Internet DRAFT - draft-mhkk-dmm-mup-architecture
draft-mhkk-dmm-mup-architecture
Internet Engineering Task Force S. Matsushima
Internet-Draft K. Horiba
Intended status: Standards Track A. Khan
Expires: 4 September 2024 Y. Kawakami
SoftBank
T. Murakami
K. Patel
Arrcus, Inc
M. Kohno
T. Kamata
P. Camarillo
J. Horn
Cisco Systems, Inc.
D. Voyer
Bell Canada
S. Zadok
I. Meilik
Broadcom
A. Agrawal
K. Perumal
Intel
3 March 2024
Mobile User Plane Architecture for Distributed Mobility Management
draft-mhkk-dmm-mup-architecture-00
Abstract
This document defines the Mobile User Plane (MUP) architecture for
Distributed Mobility Management. The requirements for Distributed
Mobility Management described in [RFC7333] can be satisfied by
routing fashion.
In MUP Architecture, session information between the entities of the
mobile user plane is turned to routing information so that mobile
user plane can be integrated into dataplane.
MUP architecture is designed to be pluggable user plane part of
existing mobile service architectures, enabled by auto-discovery for
the use plane. Segment Routing provides network programmability for
a scalable option with it.
While MUP architecture itself is independent from a specific
dataplane protocol, several dataplane options are available for the
architecture. This document describes IPv6 dataplane in Segment
Routing case due to the DMM requirement, and is suitable for mobile
services which require a large IP address space.
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Status of This Memo
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This Internet-Draft will expire on 4 September 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Architecture Principles . . . . . . . . . . . . . . . . . . . 5
4. Mobile User Plane Segment . . . . . . . . . . . . . . . . . . 7
4.1. Dataplane Considerations . . . . . . . . . . . . . . . . 8
5. Distribution of Mobile User Plane Segment Information . . . . 8
5.1. Direct Segment Discovery Route . . . . . . . . . . . . . 9
5.2. Interwork Segment Discovery Route . . . . . . . . . . . . 9
6. Distribution of Session Transformed Route . . . . . . . . . . 10
6.1. Type 1 Session Transformed Route . . . . . . . . . . . . 10
6.2. Type 2 Session Transformed Route . . . . . . . . . . . . 10
6.3. MUP Controller . . . . . . . . . . . . . . . . . . . . . 11
7. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 11
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7.1. SR Network Accommodating Existing Mobile Network
Services . . . . . . . . . . . . . . . . . . . . . . . . 11
7.2. MUP PE Deployment at All SR Domain Edges . . . . . . . . 13
7.3. Adding Direct Segment with New MUP PE . . . . . . . . . . 15
7.4. Collapsed MUP PE Deployment . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 20
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 21
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
Mobile services require IP connectivity for communication between the
entities of mobile service architecture [RFC5213][TS.23501].
In PMIPv6 [RFC5213], IP connectivity is required between LMA and MAG,
as well as LMA and Internet. In 3GPP 5G [TS.23501], IP connectivity
for N3 interface between gNodeB(es) and UPFs is required, as well as
for N6 interface between UPFs and DNs (Data Network).
These IP connectivities may be covered by multiple dataplane
networks, such as IPv4, IPv6, MPLS, or bunch of dataplane protocols.
When just one dataplane protocol network is adopted for simplicity,
it is expected that the address space of the dataplane network should
be large enough to cover a vast number of nodes, such as millions of
base stations. For this reason, use of IPv6 dataplane looks
sufficiently suitable.
IPv6 dataplane has been able to instantiate Segment Routing over IPv6
(SRv6) with network programming capability described in [RFC8986].
SRv6 network programmability enhances IPv6 dataplane to be integrated
with mobile user plane [RFC9433]. It will make an entire IPv6
network support the user plane in a very efficient distributed
routing fashion.
On the other hand, the requirements for Distributed Mobility
Management (DMM) described in [RFC7333] can be satisfied by session
management based solutions. [RFC8885] defines protocol extension to
PMIPv6 for the DMM requirements. 3GPP 5G defines an architecture in
which multiple session anchors can be added to one mobility session
by the session management.
