The Case for Enterprise-Ready Virtual Private Clouds

The Case for Enterprise-Ready Virtual Private Clouds Timothy Wood§ Alexandre Gerber† K.K. Ramakrishnan† Prashant Shenoy§ Jacobus Van der Merwe† §University of Massachusetts Amherst †AT&T Labs - Research {twood,shenoy}@cs.umass.edu {gerber,kkrama,kobus}@research.att.com Abstract tegrated into an enterprise’s current infrastructure without having to deal with substantial configuration, address Cloud computing platforms such as Amazon EC2 provide customers with flexible, on demand resources at low cost. How- management, or security concerns. Instead, current com- ever, while existing offerings are useful for providing basic mercial solutions present cloud servers as isolated enti- computation and storage resources, they fail to provide the se- ties with their own IP address space that is outside of curity and network controls that many customers would like. In the customer’s control. The separation of cloud and en- this work we argue that cloud computing has a great potential terprise resources increases software and configuration to change how enterprises run and manage their IT systems, but complexity when deploying services that must communi- that to achieve this, more comprehensive control over network cate with an enterprise’s private network. This can lead to resources and security need to be provided for users. Towards security concerns since enterprise customers must utilize this goal, we propose CloudNet, a cloud platform architecture IP addresses on the public Internet in order to link appli- which utilizes virtual private networks to securely and seam- cation components in the cloud to their own sites. It is left lessly link cloud and enterprise sites. to the customer to manage security on the cloud resources and the enterprise network through firewall rules. Finally, 1 Introduction existing cloud services focus on storage and computa- Cloud computing enables enterprises large and small to tion resources, and do not allow for control over network manage resources better – some because they no longer resources either within the cloud or the network linking need to invest in local IT resources and instead can lease enterprise and cloud sites. The lack of coordination be- cheaper, on-demand resources from providers, and oth- tween network and cloud resources leaves the customer ers because they can utilize the flexibility of cloud re- again responsible for independently arranging for traffic sources to dynamically meet peak demand without in- isolation and bandwidth guarantees with a separate net- vesting in in-house resources. Cloud computing is a work service provider. natural fit for enterprise customers since it enables out- To overcome these deficiencies, we propose the en- sourcing of another set of non core competencies: IT hancement of the cloud computing framework to seam- infrastructure selection, ordering, deployment, and man- lessly integrate virtual private networks (VPNs). To this agement. Cloud computing allows enterprises to obtain end, we propose CloudNet, which joins VPNs and cloud as much computation and storage resources as they re- computing. CloudNet uses VPNs to provide secure com- quire, while only paying for the precise amount that they munication channels and to allow customer’s greater con- use. Since cloud platforms rely on virtualization, new re- trol over network provisioning and configuration. sources can be quickly and dynamically added to a cus- However, there are challenges to be dealt with when tomer’s resource pool within minutes. From a cloud com- combining VPNs and cloud platforms. First, creat- puting service provider’s perspective, server virtualiza- ing VPN endpoints requires coordination between the tion allows them to flexibly multiplex resources among network operator and cloud service provider; existing customers without needing to dedicate physical resources cloud services do not provide sufficient “hooks” to al- individually. These features have driven the growth of low cloud resources to be securely attached to a VPN commercial cloud computing services, making them in- endpoint. Next, provider provided VPNs typically ex- creasingly popular and economical. tend only between edge routers within the provider net- However, current cloud computing services need to work. Cloud operators must ensure that network iso- further evolve to fully meet the needs of businesses. It lation extends through any local network infrastrcuture, is highly desirable that cloud resources be seamlessly in- e.g., switches and routers, within the cloud site itself. Fi- 1 nally, VPNs have traditionally been provisioned at man- Two additional types of cloud computing environ- agement timescales mainly because the endpoints of a ments have been developed to help with these concerns: VPN were expected to remain static for long periods private and overflow clouds [2]. In a private cloud, of time. In cloud computing, however, flexibility and the customer is given exclusive access to a portion of rapid provisioning are key requirements, and it is essen- a data center which then manages the resources using tial that the network transparency and secure communica- cloud computing techniques. Overflow clouds are used tion channels provided by VPNs remain effective despite as backup service pools that are only used when an enter- rapid changes in server and network configuration. prise’s own resources are completely saturated. These In this work we present the CloudNet architecture, techniques allow for enterprises to obtain some of the which uses the idea of Virtual Private Clouds to create benefits of cloud computing while reducing the security flexible, secure resource pools transparently connected to concerns related to using public clouds. However, the enterprises via VPNs. CloudNet achieves these goals by network transparency and resource control issues remain. automating the creation and management of VPN end- Our work attempts to make any type of cloud more trans- points and allowing for explicit coordination between the parent, secure, and flexible. cloud platform and the network service provider. Virtual Private Networks: In this work we focus on VPNs provided by a network operator, as opposed to 2 Background & Related Work technologies such as IPSec VPNs that create software tunnels between each end host. Network based VPNs Commercial Platforms: Cloud computing has rapidly are typically realized and enabled by multiprotocol la- grown in popularity over the last few years due to the bel switching (MPLS) provider networks, following the reemergence of virtualization as an efficient method of “hoses model” [4] and are already commonly used by flexibly sharing resources. There are many different many enterprises. Provider based VPNs can provide ei- types of cloud computing services ranging from web ther layer-3 VPNs following RFC 2547, or layer-2 vir- based word processors and email clients to application tual private LAN Service (VPLS) VPNs according to development platforms like Google App Engine [6] to RFC 4761. CloudNet relies on network based VPNs virtual infrastructure providers like Amazon EC2 [1] that since they require no endhost configuration, have lower lease full virtual machines to customers. The authors overheads, and can provide additional services from the of [2] provide a good overview of the various types of network provider such as resource reservation. While cloud computing platforms, as well as many of the chal- these VPNs currently require long setup periods, our lenges and benefits of cloud computing. In this work work is investigating methods for automating their de- we focus on Infrastructure as a Service (IaaS) providers ployment to allow for rapid changes in VPN topologies. since they provide the greatest flexibility for enterprise Related Work: In this work we focus on providing users who already have large software systems that they networking support for enterprise cloud platforms with would like to move “to the cloud” with minimal changes. VPNs. While they do not target enterprise applications, Existing IaaS platforms such as EC2 already allow both the Virtuoso and VIOLIN projects address a sim- customers to lease storage and computation resources on ilar problem of managing networks of virtual machines demand. While EC2 allows control over the type of CPU hosted across multiple grid computing sites [10, 9]. Both and storage available to each virtual machine instance, it systems use overlay networks to intercept VM traffic and has more limited controls over the network setup, partic- tunnel it between sites. This requires additional software ularly for enterprise customers looking to securely con- to be run at each site to create the overlay network. In nect cloud resources to their existing infrastructure. EC2 our work, we leverage existing technology available from allows for the specification of either public or internal network providers such as Layer 2 and 3 VPNs to not (cloud only) network interfaces for each VM, although only create seamless connections between sites, but to the precise placement and IP details are determined by provide greater security, and resource control as well. the provider. EC2 also allows for Security Groups to be created which specify firewall rules for each VM. While 3 Challenges & Insights firewalls provide very fine grain access controls, a higher level of abstraction is useful when trying to cleanly link Cloud computing has seen widespread adoption for pub- different enterprise and cloud sites. Managing complex lic web services and infrequent batch-style

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