Network Working Group L. Dunbar Internet Draft A. Malis Intended status: Informational Huawei Expires: August 6, 2019 C. Jacquenet Orange February 6, 2019 Gap Analysis of Interconnecting Underlay with Cloud Overlay draft-dm-net2cloud-gap-analysis-04 Abstract This document analyzes the technological gaps when using SD-WAN to interconnect workloads & apps hosted in various locations, especially cloud data centers when the network service providers do not have or have limited physical infrastructure to reach the locations [Net2Cloud-problem]. 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), 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 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on July 6, 2019. xxx, et al. Expires August 6, 2019 [Page 1] Internet-Draft Net2Cloud Gap Analysis February 2019 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 (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...................................................2 2. Conventions used in this document..............................3 3. Gap Analysis of C-PEs Registration Protocol....................4 4. Gap Analysis in aggregating VPN paths and Internet paths.......5 4.1. Gap analysis of Using BGP to cover SD-WAN paths...........6 4.2. Gaps in preventing attacks from Internet facing ports.....9 5. Gap analysis of CPEs not directly connected to VPN PEs........10 5.1. Gap Analysis of Floating PEs to connect to Remote CPEs...11 5.2. NAT Traversal............................................12 5.3. Complication of using BGP between PEs and remote CPEs via Internet......................................................12 5.4. Designated Forwarder to the remote edges.................13 5.5. Traffic Path Management..................................13 6. Manageability Considerations..................................14 7. Security Considerations.......................................14 8. IANA Considerations...........................................14 9. References....................................................14 9.1. Normative References.....................................15 9.2. Informative References...................................15 10. Acknowledgments..............................................16 1. Introduction [Net2Cloud-Problem] describes the problems that enterprises face today in transitioning their IT infrastructure to support digital Dunbar, et al. Expires August 6, 2019 [Page 2] Internet-Draft Net2Cloud Gap Analysis February 2019 economy, such as connecting enterprises' branch offices to dynamic workloads in different Cloud DCs. This document analyzes the technological gaps to interconnect dynamic workloads & apps hosted in various locations and in Cloud DCs that the enterprise existing VPN service provider might not have or have limited the physical infrastructure to reach. When enterprise' VPN service providers do not have or have insufficient bandwidth to reach a location, SD-WAN is emerged as way to aggregate bandwidth of multiple networks, such as MPLS VPN, Public Internet, etc. This document primarily focuses on the technological gaps of SD-WAN. For ease of description, SD-WAN edge, SD-WAN end points, C-PE, or CPE are used interchangeably throughout this document. 2. Conventions used in this document Cloud DC: Third party Data Centers that usually host applications and workload owned by different organizations or tenants. Controller: Used interchangeably with SD-WAN controller to manage SD-WAN overlay path creation/deletion and monitor the path conditions between sites. CPE-Based VPN: Virtual Private Secure network formed among CPEs. This is to differentiate from most commonly used PE- based VPNs a la RFC 4364. OnPrem: On Premises data centers and branch offices SD-WAN: Software Defined Wide Area Network. In this document, "SD-WAN" refers to the solutions specified by ONUG (Open Network User Group), https://www.onug.net/software- defined-wide-area-network-sd-wan/, which is about pooling WAN bandwidth from multiple underlay networks to get better WAN bandwidth management, visibility & control. When the underlay networks are private Dunbar, et al. Expires August 6, 2019 [Page 3] Internet-Draft Net2Cloud Gap Analysis February 2019 networks, traffic can traverse without additional encryption; when the underlay networks are public, such as Internet, some traffic needs to be encrypted when traversing through (depending on user provided policies). 