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As a reminder, the user plane related requirements in [RFC7333] are
reproduced here:
REQ1: Distributed mobility management
IP mobility, network access solutions, and forwarding
solutions provided by DMM MUST enable traffic to avoid
traversing a single mobility anchor far from the optimal
route. It is noted that the requirement on distribution
applies to the data plane only.
REQ3: IPv6 deployment
DMM solutions SHOULD target IPv6 as the primary deployment
environment and SHOULD NOT be tailored specifically to
support IPv4, particularly in situations where private IPv4
addresses and/or NATs are used.
REQ4: Existing mobility protocols
A DMM solution MUST first consider reusing and extending IETF
standard protocols before specifying new protocols.
REQ5: Coexistence with deployed networks/hosts and operability
across different networks
A DMM solution may require loose, tight, or no integration
into existing mobility protocols and host IP stacks.
Regardless of the integration level, DMM implementations MUST
be able to coexist with existing network deployments, end
hosts, and routers that may or may not implement existing
mobility protocols. Furthermore, a DMM solution SHOULD work
across different networks, possibly operated as separate
administrative domains, when the needed mobility management
signaling, forwarding, and network access are allowed by the
trust relationship between them.
This document defines the Mobile User Plane (MUP) architecture for
Distributed Mobility Management. MUP is not a mobility management
system itself, but an architecture enables the dataplanes to
integrate mobile user plane into it for the IP networks.
Although MUP architecture is independent from a specific dataplane
protocol, this document describes IPv6 dataplane in Segment Routing
case due to the DMM requirement, and as a suitable solution for
scalable mobile service deployments. Other dataplane options is out
of scope of this document, and may be written in the future.
In this routing paradigm, session information from a mobility
management system will be transformed to routing information. It
means that mobile user plane specific nodes for the anchor or
intermediate points are no longer required. The user plane anchor
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and intermediate functions can be supported by MUP enabled networks
(REQ1), not to mention that MUP will naturally be deployed over IPv6
networks (REQ3).
MUP architecture is independent from the mobility management system.
For the requirements (REQ4, 5), MUP architecture is designed to be
pluggable user plane part of existing mobile service architectures.
Those existing architectures are for example defined in [RFC5213],
[TS.23501], or if any.
The level of MUP integration for mobile networks running based on the
existing architecture will be varied and depending on the level of
MUP awareness of the control and user plane entities.
Specifying how to modify the existing architecture to integrate MUP
is out of scope of this document. What this document provides for
the existing architecture is an interface for MUP which the existing
or future architectures can easily integrate.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Terminology
MUP: Mobile User Plane
MUP Segment: Representation of mobile user plane segment
MUP PE: MUP aware Provider Edge node
MUP Controller: Controller node for MUP networks
UE: User Equipment, as per [TS.23501]
MN: Mobile Node, as per [RFC5213]
3. Architecture Principles
This section describes the principles for MUP architecture that guide
its design and operation.
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The first key principle is the abstraction of the mobile user plane.
A network segment consists of a mobile service is abstracted and
represented as a MUP segment. It is noted that MUP segment described
in this document is NOT Segment Routing[RFC8402] specific, as
"segment" is widely common terminology through many networking
technologies, and is defined in each technology context.
A MUP PE may accommodate MUP segment(s), such as an Interwork Segment
and/or a Direct Segment described in Section 4. Figure 1 depicts the
overview.
* Mobility *
* Management *
* System *
*........*
|
Session Information
|
______________v______________
_______ / |MUP-C| \ _______
/ \ / +-----+ \ / \
/Interwork\__ | | __/ Direct \
\ Segment / \ |-------+ +------| / \ Segment /
\_______/ \| MUP PE| MUP |MUP PE|/ \_______/
_______ /|-------+ Network +------|\ _______
/ \ / | | \ / \
/ Direct \_/ \ / \_/Interwork\
\ Segment / \____________________________/ \ Segment /
\_______/ \_______/
Figure 1: Overview of MUP Architecture
The second principle is auto-discovery for MUP segment. A MUP PE
should be able to discover a MUP segment in a remote MUP PE. In MUP
architecture, the remote MUP PE should advertise an auto-discovery
route for a hosted MUP segment. The MUP PE can discover the MUP
segment in the remote MUP PE when the MUP PE finds the MUP segment
information in the received auto-discovery route from the remote MUP
PE.
