Network Working Group L. Dunbar Internet Draft J. Kaippallimalil Intended status: Standard Futurewei Expires: April 27, 2021 October 27, 2020 IPv6 Solution for 5G Edge Computing Sticky Service draft-dunbar-6man-5g-edge-compute-sticky-service-00 Abstract This draft describes an IPv6 solution that enables packets from an application on a UE (User Equipment) sticking to the same application server location when the UE moves from one 5G cell site to another. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, except to publish it as an RFC and to translate it into languages other than English. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt xxx, et al. Expires April 27, 2021 [Page 1] Internet-Draft IPv6 for 5G Edge Sticky Service The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on April 7, 2021. Copyright Notice Copyright (c) 2020 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 (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 1.1. 5G Edge Computing Background................................ 3 1.2. Problem #1: ANYCAST in 5G EC Environment.................... 4 1.3. Problem #2: sticking to original App Server................. 5 1.4. Problem #3: Application Server Relocation................... 5 2. Conventions used in this document............................. 6 3. Proposed IPv6 Based Solution.................................. 7 3.1. Solution Overview........................................... 8 3.2. Ensure one IPv6 Flow Go to the Same Location................ 9 3.3. Discover the Egress Routers for App Servers................ 10 3.4. Using Destination Extension Header......................... 10 3.5. Using IPv6 Routing Extension Header........................ 13 4. Achieve Sticky Service without dependence on UE.............. 14 5. Forwarding to the desired A-ER without using Tunnel.......... 15 6. Manageability Considerations................................. 16 7. Security Considerations...................................... 17 8. IANA Considerations.......................................... 17 9. References................................................... 17 9.1. Normative References....................................... 17 9.2. Informative References..................................... 17 10. Acknowledgments............................................. 18 Dunbar, et al. Expires April 27, 2021 [Page 2] Internet-Draft IPv6 for 5G Edge Sticky Service 1. Introduction 1.1. 5G Edge Computing Background As described in [5G-EC-Metrics], one Application can have multiple Application Servers hosted in different Edge Computing data centers that are close in proximity. Those Edge Computing (mini) data centers are usually very close to, or co-located with, 5G base stations, with the goal to minimize latency and optimize the user experience. When a UE (User Equipment) initiates application packets using the destination address from a DNS reply or from its own cache, the packets from the UE are carried in a PDU session through 5G Core [5GC] to the 5G UPF-PSA (User Plan Function - PDU Session Anchor). The UPF-PSA decapsulate the 5G GTP outer header and forwards the packets from the UEs to the Ingress router of the Edge Computing (EC) Local Data Network (LDN). The LDN for 5G EC, which is the IP Networks from 5GC perspective, is responsible for forwarding the packets to the intended destinations. When the UE moves out of coverage of its current gNB (next generation Node B) (gNB1), handover procedures are initiated and the 5G SMF (Session Management Function) also selects a new UPF-PSA. The standard handover procedures described in 3GPP TS 23.501 and TS 23.502 are followed. When the handover process is complete, the UE has a new IP address and the IP point of attachment is to the new UPF-PSA. 5GC may maintain a path from the old UPF to new the UPF for a short period of time for SSC [Session and Service Continuity] mode 3 to make the handover process more seamless. Dunbar, et al. Expires April 27, 2021 [Page 3] Internet-Draft IPv6 for 5G Edge Sticky Service +--+ |UE|---\+---------+ +------------------+ +--+ | 5G | +---------+ | S1: aa08::4450 | +--+ | Site +--++---+ +----+ | |UE|----| A |PSA| Ra| | R1 | S2: aa08::4460 | +--+ | +---+---+ +----+ | +---+ | | | | | S3: aa08::4470 | |UE1|---/+---------+ | | +------------------+ +---+ |IP Network | L-DN1 |(3GPP N6) | | | | +------------------+ | UE1 | | | S1: aa08::4450 | | moves to | +----+ | | Site B | | R3 | S2: aa08::4460 | v | +----+ | | | | S3: aa08::4470 | | | +------------------+ | | L-DN3 +--+ | | |UE|---\+---------+ | | +------------------+ +--+ | 5G | | | | S1: aa08::4450 | +--+ | Site +--++-+--+ +----+ | |UE|----| B |PSA| Rb | | R2 | S2: aa08::4460 | +--+ | +--++----+ +----+ | +--+ | | +-----------+ | S3: aa08::4470 | |UE|---/+---------+ +------------------+ +--+ L-DN2 Figure 1: App Servers in different edge DCs 1.2. Problem #1: ANYCAST in 5G EC Environment Increasingly, Anycast is used extensively by various application providers and CDNs because it is possible to dynamically load balance across multiple locations of the same address based on network conditions. BGP is an integral part in the way IP anycast usually functions. Within BGP routing there are multiple routes for the same IP address which are pointing to different locations. Application Server location selection using Anycast address leverages the proximity information present in the network Dunbar, et al. Expires April 27, 2021 [Page 4] Internet-Draft IPv6 for 5G Edge Sticky Service (routing) layer and eliminates the single point of failure and bottleneck at the DNS resolvers and application layer load balancers. Another benefit of using ANYCAST address is removing the dependency on UEs that use their cached IP addresses instead of querying DNS when they move to a new location. But, having multiple locations for the same ANYCAST address in 5G Edge Computing environment can be problematic because all those edge computing Data Centers can be close in proximity. There might not be any difference in the routing cost to reach the Application Servers in different Edge DCs. Same routing cost to multiple ANYCAST locations can cause packets from one flow to be forwarded to different locations, which can cause service glitches. 1.3. Problem #2: sticking to original App Server When a UE moves to a new location but continues the same application flow, routers at the new location might choose the App Server closer to the new location. As shown in the figure below, when the UE1 in 5G-site-A moves to the 5G-Site-B, the router directly connected to 5G PSA2 might forward the packets destined towards the S1: aa08::4450 to the instance located in L-DN2 because L-DN2 has the lowest cost based on routing. This is not the desired behavior for some services, which are called Sticky Services in this document. Even for some advanced applications with built-in mechanisms to re-sync the communications at the application layer after switching to a new location, service glitches are very often experienced by users. It worth noting that not all services need to be sticky. We assume only a subset of services are, and the Network is informed of the services that need to be sticky, usually by requests from application developers or controllers. This document describes an IPv6 based network layer solution to stick the packets belonging to the same flow of a UE to its original App Server location after the UE is anchored to a new UPF-PSA. 1.4. Problem #3: Application Server Relocation When an Application Server is added to, moved, or deleted from a 5G Edge Computing Data Center, the routing protocol has to Dunbar, et al. Expires April 27, 2021 [Page 5] Internet-Draft IPv6 for 5G Edge Sticky Service propagate the changes to 5G PSA or the PSA adjacent routers. After the change, the cost associated with the site [5G-EC- Metrics] might change as well. Note: for the ease of description, the Edge Application Server and Application Server are used interchangeably throughout this document. 2. Conventions used in this document A-ER: Egress Router to an Application Server, [A-ER] is used to describe the last router that the Application Server is attached. For 5G EC environment, the A-ER can be the gateway router to a (mini) Edge Computing Data Center. Application Server: An application server is a physical or virtual server that host the software system for the application. Application Server Location: Represent a cluster of servers at one location serving the same Application. One application may have a Layer 7 Load balancer, whose address(es) are reachable from external IP network, in front of a set of application servers. From IP network perspective, this whole group of servers are considered as the Application server at the location. Edge Application Server: used interchangeably with Application Server throughout this document. EC: Edge Computing Edge Hosting Environment: An environment providing support required for Edge Application Server's execution. Dunbar, et al. Expires April 27, 2021 [Page 6] Internet-Draft IPv6 for 