Internet DRAFT - draft-ietf-rtgwg-net2cloud-problem-statement
draft-ietf-rtgwg-net2cloud-problem-statement
RTG Working Group L. Dunbar
Internet Draft Futurewei
Intended status: Informational A. Malis
Expires: August 27, 2024 Malis Consulting
C. Jacquenet
Orange
M. Toy
Verizon
K. Majumdar
Microsoft
February 27, 2024
Dynamic Networks to Hybrid Cloud DCs: Problems and Mitigation
Practices
draft-ietf-rtgwg-net2cloud-problem-statement-36
Abstract
This document describes a set of network-related problems
enterprises face at the time of writing this document (2023) when
interconnecting their branch offices with dynamic workloads in
third-party data centers (DCs) (a.k.a. Cloud DCs). These problems
are mainly from enterprises with conventional VPN services that want
to leverage those networks (instead of altogether abandoning them).
This document also describes various mitigation practices and
actions to soften the issues induced by these problems.
Status of this Memo
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This Internet-Draft will expire on August 27, 2024.
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Table of Contents
1. Introduction...................................................3
2. Definition of Terms............................................3
3. Issues and Mitigation Methods of Connecting to Cloud DCs.......4
3.1. Increased BGP Peering Errors and Mitigation Methods.......4
3.2. Site Failures and Methods to Minimize Impacts.............6
3.3. Limitations of DNS-based Cloud DC Location Selection......6
3.4. Network Issues for 5G Edge Clouds and Mitigation Methods..7
3.5. DNS Practices for Hybrid Workloads........................8
3.6. NAT Practices for Accessing Cloud Services................9
3.7. Cloud Discovery Practices.................................9
4. Dynamic Connecting Enterprise Sites with Cloud DCs............10
4.1. Sites to Cloud DC........................................10
4.2. Inter-Cloud Connection...................................12
4.3. Extending Private VPNs to Hybrid Cloud DCs...............14
5. Methods to Scale IPsec Tunnels to Cloud DCs...................15
5.1. Scale IPsec Tunnels Management...........................15
5.2. CPEs Interconnection Over the Public Internet............16
6. Requirements for Networks Connecting Cloud Data Centers.......16
7. Security Considerations.......................................17
8. IANA Considerations...........................................18
9. References....................................................19
9.1. Normative References.....................................19
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9.2. Informative References...................................20
10. Acknowledgments..............................................21
1. Introduction
With the advent of widely available Cloud data centers (DCs)
providing services in various geographic locations and advanced
tools for monitoring and predicting application behaviors, it is
tempting for enterprises to instantiate applications and workloads
in Cloud DCs. Some enterprises prefer specific applications to be
located close to the end users accessing these services, as the
proximity can improve end-to-end latency. In addition, applications
and workloads in Cloud DCs can be shut down or moved along with end
users in motion thereby modifying the networking connection of
subsequently relocated applications and workloads.
Cloud services are generally exposed, on-demand services that claim
to be scalable, highly available, and have usage-based billing. Most
Cloud Operators provide Cloud network functions, such as virtual
Firewall services, virtual private clouds services, and virtual
Private Branch eXchange (PBX) services, including voice and video
conferencing systems. A Cloud DC is a shared infrastructure that
hosts services to many customers.
This document describes the network-related problems enterprises
face at the time of writing this document when interconnecting their
branch offices with dynamic workloads in Cloud DCs and the
mitigation practices to get around those problems.
2. Definition of Terms
Cloud DCs: Third party Data Centers that usually host applications
and workloads owned by different organizations or
tenants.
Heterogeneous Cloud: applications and workloads split among Cloud
DCs owned or managed by different operators.
Hybrid Clouds: A hybrid cloud is a mixed computing environment where
applications are run using a combination of computing,
storage, and services in different public clouds and
private clouds, including on-premises data centers or
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"edge" locations. <https://cloud.google.com/learn/what-
is-hybrid-cloud>.
IXPs: Internet exchange points (IXes or IXPs) are the common
grounds of IP networking, allowing participating
Internet service providers (ISPs) to exchange data
destined for their respective networks.
<https://en.wikipedia.org/wiki/Internet_exchange_point>.
SD-WAN An overlay connectivity service that optimizes transport
of IP Packets over one or more Underlay Connectivity
Services by recognizing applications (Application Flows)
and determining forwarding behavior by applying Policies
to them. [MEF-70.1]
VPC: A Virtual Private Cloud is a virtual network dedicated
to one client account. It is logically isolated from
other virtual networks in a Cloud DC. Each client can
launch his/her desired resources, such as compute,
storage, or network functions into his/her VPC. At the
time of writing this document, most Cloud operators'
VPCs only support private addresses, some support IPv4
only, others support IPv4/IPv6 dual stack.
