Computing Aware Traffic Steering Consideration for Mobile User Plane Architecture
draft-dcn-dmm-cats-mup-02
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| Last updated | 2024-07-30 (Latest revision 2024-06-28) | ||
| Replaces | draft-duongph-dmm-computing-aware-ts-mup-sr | ||
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draft-dcn-dmm-cats-mup-02
Distributed Mobility Management N. Tran
Internet-Draft Y. Kim
Intended status: Informational Soongsil University
Expires: 31 January 2025 30 July 2024
Computing Aware Traffic Steering Consideration for Mobile User Plane
Architecture
draft-dcn-dmm-cats-mup-02
Abstract
The document [I-D.draft-mhkk-dmm-srv6mup-architecture] describes the
Mobile User Plane (MUP) architecture for Distributed Mobility
Management. The proposed architecture converts the user mobility
session information from the control plane entity to an IPv6
dataplane routing information. When there are multiple candidate
instances located at different location to serve an user request, the
MUP Provider Edge (PE) might prioritize the closest service location.
However, the closest routing path might not be the optimal route.
This document discusses how the mentioned MUP architecture can be
leveraged to set up dataplane routing paths to the optimal service
instance location with the assistance of computing-aware traffic
steering capabilities. For each session request, based on the up-to-
date collected computing and network information, the MUP controller
can convert the session information to the optimal route.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 31 January 2025.
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology used in this draft . . . . . . . . . . . . . . . 3
3. MUP enhancement requirements for supporting CATS . . . . . . 4
4. MUP enhancement considerations for supporting CATS . . . . . 5
4.1. CATS-MUP Centralized Deployment case . . . . . . . . . . 5
4.1.1. MUP Route enhancements . . . . . . . . . . . . . . . 5
4.1.2. Deployment architecture . . . . . . . . . . . . . . . 6
4.2. CATS-MUP Distributed Deployment case . . . . . . . . . . 8
4.2.1. MUP Route enhancements . . . . . . . . . . . . . . . 8
4.2.2. Deployment architecture . . . . . . . . . . . . . . . 9
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The document [I-D.draft-mhkk-dmm-srv6mup-architecture] describes the
Mobile User Plane architecture for Distributed Mobility Management.
This architecture is composed of a MUP controller and multiple MUP
PEs. When applying the MUP architecture in 5G network, the MUP PEs
accomodate the N3 RAN network as Interwork Segment or the N6 DN
network as Direct Segment. The MUP PEs advertises the Interwork and
Discovery Segment dataplane network reachability (e.g. Segment
Routing IPv6 segment identifier (SRv6 SID)) to the MUP network via
the interwork and direct segment Discovery routes. Meanwhile, the
MUP controller transformed the received user mobility session
information to the corresponding interwork and direct segment
information. Then, it advertises the transformed information to MUP
PEs via Session Transformed routes. The MUP PEs use the matching
Discovery routes to resolve the Session Transformed routes and
forward the packet through the MUP SRv6 network.
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This document discusses the optimal route configuration problem when
applying the mentioned MUP architecture in a network scenario where
an user request can be served by multiple computing instances of the
same service located at different locations. The closest
geographical service location to users might not be the optimal
service instance's location as pointed out in the problem statement
document of IETF Computing-Aware Traffic Steering (CATS) working
group [I-D.draft-ietf-cats-usecases-requirements]. In this scenario,
an optimal service instance location can be decided at the mobile
control plane or data plane.
In the control plane case, it is possible to use an Application
Function (AF) to determine the optimal service instance and influence
the 5G control plane to select the DN corresponding to the chosen
instance. The MUP-C only needs to transform the optimal DN
information in the session information into the corresponding route.
Meanwhile, in the data plane approach, the MUP-C should decide the
optimal service instance location by itself and transform the
unoptimal session information into the optimal route based on its
decision. The data plane approach can avoid additional signalling
procedure at the control plane of the other approach. It also
supports IP Routing paradigm benefit of SRv6 mobile user plane as
mentioned in the edge computing use case of the document
[I-D.draft-ietf-dmm-srv6mob-arch].
Therefore, a solution to integrate CATS capabilities into the
mentioned MUP architecture is presented in this document. By
considering service computing and network information of all
candidate service instances, the MUP controller can convert the
session information into the optimal dataplane route.
This document is proposed to discuss a possible extension
consideration of the original MUP architecture
document[I-D.draft-mhkk-dmm-srv6mup-architecture]. Regarding the
Distributed Mobility Management requirements described in [RFC7333],
the MUP architecture can partly address the "Non-optimal routes"
problem and the "Multicast considerations" requirement by integrating
CATS capabilties. As described in [RFC4786], anycast is the practice
of making a particular service address available in multiple
locations. Anycast support could be in the scope of multicast
support for distributed mobility management.
