Did you hear about the scorpion who asked the frog for a ride across the river? Of course, the frog denied his request at first saying, “If I let you on my back, you will bite me and I will die.” The scorpion replied, “I promise I will not bite you if you would please give me a ride.” The frog relented and the scorpion hopped on. In the middle of the river, the scorpion bit the frog. The frog cried out, “Why did you do that? Now we both will die.” The scorpion replied, “I am a scorpion, that is what I do.”
Certain events are predestined to happen regardless of whether we plan for them or not. Networks grow, it is what they do. So, it is better to plan ahead for eventual growth than to be caught off guard.
In early planning sessions for new networks, conversations center around real estate, hub locations, network topology, cloud usage assessment, switches, routers, and tools for monitoring and security. Often neglected in the initial design plan is visibility connectivity. That is how to best connect and utilize specialized tools for monitoring and security.
Network tools can be connected to links in a few different ways such as direct connection, SPAN ports, and Network TAPs. Here are the differences and potential issues with each:
Direct Connect - Connecting tools directly on links carries the risk of losing live traffic if the unit goes offline. Maintenance becomes difficult because you need to take the link down to perform updates on each tool. It is expensive. Putting all the specialized tools needed to support every link can quickly break the budget. Directly connecting multiple tools in series on a link can reduce overall network reliability and availability.
SPAN Ports - Switched Port Network Access (SPAN) ports are readily available on switches. However, they are not designed for use with many types of tools. There is limited access to usually two ports per switch. Increased power consumption and doubling of internal switch traffic can be troublesome to switch management and to the budget. The accuracy of mirrored data is an issue due to randomly dropped packets during busy hours. SPAN ports also do not pass errors, runts, and dropped packets which can cause accuracy issues when using data for diagnostics or network planning.
Network TAPs - Using TAPs as an independent connection for visibility tools has many advantages. TAPs can aggregate traffic on underutilized links allowing multiple links to be connected to a single tap. This can be a big cost-saving feature in large networks. TAPs can connect to copper or fiber optic links. Optical taps require no power and very little rack space. This can reduce the overall cost of deploying tools. TAPs provide fail-safe connections keeping live network traffic flowing during times of maintenance, power, or other issues that may require tools to go offline. TAPs can regenerate data and send it to multiple tools which can be a big cost saver when designing visibility tools into your network.
Choosing the right fools and the best method for connecting tools is an important piece of the network design process. It is also critical to plan for the inevitable growth of the network while developing the original plan. However, growing existing networks also requires a coordinated plan for visibility to prevent a slow march to an unmanageable situation.
As discussed in the introduction, networks grow. Any network design plan should include a path for network growth. A visibility strategy should be part of that growth plan. When networks grow in a piecemeal fashion, it is tempting to just add a link here or there as the momentary demand requires. However, growth without a plan can become expensive and create a management nightmare.