Visibility is key for today’s Network Engineers and Managers. Visibility is a MUST when thinking about network security and compliance requirements and soon GDPR. I want to focus on the need for real visibility that only TAPs provide versus the totally misunderstood marketing ploy of SPAN!
SPAN generally stands for Switch Port for Analysis and was a great way to effortlessly and non-intrusively acquire data for analysis. By definition, a SPAN Port usually indicates the ability to copy traffic from any or all data ports to a single unused port but also usually disallows bidirectional traffic on that port to protect against backflow of traffic into the network.
SPAN is and was a market add-on for switches. It is a bus sharing technology where the output is at the mercy of the switch’s primary goal – getting packets to the correct IP addresses, and not to share those packets until the bus has time/bandwidth to do so. In the meantime packets (time relevance is loss) are held, groomed and/or dropped. That is why any visibility of data packets through a SPAN port results in out-of-time relevance, dropped frames and groomed information.
SPAN was not built for true visibility access and does not meet the criteria for compliance and security monitoring. Oh! I left out that switches can easily be hacked, thus even further reducing the value of SPAN for high level visibility.
That’s not to say SPAN is all bad, but one must be aware of its limitations. Since managed switches are an integral part of the infrastructure, one must be careful not to establish a fault or failure point. Understanding what can be monitored is important for success since SPAN ports are often overused leading to drop frames, all due to the fact that LAN switches are designed to groom data (change timing, add delay) and extract bad frames as well as ignore all layer 1 & 2 information.
When dealing with Data Security Compliance, the combination of the facts that SPAN ports limit views, are not secure and that they are transporting monitored traffic through the production network could prove itself to be unacceptable in a court of law.
When used within its limits and properly focused, SPAN is a valuable resource to managers and monitoring systems. However, for 100% guaranteed visibility of network traffic there is NO replacement for a passive Network TAP! The TAP is a necessity for meeting many of today’s visibility access requirement,s and as we approach larger deployments of 10 Gigabit, SPAN access limitations will become more of an issue and failure as a viable access point.
For today’s network security, compliance assurance, and efficiency measurements for Real Time flows like Voice and Video, packet brokers and deep capture technologies the ONLY true visibility access method is a TAP.
TAPs are the best method to feed the expensive equipment one needs to ensure your network’s viability, and collect evidence of security issues so that attacks, data leaks and network breaches can be quickly identified and resolved.
REAL DATA VISIBILITY can ONLY be achieved by TAPs!
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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.