Section 5 in this document defines auto-discovery route for each type
of MUP segment discovery.
It is noted that the auto-discovery route must be independent from a
specific dataplane. But with an attribute for the specific
dataplane, the auto-discovery route indicates specific dataplane
behavior required for the MUP segment.
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The third principle is that transforming session information to
routing information. A MUP Controller (MUP-C) advertises MUP PE(s)
routing information for a UE or a MN, transformed from the input of
corresponding session information in mobility management systems. In
MUP architecture, it is called session-transformed route.
Section 6 in this document defines each type of session-transformed
route. The session-transformed route must also be dataplane
independent.
A MUP PE should resolve reachability for a received session-
transformed route (ST route for short). When the MUP PE succeeds to
resolve the ST route reachability with a MUP segment in local, or in
remote via an auto-discovery route, and an appropriate dataplane
behavior indicated in it for the ST route, the MUP PE can perform the
dataplane action to the corresponding packet received from a local
MUP segment.
The MUP PE sends the packet toward the egress MUP segment after the
dataplane action applied to the packet. The egress MUP segment may
exist in local, or in a remote MUP PE. In latter case, the remote
MUP PE applies the dataplane action indicated by the received packet,
and sends it out to the egress MUP segment.
The illustrations are described in Section 7.
To carry these new routing information, this architecture requires
extending the existing routing protocols. Any routing protocol can
be used to carry this information but this document recommends using
BGP. Thus, this document describes extensions on BGP as an example.
4. Mobile User Plane Segment
This document defines two types of Mobile User Plane (MUP) segment.
A MUP segment represents a network segment consisting of a mobile
service. The MUP segment can be created by a MUP PE which provides
connectivity for the mobile user plane.
Direct Segment is a type of MUP segment that provides connectivity
between MUP segments through the MUP networks. Interwork Segment is
another type of MUP segment. It provides connectivity between a user
plane protocol of existing or future mobile service architecture and
other MUP segments through the MUP networks.
A MUP PE may be instantiated as a physical node or a virtual node.
The MUP PE may also be instantiated on a device which accommodates a
mobile user plane node of a mobility management system.
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4.1. Dataplane Considerations
As in Section 1, this document describes IPv6 dataplane in Segment
Routing case due to the DMM requirement, and as a suitable solution
for scalable mobile service deployments.
When SRv6 is adopted as the dataplane, an SRv6 SID (Segment
Identifier) can represent a MUP segment. The SID can be any behavior
defined in [RFC8986], [RFC9433], or any other extensions for further
use cases. The behavior of the MUP segment will be chosen by the
role of the representing MUP segment.
For example, in case of a MUP PE interfaces to 5G user plane on the
access side defined as "N3" in [TS.23501], the MUP PE accommodates
the N3 network as Interwork Segment in a routing instance and then
the behavior of created segment SID by the MUP PE will be
"End.M.GTP4.E", or "End.M.GTP6.E". In this case, the MUP PE may
associate the SID to the routing instance for the N3 access network
(N3RAN).
Another example here is that a MUP PE interfaces to 5G DN on the core
side defined as "N6" in [TS.23501], the MUP PE accommodates the N6
network in a routing instance as Direct Segment and then the behavior
of the created segment SID by the MUP PE will be "End.DT4",
"End.DT6", or "End.DT2". In this case, the MUP PE may associate the
SID to the routing instance for the N6 data network (N6DN).
5. Distribution of Mobile User Plane Segment Information
Distribution of MUP segment information can be done by advertising
routing information with the MUP segment for mobile service. A MUP
PE distributes MUP segment information when a MUP segment is
connected to the MUP PE.