5G Edge Sticky Service NOTE: The above terminologies are the same as those used in 3GPP TR 23.758 Edge DC: Edge Data Center, which provides the Edge Computing Hosting Environment. It might be co-located with 5G Base Station and not only host 5G core functions. gNB next generation Node B L-DN: Local Data Network PSA: PDU Session Anchor (UPF) SSC: Session and Service Continuity UE: User Equipment UPF: User Plane Function The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Proposed IPv6 Based Solution Many Mobile operators have adopted IPv6, at least on the UE side. With IPv6, routers within one Local Data Network can utilize the Flow Label in IPv6 Header to avoid sending packets from the same flow to the App Server at different locations with the same cost, (which is a great benefit for migrating to IPv6 network). The solution described in this section is for the ingress router in the new LDN to steer an application flow from a UE to the App Server at the location that was used by the UE before the move. Dunbar, et al. Expires April 27, 2021 [Page 7] Internet-Draft IPv6 for 5G Edge Sticky Service 3.1. Solution Overview Here are some assumptions for the solution: - Network is aware of the Sticky Services, by the Sticky Service Identifiers, which can be ANYCAST addresses or regular IP addresses. If an application service needs to be sticky in the 5G Edge Computing environment, the service ID is registered with the 5G Edge Computing controller. From the network perspective, a sticky service is no longer sticky if there are no packets from the UE towards the service ID for a specified time. The Timer should be larger than a typical TCP session Timeout value. Here is the overview of the proposed solution: - Each Sticky service is assigned with a service ID, which can be one or a group of ANYCAST addresses. It is out of the scope of this document on how the Sticky Service ID is generated. - Routers that have the Sticky service servers (physical or virtual) directly attached, a.k.a. egress routers in this document, are configured with the ACLs that can filter out the packets towards and from the attached App Servers. Those egress routers usually are the Gateway routers to the Edge computing DC, When the Egress router filters out packets that match the Sticky Service ID ACLs from the App Servers directly attached, it inserts a Sticky-Dst-SubTLV [Section 3.4]in the IPv6 extension header before forwarding the packets to its destination (i.e. the UE). - It is expected that application client on a UE copy the extension header from its received IPv6 header to the subsequent packets belonging to the same application if the application prefers to same server instance when UE moves. Dunbar, et al. Expires April 27, 2021 [Page 8] Internet-Draft IPv6 for 5G Edge Sticky Service For UEs that cannot perform this procedure, section 4 and 5 describes the detailed steps. - Ingress routers in the 5G LDN are also configured with the ACLs that can filter out packets whose destination addresses match with the Sticky Service Identifiers. When an ingress router filters out packets based on the Sticky Service ACL, it extracts the Sticky-Dst-SubTLV from the packet header if the packet header has the Sticky-Dst- SubTLV. The ingress router forwards the packets to the egress router extracted from the Sticky-Dst-SubTLV. If the Packet Header doesn't have the Sticky-Dst-SubTLV or fail to match the Sticky Service ACL, the packets are forwarded based on the least cost [5G-EC-Metrics]. 3.2. Ensure one IPv6 Flow Go to the Same Location RFC8200 specifies the IPv6 Header with the following required fields plus multiple extension headers. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label(20 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Source Address + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Destination Address + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ For most cases, it is preferable for the routers not to split packets from one flow to the App Server located at different Edge DCs to minimize the service glitches. The TCP based session can be interrupted when packets from one flow are sent to different instances. The site-specific ingress routers can use the IPv6 header Flow Label field to ensure the packets from one flow are forwarded to the same Egress router to which the App Server with the ANYCAST address is attached. Dunbar, et al. Expires April 27, 2021 [Page 9] Internet-Draft IPv6 for 5G Edge Sticky Service 3.3. Discover the Egress Routers for App