Network Working Group                                    L. Dunbar
Internet Draft                                           Futurewei
Intended status: Informational                            A. Malis
Expires: September 8, 2020                              Independent

                                                       C. Jacquenet
                                                      March 8, 2020

           Gap Analysis of Dynamic Networks to Hybrid Cloud DCs


   This document analyzes the technological gaps, especially IETF
   protocols gaps, to achieve dynamically interconnecting workloads and
   applications hosted in Hybrid Cloud Data Centers.

Status of this Memo

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   This Internet-Draft will expire on September 8, 2020.

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Copyright Notice

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Table of Contents

   1. Introduction...................................................3
   2. Conventions used in this document..............................3
   3. Gap Analysis for Accessing Cloud Resources.....................4
   4. Gap Analysis of Overlay Edge Node's WAN Ports Management.......4
   5. Aggregating VPN paths and Internet paths.......................6
      5.1. Control Plane for Overlay over Heterogeneous Networks.....7
      5.2. Using BGP UPDATE Messages.................................8
      5.3. SECURE-L3VPN/EVPN.........................................9
      5.4. Preventing attacks from Internet-facing ports............10
   6. C-PEs not directly connected to VPN PEs.......................10
      6.1. Floating PEs to connect to Remote CPEs...................13
      6.2. NAT Traversal............................................13
      6.3. Complexity of using BGP between PEs and remote CPEs via
      6.4. Designated Forwarder to the remote edges.................14
      6.5. Traffic Path Management..................................15
   7. Manageability Considerations..................................15
   8. Security Considerations.......................................15
   9. IANA Considerations...........................................16
   10. References...................................................16
      10.1. Normative References....................................16
      10.2. Informative References..................................16
   11. Acknowledgments..............................................17

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1. Introduction

   [Net2Cloud-Problem] describes the problems enterprises face today
   when interconnecting their branch offices with dynamic workloads in
   third party data centers (a.k.a. Cloud DCs). This document analyzes
   the IETF routing protocols to identify if there are gaps or if
   protocol extension might be needed.

   For the sake of readability, an edge, an endpoint, C-PE, or CPE are
   used interchangeably throughout this document. However, each term
   has some minor emphasis, especially when used in other related

     . Edge: could include multiple devices (virtual or physical);
     . endpoint: to refer to a WAN port of an Edge device;
     . C-PE: more for provider owned edge, e.g. for SECURE-EVPN's PE
        based VPN, where PE is the edge node;
     . CPE: more for enterprise owned edge.

2. Conventions used in this document

   Cloud DC:   Third party Data Centers that usually host applications
               and workload owned by different organizations or

   Controller: Used interchangeably with Overlay controller to manage
               overlay path creation/deletion and monitor the path
               conditions between sites.

   CPE-Based VPN: Virtual Private Network designed and deployed from
               CPEs. This is to differentiate from most commonly used
               PE-based VPNs a la RFC 4364.

   OnPrem:     On Premises data centers and branch offices

   SDWAN:      Software Defined Wide Area Network, "SDWAN" refers to
               the solutions of pooling WAN bandwidth from multiple
               underlay networks to get better WAN bandwidth

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               management, visibility & control. When the underlay is a
               private network, traffic may be forwarded without any
               additional encryption; when the underlay networks are
               public, such as the Internet, some traffic needs to be
               encrypted when passing through (depending on user-
               provided policies).

3. Gap Analysis for Accessing Cloud Resources

   Many problems described in the [Net2Cloud-Problem] are not in the
   scope of IETF, let alone IETF Routing area. Therefore, this document
   will not cover the detailed protocol gaps analysis for security,
   identity management or DNS for Cloud Resources.

4. Gap Analysis of Overlay Edge Node's WAN Ports Management

   Very often the Hybrid Cloud DCs are interconnected by overlay
   networks that arch over many different types of networks, such as
   VPN, public internet, wireless, etc. Sometimes the enterprises' VPN
   providers do not have direct access to the Cloud DCs that are
   optimal for some specific applications or workloads.

   Under those circumstances, the overlay network' edges can have WAN
   ports facing networks provided by different ISPs, some can be
   untrusted public internet, some can be trusted provider VPN, some
   can be Cloud internal networks, and some can be others.

