Network Working Group L. Dunbar
Internet Draft Futurewei
Intended status: Informational Andy Malis
Expires: December 29, 2022 Malis Consulting
C. Jacquenet
Orange
M. Toy
Verizon
K. Majumdar
Microsoft
June 29, 2022
Dynamic Networks to Hybrid Cloud DCs Problem Statement
draft-ietf-rtgwg-net2cloud-problem-statement-14
Abstract
This document describes the network-related problems enterprises
face today when interconnecting their branch offices with dynamic
workloads in third-party data centers (a.k.a. Cloud DCs). There can
be many problems associated with connecting to or among Clouds; the
Net2Cloud problem statements are mainly for enterprises who already
have traditional MPLS services and are interested in leveraging
those networks (instead of completely abandoning them). This
document aims to describe the problems of continuing using the MPLS
networks when connecting workloads in the Cloud, and to clarify
additional work in the IETF Routing area. Other problems are out of
the scope of this document.
Current operational problems are examined to determine whether there
is a need to improve existing protocols or whether a new protocol is
necessary to solve them.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
xxx, et al. [Page 1]
Internet-Draft Net2Cloud Problem Statement March 2022
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on December 29, 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction...................................................3
1.1. Key Characteristics of Cloud Services:....................3
1.2. Connecting to Cloud Services..............................3
1.3. Reaching App instances in the optimal Cloud DC locations..4
2. Definition of terms............................................5
3. High Level Issues of Connecting to Cloud DCs...................6
3.1. More BGP errors triggered by large number of peers........6
3.2. Network failures that may lead to massive routes changes..6
3.3. 5G Edge Clouds............................................7
Dunbar, et al. [Page 2]
Internet-Draft Net2Cloud Problem Statement March 2022
3.4. Security Issues...........................................7
3.5. Authorization and Identity Management.....................8
3.6. API abstraction...........................................9
3.7. DNS for Cloud Resources...................................9
3.8. NAT for Cloud Services...................................10
3.9. Cloud Discovery..........................................11
4. Interconnecting Enterprise Sites with Cloud DCs...............11
4.1. Sites to Cloud DC........................................12
4.2. Inter-Cloud Interconnection..............................14
5. Problems with MPLS-based VPNs extending to Hybrid Cloud DCs...15
6. Problem with using IPsec tunnels to Cloud DCs.................17
6.1. Scaling Issues with IPsec Tunnels........................17
6.2. Poor performance when overlay public internet............17
7. End-to-End Security Concerns for Data Flows...................18
8. Requirements for Dynamic Cloud Data Center VPNs...............18
9. Security Considerations.......................................19
10. IANA Considerations..........................................19
11. References...................................................19
11.1. Normative References....................................19
11.2. Informative References..................................19
12. Acknowledgments..............................................20
1. Introduction
1.1. Key Characteristics of Cloud Services:
Key characteristics of Cloud Services are on-demand, scalable,
highly available, and usage-based billing. Cloud Services, such as,
compute, storage, network functions (most likely virtual), third
party managed applications, etc. are usually hosted and managed by
third parties Cloud Operators. Here are some examples of Cloud
network functions: Virtual Firewall services, Virtual private
network services, Virtual PBX services including voice and video
conferencing systems, etc. Cloud Data Center (DC) is shared
infrastructure that hosts the Cloud Services to many customers.
1.2. Connecting to Cloud Services
With the advent of widely available third-party cloud DCs and
services in diverse geographic locations and the advancement of
tools for monitoring and predicting application behaviors, it is
very attractive for enterprises to instantiate applications and
workloads in locations that are geographically closest to their end-
users. Such proximity can improve end-to-end latency and overall
Dunbar, et al. [Page 3]
Internet-Draft Net2Cloud Problem Statement March 2022
user experience. Conversely, an enterprise can easily shutdown
applications and workloads whenever end-users are in motion (thereby
modifying the networking connection of subsequently relocated
applications and workloads). In addition, enterprises may wish to
take advantage of more and more business applications offered by
cloud operators.
The networks that interconnect hybrid cloud DCs must address the
following requirements:
- to access all workloads in the desired cloud DCs:
Many enterprises include cloud in their disaster recovery
strategy, such as enforcing periodic backup policies within the
cloud, or running backup applications in the Cloud.
