DMM Working Group S. Matsushima
Internet-Draft SoftBank
Intended status: Standards Track C. Filsfils
Expires: January 9, 2020 M. Kohno
P. Camarillo
Cisco Systems, Inc.
D. Voyer
Bell Canada
C. Perkins
Futurewei
July 8, 2019
Segment Routing IPv6 for Mobile User Plane
draft-ietf-dmm-srv6-mobile-uplane-05
Abstract
This document shows the applicability of SRv6 (Segment Routing IPv6)
to the user-plane of mobile networks. The network programming nature
of SRv6 accomplish mobile user-plane functions in a simple manner.
The statelessness of SRv6 and its ability to control both service
layer path and underlying transport can be beneficial to the mobile
user-plane, providing flexibility, end-to-end network slicing and SLA
control for various applications. This document describes the SRv6
mobile user plane behavior and defines the SID functions for that.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 9, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Predefined SRv6 Functions . . . . . . . . . . . . . . . . 4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. A 3GPP Reference Architecture . . . . . . . . . . . . . . . . 6
5. User-plane behaviors . . . . . . . . . . . . . . . . . . . . 7
5.1. Traditional mode . . . . . . . . . . . . . . . . . . . . 7
5.1.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 8
5.1.2. Packet flow - Downlink . . . . . . . . . . . . . . . 8
5.1.3. IPv6 user-traffic . . . . . . . . . . . . . . . . . . 9
5.2. Enhanced Mode . . . . . . . . . . . . . . . . . . . . . . 9
5.2.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 10
5.2.2. Packet flow - Downlink . . . . . . . . . . . . . . . 11
5.2.3. IPv6 user-traffic . . . . . . . . . . . . . . . . . . 11
5.3. Enhanced mode with unchanged gNB GTP behavior . . . . . . 11
5.3.1. Interworking with IPv6 GTP . . . . . . . . . . . . . 12
5.3.2. Interworking with IPv4 GTP . . . . . . . . . . . . . 15
5.3.3. Extensions to the interworking mechanisms . . . . . . 17
6. SRv6 SID Mobility Functions . . . . . . . . . . . . . . . . . 18
6.1. Args.Mob.Session . . . . . . . . . . . . . . . . . . . . 18
6.2. End.MAP . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.3. End.M.GTP6.D . . . . . . . . . . . . . . . . . . . . . . 19
6.4. End.M.GTP6.E . . . . . . . . . . . . . . . . . . . . . . 19
6.5. End.M.GTP4.E . . . . . . . . . . . . . . . . . . . . . . 20
6.6. T.M.GTP4.D . . . . . . . . . . . . . . . . . . . . . . . 21
6.7. End.Limit: Rate Limiting function . . . . . . . . . . . . 22
7. SRv6 supported 3GPP PDU session types . . . . . . . . . . . . 22
8. Network Slicing Considerations . . . . . . . . . . . . . . . 23
9. Control Plane Considerations . . . . . . . . . . . . . . . . 23
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10. Security Considerations . . . . . . . . . . . . . . . . . . . 24
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
14.1. Normative References . . . . . . . . . . . . . . . . . . 24
14.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Implementations . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction
In mobile networks, mobility management systems provide connectivity
while mobile nodes move. While the control-plane of the system
signals movements of a mobile node, the user-plane establishes a
tunnel between the mobile node and its anchor node over IP-based
backhaul and core networks.
This document shows the applicability of SRv6 (Segment Routing IPv6)
to those mobile networks. SRv6 provides source routing to networks
so that operators can explicitly indicate a route for the packets to
and from the mobile node. SRv6 endpoint nodes serve as the anchors
of mobile user-plane.
2. Conventions and Terminology
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 [RFC2119].
2.1. Terminology
o AMBR: Aggregate Maximum Bit Rate
o APN: Access Point Name (commonly used to identify a network or
class of service)
o BSID: SR Binding SID [RFC8402]
o CNF: Cloud-native Network Function
o gNB: gNodeB
o NH: The IPv6 next-header field.
o NFV: Network Function Virtualization
o PDU: Packet Data Unit
o Session: TBD...
o SID: A Segment Identifier which represents a specific segment in a
segment routing domain.
o SRH: The Segment Routing Header.
[I-D.ietf-6man-segment-routing-header]
o TEID: Tunnel Endpoint Identifier
o UE: User Equipment
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o UPF: User Plane Function
o VNF: Virtual Network Function
2.2. Conventions
o NH=SRH means that NH is 43 with routing type 4.
o Multiple SRHs may be present inside each packet, but they must
follow each other. The next-header field of each SRH, except the
last one, must be NH-SRH (43 type 4).
o For simplicity, no other extension headers are shown except the
SRH.
o The SID type used in this document is IPv6 address (also called
SRv6 Segment or SRv6 SID).
o gNB::1 is an IPv6 address (SID) assigned to the gNB.
o U1::1 is an IPv6 address (SID) assigned to UPF1.
o U2::1 is an IPv6 address (SID) assigned to UPF2.
o U2:: is some other IPv6 address (SID) assigned to UPF2.
o A SID list is represented as <S1, S2, S3> where S1 is the first
SID to visit, S2 is the second SID to visit and S3 is the last SID
to visit along the SR path.
o (SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with:
* IPv6 header with source and destination addresses SA and DA
respectively, and next-header SRH, with SID list <S1, S2, S3>
with SegmentsLeft = SL
* The payload of the packet is not represented.
o Note the difference between the <> and () symbols: <S1, S2, S3>
represents a SID list where S1 is the first SID and S3 is the last
SID. (S3, S2, S1; SL) represents the same SID list but encoded in
the SRH format where the rightmost SID in the SRH is the first SID
and the leftmost SID in the SRH is the last SID. When referring
to an SR policy in a high-level use-case, it is simpler to use the
<S1, S2, S3> notation. When referring to an illustration of the
detailed behavior, the (S3, S2, S1; SL) notation is more
convenient.
o SRH[SL] represents the SID pointed by the SL field in the first
SRH. In our example, SRH[2] represents S1, SRH[1] represents S2
and SRH[0] represents S3.
o SRH[SL] can be different from the DA of the IPv6 header.
