Network Working Group L. Dunbar Internet Draft Futurewei Intended status: Informational Andy Malis Expires: Dec 2019 Independent C. Jacquenet Orange M. Toy Verizon September 23, 2019 Dynamic Networks to Hybrid Cloud DCs Problem Statement draft-ietf-rtgwg-net2cloud-problem-statement-04 Abstract This document describes the problems that enterprises face today when interconnecting their branch offices with dynamic workloads in third party data centers (a.k.a. Cloud DCs). It examines some of the approaches interconnecting cloud DCs with enterprises' on-premises DCs & branch offices. This document also describes some of the network problems that many enterprises face when they have workloads & applications & data split among different data centers, especially for those enterprises with multiple sites that are already interconnected by VPNs (e.g., MPLS L2VPN/L3VPN). Current operational problems are examined to determine whether there is a need to improve existing protocols or whether a new protocol is necessary to solve them. 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. xxx, et al. Expires March 23, 2020 [Page 1] Internet-Draft Net2Cloud Problem Statement September 2019 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 March 23, 2009. 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...................................................3 1.1. On the evolution of Cloud DC connectivity.................3 1.2. The role of SD-WAN techniques in Cloud DC connectivity....4 2. Definition of terms............................................4 3. Interconnecting Enterprise Sites with Cloud DCs................5 3.1. Multiple connections to workloads in a Cloud DC...........5 3.2. Interconnect Private and Public Cloud DCs.................7 3.3. Desired Properties for Networks that interconnect Hybrid Clouds.........................................................8 4. Multiple Clouds Interconnection................................9 4.1. Multi-Cloud Interconnection...............................9 4.2. Desired Properties for Multi-Cloud Interconnection.......11 Dunbar, et al. Expires Dec 23, 2019 [Page 2] Internet-Draft Net2Cloud Problem Statement September 2019 5. Problems with MPLS-based VPNs extending to Hybrid Cloud DCs...11 6. Problem with using IPsec tunnels to Cloud DCs.................13 6.1. Complexity of multi-point any-to-any interconnection.....13 6.2. Poor performance over long distance......................14 6.3. Scaling Issues with IPsec Tunnels........................14 7. Problems of Using SD-WAN to connect to Cloud DCs..............15 7.1. SD-WAN among branch offices vs. interconnect to Cloud DCs15 8. End-to-End Security Concerns for Data Flows...................18 9. Requirements for Dynamic Cloud Data Center VPNs...............18 10. Security Considerations......................................19 11. IANA Considerations..........................................19 12. References...................................................19 12.1. Normative References....................................19 12.2. Informative References..................................19 13. Acknowledgments..............................................20 1. Introduction 1.1. On the evolution of Cloud DC connectivity The ever-increasing use of cloud applications for communication services change the way corporate business works and shares information. Such cloud applications use resources hosted in third party DCs that also host services for other customers. With the advent of widely available third-party cloud DCs in diverse geographic locations and the advancement of tools for monitoring and predicting application behaviors, it is technically feasible for enterprises to instantiate applications and workloads in locations that are geographically closest to their end-users. Such proximity improves end-to-end latency and overall user experience. Conversely, an enterprise can easily shutdown applications and workloads whenever end-users are in motion (thereby modifying the networking connection of subsequently relocated applications and workloads). In addition, an enterprise may wish to take advantage of more and more business applications offered by third party private cloud DCs. Most of those enterprise branch offices & on-premises data centers are already connected via VPNs, such as MPLS-based L2VPNs and L3VPNs. Then connecting to the cloud-hosted resources may not be straightforward if the provider of the VPN service does