- Global reachability from different geographical zones, thereby
facilitating the proximity of applications as a function of the
end users' location, to improve latency.
- Elasticity: prompt connection to newly instantiated
applications at Cloud DCs when usages increase and prompt
release of connection after applications at locations being
removed when demands change.
- Scalable policy management: apply the appropriate polices to
the newly instantiated application instances at any Cloud DC
location.
1.3. Reaching App instances in the optimal Cloud DC locations
Many applications have multiple instances instantiated in different
Cloud DCs. The current state of the art solutions is typically based
on DNS assisted with load balancer by responding a FQDN (Fully
Qualified Domain Name) inquiry with an IP address of the closest or
lowest cost DC that can reach the instance. Here are some problems
associated with DNS based solutions:
- Dependent on client behavior
- Client can cache results indefinitely
- Client may not receive service even though there are
servers available (before cache timeout) in other Cloud
DCs.
Dunbar, et al. [Page 4]
Internet-Draft Net2Cloud Problem Statement March 2022
- No inherent leverage of proximity information present in the
network (routing) layer, resulting in loss of performance
- Client on the west coast can be mapped to a DC on the east
coast
- Inflexible traffic control:
- Local DNS resolver become the unit of traffic management.
This requires DNS to receive periodical update of the
network condition, which is difficult.
2. Definition of terms
Cloud DC: Third party Data Centers that usually host applications
and workload owned by different organizations or
tenants.
Controller: Used interchangeably with SD-WAN controller to manage
SD-WAN overlay path creation/deletion and monitoring the
path conditions between two or more sites.
DSVPN: Dynamic Smart Virtual Private Network. DSVPN is a secure
network that exchanges data between sites without
needing to pass traffic through an organization's
headquarter virtual private network (VPN) server or
router.
Heterogeneous Cloud: applications and workloads split among Cloud
DCs owned or managed by different operators.
Hybrid Clouds: Hybrid Clouds refers to an enterprise using its own
on-premises DCs in addition to Cloud services provided
by one or more cloud operators. (e.g. AWS, Azure,
Google, Salesforces, SAP, etc).
VPC: Virtual Private Cloud is a virtual network dedicated to
one client account. It is logically isolated from other
virtual networks in a Cloud DC. Each client can launch
his/her desired resources, such as compute, storage, or
network functions into his/her VPC. Most Cloud
Dunbar, et al. [Page 5]
Internet-Draft Net2Cloud Problem Statement March 2022
operators' VPCs only support private addresses, some
support IPv4 only, others support IPv4/IPv6 dual stack.
3. High Level Issues of Connecting to Cloud DCs
There are many problems associated with connecting to hybrid Cloud
Services, many of which are out of the IETF scope. This section is
to identify some of the high-level problems that can be addressed by
IETF, especially by Routing area. Other problems are out of the
scope of this document. By no means has this section covered all
problems for connecting to Hybrid Cloud Services, e.g. difficulty in
managing cloud spending is not discussed here.
3.1. More BGP errors triggered by large number of peers
Many network service providers have limited number of BGP peers and
usually have prior negotiated peering policies with their BGP peers.
Cloud GWs need to peer with many more parties, via private circuits
or IPsec over public internet. Many of those peering parties may not
be traditional network service providers. Their BGP configurations
practices might not be consistent, and some are done by less
experienced personnel.
All those can contribute to increased BGP peering errors, such as
capability mismatch, BGP cease notification, unwanted route leaks,
missing Keepalives, etc.
3.2. Network failures that may lead to massive routes changes
As described in RFC7938, Cloud DC BGP might not have an IGP to route
around link/node failures within the ASes. Fiber-cut is not uncommon
within Cloud DCs or between sites. Sometimes, an entire cloud data
center goes dark caused by a variety of reasons, such as too many
changes and updates at once, changes of outside of maintenance
windows, cybersecurity threats attacks, cooling failures,
insufficient backup power, etc. When those events happen, massive
numbers of routes need to be changed.
The large number of routes switching over to another site can also
cause overloading that triggers more failures.
Dunbar, et al. [Page 6]
Internet-Draft Net2Cloud Problem Statement March 2022
In addition, the routes (IP addresses) in a Cloud DC cannot be
aggregated nicely, triggering very large number of BGP UPDATE
messages when a failure occurs.
