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Network Monitoring 101: Are SDN & Monitoring Tools The Same?

February 4, 2015

When it comes to protecting and monitoring your network, there are several different ways to approach these critical tasks. In recent years, SDN and network virtualization have redefined the way in which some network engineers address these needs.

Relatively unproven and still largely misunderstood, has SDN replaced costly monitoring tools? Are they one in the same? 

Are SDN And Monitoring Tools The Same?

Software-defined networking can be used to replicate the functions of switches and load balancers, but it does not replace the functions and benefits of monitoring tools themselves.

SDN separates the control and forwarding planes to virtualize the function of forwarding network traffic from one part of your network to another. Using programmable policies, software dictates how and where your traffic flows.

It does not replace your monitoring tools; it changes the way in which you pass information from your physical network to these applications.

So, what's the benefit of using a software-defined network for packet forwarding?

SPAN and monitor ports have severe limitations. The risk of oversubscription and dropped packets has steered engineers toward network TAPs and packet monitoring switches instead, for their obvious benefits. The potential downside to these solutions is the relative cost. Many companies choose to seek more inexpensive alternatives, though often at the price of their network security, visibility, and data collection.

On the other hand, with an SDN controller and low-cost, bare-metal switches, you’re able to create a simple and dynamic packet monitoring system to analyze the traffic on your network.

The issue is whether or not this method is truly ready to functionally replace a system of pre-programmed switches from companies such as Cisco.

 

Learn more about SDN and NFV!

The Modern Limitations Of SDN

According to Lee Doyle of Doyle Research, via SearchSDN, “We often hear that SDN and network virtualization will optimize network performance and bring advanced capabilities to network management. That will be true in the long term, but first we must get through the early stages of these technologies, when the shift in network architecture could make monitoring and visibility even more challenging.”

The complications mostly revolve around the increasing network speeds. Data centers are migrating to 10 GbE environments, and with information traveling faster and faster, your network must be able to handle a greater load. In many cases, network TAPs and FABs (filtering aggregating load balancers) are used to dissect packet information and mitigate the risk of oversubscription. The added demand of monitoring both physical and virtual environments creates another layer of complication.

The need for complete network visibility is essential, and that may prove to be more difficult today. SDN might be more affordable if you’re designing an entirely new network. But, if you’ve already implemented a system of performance monitoring tools and switches, you have to undergo a complete overhaul of your network. And even when you do configure SDN, you must still ensure that you have a visibility plane into all of the data you need. Without it, no method is positioned to help you protect and monitor your network.

 

If you want to learn more about the promises of SDN, NFV and the importance of maintaining 100% network visibility as you make the transition, download our free white paperArchitecting Data Centers for SDN and NFV - In 40G and 100G Environments

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Contact us now to secure and optimized your network operations

Heartbeats Packets Inside the Bypass TAP

If the inline security tool goes off-line, the TAP will bypass the tool and automatically keep the link flowing. The Bypass TAP does this by sending heartbeat packets to the inline security tool. As long as the inline security tool is on-line, the heartbeat packets will be returned to the TAP, and the link traffic will continue to flow through the inline security tool.

If the heartbeat packets are not returned to the TAP (indicating that the inline security tool has gone off-line), the TAP will automatically 'bypass' the inline security tool and keep the link traffic flowing. The TAP also removes the heartbeat packets before sending the network traffic back onto the critical link.

While the TAP is in bypass mode, it continues to send heartbeat packets out to the inline security tool so that once the tool is back on-line, it will begin returning the heartbeat packets back to the TAP indicating that the tool is ready to go back to work. The TAP will then direct the network traffic back through the inline security tool along with the heartbeat packets placing the tool back inline.

Some of you may have noticed a flaw in the logic behind this solution!  You say, “What if the TAP should fail because it is also in-line? Then the link will also fail!” The TAP would now be considered a point of failure. That is a good catch – but in our blog on Bypass vs. Failsafe, I explained that if a TAP were to fail or lose power, it must provide failsafe protection to the link it is attached to. So our network TAP will go into Failsafe mode keeping the link flowing.

Glossary

  1. Single point of failure: a risk to an IT network if one part of the system brings down a larger part of the entire system.

  2. Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.

  3. Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.

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