Understanding and maintain control of your network is a constant, uphill battle. With the increase in network virtualization, BYOD, and growing number of security threats, network monitoring is more important than ever. It’s well documented that the foundation of any good visibility fabric comes from using network Test Access Points (TAPs), but then where does all that TAP’d traffic go? The answer should be, to a Network Packet Broker.
This is the first blog in a three-part series highlighting the Network Packet Broker
Blog 1: What is a Network Packet Broker?
Blog 2: Understanding NPB advanced features
Blog 3: Selecting the right NPB for your network
Network Packet Broker’s (NPBs) are devices that do just what the name suggests, they “broker” incoming network traffic to any number of security, application performance monitoring, or network forensic tools.The need to “broker” packets before they’re sent to tools comes from 2 major driving forces. First, the throughput of tools is limited, second, every tool requires a different subset of traffic to maximize performance.
NPBs are designed to deliver only the traffic of interest required by any specific tool. NPBs achieve this by using a variety of filtering options that will be explained in detail in the next blog in this series. NPBs act as the man-in-the-middle between TAP/SPAN ports and the tool itself and should be designed with 4 different deployment scenarios in mind:
In this application the most important function of the NPB is its filtering capability. Most tools currently deployed handle up to 10Gbps of traffic at any given time. If the incoming TAP traffic is 40Gbps, the traffic needs to be filtered by a factor of 4. The NPB needs to ensure the traffic is filtered adequately to meet this limitation while providing every packet the tool needs to do its job.
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This application builds on the previous, but now the NPB needs to support aggregation. Aggregation allows the user to setup single filters that will be applied to all incoming traffic streams, reducing the setup time/complexity of the device. Aggregation also ensures the tool receives traffic from multiple streams.
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This application builds on the first, however, the NPB now needs to be able to replicate and/or load balance traffic. The traffic needs to be replicated/mirrored/copied to ensure each tool has access to any necessary packets. To properly handle this application, the NPB must also support egress filtering, to allow unique filters criteria for each different tool. If multiple tools require the same filtered traffic, the NPB must also support load balancing and options on how to load balance. Well designed NPB’s should support configurable hash-based load balancing, round-robin and weighted round-robin options.
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The final application builds on the previous three and uses filtering, aggregation and load balancing to guarantee each tool operates at its maximum efficiency.
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If TAPs are the foundation, NPBs are the load bearing structural element of a well-designed visibility fabric. They offer many advanced features to ensure each tool operates to its full potential, by individually tailoring each egress stream to meet the needs of any tool. Subsequent blogs in this series will dive into much greater detail on these advanced features and how to select the right NPB for your network.
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.
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.
Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.
Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.