not have direct connections to the corresponding cloud DCs. Under those circumstances, the enterprise can upgrade the CPEs deployed in its Dunbar, et al. Expires Dec 23, 2019 [Page 3] Internet-Draft Net2Cloud Problem Statement September 2019 various premises to utilize SD-WAN techniques to reach cloud resources (without any assistance from the VPN service provider), or wait for their VPN service provider to make new agreements with data center providers to connect to the cloud resources. Either way has additional infrastructure and operational costs. In addition, more enterprises are moving towards hybrid cloud DCs, i.e. owned or operated by different Cloud operators, to maximize the benefits of geographical proximity, elasticity and special features offered by different cloud DCs. 1.2. The role of SD-WAN techniques in Cloud DC connectivity This document discusses the issues associated with connecting enterprise's workloads/applications instantiated in multiple third- party data centers (a.k.a. Cloud DCs) and its on-prem data centers. Very often, the actual Cloud DCs that host the workloads/applications can be transient. SD-WAN, initially launched to maximize bandwidths between locations by aggregating multiple paths managed by different service providers, has expanded to include flexible, on-demand, application- based connections established over any networks to access dynamic workloads in Cloud DCs. Therefore, this document discusses the use of SD-WAN techniques to improve enterprise-to-cloud DC and cloud DC-to-cloud DC connectivity. 2. Definition of terms 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 monitoring the path conditions between two or more sites. DSVPN: Dynamic Smart Virtual Private Network. DSVPN is a secure network that exchanges data between sites without needing to pass traffic through an organization's Dunbar, et al. Expires Dec 23, 2019 [Page 4] Internet-Draft Net2Cloud Problem Statement September 2019 headquarter virtual private network (VPN) server or router. Heterogeneous Cloud: applications and workloads split among Cloud DCs owned or managed by different operators. Hybrid Clouds: Hybrid Clouds refers to an enterprise using its own on-premises DCs in addition to Cloud services provided by one or more cloud operators. (e.g. AWS, Azure, Google, Salesforces, SAP, etc). SD-WAN: Software Defined Wide Area Network. In this document, "SD-WAN" refers to the solutions of pooling WAN bandwidth from multiple underlay networks to get better WAN bandwidth management, visibility & control. When the underlay networks are private 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). VPC: Virtual Private Cloud is a virtual network dedicated to one client account. It is logically isolated from other virtual networks in a Cloud DC. Each client can launch his/her desired resources, such as compute, storage, or network functions into his/her VPC. Most Cloud operators' VPCs only support private addresses, some support IPv4 only, others support IPv4/IPv6 dual stack. 3. Interconnecting Enterprise Sites with Cloud DCs 3.1. Multiple connections to workloads in a Cloud DC Most Cloud operators offer some type of network gateway through which an enterprise can reach their workloads hosted in the Cloud DCs. For example, AWS (Amazon Web Services) offers the following options to reach workloads in AWS Cloud DCs: - AWS Internet gateway allows communication between instances in AWS VPC and the internet. Dunbar, et al. Expires Dec 23, 2019 [Page 5] Internet-Draft Net2Cloud Problem Statement September 2019 - AWS Virtual gateway (vGW) where IPsec tunnels [RFC6071] are established between an enterprise's own gateway and AWS vGW, so that the communications between those gateways can be secured from the underlay (which might be the public Internet). - AWS Direct Connect, which allows enterprises to purchase direct connect from network service providers to get a private leased line interconnecting the enterprises gateway(s) and the AWS Direct Connect routers. In addition, an AWS Transit Gateway can be used to interconnect multiple VPCs in different Availability Zones. AWS Transit Gateway acts as a hub that controls how traffic is forwarded among all the connected networks which act like spokes. As an example, some branch offices of an enterprise can connect to over the Internet to reach AWS's vGW via IPsec tunnels. Other branch offices of the same enterprise can connect to AWS DirectConnect via a private network (without any encryption). ). It is important for enterprises to be able to observe the specific behaviors when connected by different connections. Figure below shows an example of some tenants' workloads are accessible via a virtual router connected by AWS Internet Gateway; some are accessible via AWS vGW, and others are accessible via AWS Direct Connect. vR1 uses IPsec to establish secure tunnels over the Internet to avoid paying extra fees for the IPsec features provided by AWS vGW. Some tenants can deploy separate virtual routers to connect to internet traffic and to traffic from the secure channels from vGW and DirectConnect, e.g. vR1 & vR2. Others may have one virtual router connecting to both types of traffic. Customer Gateway can be customer owned router or ports physically connected to AWS Direct Connect GW. Dunbar, et al. Expires Dec 23, 2019 [Page 6] Internet-Draft Net2Cloud Problem Statement September 2019 +------------------------+ | ,---. ,---. | | (TN-1 ) ( TN-2)| | `-+-' +---+ `-+-' | | +----|vR1|----+ | | ++--+ | | | +-+----+ | | /Internet\ For External | +-------+ Gateway +---------------------- | \ / to reach via Internet | +-+----+ | | | ,---. ,---. | | (TN-1 ) ( TN-2)| | `-+-' +---+ `-+-' | | +----|vR2|----+ | | ++--+ | | | +-+----+ | | / virtual\ For IPsec Tunnel | +-------+ Gateway +---------------------- | | \ / termination | | +-+----+ | | | | | +-+----+ +------+ | | / \ For Direct /customer\ | +-------+ Gateway +----------+ gateway | | \ / Connect \ / | +-+----+ +------+ | | +------------------------+ Figure 1: Examples of Multiple Cloud DC connections. 3.2. Interconnect Private and Public Cloud DCs It is likely that hybrid designs will become the rule for cloud services, as more enterprises see the benefits of integrating public and private cloud infrastructures. However, enabling the growth of hybrid cloud deployments in the enterprise requires fast and safe interconnection between public and private cloud services. For an enterprise to connect to applications & workloads hosted in multiple Cloud DCs, the enterprise can use IPsec tunnels established over the Internet or a (virtualized) leased line service to connect its on-premises gateways to each of the Cloud DC's gateways, virtual Dunbar, et al. Expires Dec 23, 2019 [Page 7] Internet-Draft Net2Cloud Problem Statement September 2019 routers instantiated in the Cloud DCs, or any other suitable design (including a combination thereof). Some enterprises prefer to instantiate their own virtual CPEs/routers inside the Cloud DC to connect the workloads within the Cloud DC. Then an overlay path is established between customer gateways to the virtual CPEs/routers for reaching the workloads inside the cloud DC. 3.3. Desired Properties for Networks that interconnect Hybrid Clouds The networks that interconnect hybrid cloud DCs must address the following requirements: - High availability to access all workloads in the desired cloud DCs. Many enterprises include cloud infrastructures in their disaster recovery strategy, e.g., by enforcing periodic backup policies within the cloud, or by running backup applications in the Cloud, etc. Therefore, the connection to the cloud DCs may not be permanent, but rather needs to be on-demand. - Global reachability from different geographical zones, thereby facilitating the proximity of applications as a function of the end users' location, to improve latency. - Elasticity: prompt connection to newly instantiated applications at Cloud DCs when usages increase and prompt release of connection after applications at locations being removed when demands change. Some enterprises have front-end web portals running in cloud DCs and database servers in their on-premises DCs. Those Front- end web portals need to be reachable from the public Internet. The backend connection to the sensitive data in database servers hosted in the on-premises DCs might need secure connections. - Scalable security management. IPsec is commonly used to interconnect cloud gateways with CPEs deployed in the enterprise premises. For enterprises with a large number or branch offices, managing the IPsec's Security Associations among many nodes can be very difficult. Dunbar, et al. Expires Dec 23, 2019 [Page 8] Internet-Draft Net2Cloud Problem Statement September 2019 4. Multiple Clouds Interconnection 4.1. Multi-Cloud Interconnection Enterprises today can instantiate their workloads or applications in Cloud DCs owned by different Cloud