Servers As shown in the Figure 1 above, the App Servers at each Edge DC are attached to one or two routers, which are usually the Gateway routers to the Edge DC. The DC Gateway routers can discover if there are any App Servers locally attached by sending ARP/ND scan of the ANYCAST address. They can propagate the addresses of the attached App Servers via BGP or IGP to other routers. When BGP is used, the Gateway router can use the Tunnel-Encap NLRI to inform other routers of the attached App Servers together with the supported encapsulation tunnels [Tunnel-Encap]. For the sake of easy description, those Gateway routers are called Egress routers to the App Servers, or A-ER, throughout this document. The routers directly connected to the 5G PSA (Packet Session Anchor) learn the addresses of the egress routers that the Edge Servers are attach via BGP UPDATE messages advertised from those egress routers. For the sake of easy description, the routers that are directly connected to PSA in each 5G site are called 5G site-specific Ingress Routers to the Local Data Network. The 5G site-specific ingress routers learn the egress routers to the App Servers by the BGP UPDATE messages or the IGP advertisement originated from those routers. The following subsections describe how the RFC8200 specified IPv6 extension headers, Destination Header or routing Header, are used to achieve the goal for sticky to original App Server location after the UE moves. 3.4. Using Destination Extension Header A new Sticky-Dst-SubTLV is added to the IPv6 Destination Options header. The IPv6 Destination Optino Header is specified by RFC8200 as having a Next Header value of 60: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | | Sticky-Dst-SubTLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Dunbar, et al. Expires April 27, 2021 [Page 10] Internet-Draft IPv6 for 5G Edge Sticky Service Sticky-Dst-SubTLV is specified as: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sticky-Type | Len | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Flow Label of the original flow(20 bits| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Original egress Router Identifier or Tunnel Endpoint subTLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sticky-Type = 1: indicate the 32 bits identifier is used to represent the Egress Router to an App Server. Original egress Router Identifier: assume that all the egress routers in the 5G Edge computing environment have a 32-bit identifier even though they might use an IPv6 address. Sticky-Type = 2: indicate Tunnel Endpoint SubTLV [Tunnel- Encap] used to represent the Egress router from the original site before the UE moves to the new site. Here is the processing at the Egress router: - An Egress router is configured with an ACL for filtering out addresses of the App Servers that need sticky service. Let's assume that each Sticky Service can be identified by a Sticky Service ID, which can be one or a set of ANYCAST addresses. Note, not all applications need sticky service. Using an ACL can greatly reduce the processing on the routers. - When an egress router receives a packet from an attached App Server that matches the ACL, the egress router inserts the Destination Extension Header with the Sticky-Dst- SubTLV to the data packet Header before forwarding the packet back to the UE. Dunbar, et al. Expires April 27, 2021 [Page 11] Internet-Draft IPv6 for 5G Edge Sticky Service Here are the steps to build the Sticky-Dst-subTLV: - Copy the flow label from the received packet into the Flow Label Field of the Sticky-DST-subTLV - If the egress router has its unique 32 bits identifier, such as the router's IPv4 loopback address, then: o Set Sticky-Type = 1; o Copy its own 32 bits identifier to the Original Egress Router Identifier field; - Else o Set Sticky-Type = 2; o build the Tunnel-Endpoint SubTLV per Tunnel-Encap and insert into the field; Here is the Expected behavior at the UE: For edge computing services that need sticky service while UEs roaming among multiple 5G sites, the UEs need to extract the Destination Extension Header field from packets received from the App Server and inserts the extracted Destination Extension Header into the subsequent packets belonging to the same flow. Granted, it might take some time for Edge Computing clients to adopt the practice of copying the IPv6 Destination Extension Header field from the received packets to the subsequent packets belonging to the same flow. However, once the egress routers and ingress routers for 5G