< draft-ietf-rtgwg-net2cloud-gap-analysis-03.txt   draft-ietf-rtgwg-net2cloud-gap-analysis-04.txt >
Network Working Group L. Dunbar Network Working Group L. Dunbar
Internet Draft Futurewei Internet Draft Futurewei
Intended status: Informational A. Malis Intended status: Informational A. Malis
Expires: May 1, 2020 Independent Expires: September 8, 2020 Independent
C. Jacquenet
Orange C. Jacquenet
November 1, 2019 Orange
March 8, 2020
Gap Analysis of Dynamic Networks to Hybrid Cloud DCs Gap Analysis of Dynamic Networks to Hybrid Cloud DCs
draft-ietf-rtgwg-net2cloud-gap-analysis-03 draft-ietf-rtgwg-net2cloud-gap-analysis-04
Abstract Abstract
This document analyzes the technological gaps when using SDWAN to This document analyzes the technological gaps, especially IETF
dynamically interconnect workloads and applications hosted in protocols gaps, to achieve dynamically interconnecting workloads and
rd various 3 party cloud data centers. applications hosted in Hybrid Cloud Data Centers.
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
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This Internet-Draft will expire on May 1, 2009. This Internet-Draft will expire on September 8, 2020.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction...................................................2 1. Introduction...................................................3
2. Conventions used in this document..............................3 2. Conventions used in this document..............................3
3. Gap Analysis of C-PEs WAN Port Management......................4 3. Gap Analysis for Accessing Cloud Resources.....................4
4. Aggregating VPN paths and Internet paths.......................6 4. Gap Analysis of Overlay Edge Node's WAN Ports Management.......4
4.1. Key Control Plane Components of SDWAN Overlay.............7 5. Aggregating VPN paths and Internet paths.......................6
4.2. Using BGP UPDATE Messages.................................8 5.1. Control Plane for Overlay over Heterogeneous Networks.....7
4.3. SECURE-L3VPN/EVPN.........................................9 5.2. Using BGP UPDATE Messages.................................8
4.4. Preventing attacks from Internet-facing ports............10 5.3. SECURE-L3VPN/EVPN.........................................9
5. C-PEs not directly connected to VPN PEs.......................11 5.4. Preventing attacks from Internet-facing ports............10
5.1. Floating PEs to connect to Remote CPEs...................13 6. C-PEs not directly connected to VPN PEs.......................10
5.2. NAT Traversal............................................13 6.1. Floating PEs to connect to Remote CPEs...................13
5.3. Complexity of using BGP between PEs and remote CPEs via 6.2. NAT Traversal............................................13
6.3. Complexity of using BGP between PEs and remote CPEs via
Internet......................................................13 Internet......................................................13
5.4. Designated Forwarder to the remote edges.................14 6.4. Designated Forwarder to the remote edges.................14
5.5. Traffic Path Management..................................15 6.5. Traffic Path Management..................................15
6. Manageability Considerations..................................15 7. Manageability Considerations..................................15
7. Security Considerations.......................................15 8. Security Considerations.......................................15
8. IANA Considerations...........................................16 9. IANA Considerations...........................................16
9. References....................................................16 10. References...................................................16
9.1. Normative References.....................................16 10.1. Normative References....................................16
9.2. Informative References...................................16 10.2. Informative References..................................16
10. Acknowledgments..............................................17 11. Acknowledgments..............................................17
1. Introduction 1. Introduction
[Net2Cloud-Problem] describes the problems that enterprises face [Net2Cloud-Problem] describes the problems enterprises face today
today in transitioning their IT infrastructure to support digital when interconnecting their branch offices with dynamic workloads in
economy, such as connecting enterprises' branch offices to dynamic third party data centers (a.k.a. Cloud DCs). This document analyzes
workloads in different Cloud DCs. the IETF routing protocols to identify if there are gaps or if
protocol extension might be needed.
This document analyzes the technological gaps to interconnect
dynamic workloads & apps hosted in cloud data centers that the
enterprise's VPN service provider may not own/operate or may be
unable to provide the enterprise with the required connectivity to
access such locations. When VPN service providers have insufficient
bandwidth to reach a location, SDWAN techniques can be used to
aggregate bandwidth of multiple networks, such as MPLS VPNs or the
Public Internet to achieve better performance. This document
primarily focuses on the technological gaps raised by using SDWAN
techniques to connect enterprise premises to cloud data centers
operated by third parties.
For the sake of readability, a SDWAN edge, a SDWAN endpoint, C-PE, For the sake of readability, an edge, an endpoint, C-PE, or CPE are
or CPE are used interchangeably throughout this document. However, used interchangeably throughout this document. However, each term
each term has some minor emphasis, especially when used in other has some minor emphasis, especially when used in other related
related documents: documents:
. SDWAN Edge: could include multiple devices (virtual or . Edge: could include multiple devices (virtual or physical);
physical); . endpoint: to refer to a WAN port of an Edge device;
. SDWAN endpoint: to refer to a WAN port of SDWAN devices or a . C-PE: more for provider owned edge, e.g. for SECURE-EVPN's PE
single SDWAN device; based VPN, where PE is the edge node;
. C-PE: more for provider owned SDWAN edge, e.g. for SECURE- . CPE: more for enterprise owned edge.
EVPN's PE based VPN, when PE is the edge node of SDWAN;
. CPE: more for enterprise owned SDWAN edge.