A MUP Segment Discovery route is routing information that associates
the MUP segment with network reachability. This document defines the
basic discovery route types, Direct Segment Discovery route, and
Interwork Segment Discovery route. Other types of segment discovery
route may be mobile service architecture specific. Defining the
architecture specific network reachability is out of scope of this
document and it will be specified in another document.
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5.1. Direct Segment Discovery Route
When a MUP PE accommodates a network through an interface or a
routing instance as a Direct Segment, the MUP PE advertises the
corresponding Direct Segment Discovery (DSD) route for the interface
or the routing instance to the SR domain. The DSD route includes an
address of the MUP PE in the network reachability information (NLRI)
with an extended community indicating the corresponding Direct
Segment. Dataplane specific attribute should be attached to the DSD
route, as a auto-discovery route, which itself must be dataplane
independent defined in Section 3.
For example in 3GPP 5G specific case with SRv6 dataplane, an MUP PE
may connect to N6 interface on a DN side, and a DSD route for the DN
will be advertised with an address of the MUP PE in NLRI, an
corresponding SRv6 SID in the SRv6 specific attribute, and a Direct
Segment extended community to the routing instance for the DN from
the MUP PE.
When a MUP PE receives a DSD route from other PEs, the MUP PE keeps
the received DSD route in the RIB. The MUP PE uses the received DSD
route to resolve Type 2 session transformed routes reachability,
described in Section 6.2. If the DSD route resolves reachability for
the endpoints, and match the Direct Segment extended community of the
Type 2 session transformed routes, the MUP PE updates the FIB entry
for the Type 2 session transformed route with the SID of the matched
DSD route.
5.2. Interwork Segment Discovery Route
When a PE accommodates a network through an interface or a routing
instance for the user plane protocol of the mobile service
architecture as an Interwork Segment, the PE advertises the
corresponding Interwork Segment Discovery (ISD) route with the
prefixes of the Interwork Segment. Dataplane specific attribute
should be attached to the ISD route, as a auto-discovery route, which
itself must be dataplane independent defined in Section 3.
For example in 3GPP 5G specific case with SRv6 dataplane, an MUP PE
may connect to N3 network accommodating a RAN, and a ISD route will
be advertised with IP prefix(es) of the N3 RAN in NLRI, and an
corresponding SRv6 SID in the SRv6 specific attribute.
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When a MUP PE receives a ISD route, the MUP PE keeps the received ISD
routes in the RIB. The MUP PE uses the received ISD routes to
resolve the reachability for remote endpoint of Type 1 session
transformed routes, described in Section 6.1. If the ISD route
resolves the reachability for Type 1 session transformed routes, the
MUP PE updates the FIB entry for the prefix of Type 1 session
transformed route with the SID of the matched ISD route.
The received ISD routes MUST be used to resolve reachability for the
remote endpoints of Type 1 session transformed routes. The
connectivity among the routing instances for Interwork Segments may
be advertised as VPN routes. This is to avoid forwarding entries to
the prefixes of Interwork Segment mingled in the other type of
routing instance. A MUP PE may discard the received ISD route if the
Route Target extended communities of the route does not meet the MUP
PE's import policy.
6. Distribution of Session Transformed Route
MUP architecture defines two types of session transformed route.
6.1. Type 1 Session Transformed Route
First type route, called Type 1 Session Transformed route, encodes IP
prefix(es) for a UE or MN in a BGP MP-NLRI attribute with associated
session information of the tunnel endpoint identifier on the access
side. The MUP-C advertises the Type 1 Session Transformed route with
the Route Target extended communities for the UE or MN to the MUP
networks.
A MUP PE may receive the Type 1 Session Transformed routes from the
MUP-C in the MUP networks. The MUP PE may keep the received Type 1
Session Transformed routes advertised from the MUP-C. The receiving
MUP PE will perform the importing of the received Type 1 Session
Transformed routes in the configured routing instances based on the
Route Target extended communities. A MUP PE may discard the received
Type 1 Session Transformed route if the MUP PE fails to import the
route based on the Route Target extended communities.