providers, e.g. AWS, Azure, GoogleCloud, Oracle, etc. Interconnecting those workloads involves three parties: The Enterprise, its network service providers, and the Cloud providers. All Cloud Operators offer secure ways to connect enterprises' on- prem sites/DCs with their Cloud DCs. Some Cloud Operators allow enterprises to connect via private networks. For example, AWS's DirectConnect allows enterprises to use rd 3 party provided private Layer 2 path from enterprises' GW to AWS DirectConnect GW. Microsoft's ExpressRoute allows extension of a private network to any of the Microsoft cloud services, including Azure and Office365. ExpressRoute is configured using Layer 3 routing. Customers can opt for redundancy by provisioning dual links from their location to two Microsoft Enterprise edge routers (MSEEs) located within a third-party ExpressRoute peering location. The BGP routing protocol is then setup over WAN links to provide redundancy to the cloud. This redundancy is maintained from the peering data center into Microsoft's cloud network. Google's Cloud Dedicated Interconnect offers similar network connectivity options as AWS and Microsoft. One distinct difference, however, is that Google's service allows customers access to the entire global cloud network by default. It does this by connecting your on-premises network with the Google Cloud using BGP and Google Cloud Routers to provide optimal paths to the different regions of the global cloud infrastructure. All those connectivity options are between Cloud providers' DCs and the Enterprises, but not between cloud DCs. For example, to connect applications in AWS Cloud to applications in Azure Cloud, there must be a third-party gateway (physical or virtual) to interconnect the AWS's Layer 2 DirectConnect path with Azure's Layer 3 ExpressRoute. Enterprises can also instantiate their own virtual routers in different Cloud DCs and administer IPsec tunnels among them, which by itself is not a trivial task. Or by leveraging open source VPN software such as strongSwan, you create an IPSec connection to the Azure gateway using a shared key. The strong swan instance within AWS not only can connect to Azure but can also be used to facilitate traffic to other nodes within the AWS VPC by configuring forwarding Dunbar, et al. Expires Dec 23, 2019 [Page 9] Internet-Draft Net2Cloud Problem Statement September 2019 and using appropriate routing rules for the VPC. Most Cloud operators, such as AWS VPC or Azure VNET, use non-globally routable CIDR from private IPv4 address ranges as specified by RFC1918. To establish IPsec tunnel between two Cloud DCs, it is necessary to exchange Public routable addresses for applications in different Cloud DCs. [BGP-SDWAN] describes one method. Other methods are worth exploring. In summary, here are some approaches, available now (which might change in the future), to interconnect workloads among different Cloud DCs: a) Utilize Cloud DC provided inter/intra-cloud connectivity services (e.g., AWS Transit Gateway) to connect workloads instantiated in multiple VPCs. Such services are provided with the cloud gateway to connect to external networks (e.g., AWS DirectConnect Gateway). b) Hairpin all traffic through the customer gateway, meaning all workloads are directly connected to the customer gateway, so that communications among workloads within one Cloud DC must traverse through the customer gateway. c) Establish direct tunnels among different VPCs (AWS' Virtual Private Clouds) and VNET (Azure's Virtual Networks) via client's own virtual routers instantiated within Cloud DCs. DMVPN (Dynamic Multipoint Virtual Private Network) or DSVPN (Dynamic Smart VPN) techniques can be used to establish direct Multi-point-to-Point or multi-point-to multi-point tunnels among those client's own virtual routers. Approach a) usually does not work if Cloud DCs are owned and managed by different Cloud providers. Approach b) creates additional transmission delay plus incurring cost when exiting Cloud DCs. For the Approach c), DMVPN or DSVPN use NHRP (Next Hop Resolution Protocol) [RFC2735] so that spoke nodes can register their IP addresses & WAN ports with the hub node. The IETF ION (Internetworking over NBMA (non-broadcast multiple access) WG standardized NHRP for connection-oriented NBMA network (such as ATM) network address resolution more than two decades ago. There are many differences between virtual routers in Public Cloud DCs and the nodes in an NBMA network. NHRP cannot be used for Dunbar, et al. Expires Dec 23, 2019 [Page 10] Internet-Draft Net2Cloud Problem Statement September 2019 registering virtual routers in Cloud DCs unless an extension of such protocols is developed for that purpose, e.g. taking NAT or dynamic addresses into consideration. Therefore, DMVPN and/or DSVPN cannot be used directly for connecting workloads in hybrid Cloud DCs. Other protocols such as BGP can be used, as described in [BGP- SDWAN]. 