2. Conventions used in this document 2. Conventions used in this document
Cloud DC: Third party Data Centers that usually host applications Cloud DC: Third party Data Centers that usually host applications
and workload owned by different organizations or and workload owned by different organizations or
tenants. tenants.
Controller: Used interchangeably with SDWAN controller to manage Controller: Used interchangeably with Overlay controller to manage
SDWAN overlay path creation/deletion and monitor the overlay path creation/deletion and monitor the path
path conditions between sites. conditions between sites.
CPE-Based VPN: Virtual Private Network designed and deployed from CPE-Based VPN: Virtual Private Network designed and deployed from
CPEs. This is to differentiate from most commonly used CPEs. This is to differentiate from most commonly used
PE-based VPNs a la RFC 4364. PE-based VPNs a la RFC 4364.
OnPrem: On Premises data centers and branch offices OnPrem: On Premises data centers and branch offices
SDWAN: Software Defined Wide Area Network, "SDWAN" refers to SDWAN: Software Defined Wide Area Network, "SDWAN" refers to
the solutions of pooling WAN bandwidth from multiple the solutions of pooling WAN bandwidth from multiple
underlay networks to get better WAN bandwidth underlay networks to get better WAN bandwidth
management, visibility & control. When the underlay is a management, visibility & control. When the underlay is a
private network, traffic may be forwarded without any private network, traffic may be forwarded without any
additional encryption; when the underlay networks are additional encryption; when the underlay networks are
public, such as the Internet, some traffic needs to be public, such as the Internet, some traffic needs to be
encrypted when passing through (depending on user- encrypted when passing through (depending on user-
provided policies). provided policies).
3. Gap Analysis of C-PEs WAN Port Management 3. Gap Analysis for Accessing Cloud Resources
One of the key characteristics of the networks that interconnect Many problems described in the [Net2Cloud-Problem] are not in the
workloads in Hybrid Cloud DCs is that those networks' edges can have scope of IETF, let alone IETF Routing area. Therefore, this document
WAN ports facing networks provided by different ISPs, some can be will not cover the detailed protocol gaps analysis for security,
untrusted public internet, some can be MPLS VPN, some can be Cloud identity management or DNS for Cloud Resources.
internal networks, some can be others.
If an edge node only has one single WAN port facing untrusted 4. Gap Analysis of Overlay Edge Node's WAN Ports Management
network, then all sensitive data to/from this edge have to be
encrypted, usually by IPsec tunnels which can be terminated at the
single WAN port address or at the edge node's internal address if it
is routable in the wide area network.
If an edge node has multiple WAN ports with some facing private VPN Very often the Hybrid Cloud DCs are interconnected by overlay
and some facing public untrusted network, sensitive data can be networks that arch over many different types of networks, such as
forwarded via ports facing VPN natively without encryption and via 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
node.
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 ports facing public network with encryption. To achieve this
flexibility, it is necessary to have the IPsec tunnels terminated at flexibility, it is necessary to have the IPsec tunnels terminated at
the WAN ports facing the public networks. the WAN ports facing the untrusted networks.
In order to establish pair-wise secure encrypted connection among In order to establish pair-wise secure encrypted connection among
those WAN ports, it is necessary for peers to be informed of the WAN those WAN ports, it is necessary for peers to be informed of the WAN
port properties. port properties.
Some of those overlay networks (a.k.a. SDWAN in the context of this Some of those overlay networks (such as some deployed SDWAN
document) use the modified NHRP protocol [RFC2332] to register WAN networks) use the modified NHRP protocol [RFC2332] to register WAN
ports of the edges with their "Controller" (or NHRP server), which ports of the edges with their "Controller" (or NHRP server), which
then map a private VPN address to a public IP address of the then map a private VPN address to a public IP address of the
destination node/port. DSVPN [DSVPN] or DMVPN [DMVPN] are used to destination node/port. DSVPN [DSVPN] or DMVPN [DMVPN] are used to
establish tunnels between WAN ports of SDWAN edge nodes. establish tunnels between WAN ports of SDWAN edge nodes.
NHRP was originally intended for ATM address resolution, and as a NHRP was originally intended for ATM address resolution, and as a
result, it misses many attributes that are necessary for dynamic result, it misses many attributes that are necessary for dynamic
endpoint C-PE registration to the controller, such as: endpoint C-PE registration to the controller, such as:
- Interworking with the MPLS VPN control plane. An overlay (SDWAN) - Interworking with the MPLS VPN control plane. An overlay edge can
edge can have some ports facing the MPLS VPN network over which have some ports facing the MPLS VPN network over which packets can
packets can be forwarded without any encryption and some ports be forwarded without any encryption and some ports facing the
facing the public Internet over which sensitive traffic needs to public Internet over which sensitive traffic needs to be
be encrypted before being sent. encrypted.
- Scalability: NHRP/DSVPN/DMVPN works fine with small numbers of - Scalability: NHRP/DSVPN/DMVPN works fine with small numbers of
edge nodes. When a network has more than 100 nodes, these edge nodes. When a network has more than 100 nodes, these
protocols do not scale well. protocols do not scale well.
- NHRP does not have the IPsec attributes, which are needed for - NHRP does not have the IPsec attributes, which are needed for
peers to build Security Associations over the public internet. peers to build Security Associations over the public internet.