   If all WAN ports of an edge node are facing untrusted network, then
   all sensitive data to/from this edge have to be encrypted, usually
   by IPsec tunnels which can be terminated at the WAN port address, at
   the edge node's loopback address if the loopback address is routable
   in the wide area network, or even at the ingress ports of the edge

   If an edge node has some WAN ports facing trusted VPN and some
   facing untrusted networks, sensitive data can be forwarded through
   ports facing VPN natively without encryption and forwarded through
   ports facing public network with encryption. To achieve this

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   flexibility, it is necessary to have the IPsec tunnels terminated at
   the WAN ports facing the untrusted networks.

   In order to establish pair-wise secure encrypted connection among
   those WAN ports, it is necessary for peers to be informed of the WAN
   port properties.

   Some of those overlay networks (such as some deployed SDWAN
   networks) use the modified NHRP protocol [RFC2332] to register WAN
   ports of the edges with their "Controller" (or NHRP server), which
   then map a private VPN address to a public IP address of the
   destination node/port. DSVPN [DSVPN] or DMVPN [DMVPN] are used to
   establish tunnels between WAN ports of SDWAN 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 the controller, such as:

   - Interworking with the MPLS VPN control plane. An overlay edge can
     have some ports facing the MPLS VPN network over which packets can
     be forwarded without any encryption and some ports facing the
     public Internet over which sensitive traffic needs to be
   - Scalability: NHRP/DSVPN/DMVPN works fine with small numbers of
     edge nodes. When a network has more than 100 nodes, these
     protocols do not scale well.
   - NHRP does not have the IPsec attributes, which are needed for
     peers to build Security Associations over the public internet.
   - NHRP messages do not have any field to encode the C-PE supported
     encapsulation types, such as IPsec-GRE or IPsec-VxLAN.
   - NHRP messages do not have any field to encode C-PE Location
     identifiers, such as Site Identifier, System ID, and/or Port ID.
   - NHRP messages do not have any field to describe the gateway(s) to
     which the C-PE is attached. When a C-PE is instantiated in a Cloud
     DC, it is desirable for C-PE's owner to be informed of how/where
     the C-PE is attached.
   - NHRP messages do not have any 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,

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   [BGP-SDWAN-PORT] describes how to use BGP to distribute SDWAN edge
   properties to peers.  There is need to extend the protocol to
   register WAN ports properties to the overlay controller, which then
   propagates the information to other overlay edge nodes that are
   authenticated and authorized to communicate with them.

5. Aggregating VPN paths and Internet paths

   Most likely, enterprises (especially the largest ones) already have
   their C-PEs interconnected by providers VPNs, such as EVPN, L2VPN,
   or L3VPN, which can be PE-based or CPE-based. The commonly used PE-
   based VPNs have C-PE directly attached to PEs, therefore the
   communication between C-PEs and PEs is considered as secure. MP-BGP
   is used to learn & distribute routes among C-PEs, even though
   sometimes routes among C-PEs are statically configured on the C-PEs.

   For enterprises already interconnected by VPNs, it is desirable to
   aggregate the bandwidth among VPN paths and Internet paths by C-PEs
   adding additional ports facing public internet. Under this scenario,
   which is referred to as Overlay throughout this document, it is
   necessary for the C-PEs to manage and communicate with controller on
   how traffic are distributed among multiple heterogenous WAN underlay
   networks, and manage secure tunnels over untrusted networks
   independently from the attached clients routes.

   When using NHRP for WAN ports registration purposes, C-PEs need to
   run two separate control planes: EVPN&BGP for CPE-based VPNs, and
   NHRP & DSVPN/DMVPN for ports connected to the Internet. Two separate
   control planes not only add complexity to C-PEs, but also increase
   operational cost.

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                        +--------------|RR |----------+
                       /  Untrusted    +-+-+           \
                      /                                 \
                     /                                   \
     +----+  +---------+  packets encrypted over     +------+  +----+
     | TN3|--|         A1-----+ Untrusted    +------ B1     |--| TN1|
     +----+  | C-PE    A2-\                          | C-PE |  +----+
     +----+  |  A      A3--+--+              +---+---B2  B  |  +----+
     | TN2|--|         |   |PE+--------------+PE |---B3     |--| TN3|
     +----+  +---------+   +--+   trusted    +---+   +------+  +----+
                              |      WAN     |
     +----+  +---------+   +--+   packets    +---+   +------+  +----+
     | TN1|--|         C1--|PE| go natively  |PE |-- D1     |--| TN1|
     +----+  | C-PE    C2--+--+ without encry+---+   | C-PE |  +----+
             |  C      |      +--------------+       |  D   |
             |         |                             |      |
     +----+  |         C3--|  without encrypt over   |      |  +----+
     | TN2|--|         C4--+---- Untrusted  --+------D2     |--| TN2|
     +----+  +---------+                             +------+  +----+
       Figure 1: CPEs interconnected by VPN paths and Internet Paths

 5.1. Control Plane for Overlay over Heterogeneous Networks

   As described in [BGP-SDWAN-Usage], the Control Plane for Overlay
   network over heterogenous networks has three distinct properties:

     - WAN Port Property registration to the Overlay Controller.
          o To inform the Overlay controller and authorized peers of
             the WAN port properties of the Edge nodes. When the WAN
             ports are assigned private addresses, this step can
             register the type of NAT that translates private addresses
             into public ones.