4.2. Desired Properties for Multi-Cloud Interconnection Different Cloud Operators have different APIs to access their Cloud resources. It is difficult to move applications built by one Cloud operator's APIs to another. However, it is highly desirable to have a single and consistent way to manage the networks and respective security policies for interconnecting applications hosted in different Cloud DCs. The desired property would be having a single network fabric to which different Cloud DCs and enterprise's multiple sites can be attached or detached, with a common interface for setting desired policies. SDWAN is positioned to become that network fabric enabling Cloud DCs to be dynamically attached or detached. But the reality is that different Cloud Operators have different access methods, and Cloud DCs might be geographically far apart. More Cloud connectivity problems are described in the subsequent sections. The difficulty of connecting applications in different Clouds might be stemmed from the fact that they are direct competitors. Usually traffic flow out of Cloud DCs incur charges. Therefore, direct communications between applications in different Cloud DCs can be more expensive than intra Cloud communications. 5. Problems with MPLS-based VPNs extending to Hybrid Cloud DCs Traditional MPLS-based VPNs have been widely deployed as an effective way to support businesses and organizations that require network performance and reliability. MPLS shifted the burden of managing a VPN service from enterprises to service providers. The CPEs attached to MPLS VPNs are also simpler and less expensive, since they do not need to manage routes to remote sites; they simply pass all outbound traffic to the MPLS VPN PEs to which the CPEs are attached (albeit multi-homing scenarios require more processing logic on CPEs). MPLS has addressed the problems of scale, Dunbar, et al. Expires Dec 23, 2019 [Page 11] Internet-Draft Net2Cloud Problem Statement September 2019 availability, and fast recovery from network faults, and incorporated traffic-engineering capabilities. However, traditional MPLS-based VPN solutions are sub-optimized for connecting end-users to dynamic workloads/applications in cloud DCs because: - The Provider Edge (PE) nodes of the enterprise's VPNs might not have direct connections to third party cloud DCs that are used for hosting workloads with the goal of providing an easy access to enterprises' end-users. - It usually takes some time to deploy provider edge (PE) routers at new locations. When enterprise's workloads are changed from one cloud DC to another (i.e., removed from one DC and re- instantiated to another location when demand changes), the enterprise branch offices need to be connected to the new cloud DC, but the network service provider might not have PEs located at the new location. One of the main drivers for moving workloads into the cloud is the widely available cloud DCs at geographically diverse locations, where apps can be instantiated so that they can be as close to their end-users as possible. When the user base changes, the applications may be migrated to a new cloud DC location closest to the new user base. - Most of the cloud DCs do not expose their internal networks. An enterprise with a hybrid cloud deployment can use an MPLS-VPN to connect to a Cloud provider at multiple locations. The connection locations often correspond to gateways of different Cloud DC locations from the Cloud provider. The different Cloud DCs are interconnected by the Cloud provider's own internal network. At each connection location (gateway), the Cloud provider uses BGP to advertise all of the prefixes in the enterprise's VPC, regardless of which Cloud DC a given prefix is actually in. This can result in inefficient routing for the end-to-end data path. - Extensive usage of Overlay by Cloud DCs: Dunbar, et al. Expires Dec 23, 2019 [Page 12] Internet-Draft Net2Cloud Problem Statement September 2019 Many cloud DCs use an overlay to connect