Preparing for network virtualization

Network virtualization may demand LAN upgrades and configuration changes to achieve optimal performance.

Virtualization is expanding beyond individual servers and is moving into the network that connects an organization’s servers and storage. But the path to network virtualization isn’t always quick or easy, and IT often needs to implement changes to the physical network infrastructure to make the most out of network virtualization. This tip explores the role of network virtualization and outlines the most important upgrade strategies to consider as organizations move to 10 Gigabit LANs and beyond.

Network virtualization: Inside and out
Network virtualization is not a single component or software product. It is actually a combination of hardware and software elements that facilitate a level of abstraction that separates the network’s underlying physical hardware from the logical network entities on top of it.

There are several compelling reasons to consider network virtualization. Based on a 2011 virtualization survey conducted by TechTarget, 34% of respondents see the virtual networks as part of a larger virtualization architecture within the data center, 32% embrace the technology as a means of expanding the virtual environment and 26% believe that the technology enables better management.

And adoption of the technology is on the upswing. Based on 2011 virtualization survey data, 45% of professional IT respondents indicated that they currently use some form of network virtualization, while 60% of respondents that did not currently use the technology say that they plan to adopt it within the next 12 months.

The abstraction needed for network virtualization can be implemented in two principal ways: external or internal virtualization.

External virtualization uses virtual local area network (VLAN) software and VLAN-enabled switches to segregate a single physical LAN into multiple logical LANs, or join multiple physical LANs (even at different geographic locations) into a single logical LAN. In most cases, external network virtualization helps to control network traffic and enhance security. For example, a VLAN can be created to isolate traffic intended for accounting department users or to carry Voice over Internet Protocol or iSCSI traffic.

Internal virtualization creates virtual networks between virtual machines (VMs) on specific physical host servers. By using virtualization software to create a virtual switch within the server, VMs can exchange data directly between memory locations without ever passing traffic to the physical network. This speeds data exchange between the server’s VMs (potentially improving apparent network performance of the VMs) while reducing the bandwidth demands on the external network itself.

Both methods can be deployed together, and both help the organization shape and tailor the network to meet the organization’s unique needs.

Network planning and upgrades
A network virtualization deployment should start with a careful review of business goals before technical issues, including performance expectations. With that information in hand, IT professionals can take a much closer look at the existing network architecture and the physical components within it, such as switches and their native VLAN support, each server’s network interface card (NIC) or host bus adapter (HBA) and the virtualization software available at each server. Don’t ignore the presence of related networking systems like firewalls and load balancers.

When network administrators weigh network virtualization requirements against the available LAN infrastructure, it is possible to identify upgrade opportunities necessary to support the technology or improve performance. “Setting up network virtualization could require a complete overhaul of switches, internetworking equipment, servers, etc.,” said Rand Morimoto, president of Convergent Computing, an IT consulting company based in Oakland, Calif. “As long as it's what drives the organization closer to what they need to fulfill business needs and requirements, it's a good upgrade. If not, it's just a lot of expensive hardware and services.”

Morimoto is correct. Based on 2011 virtualization survey data, 48% of respondents have had to upgrade their physical network to support their virtual infrastructure. Table 1 shows that switch, NIC, HBA and router upgrades have been the most vital for virtual network support. But upgrades can involve every part of the network. Of the respondents that had not yet upgraded, 40% reported network upgrade plans for 2012 (also in Table 1).

Table 1–Infrastructure components upgraded to support virtual infrastructure


Upgrades in 2011

Upgrades for 2012

Network switches



Server network interface cards (NICs)



Network routers



Server host bus adapters (HBAs)             



Network cabling



Network gateways



Network appliances



Network virtualization does not solve poor architectural designs, and extreme care is needed when planning to upgrade network components or deploy network virtualization. For example, organizations that do not correctly identify the performance requirements and capabilities of their network equipment may be unable to meet their virtual network objectives.

“IT engineers begin to scramble when they forget the networking component of a virtualization project and suddenly see extreme latency,” said Bill Kleyman, virtualization architect at MTM Technologies Inc., an IT solutions provider based in Stamford, Conn. “Virtual desktops can consume a lot of I/O and networking bandwidth. Having a dedicated switching environment for the virtualization project will help alleviate issues around network speeds.”

Network virtualization planning
Network virtualization doesn’t end with an initial deployment. Administrators must consider the effects of future upgrades. The transition to fast physical networks, like 10 Gigabit, and faster infrastructures, such as 40 Gigabit and 100 Gigabit Ethernet, should readily support network virtualization, but administrators must evaluate the network virtualization to be sure that the software layer is able to accommodate the strain of significantly faster traffic speeds. “Make sure that network virtualization can handle the speeds being thrown at it,” said Dave Sobel, CEO of Evolve Technologies, an IT services company based in Fairfax, Va.

Sobel underscores the importance of preparation, planning and proof-of-concept testing prior to any network virtualization deployment or physical network upgrades. An intimate knowledge of data center applications and their network needs will also impact the effectiveness of network virtualization. “Your applications will drive the way that Ethernet is used,” he said.

And don’t overlook the role of network monitoring and capacity planning. While faster networking equipment provides faster traffic performance, uncontrolled VLAN creation can quickly strain the additional bandwidth–much the same way that uncontrolled VM sprawl can cause unexpected shortages of computing resources.

Just saying ‘no’ to network virtualization
Network virtualization can help an organization achieve security, site-to-site connectivity and geographically extended LAN capabilities that may be impossible to implement otherwise. But in spite of the potential benefits, some organizations choose to forego network virtualization or utilize alternative solutions.

TechTarget’s 2011 virtualization survey data identified a variety of specific concerns. Of the IT professionals that opted to avoid network virtualization, more than 32% reported a lack of in-house expertise, and another 30% cited budget limitations–both easily understood problems in today’s tight economy. Additional respondents noted other factors, such as a lack of suitable virtualization-aware network tools, making management more problematic. Others faced limited network bandwidth to begin with, which would limit the number of useful virtual networks or their overall performance on the current physical LAN.

Data security is often cited as a benefit of network virtualization, but Sobel points out that network virtualization presents another attack surface that hackers can potentially exploit. Consequently, there is added emphasis on proper configuration and patching to deny hackers access to the network virtualization layer. Only about 8% of survey respondents that opted to avoid network virtualization noted security as a reason, but security remains a serious concern in the IT industry.

The message is to match the business problem to the best technical solution. “Just because VLANs exist, doesn't mean you need to use them. If there is a way, architect or design something that is more appropriate, more relevant or more efficient in achieving the end result,” Morimoto said.

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