6.2. Type 2 Session Transformed Route
Second type route, called Type 2 Session Transformed route, encodes
the tunnel endpoint identifier of the session on the core side in a
BGP MP-NLRI attribute with the nature of tunnel decapsulation.
Longest match algorithm for the prefix in this type of session
transformed route should be applicable to aggregate the routes for
scale. The MUP-C advertises the Type 2 Session Transformed route
with the Route Target and Direct Segment extended communities for the
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endpoint to the MUP networks.
A MUP PE may receive the Type 2 Session Transformed routes from the
MUP-C in the SR domain. The MUP PE may keep the received Type 2
Session Transformed routes advertised from the MUP-C. The receiving
MUP PE will perform the importing of the received Type 2 Session
Transformed routes in the configured routing instances based on the
Route Target extended communities. A MUP PE may discard the received
Type 2 Session Transformed route if the MUP PE fails to import the
route based on the Route Target extended communities.
6.3. MUP Controller
A MUP Controller (MUP-C) provides an API. A consumer of the API
inputs session information for a UE or a MN from mobility management
system. The MUP-C transforms the received session information to
routing information and will advertise the session transformed routes
with the corresponding extended communities to the MUP networks.
The received session information is expected to include the UE or MN
IP prefix(es), tunnel endpoint identifiers for both ends, and any
other attributes for the mobile networks. For example in a 3GPP 5G
specific case, the tunnel endpoint identifier will be a pair of the
F-TEIDs on both the N3 access side (RAN) and core side (UPF).
7. Illustration
This section illustrates possible MUP deployments with SRv6
dataplane. 3GPP 5G is an example mobile service for the deployment
cases in this section.
7.1. SR Network Accommodating Existing Mobile Network Services
Figure 2 shows how SR networks can accommodate existing mobile
network service before enabling MUP. The PEs S1, S2, and S3 compose
an SR network. A routing instance is configured to each network of
the mobile service. N6DN in S1 and S2 are providing connectivity to
edge servers and the Internet respectively.
VRF (Virtual Routing Forwarding) is the routing instance to
accommodate MUP segments in this section. All example cases in this
section follow the typical routing policy control using the BGP
extended community described in [RFC4360] and [RFC4684]
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__ N3 /-----------+-----+------------\
/ \RAN / |MUP-C| \
/ V/v\_ | +-----+ | N6 __
\ / \ |----+ +----| DN / \
\__/ \| S1 | | S2 |----/W/w \
__ /|----+ +----| \ /
/ \__/ | +----+ | \__/
/ E/e\N6 \ | S3 | /
\ /DN \------------+----+------------/
\__/ N3UPF /\ N6UPF
X/x / \ Y/y
+-----+
| UPF |
+-----+
Figure 2
The following routing instances are configured:
* N3RAN in S1
- export route V/v with route-target (RT) community C1
- import routes which have route-target (RT) community C1 and C2
* N6DN in S1
- export route E/e with RT C4
- import routes which have RT C3 and C4
* N6DN in S2
- export route W/w with RT C4
- import routes which have RT C3 and C4
* N3UPF in S3
- export route X/x with RT C2
- import routes which have RT C1
* N6UPF in S3
- export route Y/y with RT C3
- import routes which have RT C4
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Note: The above configurations are just to provide typical IP
connectivity for 3GPP 5G. When the above configurations have
been done, each endpoint in V/v and X/x can communicate through
S1 and S3, but they can not communicate with nodes in E/e, W/w
and Y/y.
7.2. MUP PE Deployment at All SR Domain Edges
Here, the PEs S1, S2 and S3 are configured to enable MUP as follows:
* S1
- advertises Interwork type discovery route: V/v with SID S1::
- set S1:: behavior End.M.GTP4.E or End.M.GTP6.E
* S1
- advertise Direct type discovery route: MUP Direct Segment
community D1 and SID S1:1::
- set S1:1:: behavior End.DT4 or End.DT6 for the N6DN in S1
* S2
- advertise Direct type route: MUP Direct Segment community D1
and SID S2::
- set S2:: behavior End.DT4 or End.DT6 for the N6DN in S2
S1 adopts the local N6DN to prioritize the closer segment for the
same Direct Segment. Another PE may adopt D1 from S2, if the PE has
no local N6DN for D1 and closer to S2 than S1.