- NHRP messages do not have any field to encode the C-PE supported - NHRP messages do not have any field to encode the C-PE supported
encapsulation types, such as IPsec-GRE or IPsec-VxLAN. encapsulation types, such as IPsec-GRE or IPsec-VxLAN.
- NHRP messages do not have any field to encode C-PE Location - NHRP messages do not have any field to encode C-PE Location
identifiers, such as Site Identifier, System ID, and/or Port ID. identifiers, such as Site Identifier, System ID, and/or Port ID.
- NHRP messages do not have any field to describe the gateway(s) to - 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 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 DC, it is desirable for C-PE's owner to be informed of how/where
the C-PE is attached. the C-PE is attached.
- NHRP messages do not have any field to describe C-PE's NAT - 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 properties if the C-PE is using private addresses, such as the NAT
type, Private address, Public address, Private port, Public port, type, Private address, Public address, Private port, Public port,
etc. etc.
[BGP-SDWAN-PORT] describes how SDWAN edge nodes use BGP to register [BGP-SDWAN-PORT] describes how to use BGP to distribute SDWAN edge
their WAN ports properties to the SDWAN controller, which then properties to peers. There is need to extend the protocol to
propagates the information to other SDWAN edge nodes that are 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. authenticated and authorized to communicate with them.
4. Aggregating VPN paths and Internet paths 5. Aggregating VPN paths and Internet paths
Most likely, enterprises (especially the largest ones) already have Most likely, enterprises (especially the largest ones) already have
their C-PEs interconnected by providers VPNs, such as EVPN, L2VPN, 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- 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 based VPNs have C-PE directly attached to PEs, therefore the
communication between C-PEs and PEs is considered as secure. MP-BGP communication between C-PEs and PEs is considered as secure. MP-BGP
is used to learn & distribute routes among C-PEs, even though is used to learn & distribute routes among C-PEs, even though
sometimes routes among C-PEs are statically configured on the C-PEs. sometimes routes among C-PEs are statically configured on the C-PEs.
For enterprises already interconnected by VPNs, it is desirable to For enterprises already interconnected by VPNs, it is desirable to
aggregate the bandwidth among VPN paths and Internet paths by C-PEs aggregate the bandwidth among VPN paths and Internet paths by C-PEs
adding additional ports facing public internet. Under this scenario adding additional ports facing public internet. Under this scenario,
which is referred to as SDWAN Overlay throughout this document, it which is referred to as Overlay throughout this document, it is
is necessary for the C-PEs to use a protocol to register their WAN necessary for the C-PEs to manage and communicate with controller on
port properties with their SDWAN Controller(s). The information is how traffic are distributed among multiple heterogenous WAN underlay
needed for the establishment and the maintenance of Port-based IPsec networks, and manage secure tunnels over untrusted networks
SA associations among relevant C-PEs. independently from the attached clients routes.
When using NHRP for registration purposes, C-PEs need to run two When using NHRP for WAN ports registration purposes, C-PEs need to
separate control planes: EVPN&BGP for CPE-based VPNs, and NHRP & run two separate control planes: EVPN&BGP for CPE-based VPNs, and
DSVPN/DMVPN for ports connected to the Internet. Two separate NHRP & DSVPN/DMVPN for ports connected to the Internet. Two separate
control planes not only add complexity to C-PEs, but also increase control planes not only add complexity to C-PEs, but also increase
operational cost. operational cost.
+---+ +---+
+--------------|RR |----------+ +--------------|RR |----------+
/ Untrusted +-+-+ \ / Untrusted +-+-+ \
/ \ / \
/ \ / \
+----+ +---------+ packets encrypted over +------+ +----+ +----+ +---------+ packets encrypted over +------+ +----+
| TN3|--| A1-----+ Untrusted +------ B1 |--| TN1| | TN3|--| A1-----+ Untrusted +------ B1 |--| TN1|
skipping to change at page 7, line 27 skipping to change at page 7, line 27
+----+ +---------+ +--+ packets +---+ +------+ +----+ +----+ +---------+ +--+ packets +---+ +------+ +----+
| TN1|--| C1--|PE| go natively |PE |-- D1 |--| TN1| | TN1|--| C1--|PE| go natively |PE |-- D1 |--| TN1|
+----+ | C-PE C2--+--+ without encry+---+ | C-PE | +----+ +----+ | C-PE C2--+--+ without encry+---+ | C-PE | +----+
| C | +--------------+ | D | | C | +--------------+ | D |
| | | | | | | |
+----+ | C3--| without encrypt over | | +----+ +----+ | C3--| without encrypt over | | +----+
| TN2|--| C4--+---- Untrusted --+------D2 |--| TN2| | TN2|--| C4--+---- Untrusted --+------D2 |--| TN2|
+----+ +---------+ +------+ +----+ +----+ +---------+ +------+ +----+
Figure 1: CPEs interconnected by VPN paths and Internet Paths Figure 1: CPEs interconnected by VPN paths and Internet Paths
4.1. Key Control Plane Components of SDWAN Overlay 5.1. Control Plane for Overlay over Heterogeneous Networks
As described in [BGP-SDWAN-Usage], the SDWAN Overlay Control Plane As described in [BGP-SDWAN-Usage], the Control Plane for Overlay
has three distinct properties: network over heterogenous networks has three distinct properties:
- SDWAN node's WAN Port Property registration to the SDWAN - WAN Port Property registration to the Overlay Controller.