3. Issues and Mitigation Methods of Connecting to Cloud DCs
This section identifies some high-level problems that the IETF could
address, especially within the Routing area. Other Cloud DC problems
(e.g., managing cloud spending) are out of the scope of this
document.
3.1. Increased BGP Peering Errors and Mitigation Methods
Where conventional ISPs view BGP peering as a means to improve
network operations, Public Cloud DCs offer direct BGP peering to
attract more customers to use their DCs and services. As such, there
is pressure to peer more widely with more customers, including those
who may lack the expertise and experience in running complex BGP
peering relationships. This can contribute to increased BGP peering
errors such as capability mismatch, unwanted route leaks, missing
Keepalives, and errors causing BGP session resets. Capability
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mismatch can cause BGP sessions not to be adequately established.
These issues are more acute for Cloud DCs than they have been, even
though they may apply to conventional ISPs, just to a lesser degree.
Here are the recommended mitigation practices:
- If a Cloud Gateway (GW), a BGP speaker, receives from its BGP
peer a capability that it does not itself support or recognize,
it need to ignore that capability, and the BGP session need not
be terminated per [RFC5492]. When receiving a BGP UPDATE with a
malformed attribute, the revised BGP error handling procedure
in [RFC7606] should be followed instead of session resetting.
- When a Cloud DC doesn't support multi-hop eBGP peering with
external devices, as many don't, enterprise GWs need to
establish tunnels (e.g., IPsec) to the Cloud GWs to form an IP
adjacency.
- When a Cloud DC eBGP session supports a limited number of
routes from external entities, the on-premises DCs need to set
up default routes and filter as many routes as practical
replacing them with a default in the eBGP advertisement to
minimize the number of routes to be exchanged with the Cloud DC
eBGP peers.
- When a Cloud GW receives inbound routes exceeding the maximum
routes threshold for a peer, the currently common practice is
generating out-of-band alerts (e.g., Syslog entries) via the
management system or terminating the BGP session (with cease
notification messages [RFC4486] being sent). Although out of
the scope of this document, more discussion is needed in the
IETF Inter-Domain Routing (IDR) Working Group for potential in-
band or autonomous notification directly to the peers when the
inbound routes exceed the maximum routes threshold.
- Leveraging YANG models to programmatically synchronize
configurations between BGP peers (e.g., [SVC-AC]) and to adjust
the local configuration accordingly (e.g., [NTW-AC] or
[DATAMODEL-BGP]). This proactive approach reduces the
likelihood of BGP configuration issues and ensures that both
BGP peers operate with synchronized and compatible settings.
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3.2. Site Failures and Methods to Minimize Impacts
Failures within a Cloud site, which can be a building, a floor, a
pod, or a server rack, include capacity degradation or complete out-
of-service failure. Here are some events that can trigger a site
failure: a) fiber cut for links connecting to the site or among pods
within the site; b) cooling failures; c) insufficient backup power
during a power failure; d) cyber threat attacks; e) too many changes
outside of the maintenance window; etc. A fiber-cut is not uncommon
in a Cloud site or between sites.
As described in [RFC7938], a Cloud DC might not have an IGP to route
around link/node failures within its domain. When a site failure
happens, the Cloud DC GW visible to clients is running fine;
therefore, the site failure is not detectable by the clients using
Bidirectional Forwarding Detection (BFD)[RFC5880].
When a site failure occurs, many services can be impacted. When the
impacted services' IP prefixes in a Cloud DC are not aggregated
nicely, which is common, one single site failure can trigger a huge
number of BGP UPDATE messages. There are proposals, such as
[METADATA-PATH], to enhance BGP advertisements to address this
problem.
[RFC7432] specifies a mass withdrawal mechanism for EVPN to signal a
large number of routes being changed to remote PE nodes as quickly
as possible.
3.3. Limitations of DNS-based Cloud DC Location Selection
Many applications have multiple instances running in different Cloud
DCs. A commonly deployed solution has DNS server(s) responding to a
Fully Qualified Domain Name (FQDN) inquiry with an IP address of the
instance in the closest or lowest cost DC. Here are some problems
associated with DNS-based solutions:
- Dependent on client behavior
- A misbehaving client can cache results indefinitely.