     - Controller facilitated IPsec SA management and NAT information
          o It is for Overlay controller to facilitate or manage the
             IPsec configuration and peer authentication for all IPsec
             tunnels terminated at the edge nodes.

     - Establishing and Managing the topology and reachability for
        services attached to the client ports of overlay edge nodes.

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          o This is for the overlay layer's route distribution, so
             that a C-PE can populate its overlay routing table with
             entries that identify the next hop for reaching a specific
             route/service attached to remote nodes. [SECURE-EVPN]
             describes EVPN and other options.

 5.2. Using BGP UPDATE Messages

    [Tunnel-Encap] describe the BGP UPDATE Tunnel Path Attribute that
   advertise endpoints' tunnel encapsulation capability for the
   respective attached client routes encoded in the MP-NLRI Path
   Attribute. The receivers of the BGP UPDATE can use any of the
   supported encapsulations encoded in the Tunnel Path Attribute for
   the routes encoded in the MP-NLRI Path Attribute.

   Here are some of the gaps using [Tunnel-Encap] to distribute Edge
   WAN port properties:

   - [Tunnel-Encap] doesn't yet have the encoding to describe the NAT
     information for WAN ports that have private addresses. The NAT
     information needs to be propagated to the trusted peers via
     Controllers, such as the virtual C-PEs instantiated in public
     Cloud DCs.
   - It is not easy using the current mechanism in [Tunnel-Encap] to
     exchange IPsec SA specific parameters independently from
     advertising the attached clients' routes, even after adding a new
     IPsec tunnel type.
     [Tunnel-Encap] requires all tunnels updates are associated with
     routes. There can be many client routes associated with the IPsec
     tunnel between two C-PEs' WAN ports; the corresponding destination
     prefixes (as announced by the aforementioned routes) may also be
     reached through the VPN underlay without any encryption.

     The establishment of an IPsec tunnel can fail, such as due to the
     two endpoints supporting different encryption algorithms or other
     reasons. There can be multiple negotiations messages for the IPsec
     SA parameters between two end points. That is why IPsec SA
     association establishment between end points is independent from
     the policies on mapping routes to specific IPSec SA.

     If C-PEs need to establish WAN Port based IPsec SA, the
     information encoded in Tunnel Path Attribute should only apply to
     the WAN ports and should be independent of the clients' routes.

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     In addition, the Overlay IPsec SA Tunnel may need to be
     established before clients' routes are attached.

   - C-PEs tend to communicate with a subset of the other C-PEs, not
     all the C-PEs need to be connected through a mesh topology.
     Therefore, the distribution of the Overlay Edge WAN ports
     information need be be scoped to the authorized peers.


    [SECURE-L3VPN] describes how to extend the BGP/MPLS VPN [RFC4364]
   capabilities to allow some PEs to connect to other PEs via public
   networks. [SECURE-L3VPN] introduces the concept of Red Interface &
   Black Interface used by PEs, where the RED interfaces are used to
   forward traffic into the VPN, and the Black Interfaces are used
   between WAN ports through which only IPsec-protected packets are
   forwarded to the Internet or to other backbone network thereby
   eliminating the need for MPLS transport in the backbone.

   [SECURE-L3VPN] assumes PEs using MPLS over IPsec when sending
   traffic through the Black Interfaces.

   [SECURE-EVPN] describes a solution where point-to-multipoint BGP
   signaling is used in the control plane for the Scenario #1 described
   in [BGP-SDWAN-Usage]. It relies upon a BGP cluster design to
   facilitate the key and policy exchange among PE devices to create
   private pair-wise IPsec Security Associations without IKEv2 point-
   to-point signaling or any other direct peer-to-peer session
   establishment messages.