2.3. Predefined SRv6 Functions
The following functions are defined in
[I-D.ietf-spring-srv6-network-programming].
o End.DT4 means to decapsulate and forward using a specific IPv4
table lookup.
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o End.DT6 means to decapsulate and forward using a specific IPv6
table lookup.
o End.DX4 means to decapsulate the packet and forward through a
particular outgoing interface -or set of OIFs- configured with the
SID.
o End.DX6 means to decapsulate and forward through a particular
outgoing interface -or set of OIFs- configured with the SID.
o End.DX2 means to decapsulate the L2 frame and forward through a
particular outgoing interface -or set of OIFs- configured with the
SID.
o End.T means to forward using a specific IPv6 table lookup.
o End.X means to forward through a link configured with the SID.
o T.Encaps.Red means encapsulation without pushing SRH (resulting in
"Reduced" packet size).
o PSP means Penultimate Segment Pop. The packet is subsequently
forwarded without the popped SRH.
New SRv6 functions are defined in Section 6 to support the needs of
the mobile user plane.
3. Motivation
Mobility networks are becoming more challenging to operate. On one
hand, traffic is constantly growing, and latency requirements are
more strict; on the other-hand, there are new use-cases like NFV that
are also challenging network management.
The current architecture of mobile networks does not take into
account the underlying transport. The user-plane is rigidly
fragmented into radio access, core and service networks, connected by
tunneling according to user-plane roles such as access and anchor
nodes. These factors have made it difficult for the operator to
optimize and operate the data-path.
In the meantime, applications have shifted to use IPv6, and network
operators have started adopting IPv6 as their IP transport. SRv6,
the IPv6 dataplane instantiation of Segment Routing [RFC8402],
integrates both the application data-path and the underlying
transport layer into a single protocol, allowing operators to
optimize the network in a simplified manner and removing forwarding
state from the network. It is also suitable for virtualized
environments, VNF/CNF to VNF/CNF networking.
SRv6 specifies network-programming (see
[I-D.ietf-spring-srv6-network-programming]). Applied to mobility,
SRv6 can provide the user-plane functions needed for mobility
management. SRv6 takes advantage of underlying transport awareness
and flexibility to improve mobility user-plane functions.
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The use-cases for SRv6 mobility are discussed in
[I-D.camarilloelmalky-springdmm-srv6-mob-usecases].
4. A 3GPP Reference Architecture
This section presents a reference architecture and possible
deployment scenarios.
Figure 1 shows a reference diagram from the 5G packet core
architecture [TS.23501].
The user plane described in this document does not depend on any
specific architecture. The 5G packet core architecture as shown is
based on the latest 3GPP standards at the time of writing this draft.
Other architectures can be seen in [I-D.gundavelli-dmm-mfa] and
[WHITEPAPER-5G-UP].
+-----+
| AMF |
+-----+
/ | [N11]
[N2] / +-----+
+------/ | SMF |
/ +-----+
/ / \
/ / \ [N4]
/ / \ ________
/ / \ / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN /
+--+ +-----+ +------+ +------+ \________/
Figure 1: 3GPP 5G Reference Architecture
o gNB: gNodeB
o UPF1: UPF with Interfaces N3 and N9
o UPF2: UPF with Interfaces N9 and N6
o SMF: Session Management Function
o AMF: Access and Mobility Management Function
o DN: Data Network e.g. operator services, Internet access
This reference diagram does not depict a UPF that is only connected
to N9 interfaces, although the description in this document also work
for such UPFs.
Each session from an UE gets assigned to a UPF. Sometimes multiple
UPFs may be used, providing richer service functions. A UE gets its
IP address from the DHCP block of its UPF. The UPF advertises that
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IP address block toward the Internet, ensuring that return traffic is
routed to the right UPF.
5. User-plane behaviors
This section describes some mobile user-plane behaviors using SRv6.
In order to simplify the adoption of SRv6, we present two different
"modes" that vary with respect to the use of SRv6. The first one is
the "Traditional mode", which inherits the current 3GPP mobile user-
plane. In this mode there is no change to mobility networks
architecture, except that GTP-U [TS.29281] is replaced by SRv6.
The second mode is the "Enhanced mode". In this mode the SR policy
contains SIDs for Traffic Engineering and VNFs, which results in
effective end-to-end network slices.
In both, the Traditional and the Enhanced modes, we assume that the
gNB as well as the UPFs are SR-aware (N3, N9 and -potentially- N6
interfaces are SRv6).
We introduce two mechanisms for interworking with legacy access
networks (N3 interface is unmodified). In these document we
introduce them applied to the Enhanced mode, although they could be
used in combination with the Traditional mode as well.
One of these mechanisms is designed to interwork with legacy gNBs
using GTP/IPv4. The second method is designed to interwork with
legacy gNBs using GTP/IPv6.
This document uses SRv6 functions defined in
[I-D.ietf-spring-srv6-network-programming] as well as new SRv6
functions designed for the mobile user plane. The new SRv6 functions
are detailed in Section 6.
5.1. Traditional mode
In the traditional mode, the existing mobile UPFs remain unchanged
except for the use of SRv6 as the data plane instead of GTP-U. There
is no impact to the rest of mobile system.
In existing 3GPP mobile networks, an UE PDU Session is mapped 1-for-1
with a specific GTP tunnel (TEID). This 1-for-1 mapping is mirrored
here to replace GTP encapsulation with the SRv6 encapsulation, while
not changing anything else. There will be a unique SRv6 SID
associated with each UE PDU Session.
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The traditional mode minimizes the changes required to the mobile
system; it is a good starting point for forming a common basis.