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U1
|
U/u v
\__ N3 /-----------+-----+------------\
/ \RAN / |MUP-C| \
/ V/v\_ | +-----+ | N6 __
\ / \ |----+ +----| DN / \
\__/ \| S1 | | S2 |----/W/w \
__ /|----+ +----| \ /
/ \__/ | +----+ | \__/
/ E/e\N6 \ | S3 | /
\ /DN \------------+----+------------/
\__/ N3UPF /\ N6UPF
X/x / \ Y/y
+-----+
| UPF |
+-----+
Figure 3
Now, session information U1 is put to a MUP Controller, MUP-C, and
MUP-C is configured to transform U1 to the routes as follows:
* MUP-C
- attach the MUP Direct Segment ID D1 and RT C3 to the DN in U1
- transforms UE's prefix U/u, the F-TEID on access side (gNB) and
QFI in U1 to the Type 1 session transformed route for the
prefix U/u with the F-TEID, the QFI, and RT C3
- transforms F-TEID on core side (UPF) X in U1 to the Type 2
session transformed route for X with MUP segment-ID D1 and RT
C2
Then N3RAN and N6DN import route X and U/u respectively. S1 and S2
resolves U/u's remote endpoint with V/v and then install SID S1:: for
U/u in FIB. S1:: will not appear in the packet from E/e to U/u over
the wire.
As S1 adopts local N6DN for D1, N3RAN in S1 decapsulates GTP-U
packets from V/v to X and then lookup the inner packets from U/u in
N6DN after the decapsulation.
Note: When the above configurations have been done, MUP is applied
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only to the packets from/to U/u. Each endpoint in U/u, W/w and
E/e can communicate through S1 and S2. The rest of traffic
from/to other UEs go through the usual 3GPP 5G user plane path
using UPF via S3.
7.3. Adding Direct Segment with New MUP PE
Another case shown in Figure 4 is that S4 joins the SR network and
accommodates edge servers in the N6DN in S4.
U1
|
U/u v __
\__ N3 /-----------+-----+------------\ / \
/ \RAN / |MUP-C| \ __/W/w \
/ V/v\_ | +-----+ +----|_/N6\ /
\ / \ |----+ | S2 | DN \__/
\__/ \| S1 | +----| __
__ /|----+ +----|_ / \
/ \__/ | +----+ | S4 | \__/E/e \
/ \N6 \ | S3 | +----/ N6\ /
\ /DN \------------+----+------------/ DN \__/
\__/ N3UPF /\ N6UPF
X/x / \ Y/y
+-----+
| UPF |
+-----+
Figure 4
The following routing instances are configured:
* N3RAN in S1 (same with the previous case)
- export route V/v with RT C1
- import routes which have RT C1 and C2
* N6DN in S1
- export no route
- import routes which have RT C4
* N6DN in S2 (same with the previous case)
- export route W/w with RT C4
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- import routes which have RT C3 and C4
* N3UPF in S3 (same with the previous case)
- export route X/x with RT C2
- import routes which have RT C1
* N6UPF in S3 (same with the previous case)
- export route Y/y with RT C3
- import routes which have RT C4
* N6DN in S4
- export route E/e with RT C4
- import routes which have RT C3 and C4
Here, the PEs are configured to enable MUP as following:
* S1 (same with the previous case)
- advertises Interwork type route: V/v with SID S1::
- set S1:: behavior End.M.GTP4.E or End.M.GTP6.E
* S1
- advertise Direct type route: MUP Direct Segment community D1
for the local N6DN
- set S1:1:: behavior End.DT4 or End.DT6 for the N6DN in S1
* S2 (same with the previous case)
- advertise Direct type route: MUP Direct Segment community D1
and SID S2::
- set S2:: behavior End.DT4 or End.DT6 for the N6DN in S2
* S4
- advertise Direct type route: MUP Direct Segment community D2
and SID S4::
- set S4:: behavior End.DT4 or End.DT6 for the N6DN in S4
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As in the previous case, S1 adopts the local N6DN for D1 as long as
S1 prioritizes the closer segment for the same MUP Direct Segment.
