One of IoT's most emerging application protocols is Constrained Application Protocol (CoAP). The CoAP runs over UPD but not on the TCP, so it is suitable for resource-restricted IoT tiny devices. Link error causes network congestion and packet loss problems in IoT. It makes an impact on the CoAP performance. The basic design of CoAP aims at solving such challenges. However, some shortcomings in maintaining the network performance level, especially when the link error is high. There are various extensions are provided in CoAP, such as
1. Block Wise Transfer in CoAP.
2. CoAP over TCP, TLC, and Web Sockets.
3. Extended Tokens and Stateless Clients in CoAP.