wdiff draft-ietf-rtgwg-net2cloud-gap-analysis-00.txt draft-ietf-rtgwg-net2cloud-gap-analysis-01.txt

Network Working Group L. Dunbar
Internet Draft A. Malis
Intended status: Informational Huawei
Expires: August 6, September 25, 2019 C.
Jacquenet
Orange
February 12,
March 25, 2019

Gap Analysis of Interconnecting Underlay with Cloud Overlay
draft-ietf-rtgwg-net2cloud-gap-analysis-00
draft-ietf-rtgwg-net2cloud-gap-analysis-01

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].

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Table of Contents

1. Introduction...................................................2
2. Conventions used in this document..............................3
3. Gap Analysis of C-PEs Registration Protocol....................4 WAN Ports Registration...................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 for SD-WAN......................6
4.2. Gaps in preventing attacks from Internet facing 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 CPEs...12
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 Management..................................14
6. Manageability Considerations..................................14
7. Security Considerations.......................................14
8. IANA Considerations...........................................14 Considerations...........................................15
9. References....................................................14 References....................................................15
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
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 enterprise's VPN service provider might may not have own/operate
or have limited may be unable to provide the physical infrastructure required connectivity to reach. access
these locations. When enterprise' VPN service providers do not have or have
insufficient bandwidth to reach a location, SD-WAN is emerged as way techniques can be
used to aggregate bandwidth of multiple networks, such as MPLS VPN, VPNs,
the Public Internet,
etc. to achieve better performance and visibility.
This document primarily focuses on the technological gaps of SD-WAN.

For ease of description, a SD-WAN edge, a SD-WAN end points, end-point, 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 Network designed and deployed from
CPEs. This is to differentiate from most commonly used PE-
based
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" Network, "SDWAN" 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 of pooling WAN bandwidth from multiple
underlay networks to get better WAN bandwidth
management, visibility & control. When the underlay networks are is
private
networks, network, traffic can traverse without additional
encryption; when the underlay networks are public, such
as the Internet, some traffic needs to be encrypted when
traversing through (depending on user provided user-provided
policies).

3. Gap Analysis of C-PEs WAN Ports Registration Protocol

SD-WAN, conceived in

The SD-WAN WG stemmed out from ONUG (Open Network User Group) a few years ago in
2014 and was the placeholder to define SD-WAN as a means to
aggregate multiple connections underlay networks between any two points, points. SD-WAN
technology 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
ports of 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 between WAN ports of 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 over which packets can be sent
natively without encryption and some ports facing the public
Internet that requires encryption for some over which sensitive data traffic needs to
traverse. be encrypted before
being sent.
- Scalability. NHRP/DSVPN/DMVPN works fine with small number numbers 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 messages do not have any field to indicate encode the C-PE supported
encapsulation types, such as IPsec-GRE, IPsec-VxLAN, IPsec-GRE or others. IPsec-VxLAN,.
- NHRP does messages do not have any field to indicate encode C-PE Location identifier,
identifiers, such as Site Identifier, System ID, and/or Port ID.
- NHRP does messages do not have any field to describe the gateway gateway(s) to
which the C-PE is attached. When a C-PE is instantiated in a Cloud
DC, to 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 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,
etc.

[BGP-SDWAN-EXT]

[BGP-SDWAN-PORT] describes how to use BGP for SD-WAN edge nodes to
register its their WAN ports properties to the SD-WAN controller, which
then disseminates the information to other SD-WAN edge nodes that
are authenticated to communicate. before the SD-WAN controller and the other SD-WAN
edge nodes can communicate with them.

4. Gap Analysis in aggregating VPN paths and Internet paths

Most likely, enterprises especially large ones (especially the largest ones) already have
their CPEs interconnected by providers' VPNs, based upon VPN
techniques such as EVPN, L2VPN, or L3VPN. The VPN can be PE based PE-based or CPE based as shown in the
following diagram.
CPE-based. The commonly used CPE-based PE-based VPNs have CPE directly
attached to PEs, therefore the communication between CPEs & PEs is
considered as secure. BGP are MP-BGP is used to learn & 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

To use SD-WAN to aggregate paths over the Internet routes with and paths over the VPN routes, VPN, the
C-PEs C-
PEs need to have some WAN ports connected to the PEs of the VPNs and
other WAN ports connected to the Internet. It is necessary for the
CPEs to have use a registration protocol for C-PEs to so that they can register the WAN port
properties with their SD-WAN Controllers to
establish secure tunnels Controller(s): this information
conditions the establishment and the maintenance of IPsec SA
associations among relevant C-PEs.

