Emergence of wireless embedded applications is resulting in the communication among sensor nodes connected in a wireless personal area network. Sensor nodes gather the real time information and transmit it to the desired application. This requires transmission of IPv6 packets over Low-power wireless personal area network and is called 6LoWPAN. IPv6 is resource intensive protocol whereas 6LoWPAN is resource constraint due to small packet size, limited device memory, short transmission range, and less data rate of sensor nodes. Also these nodes in 6LoWPAN are mainly battery operated hence minimum power consumption is also a major constraint.
To make the efficient transmission of information in such a resource constraint network, an adaptation layer was suggested and implemented by Internet Engineering Task Force (IETF). The placing of this additional layer is in between network layer and data link layer of TCP/IP protocol stack. This paper contributes in the detailed analysis of need of adaptation layer in 6LoWPAN protocol stack. The necessity of this additional layer is justified by explaining the major functions like header compression, fragmentation and reassembly of packets and packet routing handled by it.