The draft is in good shape. It is easy to read. There is one technical point I want to raise, but not sure if anything needs to change. There are a couple of minor grammatical issues.

In section 4 it says

   Within a Data Center, servers are commonly interconnected the CLOS
   topology [CLOS].  The CLOS topology is fully non-blocking and the
   topology is realized using Equal Cost Multi-Path (ECMP).  In a CLOS
   topology, the minimum number of parallel paths between two servers is
   determined by the width of a tier-1 stage as shown in the figure 1.

Regarding number of parallel paths, isn't the the width of tier-2 a factor as well?

I found two grammar issues. One is in this first sentence. A word or two need to be added to make it a complete sentence.

In section 5 it says:

   In order to simplify layer-3 routing and operations [RFC7938], many
   data centers use BGP as a routing protocol to create both an underlay
   and overlay network for their CLOS Topologies.

"an" should be added in the last sentence so that it says "both an underlay and an overlay".