- Clients may fail to access a service even though there are
servers available in other Cloud DCs because the failing
IP address is still cached in the DNS resolver and has not
expired yet.
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- No inherent use of proximity information present in the network
(routing) layer, resulting in loss of performance.
- Inflexible traffic control:
The Local DNS resolver becomes the unit of traffic management.
This requires DNS to receive periodic updates of the network
condition, which is difficult.
One method to mitigate the problems listed above is to use anycast
[RFC4786] for the services so that network proximity and conditions
can be automatically considered in optimal path selection.
[METADATA-PATH] identifies some of the metrics that can be utilized
for the ingress routers to make path steering selections not only
based on the routing cost but also the running environment of the
edge services.
[RFC8490] and [RFC8765] on stateful DNS can be used to achieve
better performance in refreshing the cache and handling session idle
timeouts.
3.4. Network Issues for 5G Edge Clouds and Mitigation Methods
5G Edge Cloud DCs [3GPP-5G-Edge] may host edge computing
applications for ultra-low latency services on virtual or physical
servers. Those edge computing applications have low latency
connections to the UEs (User Equipment) and might have other
connections to backend servers or databases in other locations.
The low latency traffic to/from the UEs is transported through the
5G Core (gNB (Next Generation Node B))<-> UPFs (User Plane
Function)) and the 5G Local Data Networks (LDN) to the edge Cloud
DCs. The LDN's ingress routers connected to the UPFs might be co-
located with 5G Core functions in the edge Clouds. The 5G Core
functions include Radio Control Functions, Session Management
Functions (SMF), Access Mobility Functions (AMF), User Plane
Functions (UPF), and others.
Here are some network problems with connecting to the services in
the 5G Edge Clouds:
1) The difference in routing distances to server instances in
different edge Clouds is relatively small. Therefore, the
instance in the Edge Cloud with the shortest routing distance
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from a 5G UPF might not be the best in providing the overall
low latency service.
2) Capacity status at the Edge Cloud might play a more
significant role in end-to-end performance.
3) Source (UEs) can ingress from different LDN Ingress routers
due to mobility.
[METADATA-PATH] describes a mechanism to get around those problem.
[METADATA-PATH] extends the BGP UPDATE messages for a Cloud GW to
propagate the edge service-related metrics from Cloud GW to the
ingress routers so that the ingress routers can incorporate the
destination site's capabilities with the routing distance in
computing the optimal paths.
The IETF CATS (Computing-Aware Traffic Steering) working group is
examining general aspects of this space, and may come up with
protocol recommendations for this information exchange.
3.5. DNS Practices for Hybrid Workloads
DNS name resolution is essential for on-premises and cloud-based
resources. For customers with hybrid workloads, which include on-
premises and cloud-based resources, extra steps are necessary to
configure DNS to work seamlessly across both environments.
Cloud operators have their own DNS to resolve resources within their
Cloud DCs and to well-known public domains. Cloud's DNS can be
configured to forward queries to customer managed authoritative DNS
servers hosted on-premises and to respond to DNS queries forwarded
by on-premises DNS servers.
For enterprises utilizing Cloud services provided by different Cloud
operators, it is necessary to establish policies and rules on
how/where to forward DNS queries. When applications in one Cloud
need to communicate with applications hosted in another Cloud, DNS
queries from one Cloud DC could be forwarded to the enterprises' on-
premises DNS, which in turn can be forwarded to the DNS service in
another Cloud. Configuration can be complex depending on the
application communication patterns.
However, name collisions can still occur even with carefully managed
policies and configurations. If an organization uses internal names
like those under a .internal top level domain name, and wants its
services to be available via or within some other Cloud provider
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that also uses .internal, collisions might occur. Therefore, using a
global domain name is better even when an organization does not make
all its namespace globally resolvable. An organization's globally
unique DNS can include subdomains that cannot be resolved outside
certain restricted paths, zones that resolve differently based on
the origin of the query, and zones that resolve the same globally
for all queries from any source [Split-Horizon-DNS].
Globally unique names do not equate to globally resolvable names or
even global names that resolve the same way from every perspective.
Globally unique names can prevent any possibility of collisions, and
they make DNSSEC trust manageable. Consider using a registered and
FQDN from global DNS as the root for enterprise and other internal
namespaces.
3.6. NAT Practices for Accessing Cloud Services
Cloud resources, such as VMs (Virtual Machine) or application
instances, are commonly assigned with private IP addresses. By
configuration, some private subnets can have NAT functionality to
reach out to external networks, and some private subnets are
internal to a Cloud DC only.