3. Gap Analysis of C-PEs Registration Protocol SD-WAN, conceived in ONUG (Open Network User Group) a few years ago as a means to aggregate multiple connections between any two points, has emerged as an on-demand technology to securely interconnect the OnPrem branches with the workloads instantiated in Cloud DCs that do not connect to BGP/MPLS VPN PEs or have very limited bandwidth. Some SD-WAN networks use the NHRP protocol [RFC2332] to register SD- WAN edges with a "Controller" (or NHRP server), which then has the ability to map a private VPN address to a public IP address of the destination node. DSVPN [DSVPN] or DMVPN [DMVPN] are used to establish tunnels among SD-WAN edge nodes. NHRP was originally intended for ATM address resolution, and as a result, it misses many attributes that are necessary for dynamic endpoint C-PE registration to controller, such as: - Interworking with MPLS VPN control plane. A SD-WAN edge can have some ports facing MPLS VPN network and some ports facing public Internet that requires encryption for some sensitive data to traverse. - Scalability. NHRP/DSVPN/DMVPN works fine with small number of edge nodes. When a network has more than 100 nodes, the protocol does not work well. - NHRP does not have the IPsec attributes, which are needed for peers to build Security Associations over public internet. - NHRP does not have field to indicate C-PE supported encapsulation types, such as IPsec-GRE, IPsec-VxLAN, or others. - NHRP does not have field to indicate C-PE Location identifier, such as Site Identifier, System ID, and/or Port ID. - NHRP does not have field to describe the gateway to which the C-PE is attached. When a C-PE is instantiated in a Cloud DC, to Dunbar, et al. Expires August 6, 2019 [Page 4] Internet-Draft Net2Cloud Gap Analysis February 2019 establish connection to the C-PE, it is necessary to know the Cloud DC operator's Gateway to which the CPE is attached. - NHRP does not have field to describe C-PE's NAT properties if the C-PE is using private addresses, such as the NAT type, Private address, Public address, Private port, Public port, etc. [BGP-SDWAN-EXT] describes how to use BGP for SD-WAN edge nodes to register its properties to SD-WAN controller, which then disseminates the information to other SD-WAN edge nodes that are authenticated to communicate. 4. Gap Analysis in aggregating VPN paths and Internet paths Most likely, enterprises especially large ones already have their CPEs interconnected by providers' VPNs, such as EVPN, L2VPN, or L3VPN. The VPN can be PE based or CPE based as shown in the following diagram. The commonly used CPE-based VPNs have CPE directly attached to PEs, therefore the communication is considered as secure. BGP are used to distribute routes among CPEs, even though sometimes routes among CPEs are statically configured. +---+ EVPN MAC/IP BGP updates +======+RR +===========+ // +---+ \\ // \\ // <-----EVPN-VxLAN------> \\ +-+--+ ++-+ ++-+ +--+-+ | CPE|--|PE| |PE+----+ CPE| | 1 | |1 | |x | | x | +-+--+ ++-+ ++-+ +----+ | | | VPN +-+---+ +----+ | Network | PE3 | |CPE | | | |- --| 3 | +--------+ +--+--+ +-+---+ +----+ | CPE +----+ PE4 |--------+ | 4 | +---+-+ +--------+ === or \\ indicates control plane communications Figure 1: L2 or L3 VPNs over IP WAN Dunbar, et al. Expires August 6, 2019 [Page 5] Internet-Draft Net2Cloud Gap Analysis February 2019 To use SD-WAN to aggregate Internet routes with the VPN routes, the C-PEs need to have some ports connected to PEs and other ports connected to the Internet. It is necessary to have a registration protocol for C-PEs to register with their SD-WAN Controllers to establish secure tunnels among relevant C-PEs. If using NHRP for registration, C-PEs need to participate in two separate control planes: EVPN&BGP for CPE-based VPNs via links directly attached to PEs and NHRP & DSVPN/DMVPN for ports connected to internet. Two separate control planes not only add complexity to C-PEs, but also increase operational cost. +---------Internet paths--------------+ | | | +---+ | | |RR | | | +======+---+===========+ | | // \\ | | // <-----EVPN-VxLAN----> \\ | | +-+--+ ++-+ ++-+ +--+-+ (|) | | CPE|--|PE| |PE+--+ CPE| (|) +--| 1 | |1 | |x | | c |---+ +-+--+ ++-+ ++-+ +----+ | | | VPN +-+---+ +----+ +--------+ | Network | PE3 | |CPE | | CPE | | | |- --| 3 | | c | +-----+ +-+---+ +----+ +------+-+-------+ PE4 |-----+ +---+-+ Figure 2: CPEs interconnected by VPN paths and Internet Paths 4.1. Gap analysis of Using BGP to cover SD-WAN paths Since C-PE already supports BGP, it is desirable to consider using BGP to control the SD-WAN instead of two separate control planes. This section analyzes the gaps of using BGP to control SD-WAN. As described [BGP-SDWAN-Usage], SD-WAN Overlay Control Plane has three distinct functional tiers: - SD-WAN node's private address and WAN Ports/Addresses registration to the SD-WAN Controller. Dunbar, et al. Expires August 6, 2019 [Page 6] Internet-Draft Net2Cloud Gap Analysis February 2019 o It is for informing the SD-WAN controller and potential peers of the underlay networks to which the C-PE is connected. - Controller Facilitated IPsec SA management and NAT information distribution o It is for SD-WAN controller to facilitate or manage the IPsec configurations and peer authentications for all IPsec tunnels terminated at the SDWAN nodes. For some scenarios where the WAN ports are private addresses, this step is for informing the type of NAT translating the private addresses to public ones. - Establishing and Managing the topology and reachability for services attached to the client ports of SD-WAN nodes. o This is for the overlay layer's routes distribution, so that a C-PE can establish the overlay routing table that identifies the next hop for reaching a specific route/service attached to remote nodes. [SECURE-EVPN] describes EVPN and other options. RFC5512 and [Tunnel-Encap] describe methods for endpoints to advertise tunnel information and to trigger tunnel establishment. RFC5512 & [Tunnel-Encap] have the Endpoint Address to indicate IPv4 or IPv6 address format, the Tunnel Encapsulation attribute to indicate different encapsulation formats, such as L2TPv3, GRE, VxLAN, IP-in-IP, etc. There are sub-TLVs to describe the detailed tunnel information for each of the encapsulations. [Tunnel-Encap] removed SAFI =7 (which was specified by RFC5512) for distributing encapsulation tunnel information. [Tunnel-Encap] require Tunnels being associated with routes. There is also the Color sub-TLV to describe customer-specified information about the tunnels (which can be creatively used for SD- WAN) Here are some of the gaps using [Tunnel-Encap] to control SD-WAN: - Lacking C-PE Registration functionality - Lacking IPsec Tunnel type Dunbar, et al. Expires August 6, 2019 [Page 7] Internet-Draft Net2Cloud Gap Analysis February 2019 - [Tunnel-Encap] has Remote Address SubTLV, but does not have any field to indicate the Tunnel originating interface, which was in RFC5512. - The mechanisms described by [Tunnel-Encap] cannot be effectively used for SD-WAN overlay network because a SD-WAN Tunnel can be between Internet facing WAN ports of two C-PEs and needs to be established before data arrival because the tunnel establishment can fail, e.g. two end points supporting different encryption algorithms. - Client traffic (e.g. an EVPN route) can have option of going through MPLS network natively without encryption, or going through the IPsec tunnels between the internet facing WAN ports of two C- PEs. - There is no routes to be associated with the SD-WAN Tunnel between two C-PE's internet facing WAN ports, unless consider using the interface facing WAN Port addresses assigned by ISP (Internet Service Providers) as the route for the Tunnel. There is a suggestion on using a "Fake Route" for a SD-WAN node to use [Tunnel-Encap] to advertise its SD-WAN tunnel end-points properties. However, using "Fake Route" can create deployment complexity for large SD-WAN networks with many tunnels. For example, for a SD-WAN network with hundreds of nodes, with each node having many ports & many end-points to establish SD-WAN tunnels to their corresponding peers, the node would need many "fake addresses". For large SD-WAN networks (such as has more than 10000 nodes), each node might need 10's thousands of "fake addresses", which is very difficult to manage and needs lots of configuration to get the nodes provisioned. - Does not have fields to carry detailed information of the remote C-PE: such as Site-ID, System-ID, Port-ID - Does not have the proper field