Cloud Networking Brings Unique Challenges

As more businesses explore the benefits of cloud computing, network managers will have to increasingly meet the challenges of redesigning their networks to compensate for the unique needs of the cloud.

That’s the conclusion drawn from The 2011 Cloud Networking Report, a summary white paper from Ashton Metzler and Associates and Interop that details the three primary challenges facing cloud networking: data center LAN architecture, wide area networking, and network management complexity.

The data center LAN offers a particularly interesting challenge, according to the white paper’s author, Dr. Jim Metzler. To this point, LANs within data centers have compensated for the complexity of virtualization by adding multiple layers of control to network management schemes. This was done because each virtualized server contained its own virtualized switch (which Metzler refers to as a “vSwitch”). With potentially thousands of vSwitches in place, the additional layers of management–additional tiers–were added to data center networks.

Metzler argues that the opposite approach is needed, because cloud architectures are different from data centers. True cloud systems depend on automation for cloud management, and thus more server-to-server communication is required. With that kind of communication going on, Metzler reasons in the paper, less layers are needed, not more.

“One approach for improving server-to-server communications is to flatten the data center LAN from the current norm that is either a three or four tier design, to a two tier LAN design consisting of access layer and aggregation/core layer switches,” Metzler writes.

Of course, while flattening the layers in the LAN design will help, it still doesn’t directly solve the problem of what to do with all of those vSwitches floating around. Here, Metzler offers another approach: edge virtual bridging (EVB).

“With EVB, all the traffic from VMs is sent to the network access switch. If the traffic is destined for a VM on the same physical server, the access switch returns the packets to the server over the same port on which it was received; e.g., a ‘hair pin turn,'” Metzler explains. EVB is an IEEE standard that uses Virtual Ethernet Port Aggregators (VEPA) to handle this 180-degree redirection of network traffic, which gives network access switches access and control over an virtual machine traffic.

There are other approaches that can be used to manage the problem of vSwitches, of course. Distributed virtual switching, for instance, separates the control and data aspects of a vSwitch, enables third-party control software to manage the data flows of several vSwitches at the same time.

Whichever approach is used, data center LANs are a big area of improvement for cloud systems. High availability requirements will require the implementation of redundant systems, as well as improvements in Ethernet technology itself, like using a common high-speed Ethernet switching fabric to handle both storage and data traffic.

“This unified fabric offers significant cost savings in multiple areas including converged network adapters on servers and reductions in rack space, power and cooling capacity, cabling, and network management overhead,” Metzler writes. “Traditional Ethernet, however, only provides a best effort service. In order to emulate the lossless behavior of a Fibre Channel SAN, Ethernet must be enhanced in such as way that it exhibits lossless behavior.”

WAN technology needs to be renovated

WAN technology, another area that needs renovating for the cloud, hasn’t seen significant innovations for quite some time, something that Metzler argues needs to change. One potential improvement is the implementation of policy-based routers, which route traffic based on administrator-dictated policies, rather than IP addresses. This increases throughput and decreases latency, but there’s a catch: if something in the network isn’t working correctly, policy-directed packets won’t reroute automatically as “regular” IP packets can.

Here, Metzler highlights the growing use of dynamic hybrid WANs that will switch traffic intelligently based on policy and traffic need. Such dynamic WANs represent virtualized WANs, and like virtual machines, virtual WANs can be managed and budgeted on a utility-like basis.

Network management is the final area that Metzler describes as needing enhancement for cloud deployments to really work well. Increased virtualization of machines brings out all of the old problems with VM management: VM sprawl, incompatibility with network management tools, multiple hypervisors, and more.

Cloud brings a whole new cadre of issues to the table for network management. One of the biggest challenges is dealing with systems that are managed at a higher level, instead of where they normally get managed.

“Historically IT organizations focused their management efforts on individual technology domains; e.g., LAN, WAN, servers, firewalls. While that is still the most common approach to management, in the current environment a significant and growing percentage of IT organizations focus their management activities on the performance of applications and/or services,” Metzler explains.

With management focusing on the application level so much, it is predictable that network managers will increasingly need to operate with tools that are dealing with the same level. But with network topologies becoming more and more complex, managing said applications’ performance will be “an order of magnitude more difficult.” The white paper offers route analytics as one solution to getting this topology under control.

The complexity of cloud network management is certainly daunting, after reading the issues highlighted in this white paper. The positive news is that there seems to be solutions available for many of the challenges for cloud computing.

It’s also clear that the networking side will need to marshal its efforts to stay caught up with the exploding deployment rate of cloud computing.

Brian Proffitt is a technology expert who writes for a number of publications. Formerly the Community Manager for and the Linux Foundation, he is the author of 20 consumer technology books, including the most recent Take Your iPad to Work. Follow him on Twitter at @TheTechScribe.

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