Different Cloud operators support different levels of NAT
functionality. For example, AWS NAT Gateway does not currently
support connections towards, or from, VPC Endpoints, VPN, AWS Direct
Connect, or VPC Peering [AWS-NAT]. AWS Direct Connect/VPN/VPC
Peering does not currently support any NAT functionality.
Google's Cloud NAT [Google-NAT] allows Google Cloud VM instances
without external IP addresses and private Google Kubernetes Engine
(GKE) clusters to connect to the Internet. Cloud NAT implements
outbound NAT in conjunction with a default route to allow instances
to reach the Internet. It does not implement inbound NAT. Hosts
outside the VPC network can only respond to established connections
initiated by instances inside the Google Cloud; they cannot initiate
new connections to Cloud instances via NAT.
For enterprises with applications running in different Cloud DCs,
proper configuration of NAT need to be performed in Cloud DCs and
their on-premises DC.
3.7. Cloud Discovery Practices
One of the concerns of enterprises using Cloud services is the lack
of awareness of the locations of their services hosted in the Cloud,
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as Cloud operators can move the service instances from one place to
another. While the geographic locations are usually exposed to the
enterprises, such as Availability Zones or Regions, the topological
location is usually hidden. When applications in Cloud DCs
communicate with on-premises applications, it may not be clear where
the Cloud applications are located or to which VPCs they belong.
Being able to detect Cloud services' location can help on-premises
gateways (routers) to connect to services in a more optimal site
when the enterprise's end users or policies change.
For enterprises that instantiate virtual routers in Cloud DCs,
metadata can be attached (e.g., GENEVE [RFC8926] header or IPv6
optional header) to indicate additional properties, including useful
information about the sites where they are instantiated.
4. Dynamic Connecting Enterprise Sites with Cloud DCs
For many enterprises with established private VPNs (e.g., private
circuits, MPLS-based L2VPN[RFC6136]/L3VPN[RFC4364]) interconnecting
branch offices and on-premises data centers, connecting to Cloud
services will be a mix of different types of networks. When an
enterprise's existing VPN service providers do not have direct
connections to the desired cloud DCs that the enterprise prefers to
use, the enterprise faces additional infrastructure and operational
costs to utilize the Cloud services.
This section describes some mechanisms for enterprises with private
VPNs to connect to Cloud services dynamically.
4.1. Sites to Cloud DC
Most Cloud operators offer multiple types of network gateways (GWs)
through which an enterprise can reach their workloads hosted in the
Cloud DCs:
- Internet GW for services hosted in the Cloud DCs to be accessed
by external requests via Internet routable addresses. E.g., AWS
Internet GW [AWS-Cloud-WAN].
- IPsec tunnels terminating GW for establishing IPsec SAs
[RFC6071] with an enterprise's own gateway, so that the
communications between those gateways can be secured from the
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underlay (which might be the public Internet). E.g., AWS
Virtual gateway (vGW).
- Direct connect GW for enterprises to connect with Cloud
services via private leased lines provided by Network Service
Providers. E.g., AWS Direct Connect. In addition, an AWS Transit
Gateway can be used to interconnect multiple VPCs in different
Availability Zones. AWS Transit Gateway acts as a hub that
controls how traffic is forwarded among all the connected
networks which act like spokes.,
Microsoft Azure's Virtual WAN [Azure-SD-WAN] allows extension of a
private network to any of the Microsoft Cloud services, including
Azure and Office365. ExpressRoute is configured using Layer 3
routing. Customers can opt for redundancy by provisioning dual links
from their location to two Microsoft Enterprise edge routers (MSEEs)
located within a third-party ExpressRoute peering location. The BGP
routing protocol is then setup over WAN links to provide redundancy
to the cloud. This redundancy is maintained from the peering data
center into Microsoft's cloud network.
Google's Cloud Dedicated Interconnect offers similar network
connectivity options as AWS and Microsoft. One distinct difference,
however, is that Google's service allows customers access to the
entire global Cloud network by default. It does this by connecting
the on-premises network with the Google Cloud using BGP and Google
Cloud Routers to provide optimal paths to the different regions of
the global cloud infrastructure.
Figure 1 below shows an example of a portion of workloads belonging
to one tenant (e.g., TN-1) that are accessible via a virtual router
connected by AWS Internet Gateway; some of the same tenant (TN-1)
services are accessible via AWS vGW, and others are accessible via
AWS Direct Connect. The workloads belonging to one tenant can
communicate within a Cloud DC via virtual routers (e.g., vR1, vR2).