local data network support the feature, more and more Edge Computing services would want to utilize this special feature by adding this step. Section 4 describes the network layer processing if UEs do not perform the steps described here. Here is the processing at the Ingress router: - An Ingress router is configured with an ACL for filtering out the applications that need sticky service. Note, not all applications need sticky service. Using ACL can greatly reduce the processing on the routers. Dunbar, et al. Expires April 27, 2021 [Page 12] Internet-Draft IPv6 for 5G Edge Sticky Service - When an Ingress router receives a packet from the 5G PSA that matches the ACL, the Ingress router extracts the Sticky-Dst-SubTLV from the packet IPv6 header if the field exists in the packet header. - The Ingress router extracts the Flow Label and the Egress Router Identifier from the Sticky-Dst-SubTLV. - If the extracted Flow label matches the Flow Label in the IPv6 header, encapsulate the packet with the tunnel type that supported by the original egress router, using the extracted egress router address in the destination field of the outer header, and forward the packet. If Tunnel is not supported, refer to Section 5 for detailed processing. 3.5. Using IPv6 Routing Extension Header Under this option, the Sticky-Dst-SubTLV specified in Section 3.4 is inserted into Type-Specific Data field of the Routing Extension Header of the IPv6 Header. RFC8200 describes the Routing header as used by an IPv6 source to list one or more intermediate nodes to be "visited" on the way to a packet's destination. The Routing header is identified by a Next Header value of 43 in the immediately preceding header and has the following format: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segments Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | type-specific data | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ All the process for Egress router, Ingress router and UE are the same as using Destination Extension Header. Dunbar, et al. Expires April 27, 2021 [Page 13] Internet-Draft IPv6 for 5G Edge Sticky Service 4. Achieve Sticky Service without dependence on UE If UEs cannot perform the steps described in the section 3.4, LDN ingress routers have to do more. This procedure assumes that the ingress routers are configured with an ACL to filter out packets whose destination addresses match with the Sticky Service Identifier. Here are the processing steps: - When an ingress router filters out packets that match the Sticky Service ID ACL, ingress router registers its own address, the source address of the filtered packets (i.e. the UE address) and the directly connected PSA address to the 5G EC Management System, or the 5G Network Exposure Function (NEF). The registration is associated with a Timer, which should be set to larger than a typical TCP session timeout value. When the Timer expires, the registration record is considered no-longer active or self-removed. The Sticky Service Registration Record should include: o UE address o The currently anchored PSA address o The LDN router address that is directly connected to the PSA o Timer - When a UE is re-anchoring from PSA1 to PSA2 and there is an active sticky service record with the UE, 5GC EC management system sends a notification to the router that is in the sticky service record, which should be the router directly connected to the original PSA before the re-anchoring. The Notification includes the following information: o the address of the new PSA that the UE is to be anchored, i.e. the PSA2 in the example above, o the UE's new IP address - Upon receiving the Notification from the 5G EC management system, the router (i.e. the one directly connected to the Dunbar, et al. Expires April 27, 2021 [Page 14] Internet-Draft IPv6 for 5G Edge Sticky Service old PSA) sends the "Sticky Service ID" (e.g. ANYCAST Address) + Sticky-Dst-SubTLV to the router directly connected to the new PSA. - Upon receiving the Sticky-Dst-SubTLV, the router directly connected to the new PSA performs the same step as described in the Section3.4. 