Network Design Process

I had an interesting e-mail discussion with a man from Germany this week (let's call him Hans). Hans has very good technical experience working at a German service provider. He has a lot of hands-on experience troubleshooting and supporting networks. However, he's in a new job now as a pre-sales design engineer focused on small to medium enterprises. So, not only are the networks different, so is the role. His question was how to get network design training. Not specifically about OSPF or LAN switching design, but general training and guidelines for network design. I though this was an interesting question. Most Cisco training is technology focused - how to design BGP or QoS, but very little about the network design process. Cisco has developed the PDIOO (Plan, Design, Implementation, Operations, and Optimize) approach.

While this is more of a framework than specific processes for network design, it is a good place to start. I am sure people could write an entire book on Network Design, but, since this is only a blog, I will try to provide a bullet list of tasks in the "Planning" and "Design" phases using the guidelines of Top-Down Network Design. Sort of a tip list for these phases of the framework. Planning

  • Research your client - before you even meet your new client research their company. Their website and, if public, the company's SEC filings are great sources of information.
  • Develop requirements - "develop" is the key here. Customers will often (1) not know what they really want or (2) not be able to articulate it. You will need to discuss requirements several times with key stakeholders, ask detailed questions, provided what-if scenarios and listen intently to everything the customer says. Defining specific requirements can be very tricky and take a while, but in the end, it's worth it.
  • Build Relationships with Decision Makers - your success will ultimately be determined by the people you are working for. No amount of network statistics or graphs will make up for strong relationships with your customer.
  • Remember Politics - beyond building relationships, all organizations made up of people have some sort of politics. Even though it usually has a bad connotation, politics are not a bad thing; they are just how people communicate. Learning the politics of your customer's organization will make you more successful.
  • Define what is the overall driver for the project - even though the project may have a list of requirements, there will be one thing that drives the project. These can be summarized as one of three - "Cost", "Schedule" or "Performance". Does the customer need to reduce or minimize costs? Does the customer need to get it installed by a certain date? Does the customer need the best damn network money can buy? One of these will be the driver of the entire project.
  • Set the Scope of the Design - a customer asking for a DC LAN design should not have a requirement to determine best ISP BGP peering.
  • Set General Timelines - nothing exact or to a project plan level, but some general timelines so the customer can understand the impact to their business.
  • Remember Applications and Users - investigate traffic flows and user populations. The network will exist for users and their applications, so you need to understand these two groups. You wouldn't build a passenger plane without considering the people who will ride in it. Networks, outside of a lab, exist to support people using applications.
  • Understand the Current Network - most likely this project will replace an existing network, or, at least, will connect to an existing network. Get a good understanding of the current environment and how your new network will be a part of it.
  • Document everything - documentation provides two key things. First, you will not remember everything, so write everything down. Second, customers feel much more comfortable when everything is documented. It shows a level of professionalism and accountability and gives them the ability to gauge the projects status without having to rely on your memory.

I'll cover the Design phase next week. Feel free to add any to this list.

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