Different types of access require different level of security
functions. Sometimes it is not visible to end customers which type
of network access is used for a specific application instance. To
get better visibility, separate virtual routers (e.g., vR1 & vR2)
can be deployed to differentiate traffic to/from different Cloud
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GWs. It is important for some enterprises to be able to observe the
specific behaviors when connected by different connections.
A CPE (Customer Premises Equipment) can be a customer owned router
or ports physically connected to an AWS Direct Connect GW.
+------------------------+
| ,---. ,---. |
| (TN-1 ) ( TN-2)|
| `-+-' +---+ `-+-' |
| +----|vR1|----+ |
| ++--+ |
| | +-+----+
| | /Internet\ For external customers
| +-------+ Gateway +----------------------
| \ / to reach via Internet
| +-+----+
| |
| ,---. ,---. |
| (TN-1 ) ( TN-2)|
| `-+-' +---+ `-+-' |
| +----|vR2|----+ |
| ++--+ |
| | +-+----+
| | / virtual\ For IPsec Tunnel
| +-------+ Gateway +----------------------
| | \ / termination
| | +-+----+
| | |
| | + - - - - - - - - - - - - - - - --+
| | | +-+----+ +----+
| | / \ Direct / \ |
| +----|--+ Gateway +------+ Fabric|--VPN-- CPE
| \ / Connect\ edge / |
| | +-+----+ +----+
| | IXP |
| + - - - - - - - - - - - - - - - --+
+------------------------+
TN: Tenant Network. One TN can be attached to both vR1 and vR2.
Figure 1: Examples of Multiple Cloud DC connections.
4.2. Inter-Cloud Connection
The connectivity options to Cloud DCs described in Section 4.1 are
for reaching Cloud providers' DCs, but not between cloud DCs. For
example, when applications in AWS Cloud need to communicate with
applications in Azure, today's practice requires a third-party
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gateway (physical or virtual) to interconnect the AWS's Layer 2
DirectConnect path with Azure's Layer 3 ExpressRoute.
Enterprises can also instantiate their virtual routers in different
Cloud DCs and administer IPsec tunnels among them. In summary, here
are some approaches, available to interconnect workloads among
different Cloud DCs:
a) Utilize Cloud DC provided inter/intra-cloud connectivity
services (e.g., AWS Transit Gateway) to connect workloads
instantiated in multiple VPCs. Such services are provided with
the Cloud gateway to connect to external networks (e.g., AWS
DirectConnect Gateway).
b) Hairpin all traffic through the customer gateway, meaning all
workloads are directly connected to the customer gateway, so
that communications among workloads within one Cloud DC must
traverse the customer gateway.
c) Establish direct tunnels among different VPCs (AWS' Virtual
Private Clouds) and VNET (Azure's Virtual Networks) via
client's own virtual routers instantiated within Cloud DCs.
NHRP (Next Hop Resolution Protocol) [RFC2735] based multi-point
techniques can be used to establish direct multi-point-to-Point
or multi-point-to multi-point tunnels among those client's own
virtual routers.
d) Utilize a Cloud Aggregator or Cloud Services Broker (CSB) who
acts as an intermediary among cloud service providers and
network service providers to offer a combined total package for
enterprises. The Cloud Aggregator can provide the network
connections among one enterprise's services instantiated in
multiple Clouds.
Approach a) usually does not work if Cloud DCs are owned and managed
by different Cloud providers.
Approach b) creates additional transmission delay plus incurring
costs when exiting Cloud DCs.
For Approach c), [SDWAN-EDGE-DISCOVERY] describes a mechanism for
virtual routers to advertise their properties for establishing
proper IPsec tunnels among them. There could be other approaches
developed to address the problem.
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Approach d) is a method of third-party multi-cloud management
business model.
4.3. Extending Private VPNs to Hybrid Cloud DCs
Traditional private VPNs, including private circuits or MPLS-based
L2/L3 VPNs, have been widely deployed as an effective way to support
businesses and organizations that require network performance and
reliability although such services may be considered premium,
available only at additional cost. Connecting an enterprise's on-
premesis CPEs to a Cloud DC via a private VPN requires the private
VPN provider to have a direct path to the Cloud GW. When the user
base changes, the enterprise might want to migrate its
workloads/applications to a new cloud DC location closer to the new
user base. The existing private VPN provider might not have circuits
at the new location. Deploying PEs routers at new locations takes a
long time (weeks, if not months).