their gateways to the workloads located inside the DC. There is currently no standard that specifies the interworking between the Cloud Overlay and the enterprise' existing underlay networks. One of the characteristics of overlay networks is that some of the WAN ports of the edge nodes connect to third party networks. There is therefore a need to propagate WAN port information to remote authorized peers in third party network domains in addition to route propagation. Such an exchange cannot happen before communication between peers is properly secured. Another roadblock is the lack of a standard way to express and enforce consistent security policies for workloads that not only use virtual addresses, but in which are also very likely hosted in different locations within the Cloud DC [RFC8192]. The current VPN path computation and bandwidth allocation schemes may not be flexible enough to address the need for enterprises to rapidly connect to dynamically instantiated (or removed) workloads and applications regardless of their location/nature (i.e., third party cloud DCs). 6. Problem with using IPsec tunnels to Cloud DCs As described in the previous section, many Cloud operators expose their gateways for external entities (which can be enterprises themselves) to directly establish IPsec tunnels. Enterprises can also instantiate virtual routers within Cloud DCs to connect to their on-premises devices via IPsec tunnels. If there is only one enterprise location that needs to reach the Cloud DC, an IPsec tunnel is a very convenient solution. However, many medium-to-large enterprises usually have multiple sites and multiple data centers. For workloads and apps hosted in cloud DCs, multiple sites need to communicate securely with those cloud workloads and apps. This section documents some of the issues associated with using IPsec tunnels to connect enterprise premises with cloud gateways. 6.1. Complexity of multi-point any-to-any interconnection The dynamic workload instantiated in cloud DC needs to communicate with multiple branch offices and on-premises data centers. Most Dunbar, et al. Expires Dec 23, 2019 [Page 13] Internet-Draft Net2Cloud Problem Statement September 2019 enterprises need multi-point interconnection among multiple locations, which can be provided by means of MPLS L2/L3 VPNs. Using IPsec overlay paths to connect all branches & on-premises data centers to cloud DCs requires CPEs to manage routing among Cloud DCs gateways and the CPEs located at other branch locations, which can dramatically increase the complexity of the design, possibly at the cost of jeopardizing the CPE performance. The complexity of requiring CPEs to maintain routing among other CPEs is one of the reasons why enterprises migrated from Frame Relay based services to MPLS-based VPN services. MPLS-based VPNs have their PEs directly connected to the CPEs. Therefore, CPEs only need to forward all traffic to the directly attached PEs, which are therefore responsible for enforcing the routing policy within the corresponding VPNs. Even for multi-homed CPEs, the CPEs only need to forward traffic among the directly connected PEs. However, when using IPsec tunnels between CPEs and Cloud DCs, the CPEs need to compute, select, establish and maintain routes for traffic to be forwarded to Cloud DCs, to remote CPEs via VPN, or directly. 6.2. Poor performance over long distance When enterprise CPEs or gateways are far away from cloud DC gateways or across country/continent boundaries, performance of IPsec tunnels over the public Internet can be problematic and unpredictable. Even though there are many monitoring tools available to measure delay and various performance characteristics of the network, the measurement for paths over the Internet is passive and past measurements may not represent future performance. Many cloud providers can replicate workloads in different available zones. An App instantiated in a cloud DC closest to clients may have to cooperate with another App (or its mirror image) in another region or database server(s) in the on-premises DC. This kind of coordination requires predicable networking behavior/performance among those locations. 