It might be more effective to do mass reroute, similar to EVPN
[RFC7432] defined mass withdraw mechanism to signal a large number
of routes being changed to remote PE nodes as quickly as possible.
3.3. 5G Edge Clouds
5G edge cloud data centers have routers connecting to the 5G Core
functions, such as Radio Control Functions, Session Management
Function (SMF), Access Mobility Functions (AMF), User Plane
Functions (UPF), etc. Those functions need to be connected to the
Radio Data Unit (R-DU) on the Cell Tower. The UPFs need to be
connected to the 5G Local Data Networks' ingress routers which might
co-located the cloud edge data centers.
In addition, the 5G edge cloud data centers may host edge computing
servers for Ultra-low latency services that need to be near the UEs
(User equipment). Those edge computing applications need to have
very low latency to the UEs, and also connect to backend servers or
databases in another location.
3.4. Security Issues
There are many aspects of security issues in terms of networking to
clouds:
- 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 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 (RFC 7510).
Dunbar, et al. [Page 7]
Internet-Draft Net2Cloud Problem Statement March 2022
- Potential attacks from service instances within the cloud. For
example, data breaches, compromised credentials, and broken
authentication, hacked interfaces and APIs, account hijacking.
- Securing user identity management, authentication, and access
control mechanisms is important. Developing appropriate
security mechanisms (including tools to assess the robustness
of the enforced security policies) can enhance the confidence
needed by enterprises to fully take advantage of Cloud
Services.
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 visibility to data stored in Clouds. But
there is still underline security concerns on illegitimate data and
workloads access.
3.5. Authorization and Identity Management
One of the more prominent challenges for Cloud Services is Identity
Management and Authorization. The Authorization not only includes
user authorization, but also the authorization of API calls by
applications from different Cloud DCs managed by different Cloud
Operators. In addition, there are authorization for Workload
Migration, Data Migration, and Workload Management.
There are many types of users in cloud environments, e.g. end users
for accessing applications hosted in Cloud DCs, Cloud-resource users
who are responsible for setting permissions for the resources based
on roles, access lists, IP addresses, domains, etc.
There are many types of Cloud authorizations: including MAC
(Mandatory Access Control) - where each app owns individual access
permissions, DAC (Discretionary Access Control) - where each app
requests permissions from an external permissions app, RBAC (Role-
based Access Control) - where the authorization service owns roles
with different privileges on the cloud service, and ABAC (Attribute-
based Access Control) - where access is based on request attributes
and policies.
IETF hasn't yet developed comprehensive specification for Identity
management and data models for Cloud Authorizations.
Dunbar, et al. [Page 8]
Internet-Draft Net2Cloud Problem Statement March 2022
3.6. API abstraction
Different Cloud Operators have different APIs to access their Cloud
resources, security functions, the NAT, etc.
It is difficult to move applications built by one Cloud operator's
APIs to another. However, it is highly desirable to have a single
and consistent way to manage the networks and respective security
policies for interconnecting applications hosted in different Cloud
DCs.
The desired property would be having a single network fabric to
which different Cloud DCs and enterprise's multiple sites can be
attached or detached, with a common interface for setting desired
policies.
The difficulty of connecting applications in different Clouds might
be stemmed from the fact that they are direct competitors. Usually
traffic flow out of Cloud DCs incur charges. Therefore, direct
communications between applications in different Cloud DCs can be
more expensive than intra Cloud communications.
It is desirable to have a common API shim layer or abstraction for
different Cloud providers to make it easier to move applications
from one Cloud DC to another.
3.7. DNS for Cloud Resources
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 by different cloud
operators, it is necessary to establish policies and rules on
how/where to forward DNS queries to. When applications in one Cloud
Dunbar, et al. [Page 9]
Internet-Draft Net2Cloud Problem Statement March 2022
need to communication with applications hosted in another Cloud,
there could be DNS queries from one Cloud DC being forwarded to the
enterprise's on-premise DNS, which in turn be forwarded to the DNS
service in another Cloud. Needless to say, configuration can be
complex depending on the application communication patterns.
However, even with carefully managed policies and configurations,
collisions can still occur. If you use an internal name like .cloud
and then want your services to be available via or within some other
cloud provider which also uses .cloud, then it can't work.