to express IPsec attributes among the SD-WAN edge nodes to establish proper IPsec Security Associations. - Does not have proper way for two peer CPEs to negotiate IPSec keys, based on the configuration sent by the Controller. - Does not have field to indicate the UDP NAT private address <-> public address mapping - C-PEs tend to communicate with a few other CPEs, not all the C-PEs need to form mesh connections. Without any BGP extension, many Dunbar, et al. Expires August 6, 2019 [Page 8] Internet-Draft Net2Cloud Gap Analysis February 2019 nodes can get dumped with too much information of other nodes that they never need to communicate with. [VPN-over-Internet] describes a way to securely interconnect C-PEs via IPsec using BGP. This method is useful, however, it still misses some aspects to aggregate CPE-based VPN routes with internet routes that interconnect the CPEs. In addition: - The draft does not have options of C-PE having both MPLS ports and Internet ports. - The draft assumes that CPE "registers" with the RR. However, it does not say how. It assumes that the remote CPEs are pre-configured with the IPsec SA manually. In SD-WAN, Zero Touch Provisioning is expected. It is not acceptable to require manual configuration. - For RR communication with CPE, this draft only mentioned IPSec. Missing TLS/DTLS. - The draft assumes that CPEs and RR are connected with an IPsec tunnel. With zero touch provisioning, we need an automatic way to synchronize the IPsec SA between CPE and RR. The draft assumes: A CPE must also be provisioned with whatever additional information is needed in order to set up an IPsec SA with each of the red RRs - IPsec requires periodic refreshment of the keys. The draft hasn't addressed how to synchronize the refreshment among multiple nodes. - IPsec usually only sends configuration parameters to two endpoints and let the two endpoints negotiate the KEY. Now we assume that RR is responsible for creating the KEY for all endpoints. When one endpoint is compromised, all other connections are impacted. 4.2. Gaps in preventing attacks from Internet facing ports When C-PEs have ports facing Internet, it brings in the security risks of potential DDoS attacks to the C-PEs from the ports facing internet. To mitigate security risks, in addition to requring Anti-DDoS features on C-PEs to prevent major DDoS attacks, it is necessary to have ways for C-PEs to validate traffic from remote peers to prevent spoofed traffic. Dunbar, et al. Expires August 6, 2019 [Page 9] Internet-Draft Net2Cloud Gap Analysis February 2019 5. Gap analysis of CPEs not directly connected to VPN PEs Because of the ephemeral property of the selected Cloud DCs, an enterprise or its network service provider may not have the direct links to the Cloud DCs that are optimal for hosting the enterprise's specific workloads/Apps. Under those circumstances, SD-WAN is a very flexible choice to interconnect the enterprise on-premises data centers & branch offices to its desired Cloud DCs. However, SD-WAN paths over public Internet can have unpredictable performance, especially over long distances and across domains. Therefore, it is highly desirable to place as much as possible the portion of SD-WAN paths over service provider VPN (e.g., enterprise's existing VPN) that have guaranteed SLA to minimize the distance/segments over public Internet. MEF Cloud Service Architecture [MEF-Cloud] also describes a use case of network operators needing to use SD-WAN over LTE or public Internet for last mile accesses where they are not present. Under those scenarios, one or both of the SD-WAN endpoints may not directly be attached to the PEs of a VPN Domain. Using SD-WAN to connect the enterprise existing sites with the workloads in Cloud DC, the enterprise existing sites' CPEs have to be upgraded to support SD-WAN. If the workloads in Cloud DC need to be connected to many sites, the upgrade process can be very expensive. [Net2Cloud-Problem] describes a hybrid network approach that integrates SD-WAN with traditional MPLS-based VPNs, to extend the existing MPLS-based VPNs to the Cloud DC Workloads over the access paths that are not under the VPN provider control. To make it work properly, a small number of the PEs of the MPLS VPN can be designated to connect to the remote workloads via SD-WAN secure IPsec