Controller. o To inform the Overlay controller and authorized peers of
o To inform the SDWAN controller and authorized peers of the the WAN port properties of the Edge nodes. When the WAN
WAN port properties of the C-PE [SDWAN-Port]. When the WAN
ports are assigned private addresses, this step can ports are assigned private addresses, this step can
register the type of NAT that translates private addresses register the type of NAT that translates private addresses
into public ones. into public ones.
- Controller facilitated IPsec SA management and NAT information - Controller facilitated IPsec SA management and NAT information
distribution distribution
o It is for SDWAN controller to facilitate or manage the o It is for Overlay controller to facilitate or manage the
IPsec configuration and peer authentication for all IPsec IPsec configuration and peer authentication for all IPsec
tunnels terminated at the SDWAN nodes. tunnels terminated at the edge nodes.
- Establishing and Managing the topology and reachability for - Establishing and Managing the topology and reachability for
services attached to the client ports of SDWAN nodes. services attached to the client ports of overlay edge nodes.
o This is for the overlay layer's route distribution, so o This is for the overlay layer's route distribution, so
that a C-PE can populate its overlay routing table with that a C-PE can populate its overlay routing table with
entries that identify the next hop for reaching a specific entries that identify the next hop for reaching a specific
route/service attached to remote nodes. [SECURE-EVPN] route/service attached to remote nodes. [SECURE-EVPN]
describes EVPN and other options. describes EVPN and other options.
4.2. Using BGP UPDATE Messages 5.2. Using BGP UPDATE Messages
[Tunnel-Encap] describe the BGP UPDATE Tunnel Path Attribute that [Tunnel-Encap] describe the BGP UPDATE Tunnel Path Attribute that
advertise endpoints' tunnel encapsulation capability for the advertise endpoints' tunnel encapsulation capability for the
respective attached client routes encoded in the MP-NLRI Path respective attached client routes encoded in the MP-NLRI Path
Attribute. The receivers of the BGP UPDATE can use any of the Attribute. The receivers of the BGP UPDATE can use any of the
supported encapsulations encoded in the Tunnel Path Attribute for supported encapsulations encoded in the Tunnel Path Attribute for
the routes encoded in the MP-NLRI Path Attribute. the routes encoded in the MP-NLRI Path Attribute.
Here are some of the gaps using [Tunnel-Encap] to distribute SDWAN Here are some of the gaps using [Tunnel-Encap] to distribute Edge
Edge WAN port properties: WAN port properties:
- [Tunnel-Encap] doesn't yet have the encoding to describe the NAT - [Tunnel-Encap] doesn't yet have the encoding to describe the NAT
information for WAN ports that have private addresses. The NAT information for WAN ports that have private addresses. The NAT
information needs to be propagated to the trusted peers via information needs to be propagated to the trusted peers via
Controllers, such as the virtual C-PEs instantiated in public Controllers, such as the virtual C-PEs instantiated in public
Cloud DCs. Cloud DCs.
- It is not easy using the current mechanism in [Tunnel-Encap] to - It is not easy using the current mechanism in [Tunnel-Encap] to
exchange IPsec SA specific parameters independently from exchange IPsec SA specific parameters independently from
advertising the attached clients' routes, even after adding a new advertising the attached clients' routes, even after adding a new
IPsec tunnel type. IPsec tunnel type.
[Tunnel-Encap] requires all tunnels updates are associated with [Tunnel-Encap] requires all tunnels updates are associated with
routes. There can be many client routes associated with the SDWAN routes. There can be many client routes associated with the IPsec
IPsec tunnel between two C-PEs' WAN ports; the corresponding tunnel between two C-PEs' WAN ports; the corresponding destination
destination prefixes (as announced by the aforementioned routes) prefixes (as announced by the aforementioned routes) may also be
may also be reached through the VPN underlay without any reached through the VPN underlay without any encryption.
encryption.
The establishment of an IPsec tunnel can fail, such as due to the The establishment of an IPsec tunnel can fail, such as due to the
two endpoints supporting different encryption algorithms or other two endpoints supporting different encryption algorithms or other
reasons. There can be multiple negotiations messages for the IPsec reasons. There can be multiple negotiations messages for the IPsec
SA parameters between two end points. That is why IPsec SA SA parameters between two end points. That is why IPsec SA
association establishment between end points is independent from association establishment between end points is independent from
the policies on mapping routes to specific IPSec SA. the policies on mapping routes to specific IPSec SA.
If C-PEs need to establish WAN Port based IPsec SA, the If C-PEs need to establish WAN Port based IPsec SA, the
information encoded in Tunnel Path Attribute should only apply to information encoded in Tunnel Path Attribute should only apply to
the WAN ports and should be independent of the clients' routes. the WAN ports and should be independent of the clients' routes.
In addition, the SDWAN Tunnel (IPsec SA) may need to be In addition, the Overlay IPsec SA Tunnel may need to be
established before clients' routes are attached. established before clients' routes are attached.
- C-PEs tend to communicate with a subset of the other C-PEs, not - 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. all the C-PEs need to be connected through a mesh topology.
Therefore, the distribution of the SDWAN Overlay Edge WAN ports Therefore, the distribution of the Overlay Edge WAN ports
information need be be scoped to the authorized peers. information need be be scoped to the authorized peers.