Therefore, it is better to use the global domain name 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 at all 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.
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 do prevent any possibility of collision at the
present or in the future and they make DNSSEC trust manageable.
Consider using a registered and fully qualified domain name (FQDN)
from global DNS as the root for enterprise and other internal
namespaces.
3.8. NAT for Cloud Services
Cloud resources, such as VM instances, are usually assigned with
private IP addresses. By configuration, some private subnets can
have the NAT function to reach out to external network and some
private subnets are internal to Cloud only.
Different Cloud operators support different levels of NAT functions.
For example, AWS NAT Gateway does not currently support connections
towards, or from VPC Endpoints, VPN, AWS Direct Connect, or VPC
Peering. https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-
nat-gateway.html#nat-gateway-other-services. AWS Direct
Connect/VPN/VPC Peering does not currently support any NAT
functionality.
Google's Cloud NAT allows Google Cloud virtual machine (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
Dunbar, et al. [Page 10]
Internet-Draft Net2Cloud Problem Statement March 2022
allow instances to reach the Internet. It does not implement inbound
NAT. Hosts outside of VPC network can only respond to established
connections initiated by instances inside the Google Cloud; they
cannot initiate their own, new connections to Cloud instances via
NAT.
For enterprises with applications running in different Cloud DCs,
proper configuration of NAT has to be performed in Cloud DC and in
their on-premises DC.
3.9. Cloud Discovery
One of the concerns of using Cloud services is not aware where the
resource is located, especially Cloud operators can move application
instances from one place to another. When applications in Cloud
communicate with on-premise applications, it may not be clear where
the Cloud applications are located or to which VPCs they belong.
It is highly desirable to have tools to discover cloud services in
much the same way as you would discover your on-premises
infrastructure. A significant difference is that cloud discovery
uses the cloud vendor's API to extract data on your cloud services,
rather than the direct access used in scanning your on-premises
infrastructure.
Standard data models, APIs or tools can alleviate concerns of
enterprise utilizing Cloud Resources, e.g. having a Cloud service
scan that connects to the API of the cloud provider and collects
information directly.
4. Interconnecting Enterprise Sites with Cloud DCs
Considering that many enterprises already have existing VPNs (e.g.
MPLS based L2VPN or L3VPN) interconnecting branch offices & on-
premises data centers, connecting to Cloud services will be mixed of
different types of networks. When an enterprise's existing VPN
service providers do not have direct connections to the
corresponding cloud DCs that the enterprise prefers to use, the
enterprise has to face additional infrastructure and operational
costs to utilize the Cloud services.
Dunbar, et al. [Page 11]
Internet-Draft Net2Cloud Problem Statement March 2022
4.1. Sites to Cloud DC
Most Cloud operators offer some type of network gateway through
which an enterprise can reach their workloads hosted in the Cloud
DCs. AWS (Amazon Web Services) offers the following options to reach
workloads in AWS Cloud DCs:
- AWS Internet gateway allows communication between instances in
AWS VPC and the internet.
- AWS Virtual gateway (vGW) where IPsec tunnels [RFC6071] are
established between an enterprise's own gateway and AWS vGW, so
that the communications between those gateways can be secured
from the underlay (which might be the public Internet).
- AWS Direct Connect, which allows enterprises to purchase direct
connect from network service providers to get a private leased
line interconnecting the enterprises gateway(s) and the AWS
Direct Connect routers. In addition, an AWS Transit Gateway can
be used to interconnect multiple VPCs in different Availability
Zones. AWS Transit Gateway acts as a hub that controls how
traffic is forwarded among all the connected networks which act
like spokes.
Microsoft's ExpressRoute allows extension of a private network to
any of the Microsoft cloud services, including Azure and Office365.
ExpressRoute is configured using Layer 3 routing. Customers can opt
for redundancy by provisioning dual links from their location to two
Microsoft Enterprise edge routers (MSEEs) located within a third-
party ExpressRoute peering location. The BGP routing protocol is
then setup over WAN links to provide redundancy to the cloud. This
redundancy is maintained from the peering data center into
Microsoft's cloud network.