2. Terminology used in this draft
CATS-MUP-C: Computing-aware traffic steering MUP-C which integrates
CATS path selection and MUP-C features.
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Besides, this document uses the following terminologies which has
been defined in [I-D.draft-ldbc-cats-framework]
CATS: Computing-Aware Traffic Steering takes into account the dynamic
nature of computing resource metrics and network state metrics to
steer service traffic to a service instance.
Service: An offering that is made available by a provider by
orchestrating a set of resources (networking, compute, storage,
etc.). The same service can be provided in many locations; each of
them constitutes a service instance.
Service instance: An instance of running resources according to a
given service logic.
Service contact instance: A client-facing service function instance
that is responsible for receiving requests in the context of a given
service. A single service can be represented and accessed via
several contact instances that run in different regions of a network.
CATS Path Selector (C-PS): A functional entity that computes and
selects paths towards service locations and instances and which
accommodates the requirements of service requests. Such a path
computation engine takes into account the service and network status
information.
CATS Service Metric Agent (C-SMA): A functional entity that is
responsible for collecting service capabilities and status, and for
reporting them to a C-PS.
CATS Network Metric Agent (C-NMA): functional entity that is
responsible for collecting network capabilities and status, and for
reporting them to a C-PS.
3. MUP enhancement requirements for supporting CATS
This section presents 3 enhancement points that need to be added in
MUP for selecting an optimal service instance for serving an user
request.
First, the MUP architecture should be capable of identifying the
service and its candidate service instances. These service
identifiers are well defined in CATS framework document
[I-D.draft-ldbc-cats-framework], CATS Service ID (CS-ID) is used to
differentiate between different services. CATS Instance Selector ID
(CIS-ID) is used to differentiate between different service instances
of the same service.
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Second, the MUP architecture should be capable of advertising service
deployment information among its components. The egress MUP PE
attaching to the MUP direct segment should gather the corresponding
service and servince instance information (CS-ID and CIS-ID) and
avertise to the MUP environment. Different methods can be considered
for this requirement. A specific method is not considered in the
scope of this document. One example solution can be referred from
[I-D.draft-lin-idr-distribute-service-metric]. The egress routers
can advertise the edge service deployment information via a BGP NLRI
that can hold the CS-ID and CIS-ID information.
Third, the MUP architecture should be capable of advertising the
computing and network metrics (CATS metrics) related to the each
service instance. The egress MUP PE attaching to the MUP direct
segment should gather the corresponding service CATS metrics and
avertise to the MUP environment. Different methods can be considered
for this requirement. A specific method is not considered in the
scope of this document. One example solution can be referred from
[I-D.draft-ietf-idr-5g-edge-service-metadata]. The egress routers
can advertise the edge service CATS metrics via a metadata BGP path
attribute that can hold different types of CATS metric.
4. MUP enhancement considerations for supporting CATS
4.1. CATS-MUP Centralized Deployment case
4.1.1. MUP Route enhancements
Compared with the original route definition introduced in
[I-D.draft-ldbc-cats-framework], the Direct Segment Discovery Route
(DSD) and the Type 2 Session Transformed Route (T2ST) need
modifications to support the centralized CATS-MUP deployment case.
Another CATS Metrics Update Route (CMU) is also introduced.
The Direct Segment Discovery route advertises the reachability
information of the direct segment. This route is advertised from the
PEs attaching to the direct segments to the PEs attaching to the
mobile network access side. In CATS scenario, the direct segment is
a specific instance of a service. The service identifier CS-ID and
service instance identifier CIS-ID information are required in this
route. The CIS-ID can be used as the direct segment extended
community ID. The list below shows the DSD route information in
CATS-MUP centralized deployment case:
* CS-ID
* Direct Segment extended community ID/CIS-ID
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* Attached PE SID
The Type 2 Session Transformed Route convert the session information
into dataplane routing information. This route is advertised from
the CATS-MUP-C to the PEs attaching to the mobile network access
side. In CATS scenario, the direct segment is a specific instance of
a service. This route type includes the target service identifier
CS-ID and the tunnel endpoint identifier on the mobile network core
side information. The optimal service instance identifier CIS-ID
determined by the CATS-MUP-C is also required in this route
information. The list below shows the T2ST route information in
CATS-MUP centralized deployment case:
* CS-ID
* Optimal Direct Segment extended community ID/CIS-ID
* Tunnel Endpoint Identifier on the core side
The CATS Metric Update route convert the session information into
dataplane routing information. This route is advertised from the PEs
attaching to the direct segments to the CATS-MUP-C. This route type
update the CATS metrics related to the attaching service instance of
each PE to the CATS-MUP-C. The list below shows the CMU route
information in CATS-MUP centralized deployment case:
* CS-ID
* Direct Segment extended community ID/CIS-ID
* CATS metrics
4.1.2. Deployment architecture
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+----------------+
| Mobility |
| Management |
| System |
+----------------+
|
Session Information, CS-ID
|
T2ST +--------v-------+ CMU A
+-------| CATS-MUP-C |<-----+
+--|-------| +------+ |------|--+
| | | | C-PS | | | |
| | +----------------+ | | +----------+
UE- | v CMU B ^ | | | C-SMA |
\+---+ +------+ DSD A | +------+ |----------|-Service1
UE--|RAN|---| PE |<------------------|---| PE |---| Service | Instance
+---+ +------+<---------------\ \ +------+ | Site A | (CS-ID S1)
UE-/ | DSD B \ \ | +----------+ (CIS-ID S1A)
| \ \ |
| \ \ |
| \ \ |
| MUP network \ +------+ +----------+
| +-------+ \| PE |---| Service |
| | C-NMA | +------+ | Site B |-Service1
| +-------+ | |----------| Instance
+-------------------------------------+ | C-SMA | (CS-ID S1)
+----------+ (CIS-ID S1B)
Figure 1: CATS-MUP Centralized deployment option
Figure 1 describes the CATS-MUP Centralized deployment architecture.