When the private VPN network can't reach the desired Cloud DCs,
IPsec tunnels can dynamically connect the private VPN's PEs with the
desired Cloud DCs GWs. As the private VPNs provide higher quality of
services, choosing a PE closest to the Cloud GW for the IPsec tunnel
is desirable to minimize the IPsec tunnel distance over the public
Internet.
In order to support Explicit Congestion Notification (ECN) [RFC3168]
usage by private VPN traffic, the PEs that establish the IPsec
tunnels with the Cloud GW need to comply with the ECN behavior
specified by [RFC6040].
An enterprise can connect to multiple Cloud DC locations and
establish different BGP peering with Cloud GW routers at different
locations. As multiple Cloud DCs are interconnected by the Cloud
provider's own internal network, its topology and routing policies
are not transparent or even visible to the enterprise customer's on-
premises routers. One Cloud GW BGP session might advertise all of
the prefixes of the enterprise's VPC, regardless of which Cloud DC a
given prefix resides, which can cause improper optimal path
selection for on-premises routers. To get around this problem,
virtual routers in Cloud DCs can be used to attach metadata (e.g.,
in the GENEVE header or IPv6 optional header) to indicate the Geo-
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location of the Cloud DC, the delay measurement, or other relevant
data.
5. Methods to Scale IPsec Tunnels to Cloud DCs
As described in Section 4.3, IPsec tunnels can be used to
dynamically establish connection between private VPN PEs with Cloud
GWs. Enterprises can also instantiate virtual routers within Cloud
DCs to connect to their on-premises devices via IPsec tunnels.
As described in [Int-tunnels], IPsec tunnels can introduce MTU
problems. This document assumes that endpoints manage the
appropriate MTU sizes, therefore, not requiring VPN PEs to perform
fragmentation when encapsulating user payloads in the IPsec packets.
5.1. Scale IPsec Tunnels Management
IPsec tunnels are a very convenient solution for an enterprise with
a small number of locations to reach a Cloud DC. However, for a
medium-to-large enterprise with multiple sites and data centers to
fully connect to multiple cloud DCs, there are N*C*2 bi-directional
IPsec SAs (tunnels) between Cloud DC gateways and all those sites,
with N being the number of enterprise sites and C being the number
of Cloud sites. Each of those IPsec Tunnels requires pair-wise
periodic key refreshment. For a company with hundreds or thousands
of locations, managing hundreds (or even thousands) of IPsec tunnels
can be very processing intensive. That is why many Cloud operators
only allow a limited number of (IPsec) tunnels and bandwidth to each
customer.
A solution like group encryption [RFC4535] can scale the IPsec key
management. However, the drawback of group encryption is the higher
security risk of the key distribution. More details are in Section 3
(Security Considerations of [RFC4535].
[SECURE-EVPN] leverages the BGP point-to-multipoint signaling to
create private pair-wise IPsec Security Associations among peers
without IKEv2 point-to-point signaling or any other direct peer-to-
peer session establishment messages.
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5.2. CPEs Interconnection Over the Public Internet
When enterprise CPEs are far away from each other, e.g., across
country/continent boundaries, the performance of IPsec tunnels over
the public Internet can be problematic and unpredictable. Even
though there are many monitoring tools available to measure delay
and various performance characteristics of the network, the
measurement for paths over the Internet is passive and past
measurements may not represent future performance.
[MULTI-SEG-SDWAN] outlines some approaches for leveraging the Cloud
backbone to connect enterprise CPEs across diverse geographical
areas, eliminating the need for the Cloud GW to decrypt and re-
encrypt traffic from the CPEs. A thorough examination of the
security implications associated with this proposed method is
necessary. Additionally, alternative encapsulations like SRH and
VxLAN can be considered for interconnecting enterprise CPEs.
6. Requirements for Networks Connecting Cloud Data Centers
To address the issues identified in this document, network solutions
for connecting enterprises with their dynamic workloads or
applications in Cloud DCs should satisfy the following requirements:
- Should support scalable policy management for the traffic to
and from the newly instantiated application instances at any
Cloud DC location. The scalable policy management, even though
out of the scope of this document, can include centralized
policy repositories and API-driven automation.
- Should allow enterprises to take advantage of the current
state-of-the-art private VPN technologies, including the
conventional circuit-based, MPLS-based VPNs, or IPsec-based
VPNs (or any combination thereof) that run over the public
Internet.
- Should support scalable IPsec key management among all nodes
involved in DC interconnect schemes.
