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[SlideShare] TAP Toons: The Student has Become the Network Master - Part 2

October 11, 2016

Everyone has been there, new on the job, trying to get your foot in the door, among more experienced co-workers. 

Network Engineer’s are always learning and evolving, with technology changing at warp speed, the saying of "old dogs can't learn new tricks" does not apply to this crew.

In TAP Toons: The Student has Become the Network Master - Part 1, we followed our two engineers in a common scenario, using TAP vs SPAN. In response to quality complaints, our engineers realize, finding the solution is sometimes easier when you take a step back and see every bit, byte and packet®.

Now, in TAP Toons: The Student has Become the Network Master - Part 2, we find where our engineer's left off, was the data good enough in the court of law? 


Make sure you caught TAP Toons: Adventured in Network Engineering - Network vs Security, How to end the finger pointing.

 

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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.

NETWORK MANAGEMENT | THE 101 SERIES