Allan Leinwand from GigaOm wrote a great article asking “Where are the network virtual appliances?” This was followed up by another excellent post by Rich Miller.
Allan sets up the discussion describing how we’ve typically plumbed disparate physical appliances into our network infrastructure to provide discrete network and security capabilities such as load balancers, VPNs, SSL termination, firewalls, etc. He then goes on to describe the stunted evolution of virtual appliances:
To be sure, some networking devices and appliances are now available in virtual form. Switches and routers have begun to move toward virtualization with VMware’s vSwitch, Cisco’s Nexus 1000v, the open source Open vSwitch and routers and firewalls running in various VMs from the company I helped found, Vyatta. For load balancers, Citrix has released a version of its Netscaler VPX software that runs on top of its virtual machine, XenServer; and Zeus Systems has an application traffic controller that can be deployed as a virtual appliance on Amazon EC2, Joyent and other public clouds.
Ultimately I think it prudent for discussion’s sake to separate routing, switching and load balancing (connectivity) from functions such as DLP, firewalls, and IDS/IPS (security) as lumping them together actually abstracts the problem which is that the latter is completely dependent upon the capabilities and functionality of the former. This is what Allan almost gets to when describing his lament with the virtual appliance ecosystem today:
Yet the fundamental problem remains: Most networking appliances are still stuck in physical hardware — hardware that may or may not be deployed where the applications need them, which means those applications and their associated VMs can be left with major gaps in their infrastructure needs. Without a full-featured and stateful firewall to protect an application, it’s susceptible to various Internet attacks. A missing load balancer that operates at layers three through seven leaves a gap in the need to distribute load between multiple application servers. Meanwhile, the lack of an SSL accelerator to offload processing may lead to performance issues and without an IDS device present, malicious activities may occur. Without some (or all) of these networking appliances available in a virtual environment, a VM may find itself constrained, unable to take full advantage of the possible economic benefits.
I’ve written about this many, many times. In fact almost three years ago I created a presentation called “The Four Horsemen of the Virtualization Security Apocalypse” which described in excruciating detail how network virtual appliances were a big ball of fail and would be for some time. I further suggested that much of the “best-of-breed” products would ultimately become “good enough” features in virtualization vendor’s hypervisor platforms.
Why? Because there are some very real problems with virtualization (and Cloud) as it relates to connectivity and security:
- Most of the virtual network appliances, especially those “ported” from the versions that usually run on dedicated physical hardware (COTS or proprietary) do not provide feature, performance, scale or high-availability parity; most are hobbled or require per-platform customization or re-engineering in order to function.
- The resilience and high availability options from today’s off-the-shelf virtual connectivity does not pair well with the mobility and dynamism of de-coupled virtual machines; VMs are ultimately temporal and networks don’t like topological instability due to key components moving or disappearing
- The performance and scale of virtual appliances still suffer when competing for I/O and resources on the same physical hosts as the guests they attempt to protect
- Virtual connectivity is a generally a function of the VMM (or a loadable module/domain therein.) The architecture of the VMM has dramatic impact upon the architecture of the software designed to provide the connectivity and vice versa.
- Security solutions are incredibly topology sensitive. Given the scenario in #1 when a VM moves or is distributed across the pooled infrastructure, unless the security capabilities are already present on the physical host or the connectivity and security layers share a control plane (or at least can exchange telemetry,) things will simply break
- Many virtualization (and especially cloud) platforms do not support protocols or topologies that many connectivity and security virtual appliances require to function (such as multicast for load balancing)
- It’s very difficult to mimic the in-line path requirements in virtual networking environments that would otherwise force traffic passing through the connectivity layers (layers 2 through 7) up through various policy-driven security layers (virtual appliances)
- There is no common methodology to express what security requirements the connectivity fabrics should ensure are available prior to allowing a VM to spool up let alone move
- Virtualization vendors who provide solutions for the enterprise have rich networking capabilities natively as well as with third party connectivity partners, including VM and VMM introspection capabilities. As I wrote about here, mass-market Cloud providers such as Amazon Web Services or Rackspace Cloud have severely crippled networking.
- Virtualization and cloud vendors generally force many security vs. performance tradeoffs when implementing introspection capabilities in their platforms: third party code running in the kernel, scheduler prioritization issues, I/O limitations, etc.
- Much of the basic networking capabilities are being pushed lower into silicon (into the CPUs themselves) which makes virtual appliances even further removed from the guts that enable them
- Physical appliances (in the enterprise) exist en-mass. Many of them provide highly scalable solutions to the specific functions that Alan refers to. The need exists, given the limitations I describe above, to provide for integration/interaction between them, the VMM and any virtual appliances in order to offload certain functions as well as provide coverage between the physical and the logical.
What does this mean? It means that ultimately to ensure their own survival, virtualization and cloud providers will depend less upon virtual appliances and add more of the basic connectivity AND security capabilities into the VMMs themselves as its the only way to guarantee performance, scalability, resilience and satisfy the security requirements of customers. There will be new generations of protocols, APIs and control planes that will emerge to provide for this capability, but this will drive the same old integration battles we’re supposed to be absolved from with virtualization and Cloud.
Connectivity and security vendors will offer virtual replicas of their physical appliances in order to gain a foothold in virtualized/cloud environments in order to intercept traffic (think basic traps/ACL’s) and then interact with higher-performing physical appliance security service overlays or embedded line cards in service chassis. This is especially true in enterprises but poses many challenges in software-only, mass-market cloud environments where what you’ll continue to get is simply basic connectivity and security with limited networking functionality. This implies more and more security will be pushed into the guest and application logic layers to deal with this disconnect.
This is exactly where we are today with Cloud providers like Amazon Web Services: basic ingress-only filtering with a very simplistic, limited and abstracted set of both connectivity and security capability. See “Dear Public Cloud Providers: Please Make Your Networking Capabilities Suck Less. Kthxbye” Will they add more functionality? Perhaps. The question is whether they can afford to in order to limit the impact that connecitivity and security variability/instability can bring to an environment.
That said, it’s certainly achievable, if you are willing and able to do so, to construct a completely software-based networking environment, but these environments require a complete approach and stack re-write with an operational expertise that will be hard to support for those who have spent the last 20 years working in a different paradigm and that’s a huge piece of this problem.
The connectivity layer — however integrated into the virtualized and cloud environments they seem — continues to limit how and what the security layers can do and will for some time, thus limiting the uptake of virtual network and security appliances.