- Should support easy and fast, on-demand network connections to
dynamic workloads and applications in Cloud DCs and easily
reach these workloads when they migrate within or across data
centers.
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- Should support traffic steering to distribute loads across
regions/AZs based on performance/availability of workloads in
addition to the network path conditions to the Cloud DCs.
- Should support network traffic traceability, logging, and
diagnostics.
- Should support transit/spoke gateways interconnection
scalability and consistent policy enforcement as workloads are
increased/migrated. This requirement is mainly for the Cloud
Aggregators or Cloud Service Brokers who provide managed
services to enterprises over multiple Cloud service providers.
7. Security Considerations
The security issues in terms of networking to Cloud DCs include:
- Service instances in Cloud DCs are connected to users
(enterprises) via Public IP ports which are exposed to the
following security risks:
a) Potential DDoS (Distributed Denial of Service) attack to the
ports facing the untrusted network (e.g., the public internet),
which may propagate to the cloud edge resources. To mitigate
such security risk, it is necessary for the ports facing
internet to enable Anti-DDoS features.
b) Potential risk of augmenting the attack surface with inter-
Cloud DC connection by means of identity spoofing, man-in-the-
middle, eavesdropping or DDoS attacks. One example of
mitigating such attacks is using DTLS to authenticate and
encrypt MPLS-in-UDP encapsulation [RFC7510].
- Potential attacks from service instances within the cloud. For
example, data breaches, compromised credentials, and broken
authentication, hacked interfaces and APIs, and account
hijacking.
- When IPsec tunnels established from enterprise on-premises CPEs
are terminated at the Cloud DC gateway where the workloads or
applications are hosted, traffic to/from an enterprise's
workload can be exposed to others behind the data center
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gateway (e.g., exposed to other organizations that have
workloads in the same data center).
To ensure that traffic to/from workloads is not exposed to
unwanted entities, IPsec tunnels may go all the way to the
workload (servers, or VMs) within the DC.
- Group encryption [RFC4535], re-use of old keys, or other
techniques used to help scale IPsec key management comes with
security risks, such as single point of compromise, key
distribution vulnerabilities, and authentication weaknesses, to
name a few. Detailed Security Consideration (Section 3) of
[RFC4535] are all applicable.
- Striking a balance between improved IPsec tunnel management
outlined in this document and maintaining robust security is a
delicate consideration. Simplifying the IPsec tunnel management
to reduce management complexity for large SD-WAN networks might
come with the inherent risk of decreased security. Careful
consideration of the specific deployments, coupled with regular
security assessments, is crucial to ensure the integrity and
confidentiality of the transmitted data.
The Cloud DC operator's security practices can affect the overall
security posture and need to be evaluated by customers. Many Cloud
operators offer monitoring services for data stored in Clouds, such
as AWS CloudTrail, Azure Monitor, and many third-party monitoring
tools to improve the visibility of data stored in Clouds.
Solution drafts resulting from this work will address security
concerns inherent to the solution(s), including both protocol
aspects and the importance, for example, of securing workloads in
cloud DCs and the use of secure interconnection mechanisms.
A full security evaluation will be needed before [SECURE-EVPN] or
[MULTI-SEG-SDWAN] can be recommended as a solution to some problems
described in this document.
8. IANA Considerations
This document requires no IANA actions.
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9. References
9.1. Normative References
[RFC3168] K. Ramakrishnan, et al, "The Addition of Explicit
Congestion Notification (ECN) to IP", RFC3168, Sept. 2001.
[RFC4364] E. Rosen and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC4364, Feb. 2006.
[RFC4486] E. Chen and V. Gillet, "Subcodes for BGP Cease
Notification Message", RFC4486, April 2006.
[RFC4535] H. Harney, et a, "GSAKMP: Group Secure Association Key
Management Protocol", RFC4535, June 2006.
[RFC4786] J. Abley and K. Lindqvist, "Operation of Anycast
Services", RFC4786, Dec. 2006.
[RFC5492] J. Scudder and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC5492, Feb. 2009.
[RFC5880] D. Katz and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC5880, June 2010.
[RFC6040] B. Briscoe, "Tunnelling of Explicit Congestion
Notification", RFC6040, Nov 2010.
[RFC6136] A. Sajassi and D. Mohan, "Layer 2 Virtual Private Network
(L2VPN) Operations, Administration, and Maintenance (OAM)
Requirements and Framework", RFC6136, March 2011.
