Another sign for the establishment and growth of the diameter routing market - one of the leading players, Traffix Systems (background - here), completed a $7M funding, led by Bessemer Venture Partners.
The CEO, Ben Volkow (pictured), told me that the market is booming - he expects a market size of $100M for 2011. (see also "[Exact Ventures]: Diameter Router Market "will double each year through 2016" - here)
While diameter routing maybe seen as an infrastructure tool, needed in order to support other gear, sometimes customers are spending more on it compared to the products it serves. Ben mentioned a recent case in Europe in which their solution was more expensive than the PCRF systems it supports.
See also a report by WJB Capital Group - "Diameter Opportunity Looks to Continue to Expand" - here.