The Direct type route from S4 for D2 with SID S4:: will be kept in
S1.
* MUP-C (same with the previous case)
- attach the MUP Direct Segment ID D1 and RT C3 to the DN in U1
- transforms UE's prefix U/u, the F-TEID on access side (gNB) and
QFI in U1 to the Type 1 session transformed route for the
prefix U/u with the F-TEID, the QFI, and RT C3
- transforms F-TEID on core side (UPF) X in U1 to the Type 2
session transformed route for X with MUP Direct Segment
community D1 and RT C2
Then N3RAN and N6DN import route X and U/u respectively. S2 and S4
resolve U/u's remote endpoint with V/v and then install SID S1:: for
U/u in FIB.
As in the previous case, S1 adopts local N6DN for D1, N3RAN in S1
decapsulates GTP-U packets from V/v to X and then lookup the inner
packets from U/u in N6DN after the decapsulation.
For D2 on the other hand, no corresponding N6DN existed in S1.
However, E/e with RT C4 from S4 is imported into N6DN in S1 as a VPN
route, E/e is reachable from U/u via N6DN for D1 in S1.
If a session U1' includes the DN corresponding to D2, MUP-C
advertises Type 2 session transformed route X' with MUP Direct
Segment community D2, and then N3RAN in S1 instantiates H.M.GTP4.D or
End.M.GTP6.D for X with S4:: as the last SID in the received Direct
type route from S4.
Note: When the above configurations have been done, MUP is applied
only to the packets from/to U/u. Each endpoint in U/u, W/w and
E/e can communicate through S1, S2 and S4. The rest of traffic
from/to other UEs go through the usual 3GPP 5G user plane path
using UPF via S3.
7.4. Collapsed MUP PE Deployment
In this case only S1 enables MUP in a collapsed fashion. S2 and S3
are L3VPN PEs without MUP capability. In this section, S2 and S3 are
illustrated as SRv6 nodes. But they can be non-SR nodes if S1
provides SR independent connectivity to S2 and S3.
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U1
|
U/u v
\__ N3 /-----------+-----+------------\
/ \RAN / |MUP-C| \
/ V/v\_ | +-----+ | N6 __
\ / \ |----+ +----| DN / \
\__/ \| S1 | | S2 |----/W/w \
__ /|----+ +----| \ /
/ \__/ | +----+ | \__/
/ E/e\N6 \ | S3 | /
\ /DN \------------+----+------------/
\__/ N3UPF /\ N6UPF
X/x / \ Y/y
+-----+
| UPF |
+-----+
Figure 5
The difference between the previous case in Section 7.1 for the
routing instance configuration is following:
* N6DN in S1
- export route E/e with RT C4
- import routes which have RT C3, C4 and C5
Here, S1 is configured to enable MUP and S2 as an L3VPN PE is
configured as follows:
* S1
- may not advertise Interwork type discovery route for V/v
- may not advertise Direct type discovery route with MUP Direct
Segment community D1 and S1:1::
- set S1:1:: behavior End.DT4 or End.DT6 for the N6DN in S1
* S2
- set S2:: behavior End.DT4 or End.DT6 for the N6DN in S2
Now, session information U1 is added to the MUP Controller, MUP-C,
and MUP-C and S1 is configured to transform U1 to the routes as
follows:
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* MUP-C
- attach the MUP Direct Segment ID D1 and RT C5 to the DN in U1
- transforms UE's prefix U/u, the F-TEID on access side (gNB) and
QFI in U1 to the Type 1 session transformed route for the
prefix U/u with the F-TEID, the QFI, and RT C5
- transforms F-TEID on core side (UPF) X in U1 to the Type 2
session transformed route for X with MUP Direct Segment
community D1 and RT C2
* S1
- advertises U/u as an L3VPN route with RT C4 and SID S1:1::,
when the Type 1 session transformed route is imported into the
N6DN
Then the N3RAN and N6DN import route X and U/u respectively. S1
resolves U/u's remote endpoint with V/v and then create the
corresponding GTP encap entry for U/u into the N3RAN FIB. S2 will
create a regular L3VPN routing entry for U/u with SID S1:1:: in the
N6DN when S2 imports the L3VPN route with RT C4 for U/u advertised
from S1.
