.
[ETSI-MEC] ETSI, "MEC in 5G Networks", ETSI White Paper No.28, June
2018.
[I-D.ali-spring-network-slicing-building-blocks]
Ali, Z., Filsfils, C., Camarillo, P., and D. Voyer,
"Building blocks for Slicing in Segment Routing Network",
Work in Progress, Internet-Draft, draft-ali-spring-
network-slicing-building-blocks-04, 21 February 2021,
<https://datatracker.ietf.org/doc/html/draft-ali-spring-
network-slicing-building-blocks-04>.
[I-D.auge-dmm-hicn-mobility]
Auge, J., Carofiglio, G., Muscariello, L., and M.
Papalini, "Anchorless mobility through hICN", Work in
Progress, Internet-Draft, draft-auge-dmm-hicn-mobility-04,
7 July 2020, <https://datatracker.ietf.org/doc/html/draft-
auge-dmm-hicn-mobility-04>.
[I-D.auge-dmm-hicn-mobility-deployment-options]
Auge, J., Carofiglio, G., Muscariello, L., and M.
Papalini, "Anchorless mobility management through hICN
(hICN-AMM): Deployment options", Work in Progress,
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Internet-Draft, draft-auge-dmm-hicn-mobility-deployment-
options-04, 7 July 2020,
<https://datatracker.ietf.org/doc/html/draft-auge-dmm-
hicn-mobility-deployment-options-04>.
[I-D.clt-dmm-tn-aware-mobility]
Chunduri, U., Li, R., Bhaskaran, S., Kaippallimalil, J.,
Tantsura, J., Contreras, L. M., and P. Muley, "Transport
Network aware Mobility for 5G", Work in Progress,
Internet-Draft, draft-clt-dmm-tn-aware-mobility-09, 12
February 2021, <https://datatracker.ietf.org/doc/html/
draft-clt-dmm-tn-aware-mobility-09>.
[I-D.filsfils-spring-srv6-stateless-slice-id]
Filsfils, C., Clad, F., Camarillo, P., Raza, S., Voyer,
D., and R. Rokui, "Stateless and Scalable Network Slice
Identification for SRv6", Work in Progress, Internet-
Draft, draft-filsfils-spring-srv6-stateless-slice-id-07,
29 January 2023, <https://datatracker.ietf.org/doc/html/
draft-filsfils-spring-srv6-stateless-slice-id-07>.
[I-D.mhkk-dmm-srv6mup-architecture]
Matsushima, S., Horiba, K., Khan, A., Kawakami, Y.,
Murakami, T., Patel, K., Kohno, M., Kamata, T., Camarillo,
P., Horn, J., Voyer, D., Zadok, S., Meilik, I., Agrawal,
A., and K. Perumal, "Segment Routing IPv6 Mobile User
Plane Architecture for Distributed Mobility Management",
Work in Progress, Internet-Draft, draft-mhkk-dmm-srv6mup-
architecture-04, 24 October 2022,
<https://datatracker.ietf.org/doc/html/draft-mhkk-dmm-
srv6mup-architecture-04>.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008,
<https://www.rfc-editor.org/info/rfc5213>.
[TR.23725] 3GPP, "Study on enhancement of Ultra-Reliable Low-Latency
Communication (URLLC) support in the 5G Core network
(5GC)", 3GPP TR 23.725 16.2.0, June 2019.
[TR.29892] 3GPP, "Study on User Plane Protocol in 5GC", 3GPP TR
29.892 16.1.0, April 2019.
[TS.23316] 3GPP, "Wireless and wireline convergence access support
for the 5G System (5GS)", 3GPP TS 23.316 16.7.0, September
2021.
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[TS.23501] 3GPP, "System Architecture for the 5G System", 3GPP TS
23.501 15.0.0, November 2017.
[TS.29244] 3GPP, "Interface between the Control Plane and the User
Plane Nodes", 3GPP TS 29.244 15.0.0, December 2017.
[TS.29281] 3GPP, "General Packet Radio System (GPRS) Tunnelling
Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 15.1.0,
December 2017.
Authors' Addresses
Miya Kohno
Cisco Systems, Inc.
Japan
Email: mkohno@cisco.com
Francois Clad
Cisco Systems, Inc.
France
Email: fclad@cisco.com
Pablo Camarillo Garvia
Cisco Systems, Inc.
Spain
Email: pcamaril@cisco.com
Zafar Ali
Cisco Systems, Inc.
Canada
Email: zali@cisco.com
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