5. Forwarding to the desired A-ER without using Tunnel Tunneling, i.e. encapsulating packets with an outer header that has the desired A-ER router address in the destination field of the outer header can guarantee to the packets to be delivered to the egress router where the Application Server is attached. But the tunneling has the problem of single point of failure at the egress router. Or tunneling is not supported by the routers. This section describes a solution that can prioritize egress routers for receiving packets without using tunneling. Let's use this scenario to explain the solution: One Application has its Application Servers attached to four different egress routers R1, R2, R3, and R4 respectively. For packets of a flow "A", the priority is sending to the App Server attached to R1. When R1 or the App Server attached to R1 fails, the packets of the flow "A" need to be forwarded to another server of the same application attached to R2, R3, or R4, depending on the network & utilization cost [5G-EC- Metrics]. This desired feature is called Location Preferred Forwarding. Here is the procedure to achieve this type of forwarding for ANYCAST traffic: - Each App server is configured with multiple ANYCAST addresses. All of them can be used as the Sticky Service ID for the App. - Location preferred ANYCAST addresses: To make a specific location preferred. When failure occurs at the preferred location, the packets are forwarded to other locations. Dunbar, et al. Expires April 27, 2021 [Page 15] Internet-Draft IPv6 for 5G Edge Sticky Service For example, for the "App.net", four different ANYCAST addresses are allocated: L1, L2, L3, and L4: o ANYCAST address L1 has cost lowest, say 10, when attached to R1. L1 has higher cost, say 30, when attached to R2, R3, and R4. o ANYCAST L2 has the lowest cost when attached to R2. L2 has higher cost when attached to R1, R3, R4 respectively. o ANYCAST L3 has the lowest cost when attached to R3. L3 has higher cost when attached to R1, R2, R4 respectively, and o ANYCAST L4 has the lowest cost when attached to R4. L4 has higher cost for the instance attached to R1, R2, R3 respectively For sticky service that needs to be sent to the App Server attached to R1, the ingress router to which 5G PSA is directly connected, can replace the destination address for packets matching with the Sticky Service ACL with the L1 for steering the packets towards R1. If R1 fails, the packets of the Flow "App.net" can be automatically sent to R2, R3, or R4 depending the network cost without any manual intervention. For the procedure described in Section 3.4, the Application egress router needs to insert L1 into the Egress-Router-ID of the Sticky-Dst-SubTLV, so that ingress router at new 5G site can send packets to L1, which goes to R1 if there is no failure at R1, otherwise, packets are automatically forwarded to other egress routers for the Application. For initial packet, local DNS resolver can reply L1, L2, L3 or L4 depending on where the DNS request come from to steer packets towards the preferred site for the Edge Application server. 6. Manageability Considerations To be added. Dunbar, et al. Expires April 27, 2021 [Page 16] Internet-Draft IPv6 for 5G Edge Sticky Service 7. Security Considerations To be added. 8. IANA Considerations To be added. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4364] E. rosen, Y. Rekhter, "BGP/MPLS IP Virtual Private networks (VPNs)", Feb 2006. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8200] s. Deering R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", July 2017 9.2. Informative References [3GPP-EdgeComputing] 3GPP TR 23.748, "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on enhancement of support for Edge Computing in 5G Core network (5GC)", Release 17 work in progress, Aug 2020. [5G-EC-Metrics] L. Dunbar, H. Song, J. Kaippallimalil, "IP Layer Metrics for 5G Edge Computing Service", draft- dunbar-ippm-5g-edge-compute-ip-layer-metrics-00, work-in-progress, Oct 2020. Dunbar, et al. Expires April 27, 2021 [Page 17] Internet-Draft IPv6 for 5G Edge Sticky Service [RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", April 2009. [BGP-SDWAN-Port] L. Dunbar, H. Wang, W. Hao, "BGP Extension for SDWAN Overlay Networks", draft-dunbar-idr-bgp-sdwan- overlay-ext-03, work-in-progress, Nov 2018. [SDWAN-EDGE-Discovery] L. Dunbar, S. Hares, R. Raszuk, K. Majumdar, "BGP UPDATE for SDWAN Edge Discovery", draft-dunbar-idr-sdwan-edge-discovery-00, work-in- progress, July 2020. [Tunnel-Encap] E. Rosen, et al "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-10, Aug 2018. 10. Acknowledgments Acknowledgements to Donald Eastlake for their review and contributions. This document was prepared using 2-Word-v2.0.template.dot. Authors' Addresses Linda Dunbar Futurewei Email: ldunbar@futurewei.com John Kaippallimalil Futurewei Email: john.kaippallimalil@futurewei.com Dunbar, et al. Expires April 27, 2021 [Page 18]