tunnels. Those designated PEs are shown as fPE (floating PE or smart PE) in Figure 3. Once the secure IPsec tunnels are established, the workloads in Cloud DC can be reached by the enterprise's VPN without upgrading all of the enterprise's existing CPEs. The only CPE that needs to support SD-WAN would be a virtualized CPE instantiated within the cloud DC. Dunbar, et al. Expires August 6, 2019 [Page 10] Internet-Draft Net2Cloud Gap Analysis February 2019 +--------+ +--------+ | Host-a +--+ +----| Host-b | | | | (') | | +--------+ | +-----------+ ( ) +--------+ | +-+--+ ++-+ ++-+ +--+-+ (_) | | CPE|--|PE| |PE+--+ CPE| | +--| | | | | | | |---+ +-+--+ ++-+ ++-+ +----+ / | | / | MPLS +-+---+ +--+-++--------+ +------+-+ | Network |fPE-1| |CPE || Host | | Host | | | |- --| || d | | c | +-----+ +-+---+ +--+-++--------+ +--------+ |fPE-2|-----+ +---+-+ (|) (|) (|) SD-WAN (|) (|) over any access +=\======+=========+ // \ | Cloud DC \\ // \ ++-----+ \\ +Remote| | CPE | +-+----+ ----+-------+-------+----- | | +---+----+ +---+----+ | Remote | | Remote | | App-1 | | App-2 | +--------+ +--------+ Figure 3: VPN Extension to Cloud DC In Figure 3, the optimal Cloud DC to host the workloads (due to proximity, capacity, pricing, or other criteria chosen by the enterprises) does not happen to have a direct connection to the PEs of the MPLS VPN that interconnects the enterprise's existing sites. 5.1. Gap Analysis of Floating PEs to connect to Remote CPEs To extend MPLS VPNs to remote CPEs, it is necessary to establish secure tunnels (such as IPsec tunnels) between the Floating PEs and the remote CPEs. Gap: Dunbar, et al. Expires August 6, 2019 [Page 11] Internet-Draft Net2Cloud Gap Analysis February 2019 Even though a set of PEs can be manually selected to act as the floating PEs for a specific cloud data center, there are no standard protocols for those PEs to interact with the remote CPEs (most likely virtualized) instantiated in the third party cloud data centers (such as exchanging performance or route information). When there is more than one fPE available for use (as there should be for resiliency or the ability to support multiple cloud DCs scattered geographically), it is not straightforward to designate an egress fPE to remote CPEs based on applications. There is too much applications' traffic traversing PEs, and it is not feasible for PEs to recognize applications from the payload of packets. 5.2. NAT Traversal Most cloud DCs only assign private addresses to the workloads instantiated. Therefore, traffic to/from the workload usually need to traverse NAT. A SD-WAN edge node can inquire STUN (Session Traversal of UDP Through Network Address Translation RFC 3489) Server to get the NAT property, the public IP address and the Public Port number to pass to peers. 5.3. Complication of using BGP between PEs and remote CPEs via Internet Even though an EBGP (external BGP) Multi-hop design can be used to connect peers that are not directly connected to each other, there are still some complications/gaps in extending BGP from MPLS VPN PEs to remote CPEs via any access paths (e.g., Internet). The path between the remote CPEs and VPN PE can traverse untrusted nodes. EBGP Multi-hop scheme requires static configuration on both peers. To use EBGP between a PE and remote CPEs, the PE has to be manually configured with the "next-hop" set to the IP addresses of the CPEs. When remote CPEs, especially remote virtualized CPEs are dynamically instantiated or removed, the configuration on the PE Multi-Hop EBGP has to be changed accordingly. Gap: Dunbar, et al. Expires August 6, 2019 [Page 12] Internet-Draft Net2Cloud Gap Analysis February 2019 Egress peering engineering (EPE) is not enough. Running BGP on virtualized CPEs in Cloud DC requires GRE tunnels being established first, which in turn requires address and key management for the remote CPEs. RFC 7024 (Virtual Hub & Spoke) and Hierarchical VPN is not enough. Also there is a need for a method to automatically trigger configuration changes on PE when remote CPEs' are instantiated or moved (leading to an IP address change) or deleted. EBGP Multi-hop scheme does not have an embedded security mechanism. The PE and remote CPEs need secure communication channels when connecting via the public Internet. Remote CPEs, if instantiated in Cloud DC, might have to traverse NAT to reach PE. It is not clear how BGP can be used between devices outside the NAT and the entities behind the NAT. It is not clear how to configure the Next Hop on the PEs to reach private IPv4 addresses. 