Our example topology is shown in Figure 2. In traditional mode the
gNB and the UPFs are SR-aware. In the descriptions of the uplink and
downlink packet flow, A is an IPv6 address of the UE, and Z is an
IPv6 address reachable within the Data Network DN. A new SRv6
function End.MAP, defined in Section 6.2, is used.
________
SRv6 SRv6 / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| UPF1 |--------| UPF2 |--------- \ DN /
+--+ +-----+ +------+ +------+ \________/
SRv6 node SRv6 node SRv6 node
Figure 2: Traditional mode - example topology
5.1.1. Packet flow - Uplink
The uplink packet flow is as follows:
UE_out : (A,Z)
gNB_out : (gNB, U1::1) (A,Z) -> T.Encaps.Red <U1::1>
UPF1_out: (gNB, U2::1) (A,Z) -> End.MAP
UPF2_out: (A,Z) -> End.DT4 or End.DT6
When the UE packet arrives at the gNB, the gNB performs a
T.Encaps.Red operation. Since there is only one SID, there is no
need to push an SRH. gNB only adds an outer IPv6 header with IPv6 DA
U1::1. U1::1 represents an anchoring SID specific for that session
at UPF1. gNB obtains the SID U1::1 from the existing control plane
(N2 interface).
When the packet arrives at UPF1, the SID U1::1 identifies a local
End.MAP function. End.MAP replaces U1::1 by U2::1, that belongs to
the next UPF (U2).
When the packet arrives at UPF2, the SID U2::1 corresponds to an
End.DT function. UPF2 decapsulates the packet, performs a lookup in
a specific table associated with that mobile network and forwards the
packet toward the data network (DN).
5.1.2. Packet flow - Downlink
The downlink packet flow is as follows:
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UPF2_in : (Z,A)
UPF2_out: (U2::, U1::1) (Z,A) -> T.Encaps.Red <U1::1>
UPF1_out: (U2::, gNB::1) (Z,A) -> End.MAP
gNB_out : (Z,A) -> End.DX4 or End.DX6
When the packet arrives at the UPF2, the UPF2 maps that flow into a
UE PDU Session. This UE PDU Session is associated with the segment
endpoint <U1::1>. UPF2 performs a T.Encaps.Red operation,
encapsulating the packet into a new IPv6 header with no SRH since
there is only one SID.
Upon packet arrival on UPF1, the SID U1::1 is a local End.MAP
function. This function maps the SID to the next anchoring point and
replaces U1::1 by gNB::1, that belongs to the next hop.
Upon packet arrival on gNB, the SID gNB::1 corresponds to an End.DX4
or End.DX6 function. The gNB decapsulates the packet, removing the
IPv6 header and all its extensions headers, and forwards the traffic
toward the UE.
5.1.3. IPv6 user-traffic
For IPv6 user-traffic it is RECOMMENDED to perform encapsulation.
However based on local policy, a service provider MAY choose to do
SRH insertion. The main benefit is a lower overhead(40B less). In
such case, the functions used are T.Insert.Red at gNB, End.MAP at
UPF1 and End.T at UPF2 on Uplink, T.Insert.Red at UPF2, End.MAP at
UPF1 and End.X at gNB on Downlink.
5.2. Enhanced Mode
Enhanced mode improves scalability, traffic steering and service
programming [I-D.xuclad-spring-sr-service-programming], thanks to the
use of multiple SIDs, instead of a single SID as done in the
Traditional mode.
The main difference is that the SR policy MAY include SIDs for
traffic engineering and service programming in addition to the UPFs
SIDs.
The gNB control-plane (N2 interface) is unchanged, specifically a
single IPv6 address is given to the gNB.
o The gNB MAY resolve the IP address into a SID list using a
mechanism like PCEP, DNS-lookup, small augment for LISP control-
plane, etc.
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Note that the SIDs MAY use the arguments Args.Mob.Session if required
by the UPFs.
Figure 3 shows an Enhanced mode topology. In the Enhanced mode, the
gNB and the UPF are SR-aware. The Figure shows two service segments,
S1 and C1. S1 represents a VNF in the network, and C1 represents a
constraint path on a router requiring Traffic Engineering. S1 and C1
belong to the underlay and don't have an N4 interface, so they are
not considered UPFs.
+----+ SRv6 _______
SRv6 --| C1 |--[N3] / \
+--+ +-----+ [N3] / +----+ \ +------+ [N6] / \
|UE|----| gNB |-- SRv6 / SRv6 --| UPF2 |------\ DN /
+--+ +-----+ \ [N3]/ TE +------+ \_______/
SRv6 node \ +----+ / SRv6 node
-| S1 |-
+----+
SRv6 node
CNF
Figure 3: Enhanced mode - Example topology
5.2.1. Packet flow - Uplink
The uplink packet flow is as follows:
UE_out : (A,Z)
gNB_out : (gNB, S1)(U2::1, C1; SL=2)(A,Z)-> T.Encaps.Red<S1,C1,U2::1>
S1_out : (gNB, C1)(U2::1, C1; SL=1 (A,Z)
C1_out : (gNB, U2::1)(A,Z) -> PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6
UE sends its packet (A,Z) on a specific bearer to its gNB. gNB's
control plane associates that session from the UE(A) with the IPv6
address B and GTP TEID T. gNB's control plane does a lookup on B to
find the related SID list <S1, C1, U2::1>.
When gNB transmits the packet, it contains all the segments of the SR
policy. The SR policy can include segments for traffic engineering
(C1) and for service programming (S1).
Nodes S1 and C1 perform their related Endpoint functionality and
forward the packet.
When the packet arrives at UPF2, the active segment (U2::1) is an
End.DT4/6 which performs the decapsulation (removing the IPv6 header
with all its extension headers) and forwards toward the data network.
