--- 1/draft-ietf-dmm-srv6-mobile-uplane-06.txt 2019-11-04 14:13:11.605099444 -0800 +++ 2/draft-ietf-dmm-srv6-mobile-uplane-07.txt 2019-11-04 14:13:11.665100962 -0800 @@ -1,62 +1,62 @@ DMM Working Group S. Matsushima Internet-Draft SoftBank Intended status: Standards Track C. Filsfils -Expires: March 29, 2020 M. Kohno +Expires: May 7, 2020 M. Kohno P. Camarillo Cisco Systems, Inc. D. Voyer Bell Canada C. Perkins Futurewei - September 26, 2019 + November 4, 2019 Segment Routing IPv6 for Mobile User Plane - draft-ietf-dmm-srv6-mobile-uplane-06 + draft-ietf-dmm-srv6-mobile-uplane-07 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. + mobile user plane. 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 working documents as Internet-Drafts. The list of current Internet- - Drafts is at https://datatracker.ietf.org/drafts/current/. + Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on March 29, 2020. + This Internet-Draft will expire on May 7, 2020. Copyright Notice Copyright (c) 2019 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/license-info) in effect on the date of + (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 @@ -69,41 +69,43 @@ 5. User-plane behaviors . . . . . . . . . . . . . . . . . . . . 7 5.1. Traditional mode . . . . . . . . . . . . . . . . . . . . 7 5.1.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 8 5.1.2. Packet flow - Downlink . . . . . . . . . . . . . . . 8 5.2. Enhanced Mode . . . . . . . . . . . . . . . . . . . . . . 9 5.2.1. Packet flow - Uplink . . . . . . . . . . . . . . . . 10 5.2.2. Packet flow - Downlink . . . . . . . . . . . . . . . 10 5.3. Enhanced mode with unchanged gNB GTP behavior . . . . . . 11 5.3.1. Interworking with IPv6 GTP . . . . . . . . . . . . . 11 5.3.2. Interworking with IPv4 GTP . . . . . . . . . . . . . 14 - 5.3.3. Extensions to the interworking mechanisms . . . . . . 17 - 6. SRv6 SID Mobility Functions . . . . . . . . . . . . . . . . . 17 - 6.1. Args.Mob.Session . . . . . . . . . . . . . . . . . . . . 17 - 6.2. End.MAP . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 6.3. End.M.GTP6.D . . . . . . . . . . . . . . . . . . . . . . 18 - 6.4. End.M.GTP6.E . . . . . . . . . . . . . . . . . . . . . . 19 - 6.5. End.M.GTP4.E . . . . . . . . . . . . . . . . . . . . . . 20 - 6.6. T.M.GTP4.D . . . . . . . . . . . . . . . . . . . . . . . 20 - 6.7. End.Limit: Rate Limiting function . . . . . . . . . . . . 21 - 7. SRv6 supported 3GPP PDU session types . . . . . . . . . . . . 22 - 8. Network Slicing Considerations . . . . . . . . . . . . . . . 22 - 9. Control Plane Considerations . . . . . . . . . . . . . . . . 22 - 10. Security Considerations . . . . . . . . . . . . . . . . . . . 23 - 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 - 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 - 14.1. Normative References . . . . . . . . . . . . . . . . . . 24 - 14.2. Informative References . . . . . . . . . . . . . . . . . 24 - Appendix A. Implementations . . . . . . . . . . . . . . . . . . 26 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 + 5.3.3. SRv6 Drop-in Interworking . . . . . . . . . . . . . . 16 + 5.3.4. Extensions to the interworking mechanisms . . . . . . 18 + 6. SRv6 SID Mobility Functions . . . . . . . . . . . . . . . . . 18 + 6.1. Args.Mob.Session . . . . . . . . . . . . . . . . . . . . 18 + 6.2. End.MAP . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 6.3. End.M.GTP6.D . . . . . . . . . . . . . . . . . . . . . . 20 + 6.4. End.M.GTP6.D.Di . . . . . . . . . . . . . . . . . . . . . 20 + 6.5. End.M.GTP6.E . . . . . . . . . . . . . . . . . . . . . . 21 + 6.6. End.M.GTP4.E . . . . . . . . . . . . . . . . . . . . . . 22 + 6.7. T.M.GTP4.D . . . . . . . . . . . . . . . . . . . . . . . 23 + 6.8. End.Limit: Rate Limiting function . . . . . . . . . . . . 23 + 7. SRv6 supported 3GPP PDU session types . . . . . . . . . . . . 24 + 8. Network Slicing Considerations . . . . . . . . . . . . . . . 24 + 9. Control Plane Considerations . . . . . . . . . . . . . . . . 25 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 + 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 + 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 + 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 + 14.1. Normative References . . . . . . . . . . . . . . . . . . 26 + 14.2. Informative References . . . . . . . . . . . . . . . . . 27 + Appendix A. Implementations . . . . . . . . . . . . . . . . . . 28 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28 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) @@ -114,48 +116,48 @@ 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 Anchor: An topological endpoint of an UE 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 Session: Context of an UE connects to a mobile network. 