5.4. Designated Forwarder to the remote edges Among multiple floating PEs available for a remote CPE, multicast traffic from the remote CPE towards the MPLS VPN can be forwarded back to the remote CPE due to the PE receiving the multicast data frame forwarding the multicast/broadcast frame to other PEs that in turn send to all attached CPEs. This process may cause traffic loop. Therefore, it is necessary to designate one floating PE as the CPE's Designated Forwarder, similar to TRILL's Appointed Forwarders [RFC6325]. Gap: the MPLS VPN does not have features like TRILL's Appointed Forwarders. 5.5. Traffic Path Management When there are multiple floating PEs that have established IPsec tunnels to the remote CPE, the remote CPE can forward the outbound traffic to the Designated Forwarder PE, which in turn forwards the Dunbar, et al. Expires August 6, 2019 [Page 13] Internet-Draft Net2Cloud Gap Analysis February 2019 traffic to egress PEs to the destinations. However, it is not straightforward for the egress PE to send back the return traffic to the Designated Forwarder PE. Example of Return Path management using Figure 3 above. - fPE-1 is DF for communication between App-1 <-> Host-a due to latency, pricing or other criteria. - fPE-2 is DF for communication between App-1 <-> Host-b. 6. Manageability Considerations Zero touch provisioning of SD-WAN edge nodes is expected in SD- WAN deployment. It is necessary for a newly powered up SD-WAN edges to establish a secure connection (such as TLS, DTLS, etc.) to its controller. 7. Security Considerations The intention of this draft is to identify the gaps in current and proposed SD-WAN approaches that can address requirements identified in [Net2Cloud-problem]. Several of these approaches have gaps in meeting enterprise security requirements when tunneling their traffic over the Internet, as is the general intention of SD-WAN. See the individual sections above for further discussion of these security gaps. 8. IANA Considerations This document requires no IANA actions. RFC Editor: Please remove this section before publication. 9. References Dunbar, et al. Expires August 6, 2019 [Page 14] Internet-Draft Net2Cloud Gap Analysis February 2019 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 9.2. Informative References [RFC8192] S. Hares, et al, "Interface to Network Security Functions (I2NSF) Problem Statement and Use Cases", July 2017 [RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", April 2009. [BGP-SDWAN-EXT]L. Dunbar, "BGP Extension for SDWAN Overlay Networks", draft-dunbar-idr-bgp-sdwan-overlay-ext-00, Oct 2018. [BGP-SDWAN-Usage] L. Dunbar, et al, "Framework of Using BGP for SDWAN Overlay Networks", draft-dunbar-idr-sdwan-framework- 00, work-in-progress, Feb 2019. [Tunnel-Encap]E. Rosen, et al, "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-10, July 2018. [VPN-over-Internet] E. Rosen, "Provide Secure Layer L3VPNs over Public Infrastructure", draft-rosen-bess-secure-l3vpn-00, work-in-progress, July 2018 [DMVPN] Dynamic Multi-point VPN: https://www.cisco.com/c/en/us/products/security/dynamic- multipoint-vpn-dmvpn/index.html [DSVPN] Dynamic Smart VPN: http://forum.huawei.com/enterprise/en/thread-390771-1- 1.html Dunbar, et al. Expires August 6, 2019 [Page 15] Internet-Draft Net2Cloud Gap Analysis February 2019 [ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation, storage, distribution and enforcement of policies for network security", Nov 2007. [Net2Cloud-Problem] L. Dunbar and A. Malis, "Seamless Interconnect Underlay to Cloud Overlay Problem Statement", draft-dm- net2cloud-problem-statement-02, June 2018 10. Acknowledgments Acknowledgements to xxx for his review and contributions. This document was prepared using 2-Word-v2.0.template.dot. Dunbar, et al. Expires August 6, 2019 [Page 16] Internet-Draft Net2Cloud Gap Analysis February 2019 Authors' Addresses Linda Dunbar Huawei Email: Linda.Dunbar@huawei.com Andrew G. Malis Huawei Email: agmalis@gmail.com Christian Jacquenet Orange Rennes, 35000 France Email: Christian.jacquenet@orange.com Dunbar, et al. Expires August 6, 2019 [Page 17]