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5.2.2. Packet flow - Downlink
The downlink packet flow is as follows:
UPF2_in : (Z,A) -> UPF2 maps the flow w/
SID list <C1,S1, gNB>
UPF2_out: (U2::1, C1)(gNB, S1; SL=2)(Z,A) -> T.Encaps.Red
C1_out : (U2::1, S1)(gNB, S1; SL=1)(Z,A)
S1_out : (U2::1, gNB)(Z,A) -> PSP
gNB_out : (Z,A) -> End.DX4 or End.DX6
When the packet arrives at the UPF2, the UPF2 maps that particular
flow into a UE PDU Session. This UE PDU Session is associated with
the policy <C1, S1, gNB>. The UPF2 performs a T.Encaps.Red
operation, encapsulating the packet into a new IPv6 header with its
corresponding SRH.
The nodes C1 and S1 perform their related Endpoint processing.
Once the packet arrives at the gNB, the IPv6 DA corresponds to an
End.DX4 or End.DX6 (depending on the underlying traffic). The gNB
decapsulates the packet, removing the IPv6 header and all its
extensions headers and forwards the traffic toward the UE.
5.2.3. IPv6 user-traffic
For IPv6 user-traffic it is RECOMMENDED to perform encapsulation.
However based on local policy, a service provider MAY choose to do
SRH insertion. The main benefit is a lower overhead. In such case,
the functions used are T.Insert.Red at gNB and End.T at UPF2 on
Uplink, T.Insert.Red at UPF2 and End.X at gNB on Downlink.
5.3. Enhanced mode with unchanged gNB GTP behavior
This section describes two mechanisms for interworking with legacy
gNBs that still use GTP: one for IPv4, the other for IPv6.
In the interworking scenarios as illustrated in Figure 4, gNB does
not support SRv6. gNB supports GTP encapsulation over IPv4 or IPv6.
To achieve interworking, a SR Gateway (SRGW-UPF1) entity is added.
The SRGW maps the GTP traffic into SRv6.
The SRGW is not an anchor point, and maintains very little state.
For this reason, both IPv4 and IPv6 methods scale to millions of UEs.
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_______
IP GTP SRv6 / \
+--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \
|UE|------| gNB |------| UPF1 |--------| UPF2 |---------\ DN /
+--+ +-----+ +------+ +------+ \_______/
SR Gateway SRv6 node
Figure 4: Example topology for interworking
5.3.1. Interworking with IPv6 GTP
In this interworking mode the gNB uses GTP over IPv6 via the N3
interface
Key points:
o The gNB is unchanged (control-plane or user-plane) and
encapsulates into GTP (N3 interface is not modified).
o The 5G Control-Plane (N2 interface) is unmodified; one IPv6
address is needed (i.e. a BSID at the SRGW).
o The SRGW removes GTP, finds the SID list related to DA, and adds
SRH with the SID list.
o There is no state for the downlink at the SRGW.
o There is simple state in the uplink at the SRGW; using Enhanced
mode results in fewer SR policies on this node. A SR policy can
be shared across UEs.
o When a packet from the UE leaves the gNB, it is SR-routed. This
simplifies network slicing [I-D.hegdeppsenak-isis-sr-flex-algo].
o In the uplink, the IPv6 DA BSID steers traffic into an SR policy
when it arrives at the SRGW-UPF1.
An example topology is shown in Figure 5. In this mode the gNB is an
unmodified gNB using IPv6/GTP. The UPFs are SR-aware. As before,
the SRGW maps IPv6/GTP traffic to SRv6.
S1 and C1 are two service segments. S1 represents a VNF in the
network, and C1 represents a router configured for Traffic
Engineering.
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+----+
IPv6/GTP -| S1 |- ___
+--+ +-----+ [N3] / +----+ \ /
|UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] /
+--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN
GTP \ +------+ / +----+ +------+ \___
-| UPF1 |- SRv6 SRv6
+------+ TE
SR Gateway
Figure 5: Enhanced mode with unchanged gNB IPv6/GTP behavior
5.3.1.1. Packet flow - Uplink
The uplink packet flow is as follows:
UE_out : (A,Z)
gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3 unmodified
(IPv6/GTP)
SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> B is an End.M.GTP6.D
SID at the SRGW
S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z)
C1_out : (SRGW, U2::1)(A,Z) -> PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6
The UE sends a packet destined to Z toward the gNB on a specific
bearer for that session. The gNB, which is unmodified, encapsulates
the packet into IPv6, UDP and GTP headers. The IPv6 DA B, and the
GTP TEID T are the ones received in the N2 interface.
The IPv6 address that was signalled over the N2 interface for that UE
PDU Session, B, is now the IPv6 DA. B is an SRv6 Binding SID at the
SRGW. Hence the packet is routed to the SRGW.
When the packet arrives at the SRGW, the SRGW identifies B as an
End.M.GTP6.D Binding SID (see Section 6.3). Hence, the SRGW removes
the IPv6, UDP and GTP headers, and pushes an IPv6 header with its own
SRH containing the SIDs bound to the SR policy associated with this
BindingSID. There is one instance of the End.M.GTP6.D SID per PDU
type.
S1 and C1 perform their related Endpoint functionality and forward
the packet.
When the packet arrives at UPF2, the active segment is (U2::1) which
is bound to End.DT4/6. UPF2 then decapsulates (removing the outer
IPv6 header with all its extension headers) and forwards the packet
toward the data network.
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5.3.1.2. Packet flow - Downlink
The downlink packet flow is as follows:
UPF2_in : (Z,A) -> UPF2 maps the flow with
<C1, S1, SRGW::TEID,gNB>
UPF2_out: (U2::1, C1)(gNB, SRGW::TEID, S1; SL=3)(Z,A) -> T.Encaps.Red
C1_out : (U2::1, S1)(gNB, S1; SL=2)(Z,A)
S1_out : (U2::1, SRGW::TEID)(gNB, SRGW::TEID, S1, SL=1)(Z,A)
SRGW_out: (SRGW, gNB)(GTP: TEID=T)(Z,A) -> SRGW/96 is End.M.GTP6.E
gNB_out : (Z,A)
When a packet destined to A arrives at the UPF2, the UPF2 performs a
lookup in the table associated to A and finds the SID list <C1, S1,
SRGW::TEID, gNB>. The UPF2 performs a T.Encaps.Red operation,
encapsulating the packet into a new IPv6 header with its
corresponding SRH.