If using NHRP for registration, registration purposes, 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. the Internet. Two separate
control planes not only add complexity to C-PEs, but also increase
operational cost.

+---------Internet paths--------------+
| |
|

+---+
+--------------|RR |----------+
/ Untrusted +-+-+ \
/ \
/ \
+----+ +---------+ packets encrypted over +------+ +----+
| TN3|--| A1-----+ Untrusted +------ B1 |--| TN1|
+----+ | |RR | |
| +======+---+===========+ |
| // \\ | C-PE A2-\ | // <-----EVPN-VxLAN----> \\ C-PE | +----+
+----+ | +-+--+ ++-+ ++-+ +--+-+ (|) A A3--+--+ +---+---B2 B | +----+
| CPE|--|PE| |PE+--+ CPE| (|)
+--| 1 TN2|--| | |1 |PE+--------------+PE |---B3 |--| TN3|
+----+ +---------+ +--+ trusted +---+ +------+ +----+
| |x WAN |
+----+ +---------+ +--+ packets +---+ +------+ +----+
| c |---+
+-+--+ ++-+ ++-+ TN1|--| C1--|PE| go natively |PE |-- D1 |--| TN1|
+----+ | C-PE C2--+--+ without encry+---+ | C-PE | VPN +-+---+ +----+
+--------+
| Network C | PE3 +--------------+ | |CPE D |
| CPE | | | |- --| 3
+----+ | C3--| without encrypt over | c | +-----+ +-+---+ +----+
+------+-+-------+ PE4 |-----+
+---+-+
| TN2|--| C4--+---- Untrusted --+------D2 |--| TN2|
+----+ +---------+ +------+ +----+
Figure 2: 1: 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 for SD-WAN instead of two separate control planes.

This section analyzes the gaps of using BGP to control SD-WAN.

As described in [BGP-SDWAN-Usage], SD-WAN Overlay Control Plane has
three distinct functional tiers: aspects:

- SD-WAN node's private address and WAN Ports/Addresses Ports Property registration to the SD-WAN
Controller.
o It is for informing to inform the SD-WAN controller and potential peers
of the underlay networks to which WAN ports property of the C-PE is
connected. [SDWAN-Port]. When
the WAN ports are using private addresses, this step can
register the type of NAT that translate private addresses
into public ones.

- Controller Facilitated IPsec SA management and NAT information
distribution
o It is for SD-WAN controller to facilitate or manage the
IPsec configurations configuration and peer authentications authentication 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 route distribution, so
that a C-PE can establish the populate its overlay routing table with
entries that
identifies identify 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 use the Endpoint Address to indicate that indicates an
IPv4 or an IPv6 address format, address, and 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. encapsulation types.

[Tunnel-Encap] removed SAFI =7 (which was specified by RFC5512) for
distributing encapsulation tunnel information. [Tunnel-Encap]
require Tunnels being
requires that tunnels need to be 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)
WAN).

Here are some of the gaps using [Tunnel-Encap] to control SD-WAN:

- Lacking C-PE WAN Port Property Registration functionality
- Lacking IPsec Tunnel type
- [Tunnel-Encap] has Remote Address SubTLV, but does not have any
field to indicate the Tunnel originating interface, which was as defined in
RFC5512.
- The mechanisms described by [Tunnel-Encap] cannot be effectively
used for SD-WAN overlay network because a SD-WAN Tunnel can be
established between Internet facing Internet-facing WAN ports of two C-PEs and C-Pes. This
tunnel needs to be established before data arrival because the
tunnel establishment can fail, e.g. e.g., in case the two end points supporting end-points
support different encryption algorithms.
- Client traffic (e.g. an EVPN route) can have option of going either be forwarded through the MPLS network
natively without encryption, any encryption for better performance, or going through
the IPsec tunnels between the internet facing WAN Internet-facing ports of two C-
PEs. with IPsec encryption.
- There is no routes to can be many client routes associated with the SD-WAN Tunnel IPsec
tunnel between two C-PE's internet facing Internet-facing WAN ports, unless consider using but the
interface facing WAN Port addresses assigned
corresponding destination prefixes (as announced by ISP (Internet
Service Providers) as the route for
aforementioned routes) can also be reached over the Tunnel. VPN underlay
natively without encryption. A more realistic approach to separate
IPsec SA management from client routes association with IPsec.
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 raise some design
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 with their corresponding peers, the node would need as
many "fake addresses". For large SD-WAN networks (such as has those
comprised of 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 any field to carry detailed information of about the
remote
C-PE: C-PE, such as Site-ID, System-ID, Port-ID
- Does not have the proper any field to express IPsec attributes among for the SD-WAN
edge nodes to establish proper IPsec Security
Associations. Associations with others.
- Does not have any proper way for two peer CPEs to negotiate IPSec IPsec
keys, based on the configuration sent by the Controller.
- Does not have any field to indicate the UDP NAT private address
<-> public address mapping
- C-PEs tend to communicate with a few subset of the other CPEs, C-PEs, not
all the C-PEs need to form mesh connections. Without any BGP
extension, many nodes can get dumped with too much information of
coming from other nodes that they never need to communicate with.