   Both [SECURE-L3VPN] and [SECURE-EVPN] are useful, however, they both
   miss the aspects of aggregating VPN and Internet underlays. In

   - Both documents assume a client traffic is either forwarded all
     encrypted through an IPsec tunnel, or not encrypted at all through
     a different tunnel regardless which WAN ports the traffic egress
     the PEs towards WAN. For Overlay arch over trusted VPN and
     untrusted Internet, one client traffic can be forwarded encrypted
     at one time through a WAN port towards untrusted network and be
     forwarded unencrypted at different time through a WAN port to MPLS

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   - The [SECURE-L3VPN] assumes that a 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 Overlay network to
     connect Hybrid Cloud DCs, Zero Touch Provisioning is expected.
     Manual configuration is not an option, especially for the edge
     devices that are deployed in faraway places.

   - The [SECURE-L3VPN] assumes that C-PEs and RR are connected via an
     IPsec tunnel. Missing TLS/DTLS. The following assumption by
     [SECURE-L3VPN] becomes invalid for the Overlay network to connect
     Hybrid Cloud DCs where automatic synchronization of IPsec SA
     between C-PEs and RR is needed:
          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 does
     not provide any information about how to synchronize the
     refreshment among multiple nodes.
   - IPsec usually sends configuration parameters to two endpoints only
     and lets these endpoints negotiate the key. The [SECURE-L3VPN]
     assumes that the RR is responsible for creating/managing the key
     for all endpoints. When one endpoint is compromised, all other
     connections will be impacted.

5.4. Preventing attacks from Internet-facing ports

   When C-PEs have Internet-facing ports, additional security risks are

   To mitigate security risks, in addition to requiring Anti-DDoS
   features on C-PEs, it is necessary for C-PEs to support means to
   determine whether traffic sent by remote peers is legitimate to
   prevent spoofing attacks.

6. C-PEs not directly connected to VPN PEs

   Because of the ephemeral property of the selected Cloud DCs for
   specific workloads/Apps, an enterprise or its network service

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   provider may not have direct physical connections to the Cloud DCs
   that are optimal for hosting the enterprise's specific
   workloads/Apps. Under those circumstances, Overlay is a very
   flexible choice to interconnect the enterprise on-premises data
   centers & branch offices to its desired Cloud DCs.

   However, Overlay paths established over the public Internet can have
   unpredictable performance, especially over long distances and across
   operators' domains. Therefore, it is highly desirable to steer as
   much as possible the portion of Overlay paths over the enterprise's
   existing VPN that has guaranteed SLA to minimize the distance or the
   number of segments over the public Internet.

   MEF Cloud Service Architecture [MEF-Cloud] also describes a use case
   of network operators using Overlay path over LTE or the public
   Internet for last mile access where the VPN service providers cannot
   necessarily provide the required physical infrastructure.

   Under those scenarios, one or two of the Overlay endpoints may not
   be directly attached to the PEs of a VPN Domain.

   When using Overlay to connect the enterprise's existing sites to the
   workloads hosted in Cloud DCs, the corresponding C-PEs have to be
   upgraded to support the desired Overlay.  If the workloads hosted in
   Cloud DCs need to be connected to many sites, the upgrade process
   can be very expensive.

   [Net2Cloud-Problem] describes a hybrid network approach that extend
   the existing MPLS-based VPNs to the Cloud DC Workloads over the
   access paths that are not under the VPN provider's 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 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 hosted in Cloud DCs can be reached by the
   enterprise's VPN without upgrading all of the enterprise's existing
   CPEs. The only CPE that needs to support the Overlay would be a
   virtualized CPE instantiated within the cloud DC.

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   +--------+                                             +--------+
   | Host-a +--+                                     +----| Host-b |
   |        |  |                                    (')   |        |
   +--------+  |           +-----------+           (   )  +--------+
               |  +-+--+  ++-+        ++-+  +--+-+  (_)
               |  | CPE|--|PE|        |PE+--+ CPE|   |
               +--|    |  |  |        |  |  |    |---+
                  +-+--+  ++-+        ++-+  +----+
                   /       |           |
                  /        |  MPLS   +-+---+    +--+-++--------+
          +------+-+       | Network |fPE-1|    |CPE || Host   |
          | Host   |       |         |     |- --|    ||   d    |
          |   c    |       +-----+   +-+---+    +--+-++--------+
          +--------+       |fPE-2|-----+
                           +---+-+    (|)
                              (|)     (|) Overlay
                              (|)     (|) over any access
                             //   \    | Cloud DC \\
                            //      \ ++-----+       \\
                                      |  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 (as a
   function of the proximity, capacity, pricing, or other criteria
   chosen by the enterprises) does not have a direct connection to the
   PEs of the MPLS VPN that interconnects the enterprise's existing

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6.1. 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.