C1 and S1 perform their related Endpoint processing.
Once the packet arrives at the SRGW, the SRGW identifies the active
SID as an End.M.GTP6.E function. The SRGW removes the IPv6 header
and all its extensions headers. The SRGW generates new IPv6, UDP and
GTP headers. The new IPv6 DA is the gNB which is the last SID in the
received SRH. The TEID in the generated GTP header is an argument of
the received End.M.GTP6.E SID. The SRGW pushes the headers to the
packet and forwards the packet toward the gNB. There is one instance
of the End.M.GTP6.E SID per PDU type.
Once the packet arrives at the gNB, the packet is a regular IPv6/GTP
packet. The gNB looks for the specific radio bearer for that TEID
and forward it on the bearer. This gNB behavior is not modified from
current and previous generations.
5.3.1.3. Scalability
For the downlink traffic, the SRGW is stateless. All the state is in
the SRH inserted by the UPF2. The UPF2 must have the UE states since
it is the UE's session anchor point.
For the uplink traffic, the state at the SRGW does not necessarily
need to be unique per UE PDU Session; the state state can be shared
among UEs. This enables much more scalable SRGW deployments compared
to a solution holding millions of states, one or more per UE.
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5.3.1.4. IPv6 user-traffic
For IPv6 user-traffic it is RECOMMENDED to perform encapsulation.
However based on local policy, a service provider MAY choose to do
SRH insertion. The main benefit is lower overhead.
5.3.2. Interworking with IPv4 GTP
In this interworking mode the gNB uses GTP over IPv4 in the N3
interface
Key points:
o The gNB is unchanged and encapsulates packets into GTP (the N3
interface is not modified).
o In the uplink, traffic is classified by SRGW's Uplink Classifier
and steered into an SR policy. The SRGW is a UPF1 functionality
and can coexist with UPF1's Uplink Classifier functionality.
o SRGW removes GTP, finds the SID list related to DA, and adds a SRH
with the SID list.
An example topology is shown in Figure 6. In this mode the gNB is an
unmodified gNB using IPv4/GTP. The UPFs are SR-aware. As before,
the SRGW maps the IPv4/GTP traffic to SRv6.
S1 and C1 are two service segment endpoints. S1 represents a VNF in
the network, and C1 represents a router configured for Traffic
Engineering.
+----+
IPv4/GTP -| S1 |- ___
+--+ +-----+ [N3] / +----+ \ /
|UE|--| gNB |- SRv6 / SRv6 \ +----+ +------+ [N6] /
+--+ +-----+ \ [N9]/ VNF -| C1 |---| UPF2 |------\ DN
GTP \ +------+ / +----+ +------+ \___
-| UPF1 |- SRv6 SRv6
+------+ TE
SR Gateway
Figure 6: Enhanced mode with unchanged gNB IPv4/GTP behavior
5.3.2.1. Packet flow - Uplink
The uplink packet flow is as follows:
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gNB_out : (gNB, B)(GTP: TEID T)(A,Z) -> Interface N3
unchanged IPv4/GTP
SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z) -> T.M.GTP4.D function
S1_out : (SRGW, C1)(U2::1, C1; SL=1)(A,Z)
C1_out : (SRGW, U2::1) (A,Z) -> PSP
UPF2_out: (A,Z) -> End.DT4 or End.DT6
The UE sends a packet destined to Z toward the gNB on a specific
bearer for that session. The gNB, which is unmodified, encapsulates
the packet into a new IPv4, UDP and GTP headers. The IPv4 DA, B, and
the GTP TEID are the ones received at the N2 interface.
When the packet arrives at the SRGW for UPF1, the SRGW has an Uplink
Classifier rule for incoming traffic from the gNB, that steers the
traffic into an SR policy by using the function T.M.GTP4.D. The SRGW
removes the IPv4, UDP and GTP headers and pushes an IPv6 header with
its own SRH containing the SIDs related to the SR policy associated
with this traffic. The SRGW forwards according to the new IPv6 DA.
S1 and C1 perform their related Endpoint functionality and forward
the packet.
When the packet arrives at UPF2, the active segment is (U2::1) which
is bound to End.DT4/6 which performs the decapsulation (removing the
outer IPv6 header with all its extension headers) and forwards toward
the data network.
5.3.2.2. Packet flow - Downlink
The downlink packet flow is as follows:
UPF2_in : (Z,A) -> UPF2 maps flow with SID
<C1, S1,SRGW::SA:DA:TEID>
UPF2_out: (U2::1, C1)(SRGW::SA:DA:TEID, S1; SL=2)(Z,A) ->T.Encaps.Red
C1_out : (U2::1, S1)(SRGW::SA:DA:TEID, S1; SL=1)(Z,A)
S1_out : (U2::1, SRGW::SA:DA:TEID)(Z,A)
SRGW_out: (SA, DA)(GTP: TEID=T)(Z,A) -> End.M.GTP4.E
gNB_out : (Z,A)
When a packet destined to A arrives at the UPF2, the UPF2 performs a
lookup in the table associated to A and finds the SID list <C1, S1,
SRGW::SA:DA:TEID>. The UPF2 performs a T.Encaps.Red operation,
encapsulating the packet into a new IPv6 header with its
corresponding SRH.
The nodes C1 and S1 perform their related Endpoint processing.