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 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 The SID type used in this document is 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 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 @@ -296,23 +298,23 @@ 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. + networks (N3 interface is unmodified). In this 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. @@ -391,21 +393,21 @@ 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. 5.2. Enhanced Mode Enhanced mode improves scalability, traffic steering and service - programming [I-D.xuclad-spring-sr-service-programming], thanks to the + programming [I-D.ietf-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. @@ -489,22 +491,22 @@ 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. + 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. _______ IP GTP SRv6 / \ +--+ +-----+ [N3] +------+ [N9] +------+ [N6] / \ |UE|------| gNB |------| UPF1 |--------| UPF2 |---------\ DN / +--+ +-----+ +------+ +------+ \_______/ SR Gateway SRv6 node Figure 4: Example topology for interworking @@ -519,21 +521,21 @@ 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]. + simplifies network slicing [I-D.ietf-lsr-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. @@ -560,21 +562,21 @@ 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 + The IPv6 address that was signaled 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. @@ -624,26 +626,20 @@ 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. -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 @@ -737,34 +733,103 @@ 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. + for steering the different sessions in the form of a SR Policy. + However, SR policies are shared among several UE/sessions. -5.3.2.4. IPv6 user-traffic +5.3.3. SRv6 Drop-in Interworking - 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. + SRv6 drop-in interworking mode provides SRv6 user plane in between + GTP-U tunnel endpoints. This mode employs two SRGWs to do GTP-U + traffic to SRv6 mapping on one SRGW, and vice versa. -5.3.3. Extensions to the interworking mechanisms + Unlike other interworking modes, both of the mobility overlay + endpoints use GTP-U. Two SRGWs are deployed in either N3 or N9 + interface to realize an intermediate SR policy. - 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. + The SRGW behaviors for this mode are equivalent with other modes + except in IPv6 GTP case on the GTP-U to SRv6 direction. Due to that + only one exception, it is enough that this section focuses to + describe IPv6 GTP case on one direction with an illustration. + + +----+ + -| S1 |- ++-----------+ / +----+ \ +| UPF2a/gNB |- SRv6 / SRv6 \ +----+ +------+ +-------+ ++-----------+ \ [N9]/ VNF -| C1 |---| UPF1b|------| UPF2b | + GTP \ +------+ / +----+ +------+ +-------+ + -| UPF1a|- SRv6 SR Gateway-B GTP + +------+ TE + SR Gateway-A + + Figure 7: Example topology for SRv6 Drop-in + +5.3.3.1. Packet flow + + The packet flow of Figure 7 is as follows: + +UPF2a/gNB_out: (UPF2a/gNB, U2b::)(GTP: TEID T)(A,Z) +SRGW-A_out : (SRGW-A, S1)(U2b::, U1b::TEID, C1; SL=3)(A,Z) -> U2b:: is an + End.M.GTP6.D.Di + SID at SRGW-A +S1_out : (SRGW-A, C1)(U2b::, U1b::TEID, C1; SL=2)(A,Z) +C1_out : (SRGW-A, U1b::TEID)(U2b::, U1b::TEID, C1; SL=1)(A,Z) +SRGW-B_out : (SRGW-B, U2b::)(GTP: TEID T)(A,Z) -> U1b::TEID is an + End.M.GTP6.E + SID at SRGW-B +UPF2b_out : (A,Z) + + When a packet destined to Z arrives at the UPF2a, or gNB, which is + unmodified, performs encapsulates the packet into a new IPv6, UDP and + GTP headers. The IPv6 DA, U2b::, and the GTP TEID are the ones + received at the N2 interface. + + The IPv6 address that was signalled over the N2 interface for that UE + PDU Session, U2b::, is now the IPv6 DA. U2b:: is an SRv6 Binding SID + at SRGW-A. Hence the packet is routed to the SRGW. + + When the packet arrives at SRGW-A, the SRGW identifies U2b:: as an + End.M.GTP6.D.Di Binding SID (see Section 6.4). 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 Binding SID. There is one instance of the End.M.GTP6.D.Di + SID per PDU type. + + S1 and C1 perform their related Endpoint functionality and forward + the packet. + + Once the packet arrives at SRGW-B, 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 U2b:: 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 UPF2b. There is one instance + of the End.M.GTP6.E SID per PDU type. + + Once the packet arrives at UPF2b, the packet is a regular IPv6/GTP + packet. The UPF looks for the specific rule for that TEID to forward + the packet. This UPF behavior is not modified from current and + previous generations. + +5.3.4. Extensions to the interworking mechanisms + + In this section we presented three mechanisms for interworking with + gNBs and UPFs that do not support SRv6. These mechanisms are used to + support GTP over IPv4 and 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). @@ -787,29 +852,30 @@ |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. + Arg.Mob.Session is required in case that one SID aggregates multiple + PDU Session. 