The controller MUP-C in previous mentioned document is enhanced with
CATS path selection capability and renamed to CATS-MUP-C. The
optimal route configuration procedure based on this architecture is
described as follows:
Initially, when a service instance joins the MUP network, the
connecting PE advertises the DSD Route with the CS-ID, CIS-ID of the
service instance and the corresponding SRv6 SID of the attaching PE.
The PE can periodically update the CATS metrics collected from C-SMA
and C-NMA that are related to each service instance by advertising
the information in the CMU route to the CATS-MUP-C .
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When an UE request a service, during the session establishment
process, the mobility management system provides necessary session
information and requested service CS-ID to the CATS-MUP-C. An
example of this session information provisioning process can be
referred from [ieee-access-cats-mup].
The sub-component C-PS inside the CATS-MUP-C is responsible for
select optimal service instanceto serve the requested service. The
decision is based on the current CATS metrics updated from all CMU
routes.
Based on this decision, the CATS-MUP-C attaches the corresponding
CIS-ID value of the chosen service instance to the T2ST route along
with the session tunnel endpoint identifier. The CATS-MUP-C then
advertises this Session Transformed route to the MUP PE connecting to
the N3 RAN.
After receiving the T2ST route, the MUP PE resolve it with the DSD
Route that has the matching CIS-ID value. Because this value is CIS-
ID of the optimal service instance selected by the CATS-MUP-C, the UE
packets will be forwarded to the optimal service instance.
The CATS metric collection method and CATS optimal service instance
selection method are out of scope of this document.
4.2. CATS-MUP Distributed Deployment case
4.2.1. MUP Route enhancements
Compared with the original route definition introduced in
[I-D.draft-ldbc-cats-framework], the Direct Segment Discovery Route
(DSD) and the Type 2 Session Transformed Route (T2ST) need
modifications to support the distributed CATS-MUP deployment case.
The Direct Segment Discovery route advertises the reachability
information of the direct segment. This route is advertised from the
PEs attaching to the direct segments to the PEs attaching to the
mobile network access side. For the distributed CATS-MUP deployment
case, in addition to the CS-ID and the CIS-ID, the CATS metrics of
the corresponding service instance of the PE is also included. The
CIS-ID can be used as the direct segment extended community ID. The
list below shows the DSD route information in CATS-MUP centralized
deployment case:
* CS-ID
* Direct Segment extended community ID/CIS-ID
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* CATS metrics
* Attached PE SID
The Type 2 Session Transformed Route convert the session information
into dataplane routing information. This route is advertised from
the CATS-MUP-C to the PEs attaching to the mobile network access
side. For the distributed CATS-MUP deployment case, this route type
only includes the target service identifier CS-ID and the tunnel
endpoint identifier on the mobile network core side information. The
list below shows the T2ST route information in CATS-MUP centralized
deployment case:
* CS-ID
* Tunnel Endpoint Identifier on the core side
4.2.2. Deployment architecture
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+----------------+
| Mobility |
| Management |
| System |
+----------------+
|
Session Information, CS-ID
|
T2ST +--------v-------+
+-------| |
+--|-------| MUP-C |---------+
| | | | |
| | +----------------+ | +----------+
UE- | v | | C-SMA |
\+---+ +------+ DSD A +------+ |----------|-Service1
UE--|RAN|---| PE |<----------------------| PE |---| Service | Instance
+---+ +------+<---------------\ +------+ | Site A | (CS-ID S1)
UE-/ | C-PS | DSD B \ | +----------+ (CIS-ID S1A)
+------+ \ |
| \ |
| \ |
| MUP network \ +------+ +----------+
| +-------+ \| PE |---| Service |
| | C-NMA | +------+ | Site B |-Service1
| +-------+ | |----------| Instance
+-------------------------------------+ | C-SMA | (CS-ID S1)
+----------+ (CIS-ID S1B)
Figure 2: CATS-MUP Distributed deployment option
Figure 2 describes the CATS-MUP Distributed deployment architecture.