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Once the packet arrives at the SRGW, the SRGW identifies the active
SID as an End.M.GTP4.E function. The SRGW removes the IPv6 header
and all its extensions headers. The SRGW generates an IPv4, UDP and
GTP headers. The IPv4 SA and DA are received as SID arguments. The
TEID in the generated GTP header is also the arguments of the
received End.M.GTP4.E SID. The SRGW pushes the headers to the packet
and forwards the packet toward the gNB.
When the packet arrives at the gNB, the packet is a regular IPv4/GTP
packet. The gNB looks for the specific radio bearer for that TEID
and forward it on the bearer. This gNB behavior is not modified from
current and previous generations.
5.3.2.3. Scalability
For the downlink traffic, the SRGW is stateless. All the state is in
the SRH inserted by the UPF. The UPF must have this UE-base state
anyway (since it is its anchor point).
For the uplink traffic, the state at the SRGW is dedicated on a per
UE/session basis according to an Uplink Classifier. There is state
for steering the different sessions on a SR policies. However, SR
policies are shared among several UE/sessions.
5.3.2.4. IPv6 user-traffic
For IPv6 user-traffic it is RECOMMENDED to perform encapsulation.
Based on local policy, a service provider MAY choose to do SRH
insertion. The main benefit is a lower overhead.
5.3.3. Extensions to the interworking mechanisms
In this section we presented two mechanisms for interworking with
gNBs that do not support SRv6. These mechanism are done to support
GTP over IPv4 and GTP over IPv6.
Even though we have presented these methods as an extension to the
"Enhanced mode", it is straightforward in its applicability to the
"Traditional mode".
Furthermore, although these mechanisms are designed for interworking
with legacy RAN at the N3 interface, these methods could also be
applied for interworking with a non-SRv6 capable UPF at the N9
interface (e.g. L3-anchor is SRv6 capable but L2-anchor is not).
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6. SRv6 SID Mobility Functions
6.1. Args.Mob.Session
Args.Mob.Session provide per-session information for charging,
buffering and lawful intercept (among others) required by some mobile
nodes. The Args.Mob.Session argument format is used in combination
with End.Map, End.DT and End.DX functions. Note that proposed format
is applicable for 5G networks, while similar formats could be
proposed for legacy networks.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QFI |R|U| PDU Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PDU Sess(cont')|
+-+-+-+-+-+-+-+-+
Args.Mob.Session format
o QFI: QoS Flow Identifier [TS.38415]
o R: Reflective QoS Indication [TS.23501]. This parameter indicates
the activaton of reflective QoS towards the UE for the transfered
packet. Reflective QoS enables the UE to map UL User Plane
traffic to QoS Flows without SMF provided QoS rules.
o U: Unused and for future use. MUST be 0 on transmission and
ignored on receipt.
o PDU Session ID: Identifier of PDU Session. The GTP-U equivalent
is TEID.
Since the SRv6 function is likely NOT to be instantiated per PDU
session, Args.Mob.Session helps the UPF to perform the functions
which require per QFI and/or per PDU Session granularity.
6.2. End.MAP
The "Endpoint function with SID mapping" function (End.MAP for short)
is used in several scenarios. Particularly in mobility, End.MAP is
used in the UPFs for the PDU Session anchor functionality.
When a SR node N receives a packet destined to S and S is a local
End.MAP SID, N does the following:
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1. Lookup the IPv6 DA in the mapping table
2. update the IPv6 DA with the new mapped SID ;; Ref1
3. IF segment_list > 1
4. insert a new SRH
5. forward according to the new mapped SID
Ref1: The SIDs in the SRH are NOT modified.
6.3. End.M.GTP6.D
The "Endpoint function with IPv6/GTP decapsulation into SR policy"
function (End.M.GTP6.D for short) is used in interworking scenario
for the uplink toward from the legacy gNB using IPv6/GTP. Suppose,
for example, this SID is associated with an SR policy <S1, S2, S3>
and an IPv6 Source Address A.
When the SR Gateway node N receives a packet destined to S and S is a
local End.M.GTP6.D SID, N does:
1. IF NH=UDP & UDP_DST_PORT = GTP THEN
2. copy TEID to form SID S3
3. pop the IPv6, UDP and GTP headers
4. push a new IPv6 header with a SR policy in SRH <S1, S2, S3>
5. set the outer IPv6 SA to A
6. set the outer IPv6 DA to S1
7. set the outer IPv6 NH ;; Ref1
8. forward according to the S1 segment of the SRv6 Policy
9. ELSE
10. Drop the packet
Ref1: The NH is set based on the SID parameter. There is one
instantiation of the End.M.GTP6.D SID per PDU Session Type, hence the
NH is already known in advance. For the IPv4v6 PDU Session Type, in
addition we inspect the first nibble of the PDU to know the NH value.
The prefix of last segment(S3 in above example) SHOULD be followed by
an Arg.Mob.Session argument space which is used to provide the
session identifiers.
The prefix of A SHOULD be an End.M.GTP6.E SID instantiated at an SR
gateway.
6.4. End.M.GTP6.E
The "Endpoint function with encapsulation for IPv6/GTP tunnel"
function (End.M.GTP6.E for short) is used in interworking scenario
for the downlink toward the legacy gNB using IPv6/GTP.
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The prefix of End.M.GTP6.E SID MUST be followed by the
Arg.Mob.Session argument space which is used to provide the session
identifiers.
When the SR Gateway node N receives a packet destined to S, and S is
a local End.M.GTP6.E SID, N does the following:
1. IF NH=SRH & SL = 1 THEN ;; Ref1
2. store SRH[0] in variable new_DA
3. store TEID in variable new_TEID from IPv6 DA ;; Ref2
4. pop IP header and all its extension headers
5. push new IPv6 header and GTP-U header
6. set IPv6 DA to new_DA
7. set IPv6 SA to A
8. set GTP_TEID to new_TEID
9. lookup the new_DA and forward the packet accordingly
10. ELSE
11. Drop the packet
Ref1: An End.M.GTP6.E SID MUST always be the penultimate SID.