   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 purposes or the ability to support multiple cloud
   DCs geographically scattered), 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

6.2. NAT Traversal

   Cloud DCs that only assign private IPv4 addresses to the
   instantiated workloads assume that traffic to/from the workload
   usually needs to traverse NATs.
   An overlay edge node can solicit a 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 so that
   such information can be communicated to the relevant peers.

6.3. Complexity 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 in extending BGP from MPLS VPN PEs to
   remote CPEs via any access path (e.g., Internet).

   The path between the remote CPEs and VPN PEs that maintain VPN
   routes may very well traverse untrusted nodes.

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   EBGP Multi-hop design 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 address of the CPEs.
   When remote CPEs, especially remote virtualized CPEs are dynamically
   instantiated or removed, the configuration of Multi-Hop EBGP on the
   PE has to be changed accordingly.

     Egress peering engineering (EPE) is not sufficient. Running BGP on
     virtualized CPEs in Cloud DCs requires GRE tunnels to be
     established first, which requires the remote CPEs to support
     address and key management capabilities. RFC 7024 (Virtual Hub &
     Spoke) and Hierarchical VPN do not support the required

     Also, there is a need for a mechanism to automatically trigger
     configuration changes on PEs when remote CPEs' are instantiated or
     moved (leading to an IP address change) or deleted.

     EBGP Multi-hop design does not include a security mechanism by
     default. The PE and remote CPEs need secure communication channels
     when connecting via the public Internet.

   Remote CPEs, if instantiated in Cloud DCs, might have to traverse
   NATs to reach PEs. It is not clear how BGP can be used between
   devices located beyond the NAT and the devices located behind the
   NAT. It is not clear how to configure the Next Hop on the PEs to
   reach private IPv4 addresses.

6.4. Designated Forwarder to the remote edges

   Among the multiple floating PEs that are reachable from a remote
   CPE, multicast traffic sent by the remote CPE towards the MPLS VPN
   can be forwarded back to the remote CPE due to the PE receiving the
   multicast packets forwarding the multicast/broadcast frame to other
   PEs that in turn send to all attached CPEs. This process may cause
   traffic loops.

   Therefore, it is necessary to designate one floating PE as the CPE's
   Designated Forwarder, similar to TRILL's Appointed Forwarders

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   MPLS VPNs do not have features like TRILL's Appointed Forwarders.

6.5. Traffic Path Management

   When there are multiple floating PEs that have established IPsec
   tunnels with the remote CPE, the remote CPE can forward outbound
   traffic to the Designated Forwarder PE, which in turn forwards
   traffic to egress PEs and then to the final 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.

7. Manageability Considerations

     Zero touch provisioning of Overlay networks to interconnect Hybrid
     Clouds is highly desired. It is necessary for a newly powered up
     edge node to establish a secure connection (by means of TLS, DTLS,
     etc.) with its controller.

8. Security Considerations

     Cloud Services is built upon shared infrastructure, therefore not
     secure by nature.

     Secure user identity management, authentication, and access
     control mechanisms are important. Developing appropriate security
     measurements can enhance the confidence needed by enterprises to
     fully take advantage of Cloud Services.

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9. IANA Considerations

   This document requires no IANA actions. RFC Editor: Please remove
   this section before publication.

10. References

10.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2. 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-PORT]L. Dunbar, et al, "Subsequent Address Family
             Indicator for SDWAN Ports", draft-dunbar-idr-sdwan-port-
             safi-00, Work-in-progress, March 2019.

   [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.

   [SECURE-EVPN A. Sajassi, et al, draft-sajassi-bess-secure-evpn-01,
             work in progress, March 2019.

   [SECURE-L3VPN] E. Rosen, "Provide Secure Layer L3VPNs over Public
             Infrastructure", draft-rosen-bess-secure-l3vpn-00, work-
             in-progress, July 2018

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   [DMVPN] Dynamic Multi-point VPN:

   [DSVPN] Dynamic Smart VPN:

   [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

11. Acknowledgments

   Acknowledgements to John Drake for his review and contributions.
   Many thanks to John Scudder for stimulating the clarification
   discussion on the Tunnel-Encap draft so that our gap analysis can be
   more accurate.

   This document was prepared using

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Authors' Addresses

   Linda Dunbar

   Andrew G. Malis

   Christian Jacquenet
   Rennes, 35000

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