4.3. SECURE-L3VPN/EVPN 5.3. SECURE-L3VPN/EVPN
[SECURE-L3VPN] describes how to extend the BGP/MPLS VPN [RFC4364] [SECURE-L3VPN] describes how to extend the BGP/MPLS VPN [RFC4364]
capabilities to allow some PEs to connect to other PEs via public capabilities to allow some PEs to connect to other PEs via public
networks. [SECURE-L3VPN] introduces the concept of Red Interface & networks. [SECURE-L3VPN] introduces the concept of Red Interface &
Black Interface used by PEs, where the RED interfaces are used to Black Interface used by PEs, where the RED interfaces are used to
forward traffic into the VPN, and the Black Interfaces are used forward traffic into the VPN, and the Black Interfaces are used
between WAN ports through which only IPsec-protected packets are between WAN ports through which only IPsec-protected packets are
forwarded to the Internet or to other backbone network thereby forwarded to the Internet or to other backbone network thereby
eliminating the need for MPLS transport in the backbone. eliminating the need for MPLS transport in the backbone.
[SECURE-L3VPN] assumes PEs using MPLS over IPsec when sending [SECURE-L3VPN] assumes PEs using MPLS over IPsec when sending
traffic through the Black Interfaces. traffic through the Black Interfaces.
[SECURE-EVPN] describes a solution where point-to-multipoint BGP [SECURE-EVPN] describes a solution where point-to-multipoint BGP
signaling is used in the control plane for the SDWAN Scenario #1 signaling is used in the control plane for the Scenario #1 described
described in [BGP-SDWAN-Usage]. It relies upon a BGP cluster design in [BGP-SDWAN-Usage]. It relies upon a BGP cluster design to
to facilitate the key and policy exchange among PE devices to create facilitate the key and policy exchange among PE devices to create
private pair-wise IPsec Security Associations without IKEv2 point- private pair-wise IPsec Security Associations without IKEv2 point-
to-point signaling or any other direct peer-to-peer session to-point signaling or any other direct peer-to-peer session
establishment messages. establishment messages.
Both [SECURE-L3VPN] and [SECURE-EVPN] are useful, however, they both Both [SECURE-L3VPN] and [SECURE-EVPN] are useful, however, they both
miss the aspects of aggregating VPN and Internet underlays. In miss the aspects of aggregating VPN and Internet underlays. In
summary: summary:
- Both documents assume a client traffic is either forwarded all - Both documents assume a client traffic is either forwarded all
encrypted through an IPsec tunnel, or not encrypted at all through encrypted through an IPsec tunnel, or not encrypted at all through
a different tunnel regardless which WAN ports the traffic egress a different tunnel regardless which WAN ports the traffic egress
the PEs towards WAN. In SDWAN, one client traffic can be forwarded the PEs towards WAN. For Overlay arch over trusted VPN and
encrypted at one time through a WAN port towards untrusted network untrusted Internet, one client traffic can be forwarded encrypted
and be forwarded unencrypted at different time through a WAN port at one time through a WAN port towards untrusted network and be
to MPLS VPN. forwarded unencrypted at different time through a WAN port to MPLS
VPN.
- The [SECURE-L3VPN] assumes that a CPE "registers" with the RR. - The [SECURE-L3VPN] assumes that a CPE "registers" with the RR.
However, it does not say how. It assumes that the remote CPEs are However, it does not say how. It assumes that the remote CPEs are
pre-configured with the IPsec SA manually. In SDWAN, Zero Touch pre-configured with the IPsec SA manually. In Overlay network to
Provisioning is expected. Manual configuration is not an option, connect Hybrid Cloud DCs, Zero Touch Provisioning is expected.
especially for the edge devices that are deployed in faraway Manual configuration is not an option, especially for the edge
places. devices that are deployed in faraway places.
- The [SECURE-L3VPN] assumes that C-PEs and RR are connected via an - The [SECURE-L3VPN] assumes that C-PEs and RR are connected via an
IPsec tunnel. Missing TLS/DTLS. The following assumption by IPsec tunnel. Missing TLS/DTLS. The following assumption by
[SECURE-L3VPN] becomes invalid for SDWAN environment where [SECURE-L3VPN] becomes invalid for the Overlay network to connect
automatic synchronization of IPsec SA between C-PEs and RR is Hybrid Cloud DCs where automatic synchronization of IPsec SA
needed: between C-PEs and RR is needed:
A CPE must also be provisioned with whatever additional A CPE must also be provisioned with whatever additional
information is needed in order to set up an IPsec SA with information is needed in order to set up an IPsec SA with
each of the red RRs each of the red RRs
- IPsec requires periodic refreshment of the keys. The draft does - IPsec requires periodic refreshment of the keys. The draft does
not provide any information about how to synchronize the not provide any information about how to synchronize the
refreshment among multiple nodes. refreshment among multiple nodes.
- IPsec usually sends configuration parameters to two endpoints only - IPsec usually sends configuration parameters to two endpoints only
and lets these endpoints negotiate the key. The [SECURE-L3VPN] and lets these endpoints negotiate the key. The [SECURE-L3VPN]
assumes that the RR is responsible for creating/managing the key assumes that the RR is responsible for creating/managing the key
for all endpoints. When one endpoint is compromised, all other for all endpoints. When one endpoint is compromised, all other
connections will be impacted. connections will be impacted.