Ref2: TEID is extracted from the argument space of the current SID.
The source address A SHOULD be an End.M.GTP6.D SID instantiated at an
SR gateway.
6.5. End.M.GTP4.E
The "Endpoint function with encapsulation for IPv4/GTP tunnel"
function (End.M.GTP4.E for short) is used in the downlink when doing
interworking with legacy gNB using IPv4/GTP.
When the SR Gateway node N receives a packet destined to S and S is a
local End.M.GTP4.E SID, N does:
1. IF (NH=SRH and SL = 0) or ENH=4 THEN
2. store IPv6 DA in buffer S
3. store IPv6 SA in buffer S'
4. pop the IPv6 header and its extension headers
5. push UDP/GTP headers with GTP TEID from S
6. push outer IPv4 header with SA, DA from S' and S
7. ELSE
8. Drop the packet
The End.M.GTP4.E SID in S has the following format:
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0 127
+-----------------------+-------+----------------+---------+
| SRGW-IPv6-LOC-FUNC |IPv4DA |Args.Mob.Session|0 Padded |
+-----------------------+-------+----------------+---------+
128-a-b-c a b c
End.M.GTP4.E SID Encoding
S' has the following format:
0 127
+----------------------+--------+--------------------------+
| Source UPF Prefix |IPv4 SA | any bit pattern(ignored) |
+----------------------+--------+--------------------------+
128-a-b a b
IPv6 SA Encoding for End.M.GTP4.E
6.6. T.M.GTP4.D
The "Transit with tunnel decapsulation and map to an SRv6 policy"
function (T.M.GTP4.D for short) is used in the direction from legacy
user-plane to SRv6 user-plane network.
When the SR Gateway node N receives a packet destined to a IW-
IPv4-Prefix, N does:
1. IF Payload == UDP/GTP THEN
2. pop the outer IPv4 header and UDP/GTP headers
3. copy IPv4 DA, TEID to form SID B
4. copy IPv4 SA to form IPv6 SA B'
5. encapsulate the packet into a new IPv6 header ;;Ref1
6. set the IPv6 DA = B
7. forward along the shortest path to B
8. ELSE
9. Drop the packet
Ref1: The NH value is identified by inspecting the first nibble of
the inner payload.
The SID B has the following format:
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0 127
+-----------------------+-------+----------------+---------+
|Destination UPF Prefix |IPv4DA |Args.Mob.Session|0 Padded |
+-----------------------+-------+----------------+---------+
128-a-b-c a b c
T.M.GTP4.D SID Encoding
The SID B MAY be an SRv6 Binding SID instantiated at the first UPF
(U1) to bind a SR policy [I-D.ietf-spring-segment-routing-policy].
The prefix of B' SHOULD be an End.M.GTP4.E SID with its format
instantiated at an SR gateway with the IPv4 SA of the receiving
packet.
6.7. End.Limit: Rate Limiting function
The mobile user-plane requires a rate-limit feature. For this
purpose, we define a new function "End.Limit". The "End.Limit"
function encodes in its arguments the rate limiting parameter that
should be applied to this packet. Multiple flows of packets should
have the same group identifier in the SID when those flows are in an
same AMBR group. The encoding format of the rate limit segment SID
is as follows:
+----------------------+----------+-----------+
| LOC+FUNC rate-limit | group-id | limit-rate|
+----------------------+----------+-----------+
128-i-j i j
End.Limit: Rate limiting function argument format
If the limit-rate bits are set to zero, the node should not do rate
limiting unless static configuration or control-plane sets the limit
rate associated to the SID.
7. SRv6 supported 3GPP PDU session types
The 3GPP [TS.23501] defines the following PDU session types:
o IPv4
o IPv6
o IPv4v6
o Ethernet
o Unstructured
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SRv6 supports all the 3GPP PDU session types without any protocol
overhead by using the corresponding SRv6 functions (End.DX4, End.DT4
for IPv4 PDU sessions; End.DX6, End.DT6, End.T for IPv6 PDU sessions;
End.DT46 for IPv4v6 PDU sessions; End.DX2 for L2 PDU sessions;
End.DX2 for Unstructured PDU sessions).
8. Network Slicing Considerations
A mobile network may be required to implement "network slices", which
logically separate network resources. User-plane functions
represented as SRv6 segments would be part of a slice.
[I-D.ietf-spring-segment-routing-policy] describes a solution to
build basic network slices with SR. Depending on the requirements,
these slices can be further refined by adopting the mechanisms from:
o IGP Flex-Algo [I-D.hegdeppsenak-isis-sr-flex-algo]
o Inter-Domain policies
[I-D.ietf-spring-segment-routing-central-epe]
Furthermore, these can be combined with ODN/AS
[I-D.ietf-spring-segment-routing-policy] for automated slice
provisioning and traffic steering.
Further details on how these tools can be used to create end to end
network slices are documented in
[I-D.ali-spring-network-slicing-building-blocks].
9. Control Plane Considerations
This document focuses on user-plane behavior and its independence
from the control plane.
The control plane could be the current 3GPP-defined control plane
with slight modifications to the N4 interface [TS.29244].
Alternatively, SRv6 could be used in conjunction with a new mobility
control plane as described in LISP [I-D.rodrigueznatal-lisp-srv6],
hICN [I-D.auge-dmm-hicn-mobility-deployment-options], MFA
[I-D.gundavelli-dmm-mfa] or in conjunction with FPC
[I-D.ietf-dmm-fpc-cpdp]. The analysis of new mobility control-planes
and its applicability to SRv6 is out of the scope of this document.
Section 11 allocates SRv6 endpoint function types for the new
functions defined in this document. Control-plane protocols are
expected to use these function type codes to signal each function.
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SRv6's network programming nature allows a flexible and dynamic UPF
placement.