The optimal route configuration procedure based on this architecture
is described as follows:
Initially, when a service instance joins the MUP network, the
connecting PE advertises the DSD Route with the CS-ID, CIS-ID and the
current CATS metrics of the service instance and the corresponding
SRv6 SID of the attaching PE. The DSD is re-advertised whenever new
CATS metrics corresponding to the related service instance is
updated.
When an UE request a service, during the session establishment
process, the mobility management system provides necessary session
information and requested service CS-ID to the MUP-C. An example of
this session information provisioning process can be referred from
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[ieee-access-cats-mup]. The MUP-C provides session information and
CS-ID of the request to the PE connecting to the N3 RAN via the T2ST
route.
The C-PS at the PE connecting to the N3 RAN considers all candidate
service instances corresponding to the CS-ID recieved from the T2ST
route. Based on the current CATS metrics of all candidate service
instance obtained from the DSD routes, the C-PS determines the
optimal service instance. The UE packets will be forwarded to the
that instance based on its corresponding PE SID in the DSD route.
The CATS metric collection method and CATS optimal service instance
selection method are out of scope of this document.
5. References
5.1. Informative References
[I-D.draft-ietf-cats-usecases-requirements]
Yao, K., Trossen, D., Boucadair, M., Contreras, LM., Shi,
H., Li, Y., Zhang, S., and Q. An, "Mobile User Plane
Architecture using Segment Routing for Distributed
Mobility Management", 2 January 2024,
<https://datatracker.ietf.org/doc/draft-ietf-cats-
usecases-requirements/>.
[I-D.draft-ietf-dmm-srv6mob-arch]
Kohno, M., Clad, F., Camarillo, P., Ali, Z., and L. Jalil,
"Architecture Discussion on SRv6 Mobile User plane", 15
February 2024, <https://datatracker.ietf.org/doc/draft-
ietf-dmm-srv6mob-arch/>.
[I-D.draft-ietf-idr-5g-edge-service-metadata]
Dunbar, L., Majumdar, K., Li, C., Mishra, G., and Z. Du,
"Distribute Service Metric By BGP", 22 July 2024,
<https://datatracker.ietf.org/doc/draft-ietf-idr-5g-edge-
service-metadata/>.
[I-D.draft-ldbc-cats-framework]
Li, C., Du, Z., Boucadair, M., Contreras, L. M., Drake,
J., Huang, D., and G. S. Mishra, "A Framework for
Computing-Aware Traffic Steering (CATS)", Work in
Progress, Internet-Draft, draft-ldbc-cats-framework-03, 22
June 2023, <https://datatracker.ietf.org/doc/html/draft-
ldbc-cats-framework-03>.
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[I-D.draft-lin-idr-distribute-service-metric]
Lin, C. and H. Yao, "Distribute Service Metric By BGP", 6
June 2024, <https://datatracker.ietf.org/doc/draft-lin-
idr-distribute-service-metric/>.
[I-D.draft-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, "Mobile User Plane Architecture using
Segment Routing for Distributed Mobility Management", Work
in Progress, Internet-Draft, mhkk-dmm-srv6mup-
architecture, 3 March 2024,
<https://datatracker.ietf.org/doc/draft-mhkk-dmm-srv6mup-
architecture/>.
[ieee-access-cats-mup]
Tran, M-N., Duong, V-B., and Y. Kim, "Design of Computing-
Aware Traffic Steering Architecture for 5G Mobile User
Plane", 24 June 2024,
<https://doi.org/10.1109/ACCESS.2024.3418960>.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", December 2006,
<https://datatracker.ietf.org/doc/rfc4786/>.
[RFC7333] Chan, H., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
"Requirements for Distributed Mobility Management", August
2014, <https://datatracker.ietf.org/doc/rfc7333/>.
Authors' Addresses
Minh-Ngoc Tran
Soongsil University
369, Sangdo-ro, Dongjak-gu
Seoul
06978
Republic of Korea
Email: mipearlska1307@dcn.ssu.ac.kr
Younghan Kim
Soongsil University
369, Sangdo-ro, Dongjak-gu
Seoul
06978
Republic of Korea
Phone: +82 10 2691 0904
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Email: younghak@ssu.ac.kr
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