4.4. Preventing attacks from Internet-facing ports 5.4. Preventing attacks from Internet-facing ports
When C-PEs have Internet-facing ports, additional security risks are When C-PEs have Internet-facing ports, additional security risks are
raised. raised.
To mitigate security risks, in addition to requiring Anti-DDoS To mitigate security risks, in addition to requiring Anti-DDoS
features on C-PEs, it is necessary for C-PEs to support means to features on C-PEs, it is necessary for C-PEs to support means to
determine whether traffic sent by remote peers is legitimate to determine whether traffic sent by remote peers is legitimate to
prevent spoofing attacks. prevent spoofing attacks.
5. C-PEs not directly connected to VPN PEs 6. C-PEs not directly connected to VPN PEs
Because of the ephemeral property of the selected Cloud DCs for Because of the ephemeral property of the selected Cloud DCs for
specific workloads/Apps, an enterprise or its network service specific workloads/Apps, an enterprise or its network service
provider may not have direct physical connections to the Cloud DCs provider may not have direct physical connections to the Cloud DCs
that are optimal for hosting the enterprise's specific that are optimal for hosting the enterprise's specific
workloads/Apps. Under those circumstances, SDWAN Overlay is a very workloads/Apps. Under those circumstances, Overlay is a very
flexible choice to interconnect the enterprise on-premises data flexible choice to interconnect the enterprise on-premises data
centers & branch offices to its desired Cloud DCs. centers & branch offices to its desired Cloud DCs.
However, SDWAN paths established over the public Internet can have However, Overlay paths established over the public Internet can have
unpredictable performance, especially over long distances and across unpredictable performance, especially over long distances and across
operators' domains. Therefore, it is highly desirable to steer as operators' domains. Therefore, it is highly desirable to steer as
much as possible the portion of SDWAN paths over the enterprise's much as possible the portion of Overlay paths over the enterprise's
existing VPN that has guaranteed SLA to minimize the distance or the existing VPN that has guaranteed SLA to minimize the distance or the
number of segments over the public Internet. number of segments over the public Internet.
MEF Cloud Service Architecture [MEF-Cloud] also describes a use case MEF Cloud Service Architecture [MEF-Cloud] also describes a use case
of network operators using SDWAN over LTE or the public Internet for of network operators using Overlay path over LTE or the public
last mile access where the VPN service providers cannot necessarily Internet for last mile access where the VPN service providers cannot
provide the required physical infrastructure. necessarily provide the required physical infrastructure.
Under those scenarios, one or two of the SDWAN endpoints may not be Under those scenarios, one or two of the Overlay endpoints may not
directly attached to the PEs of a VPN Domain. be directly attached to the PEs of a VPN Domain.
When using SDWAN to connect the enterprise's existing sites to the When using Overlay to connect the enterprise's existing sites to the
workloads hosted in Cloud DCs w, the corresponding C-PEs have to be workloads hosted in Cloud DCs, the corresponding C-PEs have to be
upgraded to support SDWAN. If the workloads hosted in Cloud DCs upgraded to support the desired Overlay. If the workloads hosted in
need to be connected to many sites, the upgrade process can be very Cloud DCs need to be connected to many sites, the upgrade process
expensive. can be very expensive.
[Net2Cloud-Problem] describes a hybrid network approach that [Net2Cloud-Problem] describes a hybrid network approach that extend
integrates SDWAN with traditional MPLS-based VPNs, to extend the the existing MPLS-based VPNs to the Cloud DC Workloads over the
existing MPLS-based VPNs to the Cloud DC Workloads over the access access paths that are not under the VPN provider's control. To make
paths that are not under the VPN provider's control. To make it work it work properly, a small number of the PEs of the MPLS VPN can be
properly, a small number of the PEs of the MPLS VPN can be designated to connect to the remote workloads via secure IPsec
designated to connect to the remote workloads via SDWAN secure IPsec
tunnels. Those designated PEs are shown as fPE (floating PE or tunnels. Those designated PEs are shown as fPE (floating PE or
smart PE) in Figure 3. Once the secure IPsec tunnels are smart PE) in Figure 3. Once the secure IPsec tunnels are
established, the workloads hosted in Cloud DCs can be reached by the established, the workloads hosted in Cloud DCs can be reached by the
enterprise's VPN without upgrading all of the enterprise's existing enterprise's VPN without upgrading all of the enterprise's existing
CPEs. The only CPE that needs to support SDWAN would be a CPEs. The only CPE that needs to support the Overlay would be a
virtualized CPE instantiated within the cloud DC. virtualized CPE instantiated within the cloud DC.
