Airbnb -- the platform that lets travellers book private spare rooms and entire homes as an alternative to traditional hotels -- is doing some booking of its own. Airbnb is in the process of raising another round of funding that will value it at $20 billion, according to sources familiar with the situation. The company is believed to be in the process of raising a war chest of close to $1 billion -- with about half of that secured. We've heard that Airbnb has been courted by investors out of Asia, as well as larger private-equity groups. We've not been able to confirm the exact names yet, but one that has come up is Fidelity. Previous investors in the company include TPG, T. Rowe Price, Dragoneer, Founders Fund, Sequoia, DST and more. Airbnb, founded in 2008 and based in San Francisco, has been on a growth tear in the last several years. It's one of the leading players in the rise of sharing economy startups, built on the idea of everyday consumers leveraging their own resources -- in this case, rooms in their homes, or the whole home itself -- in a wider marketplace. That marketplace is powered by Airbnb's tech, which makes it very fast and easy for hosts to list, and visitors to find, book and pay for a room or home. Airbnb is currently active in 34,000 cities in 190 countries. It has over 1 million listings on its platform and has racked up 30 million nights booked. Airbnb has lately been taking its expansion into a higher gear: a deal cut last year with Concur is evidence of how it is tapping into the corporate travel market; and it also announced a partnership with Deutsche Telekom earlier this week. The corporate market will potentially mean much higher margins, while the carrier deals will be one more play for gaining more critical mass, particularly among mobile users: it will be the first time that Airbnb has worked with a carrier to preload its app on millions of Android devices. But its growth has not been without hiccups. Like Uber, Airbnb has faced a lot of backlash from the business that it's disrupting -- in Airbnb's case, the hotel industry. Regulators have raised questions about the legality of private individuals renting out rooms, and the question of whether these are getting taxed adequately. Some of these, such as in its home town of SF, have been settled, while others, such as the ongoing case in New York, continue to simmer. The company has also seen a fair amount of controversy and concern over property damaged during Airbnb stays. Here, too, it's trying to address the problems: In November the company rolled out a $1 million liability insurance program for hosts. To date, Airbnb has disclosed raising close to $800 million, but as with fellow sharing-economy juggernaut Uber, the company's rapid growth is leading to a lot of investors knocking on Airbnb's door. In April 2014, the company raised $450 million at a $10 billion valuation led by TPG. In October, the company did a secondary round of $50 million at a $13 billion valuation (this was reported by the WSJ at the time; and we can confirm that was correct).