Sensors are cheap and lesser power devices. Their resources are confined within limits. They are meager in size and have wireless communication capacity within small distances. A sensor node contains a power unit, a sensing part, a processing part, a storage section and a wireless transmitter or a receiver. Wireless sensor networks usually contains a huge number of sensors with low computation capacity, storage space and communication capability. WSN are used for many purposes such as to keep track of environment, safety in airports, health care etc. Two challenging issues in WSN are scalability and path establishment.