+--------+ +--------+ +--------+ +--------+
| Host-a +--+ +----| Host-b | | Host-a +--+ +----| Host-b |
| | | (') | | | | | (') | |
+--------+ | +-----------+ ( ) +--------+ +--------+ | +-----------+ ( ) +--------+
| +-+--+ ++-+ ++-+ +--+-+ (_) | +-+--+ ++-+ ++-+ +--+-+ (_)
| | CPE|--|PE| |PE+--+ CPE| | | | CPE|--|PE| |PE+--+ CPE| |
+--| | | | | | | |---+ +--| | | | | | | |---+
+-+--+ ++-+ ++-+ +----+ +-+--+ ++-+ ++-+ +----+
/ | | / | |
/ | MPLS +-+---+ +--+-++--------+ / | MPLS +-+---+ +--+-++--------+
+------+-+ | Network |fPE-1| |CPE || Host | +------+-+ | Network |fPE-1| |CPE || Host |
| Host | | | |- --| || d | | Host | | | |- --| || d |
| c | +-----+ +-+---+ +--+-++--------+ | c | +-----+ +-+---+ +--+-++--------+
+--------+ |fPE-2|-----+ +--------+ |fPE-2|-----+
+---+-+ (|) +---+-+ (|)
(|) (|) SDWAN (|) (|) Overlay
(|) (|) over any access (|) (|) over any access
+=\======+=========+ +=\======+=========+
// \ | Cloud DC \\ // \ | Cloud DC \\
// \ ++-----+ \\ // \ ++-----+ \\
+Remote| +Remote|
| CPE | | CPE |
+-+----+ +-+----+
----+-------+-------+----- ----+-------+-------+-----
| | | |
+---+----+ +---+----+ +---+----+ +---+----+
skipping to change at page 13, line 5 skipping to change at page 13, line 5
+--------+ +--------+ +--------+ +--------+
Figure 3: VPN Extension to Cloud DC Figure 3: VPN Extension to Cloud DC
In Figure 3, the optimal Cloud DC to host the workloads (as a In Figure 3, the optimal Cloud DC to host the workloads (as a
function of the proximity, capacity, pricing, or other criteria function of the proximity, capacity, pricing, or other criteria
chosen by the enterprises) does not have a direct connection to the chosen by the enterprises) does not have a direct connection to the
PEs of the MPLS VPN that interconnects the enterprise's existing PEs of the MPLS VPN that interconnects the enterprise's existing
sites. sites.
5.1. Floating PEs to connect to Remote CPEs 6.1. Floating PEs to connect to Remote CPEs
To extend MPLS VPNs to remote CPEs, it is necessary to establish To extend MPLS VPNs to remote CPEs, it is necessary to establish
secure tunnels (such as IPsec tunnels) between the Floating PEs and secure tunnels (such as IPsec tunnels) between the Floating PEs and
the remote CPEs. the remote CPEs.
Even though a set of PEs can be manually selected to act as the 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 floating PEs for a specific cloud data center, there are no standard
protocols for those PEs to interact with the remote CPEs (most protocols for those PEs to interact with the remote CPEs (most
likely virtualized) instantiated in the third party cloud data likely virtualized) instantiated in the third party cloud data
centers (such as exchanging performance or route information). centers (such as exchanging performance or route information).
When there is more than one fPE available for use (as there should When there is more than one fPE available for use (as there should
be for resiliency purposes or the ability to support multiple cloud be for resiliency purposes or the ability to support multiple cloud
DCs geographically scattered), it is not straightforward to DCs geographically scattered), it is not straightforward to
designate an egress fPE to remote CPEs based on applications. There designate an egress fPE to remote CPEs based on applications. There
is too much applications' traffic traversing PEs, and it is not is too much applications' traffic traversing PEs, and it is not
feasible for PEs to recognize applications from the payload of feasible for PEs to recognize applications from the payload of
packets. packets.
5.2. NAT Traversal 6.2. NAT Traversal
Cloud DCs that only assign private IPv4 addresses to the Cloud DCs that only assign private IPv4 addresses to the
instantiated workloads assume that traffic to/from the workload instantiated workloads assume that traffic to/from the workload
usually needs to traverse NATs. usually needs to traverse NATs.
A SDWAN edge node can solicit a STUN (Session Traversal of UDP An overlay edge node can solicit a STUN (Session Traversal of UDP
Through Network Address Translation RFC 3489) Server to get the NAT Through Network Address Translation RFC 3489) Server to get the NAT
property, the public IP address and the Public Port number so that property, the public IP address and the Public Port number so that
such information can be communicated to the relevant peers. such information can be communicated to the relevant peers.
5.3. Complexity of using BGP between PEs and remote CPEs via Internet 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 Even though an EBGP (external BGP) Multi-hop design can be used to
connect peers that are not directly connected to each other, there connect peers that are not directly connected to each other, there
are still some complications in extending BGP from MPLS VPN PEs to are still some complications in extending BGP from MPLS VPN PEs to
remote CPEs via any access path (e.g., Internet). remote CPEs via any access path (e.g., Internet).
The path between the remote CPEs and VPN PEs that maintain VPN The path between the remote CPEs and VPN PEs that maintain VPN
routes may very well traverse untrusted nodes. routes may very well traverse untrusted nodes.
EBGP Multi-hop design requires static configuration on both peers. EBGP Multi-hop design requires static configuration on both peers.
skipping to change at page 14, line 33 skipping to change at page 14, line 33
EBGP Multi-hop design does not include a security mechanism by EBGP Multi-hop design does not include a security mechanism by
default. The PE and remote CPEs need secure communication channels default. The PE and remote CPEs need secure communication channels
when connecting via the public Internet. when connecting via the public Internet.
Remote CPEs, if instantiated in Cloud DCs, might have to traverse 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 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 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 NAT. It is not clear how to configure the Next Hop on the PEs to
reach private IPv4 addresses. reach private IPv4 addresses.