[RFC7606] E. Chen, et al "Revised Error Handling for BGP UPDATE
Messages". Aug 2015.
[RFC7432] A. Sajassi, et al "BGP MPLS-Based Ethernet VPN", RFC7432,
Feb. 2015.
[RFC7510] X. Xu, et al, "Encapsulating MPLS in UDP", RFC7510, April,
2015.
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[RFC7938] P. Lapukhov, "Use of BGP for Routing in Large-Scale Data
Centers", RFC7938, Aug. 2016.
[RFC8490] R. Bellis, et al, "DNS Stateful Operations", RFC8490,
March 2019.
[RFC8765] T. Pusateri and S. Cheshire, "DNS Push Notifications",
RFC8765, June 2020.
[RFC8926] J. Gross and T. Sridhar, "Geneve: Generic Network
Virtualization Encapsulation", RFC8926, Nov. 2020.
9.2. Informative References
[RFC2735] B. Fox, et al "NHRP Support for Virtual Private networks".
Dec. 1999.
[RFC6071] S. Frankel and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", Feb 2011.
[3GPP-5G-Edge] 3GPP TS 23.548 v18.1.1, "5G System Enhancements for
Edge Computing", April 2023.
[SDWAN-EDGE-DISCOVERY] L. Dunbar, S. Hares, R. Raszuk, K. Majumdar,
G. Mishra, V. Kasiviswanathan, "BGP UPDATE for SD-WAN Edge
Discovery", draft-ietf-idr-sdwan-edge-discovery-12, Oct
2023.
[AWS-NAT] NAT gateways - Amazon Virtual Private Cloud.
[AWS-Cloud-WAN] Introducing AWS Cloud WAN (Preview) | Networking &
Content Delivery (amazon.com).
[Azure-SD-WAN] Architecture: Virtual WAN and SD-WAN connectivity -
Azure Virtual WAN | Microsoft Learn.
[NTW-AC] M. Boucadair, et al, "A Network YANG Data Model for
Attachment Circuits", draft-ietf-opsawg-ntw-attachment-
circuit-05, Feb. 2024.
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Internet-Draft Net2Cloud Problems & Mitigations
[DATAMODEL-BGP] M. Jethanandani, K. Patel, S. Hares, "YANG Model for
Border Gateway Protocol (BGP-4)", draft-ietf-idr-bgp-
model-17, July 2023.
[Google-NAT] Cloud NAT overview | Google Cloud.
[Int-tunnels] J. Touch and W Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-13.txt, March,
2023.
[MEF-70.1] MEF 70.1 SD-WAN Service Attributes and Service Framework.
Nov. 2021.
[METADATA-PATH] L. Dunbar, et al, "BGP Extension for 5G Edge Service
Metadata" draft-ietf-idr-5g-edge-service-metadata-15, Feb.
2024.
[MULTI-SEG-SDWAN] K. Majumdar, et al, "Multi-segment SD-WAN via
Cloud DCs", draft-dmk-rtgwg-multisegment-sdwan-07, Feb
2024.
[SECURE-EVPN] A. Sajassi, et al, "Secure EVPN", draft-ietf-bess-
secure-evpn-00, June 2023.
[SVC-AC] M. Boucadair, et al. "YANG Data Models for 'Attachment
Circuits'-as-a-Service (ACaaS)", draft-ietf-opsawg-teas-
attachment-circuit-06, Feb. 2024.
[Split-Horizon-DNS] K. Tirumaleswar, et al, "Establishing Local DNS
Authority in Validated Split-Horizon Environments", draft-
ietf-add-split-horizon-authority-07, Mar. 2023.
10. Acknowledgments
Many thanks to Joel Halpern, Aseem Choudhary, Adrian Farrel, Alia
Atlas, Chris Bowers, Mohamed Boucadair, Paul Vixie, Paul Ebersman,
Timothy Morizot, Ignas Bagdonas, Donald Eastlake, Michael Huang, Liu
Yuan Jiao, Katherine Zhao, and Jim Guichard for the discussion and
contributions.
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Authors' Addresses
Linda Dunbar
Futurewei
Email: Linda.Dunbar@futurewei.com
Andrew G. Malis
Malis Consulting
Email: agmalis@gmail.com
Christian Jacquenet
Orange
Rennes, 35000
France
Email: Christian.jacquenet@orange.com
Mehmet Toy
Verizon
One Verizon Way
Basking Ridge, NJ 07920
Email: mehmet.toy@verizon.com
Kausik Majumdar
Microsoft Azure
kmajumdar@microsoft.com
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