As S1 adopts local N6DN for D1, N3RAN in S1 decapsulates GTP-U
packets from V/v to X and then lookup the inner packets from U/u in
N6DN after the decapsulation.
Note: When the above configurations have been done, MUP is applied
only to the packets from/to U/u. Each endpoint in U/u, W/w and
E/e can communicate through S1 and S2. The rest of traffic
from/to other UEs go through the usual 3GPP 5G user plane path
using UPF via S3.
8. IANA Considerations
This memo includes no request to IANA.
9. Security Considerations
TBD.
10. References
10.1. Normative References
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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>.
[RFC7333] Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
Korhonen, "Requirements for Distributed Mobility
Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,
<https://www.rfc-editor.org/info/rfc7333>.
[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>.
[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>.
10.2. Informative References
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <https://www.rfc-editor.org/info/rfc4360>.
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
R., Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
November 2006, <https://www.rfc-editor.org/info/rfc4684>.
[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>.
[RFC8885] Bernardos, CJ., de la Oliva, A., Giust, F., Zúñiga, JC.,
and A. Mourad, "Proxy Mobile IPv6 Extensions for
Distributed Mobility Management", RFC 8885,
DOI 10.17487/RFC8885, October 2020,
<https://www.rfc-editor.org/info/rfc8885>.
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[RFC9433] Matsushima, S., Ed., Filsfils, C., Kohno, M., Camarillo,
P., Ed., and D. Voyer, "Segment Routing over IPv6 for the
Mobile User Plane", RFC 9433, DOI 10.17487/RFC9433, July
2023, <https://www.rfc-editor.org/info/rfc9433>.
[TS.23501] 3GPP, "System architecture for the 5G System (5GS)", 3GPP
TS 23.501 17.2.0, 24 September 2021,
<http://www.3gpp.org/ftp/Specs/html-info/23501.htm>.
Acknowledgements
The authors would like to thank Jeffrey Zhang for his review and
discussions with the authors.
Contributors
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Authors' Addresses
Satoru Matsushima
SoftBank
Japan
Email: satoru.matsushima@g.softbank.co.jp
Katsuhiro Horiba
SoftBank
Japan
Email: katsuhiro.horiba@g.softbank.co.jp
Ashiq Khan
SoftBank
Japan
Email: ashiq.khan@g.softbank.co.jp
Yuya Kawakami
SoftBank
Japan
Email: yuya.kawakami01@g.softbank.co.jp
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Tetsuya Murakami
Arrcus, Inc.
United States of America
Email: tetsuya@arrcus.com
Keyur Patel
Arrcus, Inc.
United States of America
Email: keyur@arrcus.com
Miya Kohno
Cisco Systems, Inc.
Japan
Email: mkohno@cisco.com
Teppei Kamata
Cisco Systems, Inc.
Japan
Email: tkamata@cisco.com
Pablo Camarillo Garvia
Cisco Systems, Inc.
Spain
Email: pcamaril@cisco.com
Jakub Horn
Cisco Systems, Inc.
Czech Republic
Email: jakuhorn@cisco.com
Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
Shay Zadok
Broadcom
Israel
Email: shay.zadok@broadcom.com
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Israel Meilik
Broadcom
Israel
Email: israel.meilik@broadcom.com
Ashutosh Agrawal
Intel
United States of America
Email: ashutosh.agrawal@intel.com
Kumaresh Perumal
Intel
United States of America
Email: kumaresh.perumal@intel.com
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