5.4. Designated Forwarder to the remote edges 6.4. Designated Forwarder to the remote edges
Among the multiple floating PEs that are reachable from a remote Among the multiple floating PEs that are reachable from a remote
CPE, multicast traffic sent by the remote CPE towards the MPLS VPN 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 can be forwarded back to the remote CPE due to the PE receiving the
multicast packets forwarding the multicast/broadcast frame to other multicast packets forwarding the multicast/broadcast frame to other
PEs that in turn send to all attached CPEs. This process may cause PEs that in turn send to all attached CPEs. This process may cause
traffic loops. traffic loops.
Therefore, it is necessary to designate one floating PE as the CPE's Therefore, it is necessary to designate one floating PE as the CPE's
Designated Forwarder, similar to TRILL's Appointed Forwarders Designated Forwarder, similar to TRILL's Appointed Forwarders
[RFC6325]. [RFC6325].
MPLS VPNs do not have features like TRILL's Appointed Forwarders. MPLS VPNs do not have features like TRILL's Appointed Forwarders.
5.5. Traffic Path Management 6.5. Traffic Path Management
When there are multiple floating PEs that have established IPsec When there are multiple floating PEs that have established IPsec
tunnels with the remote CPE, the remote CPE can forward outbound tunnels with the remote CPE, the remote CPE can forward outbound
traffic to the Designated Forwarder PE, which in turn forwards traffic to the Designated Forwarder PE, which in turn forwards
traffic to egress PEs and then to the final destinations. However, traffic to egress PEs and then to the final destinations. However,
it is not straightforward for the egress PE to send back the return it is not straightforward for the egress PE to send back the return
traffic to the Designated Forwarder PE. traffic to the Designated Forwarder PE.
Example of Return Path management using Figure 3 above. Example of Return Path management using Figure 3 above.
- fPE-1 is DF for communication between App-1 <-> Host-a due to - fPE-1 is DF for communication between App-1 <-> Host-a due to
latency, pricing or other criteria. latency, pricing or other criteria.
- fPE-2 is DF for communication between App-1 <-> Host-b. - fPE-2 is DF for communication between App-1 <-> Host-b.
6. Manageability Considerations 7. Manageability Considerations
Zero touch provisioning of SDWAN edge nodes should be a major Zero touch provisioning of Overlay networks to interconnect Hybrid
feature of SDWAN deployments. It is necessary for a newly powered Clouds is highly desired. It is necessary for a newly powered up
up SDWAN edge node to establish a secure connection (by means of edge node to establish a secure connection (by means of TLS, DTLS,
TLS, DTLS, etc.) with its controller. etc.) with its controller.
7. Security Considerations 8. Security Considerations
The intention of this draft is to identify the gaps in current and Cloud Services is built upon shared infrastructure, therefore not
proposed SDWAN approaches that can address requirements identified secure by nature.
in [Net2Cloud-problem].
Several of these approaches have gaps in meeting enterprise Secure user identity management, authentication, and access
security requirements when tunneling their traffic over the control mechanisms are important. Developing appropriate security
Internet, since this is the purpose of SDWAN. See the individual measurements can enhance the confidence needed by enterprises to
sections above for further discussion of these security gaps. fully take advantage of Cloud Services.
8. IANA Considerations 9. IANA Considerations
This document requires no IANA actions. RFC Editor: Please remove This document requires no IANA actions. RFC Editor: Please remove
this section before publication. this section before publication.
9. References 10. References
9.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References 10.2. Informative References
[RFC8192] S. Hares, et al, "Interface to Network Security Functions [RFC8192] S. Hares, et al, "Interface to Network Security Functions
(I2NSF) Problem Statement and Use Cases", July 2017 (I2NSF) Problem Statement and Use Cases", July 2017
[RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation Subsequent [RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation Subsequent
Address Family Identifier (SAFI) and the BGP Tunnel Address Family Identifier (SAFI) and the BGP Tunnel
Encapsulation Attribute", April 2009. Encapsulation Attribute", April 2009.
[BGP-SDWAN-PORT]L. Dunbar, et al, "Subsequent Address Family [BGP-SDWAN-PORT]L. Dunbar, et al, "Subsequent Address Family
Indicator for SDWAN Ports", draft-dunbar-idr-sdwan-port- Indicator for SDWAN Ports", draft-dunbar-idr-sdwan-port-
skipping to change at page 17, line 21 skipping to change at page 17, line 21
1.html 1.html
[ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation, [ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation,
storage, distribution and enforcement of policies for storage, distribution and enforcement of policies for
network security", Nov 2007. network security", Nov 2007.
[Net2Cloud-Problem] L. Dunbar and A. Malis, "Seamless Interconnect [Net2Cloud-Problem] L. Dunbar and A. Malis, "Seamless Interconnect
Underlay to Cloud Overlay Problem Statement", draft-dm- Underlay to Cloud Overlay Problem Statement", draft-dm-
net2cloud-problem-statement-02, June 2018 net2cloud-problem-statement-02, June 2018
10. Acknowledgments 11. Acknowledgments
Acknowledgements to John Drake for his review and contributions. Acknowledgements to John Drake for his review and contributions.
Many thanks to John Scudder for stimulating the clarification Many thanks to John Scudder for stimulating the clarification
discussion on the Tunnel-Encap draft so that our gap analysis can be discussion on the Tunnel-Encap draft so that our gap analysis can be
more accurate. more accurate.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses Authors' Addresses
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