6.3. Scaling Issues with IPsec Tunnels IPsec can achieve secure overlay connections between two locations over any underlay network, e.g., between CPEs and Cloud DC Gateways. Dunbar, et al. Expires Dec 23, 2019 [Page 14] Internet-Draft Net2Cloud Problem Statement September 2019 If there is only one enterprise location connected to the cloud gateway, a small number of IPsec tunnels can be configured on-demand between the on-premises DC and the Cloud DC, which is an easy and flexible solution. However, for multiple enterprise locations to reach workloads hosted in cloud DCs, the cloud DC gateway needs to maintain multiple IPsec tunnels to all those locations (e.g., as a hub & spoke topology). For a company with hundreds or thousands of locations, there could be hundreds (or even thousands) of IPsec tunnels terminating at the cloud DC gateway, which is not only very expensive (because Cloud Operators usually charge their customers based on connections), but can be very processing intensive for the gateway. Many cloud operators only allow a limited number of (IPsec) tunnels & bandwidth to each customer. Alternatively, you could use a solution like group encryption where a single IPsec SA is necessary at the GW but the drawback here is key distribution and maintenance of a key server, etc. 7. Problems of Using SD-WAN to connect to Cloud DCs SD-WAN can establish parallel paths over multiple underlay networks between two locations on-demand, for example, to support the connections established between two CPEs interconnected by a traditional MPLS VPN ([RFC4364] or [RFC4664]) or by IPsec [RFC6071] tunnels. SD-WAN lets enterprises augment their current VPN network with cost- effective, readily available Broadband Internet connectivity, enabling some traffic offloading to paths over the Internet according to differentiated, possibly application-based traffic forwarding policies, or when the MPLS VPN connection between the two locations is congested, or otherwise undesirable or unavailable. 7.1. SD-WAN among branch offices vs. interconnect to Cloud DCs SD-WAN interconnection of branch offices is not as simple as it appears. For an enterprise with multiple sites, using SD-WAN overlay paths among sites requires each CPE to manage all the addresses that local hosts have the potential to reach, i.e., map internal VPN addresses to appropriate SD-WAN paths. This is similar to the complexity of Frame Relay based VPNs, where each CPE needed to maintain mesh routing for all destinations if they were to avoid an extra hop through a hub router. Even though SD-WAN CPEs can get assistance from a central controller (instead of running a routing Dunbar, et al. Expires Dec 23, 2019 [Page 15] Internet-Draft Net2Cloud Problem Statement September 2019 protocol) to resolve the mapping between destinations and SD-WAN paths, SD-WAN CPEs are still responsible for routing table maintenance as remote destinations change their attachments, e.g., the dynamic workload in other DCs are de-commissioned or added. Even though originally envisioned for interconnecting branch offices, SD-WAN offers a very attractive way for enterprises to connect to Cloud DCs. The SD-WAN for interconnecting branch offices and the SD-WAN for interconnecting to Cloud DCs have some differences: - SD-WAN for interconnecting branch offices usually have two end- points (e.g., CPEs) controlled by one entity (e.g., a controller or management system operated by the enterprise). - SD-WAN for Cloud DC interconnects may consider CPEs owned or managed by the enterprise, while remote end-points are being managed or controlled by Cloud DCs (For the ease of description, let's call such CPEs asymmetrically-managed CPEs). Dunbar, et al. Expires Dec 23, 2019 [Page 16] Internet-Draft Net2Cloud Problem Statement September 2019 - Cloud DCs may have different entry points (or devices) with one entry point that terminates a private direct connection (based upon a leased line for example) and other entry points being devices terminating the IPsec tunnels, as shown in Figure 2. Therefore, the SD-WAN design becomes asymmetric. +------------------------+ | ,---. ,---. | | (TN-1 ) ( TN-2)| TN: Tenant applications/workloads | `-+-' +---+ `-+-' | | +----|vR1|----+ | | ++--+ | | | +-+----+ | | /Internet\ One path via | +-------+ Gateway +---------------------+ | \ / Internet \ | +-+----+ \ +------------------------+ \ \ +------------------------+ native traffic \ | ,---. ,---. | without encryption| | (TN-3 ) ( TN-4)| | | `-+-' +--+ `-+-' | | +------+ | +----|vR|-----+ | +----+ CPE | | ++-+ | | +------+ | | +-+----+ | | | / virtual\ One path via IPsec Tunnel | | +-------+ Gateway +-------------------------- + | \ / Encrypted traffic over| | +-+----+ public network | +------------------------+ | | +------------------------+ | | ,---. ,---. | Native traffic | | (TN-5 ) ( TN-6)| without encryption | | `-+-' +--+ `-+-' | over secure network| | +----|vR|-----+ | | | ++-+ | | | | +-+----+ +------+ | | | / \ Via Direct /customer\ | | +-------+ Gateway +----------+ gateway |-----+ | \ / Connect \ / | +-+----+ +------+ +------------------------+Customer GW has physical connection to AWS GW Figure 2: Different Underlays to Reach Cloud DC Dunbar, et al. Expires Dec 23, 2019 [Page 17] Internet-Draft Net2Cloud Problem Statement September 2019 8. End-to-End Security Concerns for Data Flows When IPsec tunnels established from enterprise on-premises CPEs are terminated at the Cloud DC gateway where the workloads or applications are hosted, some enterprises have concerns regarding traffic to/from their workload being exposed to others behind the data center gateway (e.g., exposed to other organizations that have workloads in the same data center). To ensure that traffic to/from workloads is not exposed to unwanted entities, IPsec tunnels may go all the way to the workload (servers, or VMs) within the DC. 9. Requirements for Dynamic Cloud Data Center VPNs In order to address the aforementioned issues, any solution for enterprise VPNs that includes connectivity to dynamic workloads or applications in cloud data centers should satisfy a set of requirements: - The solution should allow enterprises to take advantage of the current state-of-the-art in VPN technology, in both traditional MPLS-based VPNs and IPsec-based VPNs (or any combination thereof) that run over the public Internet. - The solution should not require an enterprise to upgrade all their existing CPEs. - The solution should support scalable IPsec key management among all nodes involved in DC interconnect schemes. - The solution needs to support easy and fast, on-the-fly, VPN connections to dynamic workloads and applications in third party data centers, and easily allow these workloads to migrate both within a data center and between data centers. - Allow VPNs to provide bandwidth and other performance guarantees. - Be a cost-effective solution for enterprises to incorporate dynamic cloud-based applications and workloads into their existing VPN environment. Dunbar, et al. Expires Dec 23, 2019 [Page 18] Internet-Draft Net2Cloud Problem Statement September 2019 10. Security Considerations The draft discusses security requirements as a part of the problem space, particularly in sections 4, 5, and 8. Solution drafts resulting from this work will address security concerns inherent to the solution(s), including both protocol aspects and the importance (for example) of securing workloads in cloud DCs and the use of secure interconnection mechanisms. 11. IANA Considerations This document requires no IANA actions. RFC Editor: Please remove this section before publication. 12. References 12.1. Normative References 12.2. Informative References [RFC2735] B. Fox, et al "NHRP Support for Virtual Private networks". Dec. 1999. [RFC8192] S. Hares, et al "Interface to Network Security Functions (I2NSF) Problem Statement and Use Cases", July 2017 [ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation, storage, distribution and enforcement of policies for network security", Nov 2007. [RFC6071] S. Frankel and S. Krishnan, "IP Security (IPsec) and Internet Key Exchange (IKE) Document Roadmap", Feb 2011. [RFC4364] E. Rosen and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", Feb 2006 Dunbar, et al. Expires Dec 23, 2019 [Page 19] Internet-Draft Net2Cloud Problem Statement September 2019 [RFC4664] L. Andersson and E. Rosen, "Framework for Layer 2 Virtual Private Networks (L2VPNs)", Sept 2006. [BGP-SDWAN] L. Dunbar, et al. "BGP Extension for SDWAN Overlay Networks", draft-dunbar-idr-bgp-sdwan-overlay-ext-03, work-in-progress, Nov 2018. 13. Acknowledgments Many thanks to Alia Atlas, Chris Bowers, Ignas Bagdonas, Michael Huang, Liu Yuan Jiao, Katherine Zhao, and Jim Guichard for the discussion and contributions. Dunbar, et al. Expires Dec 23, 2019 [Page 20] Internet-Draft Net2Cloud Problem Statement September 2019 Authors' Addresses Linda Dunbar Futurewei Email: Linda.Dunbar@futurewei.com Andrew G. Malis Independent Email: agmalis@gmail.com Christian Jacquenet Orange Rennes, 35000 France Email: Christian.jacquenet@orange.com Mehmet Toy Verizon One Verizon Way Basking Ridge, NJ 07920 Email: mehmet.toy@verizon.com Dunbar, et al. Expires Dec 23, 2019 [Page 21]