10. Security Considerations
TBD
11. IANA Considerations
IANA is requested to allocate, within the "SRv6 Endpoint Types" sub-
registry belonging to the top-level "Segment-routing with IPv6
dataplane (SRv6) Parameters" registry
[I-D.ietf-spring-srv6-network-programming], the following values:
+-------------+-----+-------------------+-----------+
| Value/Range | Hex | Endpoint function | Reference |
+-------------+-----+-------------------+-----------+
| TBA | TBA | End.MAP | [This.ID] |
| TBA | TBA | End.M.GTP6.D | [This.ID] |
| TBA | TBA | End.M.GTP6.E | [This.ID] |
| TBA | TBA | End.M.GTP4.E | [This.ID] |
| TBA | TBA | End.Limit | [This.ID] |
+-------------+-----+-------------------+-----------+
Table 1: SRv6 Mobile User-plane Endpoint Types
12. Acknowledgements
The authors would like to thank Daisuke Yokota, Bart Peirens,
Ryokichi Onishi, Kentaro Ebisawa, Peter Bosch, Darren Dukes, Francois
Clad, Sri Gundavelli, Sridhar Bhaskaran, Arashmid Akhavain, Ravi
Shekhar and Aeneas Dodd-Noble for their useful comments of this work.
13. Contributors
Kentaro Ebisawa
Toyota Motor Corporation
Japan
Email: ebisawa@toyota-tokyo.tech
14. References
14.1. Normative References
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[]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
Routing Header (SRH)", draft-ietf-6man-segment-routing-
header-21 (work in progress), June 2019.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
bogdanov@google.com, b., and P. Mattes, "Segment Routing
Policy Architecture", draft-ietf-spring-segment-routing-
policy-03 (work in progress), May 2019.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J.,
daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
Network Programming", draft-ietf-spring-srv6-network-
programming-01 (work in progress), July 2019.
[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>.
14.2. Informative References
[I-D.ali-spring-network-slicing-building-blocks]
Ali, Z., Filsfils, C., Camarillo, P., and d.
daniel.voyer@bell.ca, "Building blocks for Slicing in
Segment Routing Network", draft-ali-spring-network-
slicing-building-blocks-01 (work in progress), March 2019.
[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", draft-auge-dmm-hicn-
mobility-deployment-options-02 (work in progress), July
2019.
[I-D.camarillo-dmm-srv6-mobile-pocs]
Camarillo, P., Filsfils, C., Bertz, L., Akhavain, A.,
Matsushima, S., and d. daniel.voyer@bell.ca, "Segment
Routing IPv6 for mobile user-plane PoCs", draft-camarillo-
dmm-srv6-mobile-pocs-02 (work in progress), April 2019.
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[I-D.camarilloelmalky-springdmm-srv6-mob-usecases]
Camarillo, P., Filsfils, C., Elmalky, H., Matsushima, S.,
daniel.voyer@bell.ca, d., Cui, A., and B. Peirens, "SRv6
Mobility Use-Cases", draft-camarilloelmalky-springdmm-
srv6-mob-usecases-01 (work in progress), January 2019.
[I-D.gundavelli-dmm-mfa]
Gundavelli, S., Liebsch, M., and S. Matsushima, "Mobility-
aware Floating Anchor (MFA)", draft-gundavelli-dmm-mfa-01
(work in progress), September 2018.
[I-D.hegdeppsenak-isis-sr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., and A. Gulko, "ISIS
Segment Routing Flexible Algorithm", draft-hegdeppsenak-
isis-sr-flex-algo-02 (work in progress), February 2018.
[I-D.ietf-dmm-fpc-cpdp]
Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S.,
Moses, D., and C. Perkins, "Protocol for Forwarding Policy
Configuration (FPC) in DMM", draft-ietf-dmm-fpc-cpdp-12
(work in progress), June 2018.
[I-D.ietf-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
Afanasiev, "Segment Routing Centralized BGP Egress Peer
Engineering", draft-ietf-spring-segment-routing-central-
epe-10 (work in progress), December 2017.
[I-D.rodrigueznatal-lisp-srv6]
Rodriguez-Natal, A., Ermagan, V., Maino, F., Dukes, D.,
Camarillo, P., and C. Filsfils, "LISP Control Plane for
SRv6 Endpoint Mobility", draft-rodrigueznatal-lisp-srv6-01
(work in progress), January 2019.
[I-D.xuclad-spring-sr-service-programming]
Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca,
d., Li, C., Decraene, B., Ma, S., Yadlapalli, C.,
Henderickx, W., and S. Salsano, "Service Programming with
Segment Routing", draft-xuclad-spring-sr-service-
programming-02 (work in progress), April 2019.
[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.
Matsushima, et al. Expires January 9, 2020 [Page 26]
Internet-Draft SRv6-mobile-uplane July 2019
[TS.29281]
3GPP, , "General Packet Radio System (GPRS) Tunnelling
Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 15.1.0,
December 2017.
[TS.38415]
3GPP, , "Draft Specification for 5GS container (TS
38.415)", 3GPP R3-174510 0.0.0, August 2017.
Appendix A. Implementations
This document introduces new SRv6 functions. These functions have an
open-source P4 implementation available in
<https://github.com/ebiken/p4srv6>.
There are also implementations in M-CORD NGIC and Open Air Interface
(OAI). Further details can be found in
[I-D.camarillo-dmm-srv6-mobile-pocs].
Authors' Addresses
Satoru Matsushima
SoftBank
Tokyo
Japan
Email: satoru.matsushima@g.softbank.co.jp
Clarence Filsfils
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Miya Kohno
Cisco Systems, Inc.
Japan
Email: mkohno@cisco.com
Pablo Camarillo Garvia
Cisco Systems, Inc.
Spain
Email: pcamaril@cisco.com
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Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
Charles E. Perkins
Futurewei Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1-408-330-4586
Email: charliep@computer.org
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