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: @@ -847,21 +914,59 @@ 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 +6.4. End.M.GTP6.D.Di + + The "Endpoint function with IPv6/GTP decapsulation into SR policy for + Drop-in Mode" function (End.M.GTP6.D.Di for short) is used in SRv6 + drop-in interworking scenario described in Section 5.3.3. The + difference between End.M.GTP6.D as another variant of IPv6/GTP + decapsulation function is that the original IPv6 DA of GTP packet is + preserved as the last SID in SRH. Suppose, for example, this SID is + associated with an SR policy 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.Di SID, N does: + + 1. IF NH=UDP & UDP_DST_PORT = GTP THEN + 2. preserve S and 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 + 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.Di 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. + +6.5. 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. 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 @@ -871,29 +976,28 @@ 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 +6.6. 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 @@ -917,25 +1021,25 @@ 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 +6.7. 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. + IPv4 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 @@ -956,21 +1060,21 @@ 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 +6.8. 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: +----------------------+----------+-----------+ @@ -987,37 +1091,37 @@ 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 - SRv6 supports all the 3GPP PDU session types without any protocol + SRv6 supports 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). + End.DT46 for IPv4v6 PDU sessions; End.DX2 for L2 PDU sessions). + Unstructured PDUs are not supported. 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 IGP Flex-Algo [I-D.ietf-lsr-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]. @@ -1081,40 +1185,40 @@ Japan Email: ebisawa@toyota-tokyo.tech 14. References 14.1. Normative References [I-D.ietf-6man-segment-routing-header] 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-23 (work in progress), September 2019. + Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header + (SRH)", draft-ietf-6man-segment-routing-header-26 (work in + progress), October 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. + Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., 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-02 (work in progress), September 2019. + Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., + Matsushima, S., and Z. Li, "SRv6 Network Programming", + draft-ietf-spring-srv6-network-programming-05 (work in + progress), October 2019. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, - DOI 10.17487/RFC2119, March 1997, - . + DOI 10.17487/RFC2119, March 1997, . [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, . 14.2. Informative References [I-D.ali-spring-network-slicing-building-blocks] Ali, Z., Filsfils, C., Camarillo, P., and d. @@ -1130,75 +1234,75 @@ 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. [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-02 (work in progress), August 2019. + Voyer, D., Cui, A., and B. Peirens, "SRv6 Mobility Use- + Cases", draft-camarilloelmalky-springdmm-srv6-mob- + usecases-02 (work in progress), August 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-lsr-flex-algo] + Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and + A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- + algo-04 (work in progress), September 2019. + [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.ietf-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-ietf-spring-sr-service- + programming-00 (work in progress), October 2019. + [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-srv6-02 (work in progress), July 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 + 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 + 3GPP, , "Interface between the Control Plane and the User Plane Nodes", 3GPP TS 29.244 15.0.0, December 2017. [TS.29281] - 3GPP, "General Packet Radio System (GPRS) Tunnelling + 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. + 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 . 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].