Joe Onisick

Upcoming Events

Where the Cloud Touches Down: Simplifying Data Center Infrastructure Management

Thursday, July 25, 2013
10:00 AM PT/1:00 PM ET

In most data centers, DCIM rests on a shaky foundation of manual record keeping and scattered documentation. OpManager replaces data center documentation with a single repository for data, QRCodes for asset tracking, accurate 3D mapping of asset locations, and a configuration management database (CMDB). In this webcast, sponsored by ManageEngine, you will see how a real-world datacenter mapping stored in racktables gets imported into OpManager, which then provides a 3D visualization of where assets actually are. You'll also see how the QR Code generator helps you make the link between real assets and the monitoring world, and how the layered CMDB provides a single point of view for all your configuration data.

Register Now!

A Network Computing Webinar:
SDN First Steps

Thursday, August 8, 2013
11:00 AM PT / 2:00 PM ET

This webinar will help attendees understand the overall concept of SDN and its benefits, describe the different conceptual approaches to SDN, and examine the various technologies, both proprietary and open source, that are emerging. It will also help users decide whether SDN makes sense in their environment, and outline the first steps IT can take for testing SDN technologies.

Register Now!

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Why We Need Network Abstraction

The move to highly virtualized data centers and cloud models is straining the network. While traditional data center networks were not designed to support the dynamic nature of today's workloads, the fact is, the emergence of highly virtualized environments is merely exposing issues that have always existed within network constructs. VLANs, VRFs, subnets, routing, security, and so on have been stretched well beyond their original intent. The way these constructs are currently used limits scale, application expansion, contraction and mobility.

VLANs are a simple example. 802.1Q tagging supports a theoretical limit of 4,096 VLANs, with actual implementation typically being lower. This means that in a multitenant environment, your scale is limited to about 4,000 tenants--in theory. In reality, the number is much lower because we tie IP subnets to VLANs, and tenants will typically require more than one subnet.

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VRFs become another issue as tenants expand. Each tenant network is different and may require separate routing decisions, overlapping subnets, and so on. This leads to hardware limitations, as VRFs are typically run as separate instances of the routing protocol, requiring CPU resources.

Security is another example of unintended interdependency. Today's networks deploy security based on constructs such as addressing, location and VLAN. This has been necessary but is not ideal. The application or service dictates security requirements, so those requirements should be coupled there instead.

Layer 2 adjacency is another complex issue for modern networks. Many applications must exist in the same Layer 2 domain to support capabilities such as virtual machine motion, which causes a need for larger and larger L2 domains. This requires that the VLANs be configured on, and trunked to, any physical switches that a VM may end up on.

While each of these constructs has individual complexities, the real problem arises with the unintended dependencies. IP addressing is broken down into subnets traditionally tied to VLANs on a 1-to-1 basis. This means that an application's L3 communication is dictated by its broadcast domain needs and vice versa. Routing is then tied to the IP scheme, and security, load balancing and quality-of-service policy is often applied based on the VLAN or subnet. These are further tied to physical location based on device configuration (including VLAN, VRF and QoS settings).

There is a need for abstraction of these constructs to provide the originally intended independence that will allow networks to scale as required. This need is shown in current standards pushes: LISP, SDN and VXLAN, for example, are all aimed in some way at removing the tie of location and allowing the application to dictate requirements rather than the infrastructure dictating it.

Within the data center, overlays such as VXLAN are one possible solution. Overlay technologies allow for independent logical networks to be built on top of existing IP infrastructure. They provide some of the abstraction tools required, such as allowing L2 adjacency across L3 networks. Additionally, overlays greatly increase the scale of constructs such as VLANs, moving from 4,000-plus logical networks well into the millions.

These overlays provide one piece of the puzzle of network abstraction. The next step is policy configuration. Rather than traditional methods of applying policy such as security, load balancing and QoS to underlying constructs, these policies should be applied to the applications themselves. Systems like OpenFlow are moving toward this through flow-level programmability, but still have a way to go.

The end goal of the modern network will be service-driven policies and controls. By removing the interdependencies that have been built into today's networks, we will gain the flexibility required by modern compute needs. The purpose of the data center is service delivery, and all aspects must be designed to accomplish that goal.

Disclaimer: This post is not intended as an endorsement for any vendors, services or products.

Joe Onisick is the Founder of Define the Cloud. You can follow his angry rants at or on Twitter @jonisick.

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