[VPN-over-Internet]

[SECURE-L3VPN] describes a way how to securely interconnect C-PEs extend the RFC4364 VPN to allow some
PEs to connect to other PEs via public networks. [SECURE-L3VPN]
introduces the concept of Red Interface & Black Interface on those
PEs, where the RED interfaces are used to forward traffic into the
VPN, and the Black Interfaces are used between WAN ports over which
only IPsec-protected packets to the Internet or other backbone
network are sent thereby eliminating the need for MPLS transport in
the backbone.

[SECURE-L3VPN] assumes PEs terminate MPLS packets, and use MPLS over
IPsec using BGP. This method 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 SDWAN Scenario #1. 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, it still misses
some they both
miss the aspects to aggregate CPE-based of aggregating VPN routes with internet routes
that interconnect the CPEs. and Internet underlays. In addition:
summary:

- The draft does These documents do not have options address the scenario of C-PE having both MPLS some
ports facing VPN PEs and
Internet ports. other ports facing the Internet.
-
- The draft [SECURE-L3VPN] 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 Manual configuration is not acceptable an option,
given the dimensioning figures but also the purpose of SD-WAN to require manual configuration.
automate configuration tasks.
- For RR communication with CPE, CPEs, this draft only mentioned IPSec. mentions 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 SAs 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 does
not provide any information about how to synchronize the
refreshment among multiple nodes.
- IPsec usually only sends configuration parameters to two endpoints only
and let the two lets these endpoints negotiate the KEY. Now we key. Let us assume that the
RR is responsible for creating the KEY key for all endpoints. endpoints: When one
endpoint is compromised, all other connections are will be impacted.

4.2. Gaps in preventing attacks from Internet facing Internet-facing ports

When C-PEs have ports facing Internet, it brings in the Internet-facing ports, additional security risks of potential DDoS attacks to the C-PEs from the ports facing
internet. are
raised.

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

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
connections to the Cloud DCs that are optimal used for hosting the
enterprise's specific workloads/Apps. Under those circumstances, SD-WAN SD-
WAN is a very flexible choice to interconnect the enterprise on-premises 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 that use SD-WAN over LTE or the public
Internet for last mile accesses access where they are not present. the VPN providers cannot
necessarily provide the required physical infrastructure.

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

Using

When using SD-WAN to connect the enterprise enterprise's existing sites with
the workloads in Cloud DC, the enterprise existing sites' corresponding CPEs have to be
upgraded to support SD-WAN. If the workloads in Cloud DC DCs 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 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 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.

+--------+ +--------+
| 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:

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),
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 packets.

5.2. NAT Traversal

Most cloud DCs only assign private addresses to the workloads
instantiated. instantiated
workloads. Therefore, traffic to/from the workload usually need needs to
traverse NAT. NATs.
A SD-WAN edge node can inquire 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 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 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 addresses 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 Multi-Hop EBGP has to be changed accordingly.

Gap:

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 mechanism to automatically trigger
configuration changes on PE PEs when remote CPEs' are instantiated or
moved (leading to an IP address change) or deleted.

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

Remote CPEs, if instantiated in Cloud DC, DCs, might have to traverse NAT
NATs 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 the multiple floating PEs that are available for a remote CPE,
multicast traffic from sent by 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. loops.

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 with the remote CPE, the remote CPE can forward the outbound
traffic to the Designated Forwarder PE, which in turn forwards the
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.

6. Manageability Considerations

Zero touch provisioning of SD-WAN edge nodes is expected in SD-
WAN SD-WAN
deployment. It is necessary for a newly powered up SD-WAN
edges edge
node to establish a secure connection (such as (by means of TLS, DTLS,
etc.)
to with 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 since this is the general intention purpose 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

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.

[BGP-SDWAN-PORT]L. Dunbar, "BGP Extension et al, "Subsequent Address Family
Indicator for SDWAN Overlay
Networks", draft-dunbar-idr-bgp-sdwan-overlay-ext-00, Oct
2018. 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.

[VPN-over-Internet]

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

[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.

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