deletions | additions       diff --git a/OpenFlow Switch.tex b/OpenFlow Switch.tex  index 0567e11..7dcc399 100644  --- a/OpenFlow Switch.tex  +++ b/OpenFlow Switch.tex 
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In the case of TCAM it adds and additional state, called a mask, that's stored. Masks are a core component of how networking works. For example, calculating forwarding addresses based on an input requires quick lookups. These lookups are essentially the flow-tables.  This specialized memory is very costly and the computer architecture is very specialized and used by network vendors as a differentiator. This leads to proprietary solutions and custom protocols that are used to update these flow-tables. To reduce cost some vendors choice to implement their architecture using RAM and x86. In these cases the vendors implement advanced software based search algorithms. This later point of using x86 in combination with OpenFlow, leads to more commodity based hardware, of which Facebook's modular switch switch\cite{facebook2015switch}  is a great example.CAMs are very expensive, so they aren't normally found in PCs. Even router vendors will sometimes skimp, opting to instead implement advanced software-based searching algorithms. Most commonly CAMs and TCAMs are found in network processing devices, including Intel IXP cards and various routers or switches.  The OpenFlow protocol defines the specific messages and message formats exchanged between controller (control plane) and device (data plane). The OpenFlow behavior specifies how the device should react in various situations and how it should respond to commands from the controller"  An OpenFlow Switch consists of one or more flow tables and a group table, which perform packet lookups and forwarding, and an OpenFlow channel to an external controller (Figure 1). The controller manages the switch via the OpenFlow protocol. Using this protocol, the controller can add, update, and delete flow entries, both reactively (in response to packets) and proactively.  While OpenFlow is only one of the technologies included under the big tent of SDN, it is the technology most closely associated with what we define as Open SDN. An important tool and catalyst for innovation,