Google's Cloud Dedicated Interconnect offers similar network
connectivity options as AWS and Microsoft. One distinct difference,
however, is that Google's service allows customers access to the
entire global cloud network by default. It does this by connecting
your on-premises network with the Google Cloud using BGP and Google
Cloud Routers to provide optimal paths to the different regions of
the global cloud infrastructure.
Figure below shows an example of some of a tenant's workloads are
accessible via a virtual router connected by AWS Internet Gateway;
Dunbar, et al. [Page 12]
Internet-Draft Net2Cloud Problem Statement March 2022
some are accessible via AWS vGW, and others are accessible via AWS
Direct Connect.
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 GWs. It
is important for some enterprises to be able to observe the specific
behaviors when connected by different connections.
Customer Gateway can be customer owned router or ports physically
connected to AWS Direct Connect GW.
+------------------------+
| ,---. ,---. |
| (TN-1 ) ( TN-2)|
| `-+-' +---+ `-+-' |
| +----|vR1|----+ |
| ++--+ |
| | +-+----+
| | /Internet\ For External
| +-------+ Gateway +----------------------
| \ / to reach via Internet
| +-+----+
| |
| ,---. ,---. |
| (TN-1 ) ( TN-2)|
| `-+-' +---+ `-+-' |
| +----|vR2|----+ |
| ++--+ |
| | +-+----+
| | / virtual\ For IPsec Tunnel
| +-------+ Gateway +----------------------
| | \ / termination
| | +-+----+
| | |
| | +-+----+ +------+
| | / \ For Direct /customer\
| +-------+ Gateway +----------+ gateway |
| \ / Connect \ /
| +-+----+ +------+
| |
+------------------------+
Figure 1: Examples of Multiple Cloud DC connections.
Dunbar, et al. [Page 13]
Internet-Draft Net2Cloud Problem Statement March 2022
4.2. Inter-Cloud Interconnection
The connectivity options to Cloud DCs described in the previous
section are for reaching Cloud providers' DCs, but not between cloud
DCs. When applications in AWS Cloud need to communicate with
applications in Azure, today's practice requires a third-party
gateway (physical or virtual) to interconnect the AWS's Layer 2
DirectConnect path with Azure's Layer 3 ExpressRoute.
Enterprises can also instantiate their own virtual routers in
different Cloud DCs and administer IPsec tunnels among them, which
by itself is not a trivial task. Or by leveraging open source VPN
software such as strongSwan, you create an IPSec connection to the
Azure gateway using a shared key. The StrongSwan instance within AWS
not only can connect to Azure but can also be used to facilitate
traffic to other nodes within the AWS VPC by configuring forwarding
and using appropriate routing rules for the VPC.
Most Cloud operators, such as AWS VPC or Azure VNET, use non-
globally routable CIDR from private IPv4 address ranges as specified
by RFC1918. To establish IPsec tunnel between two Cloud DCs, it is
necessary to exchange Public routable addresses for applications in
different Cloud DCs.
In summary, here are some approaches, available now (which might
change in the future), to interconnect workloads among different
Cloud DCs:
a) Utilize Cloud DC provided inter/intra-cloud connectivity
services (e.g., AWS Transit Gateway) to connect workloads
instantiated in multiple VPCs. Such services are provided with
the cloud gateway to connect to external networks (e.g., AWS
DirectConnect Gateway).
b) Hairpin all traffic through the customer gateway, meaning all
workloads are directly connected to the customer gateway, so
that communications among workloads within one Cloud DC must
traverse through the customer gateway.
c) Establish direct tunnels among different VPCs (AWS' Virtual
Private Clouds) and VNET (Azure's Virtual Networks) via
client's own virtual routers instantiated within Cloud DCs.
DMVPN (Dynamic Multipoint Virtual Private Network) or DSVPN
(Dynamic Smart VPN) techniques can be used to establish direct
Multi-point-to-Point or multi-point-to multi-point tunnels
among those client's own virtual routers.
Dunbar, et al. [Page 14]
Internet-Draft Net2Cloud Problem Statement March 2022
Approach a) usually does not work if Cloud DCs are owned and managed
by different Cloud providers.
Approach b) creates additional transmission delay plus incurring
cost when exiting Cloud DCs.
