Depth of the Market(DOM):
Looking at a Level 1, Level 2 or Level 3 quotes can give a trader, a basic idea of how a stock is performing at any given time.Level 1 Market Data provides the basic market data which includes Bid price, Bid size, Ask price and Ask size.
Level 2 Market Data provides more information than Level I data. Mainly, it doesn't just show the highest bid and offer, but also shows bids and offers at other prices. Now level 2 provides market depth data upto 5 best bid and ask prices.
Level 3 Market Data provides market depth data upto 20 best bid and ask prices . This primarily used by brokers and market makers.
Is Level 3 Data available free? No! The annual subscription fee is about Rs.4,00,000/- each for Capital Market and Futures & Options segment.
Real time data and info-vending services of National Stock Exchange (NSE) are provided through DotEx International Limited (DotEx). It provides NSE's market quotes and data for Capital Market Segment (CM), Futures and Options Segment (F &O), and other segments. One can check the prices and details here: NSE Real-Time Data