For the Approach c), DMVPN or DSVPN use NHRP (Next Hop Resolution
Protocol) [RFC2735] so that spoke nodes can register their IP
addresses & WAN ports with the hub node. The IETF ION
(Internetworking over NBMA (non-broadcast multiple access) WG
standardized NHRP for connection oriented NBMA network (such as ATM)
network address resolution more than two decades ago.
There are many differences between virtual routers in Public Cloud
DCs and the nodes in an NBMA network. NHRP cannot be used for
registering virtual routers in Cloud DCs unless an extension of such
protocols is developed for that purpose, e.g. taking NAT or dynamic
addresses into consideration. Therefore, DMVPN and/or DSVPN cannot
be used directly for connecting workloads in hybrid Cloud DCs.
5. Problems with MPLS-based VPNs extending to Hybrid Cloud DCs
Traditional MPLS-based VPNs have been widely deployed as an
effective way to support businesses and organizations that require
network performance and reliability. MPLS shifted the burden of
managing a VPN service from enterprises to service providers. The
CPEs attached to MPLS VPNs are also simpler and less expensive,
because they do not need to manage routes to remote sites; they
simply pass all outbound traffic to the MPLS VPN PEs to which the
CPEs are attached (albeit multi-homing scenarios require more
processing logic on CPEs). MPLS has addressed the problems of
scale, availability, and fast recovery from network faults, and
incorporated traffic-engineering capabilities.
However, traditional MPLS-based VPN solutions are sub-optimized for
connecting end-users to dynamic workloads/applications in cloud DCs
because:
- The Provider Edge (PE) nodes of the enterprise's VPNs might not
have direct connections to third party cloud DCs that are used
for hosting workloads with the goal of providing an easy access
to enterprises' end-users.
Dunbar, et al. [Page 15]
Internet-Draft Net2Cloud Problem Statement March 2022
- It takes some time to deploy provider edge (PE) routers at new
locations. When enterprise's workloads are changed from one
cloud DC to another (i.e., removed from one DC and re-
instantiated to another location when demand changes), the
enterprise branch offices need to be connected to the new cloud
DC, but the network service provider might not have PEs located
at the new location.
One of the main drivers for moving workloads into the cloud is
the widely available cloud DCs at geographically diverse
locations, where apps can be instantiated so that they can be
as close to their end-users as possible. When the user base
changes, the applications may be migrated to a new cloud DC
location closest to the new user base.
- Most of the cloud DCs do not expose their internal networks. An
enterprise with a hybrid cloud deployment can use an MPLS-VPN
to connect to a Cloud provider at multiple locations. The
connection locations often correspond to gateways of different
Cloud DC locations from the Cloud provider. The different
Cloud DCs are interconnected by the Cloud provider's own
internal network. At each connection location (gateway), the
Cloud provider uses BGP to advertise all of the prefixes in the
enterprise's VPC, regardless of which Cloud DC a given prefix
is actually in. This can result in inefficient routing for the
end-to-end data path.
Another roadblock is the lack of a standard way to express and
enforce consistent security policies for workloads that not only use
virtual addresses, but in which are also very likely hosted in
different locations within the Cloud DC [RFC8192]. The current VPN
path computation and bandwidth allocation schemes may not be
flexible enough to address the need for enterprises to rapidly
connect to dynamically instantiated (or removed) workloads and
applications regardless of their location/nature (i.e., third party
cloud DCs).
Dunbar, et al. [Page 16]
Internet-Draft Net2Cloud Problem Statement March 2022
6. Problem with using IPsec tunnels to Cloud DCs
As described in the previous section, many Cloud operators expose
their gateways for external entities (which can be enterprises
themselves) to directly establish IPsec tunnels. Enterprises can
also instantiate virtual routers within Cloud DCs to connect to
their on-premises devices via IPsec tunnels.
6.1. Scaling Issues with IPsec Tunnels
If there is only one enterprise location that needs to reach the
Cloud DC, an IPsec tunnel is a very convenient solution.
However, many medium-to-large enterprises have multiple sites and
multiple data centers. For multiple sites to communicate with
workloads and apps hosted in cloud DCs, Cloud DC gateways have to
maintain many IPsec tunnels to all those locations. In addition,
each of those IPsec Tunnels requires pair-wise periodic key
refreshment. For a company with hundreds or thousands of locations,
there could be hundreds (or even thousands) of IPsec tunnels
terminating at the cloud DC gateway, which is very processing
intensive. That is why many cloud operators only allow a limited
number of (IPsec) tunnels & bandwidth to each customer.
Alternatively, you could use a solution like group encryption where
a single IPsec SA is necessary at the GW but the drawback is key
distribution and maintenance of a key server, etc.
6.2. Poor performance when overlay public internet
When large number of IPSec encap & decap are needed, the performance
is degraded. NAT also adds performance burden.
When enterprise CPEs or gateways are far away from cloud DC gateways
or across country/continent boundaries, performance of IPsec tunnels
over the public Internet can be problematic and unpredictable. Even
though there are many monitoring tools available to measure delay
and various performance characteristics of the network, the
measurement for paths over the Internet is passive and past
measurements may not represent future performance.
Many cloud providers can replicate workloads in different available
zones. An App instantiated in a cloud DC closest to clients may have
to cooperate with another App (or its mirror image) in another
region or database server(s) in the on-premises DC. This kind of
Dunbar, et al. [Page 17]
Internet-Draft Net2Cloud Problem Statement March 2022
coordination requires predicable networking behavior/performance
among those locations.
7. End-to-End Security Concerns for Data Flows
Add description for Bucket 7 from Kausik
When IPsec tunnels established from enterprise on-premises CPEs
are terminated at the Cloud DC gateway where the workloads or
applications are hosted, some enterprises have concerns regarding
traffic to/from their workload being exposed to others behind the
data center gateway (e.g., exposed to other organizations that
have workloads in the same data center).
To ensure that traffic to/from workloads is not exposed to
unwanted entities, IPsec tunnels may go all the way to the
workload (servers, or VMs) within the DC.
8. Requirements for Dynamic Cloud Data Center VPNs
To address the aforementioned issues, any solution for enterprise
VPNs that includes connectivity to dynamic workloads or applications
in cloud data centers should satisfy a set of requirements:
- The solution should allow enterprises to take advantage of the
current state-of-the-art in VPN technology, in both traditional
MPLS-based VPNs and IPsec-based VPNs (or any combination
thereof) that run over the public Internet.
- The solution should not require an enterprise to upgrade all
their existing CPEs.
- The solution should support scalable IPsec key management among
all nodes involved in DC interconnect schemes.
- The solution needs to support easy and fast, on-the-fly, VPN
connections to dynamic workloads and applications in third
party data centers, and easily allow these workloads to migrate
both within a data center and between data centers.
- Allow VPNs to provide bandwidth and other performance
guarantees.
- Be a cost-effective solution for enterprises to incorporate
dynamic cloud-based applications and workloads into their
existing VPN environment.
Dunbar, et al. [Page 18]
Internet-Draft Net2Cloud Problem Statement March 2022
9. Security Considerations
The draft discusses security requirements as a part of the problem
space, particularly in sections 4, 5, and 8.
Solution drafts resulting from this work will address security
concerns inherent to the solution(s), including both protocol
aspects and the importance (for example) of securing workloads in
cloud DCs and the use of secure interconnection mechanisms.
10. IANA Considerations
This document requires no IANA actions. RFC Editor: Please remove
this section before publication.
11. References
11.1. Normative References
11.2. Informative References
[RFC2735] B. Fox, et al "NHRP Support for Virtual Private
networks". Dec. 1999.
[RFC8192] S. Hares, et al "Interface to Network Security Functions
(I2NSF) Problem Statement and Use Cases", July 2017
[ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation,
storage, distribution and enforcement of policies for
network security", Nov 2007.
[RFC6071] S. Frankel and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", Feb 2011.
[RFC4364] E. Rosen and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", Feb 2006
Dunbar, et al. [Page 19]
Internet-Draft Net2Cloud Problem Statement March 2022
[RFC4664] L. Andersson and E. Rosen, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", Sept 2006.
12. Acknowledgments
Many thanks to Alia Atlas, Chris Bowers, Paul Vixie, Paul Ebersman,
Timothy Morizot, Ignas Bagdonas, Michael Huang, Liu Yuan Jiao,
Katherine Zhao, and Jim Guichard for the discussion and
contributions.
Dunbar, et al. [Page 20]
Internet-Draft Net2Cloud Problem Statement March 2022
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
Dunbar, et al. [Page 21]
