"The Constrained Application Protocol (CoAP) is a RESTful transfer protocol for constrained nodes and networks. Basic CoAP messages work well for small payloads from sensors and actuators; however@ applications will need to transfer larger payloads occasionally -- for instance@ for firmware updates. In contrast to HTTP@ where TCP does the grunt work of segmenting and resequencing@ CoAP is based on datagram transports such as UDP or Datagram Transport Layer Security (DTLS). These transports only offer fragmentation@ which is even more problematic in constrained nodes and networks@ limiting the maximum size of resource representations that can practically be transferred. Instead of relying on IP fragmentation@ this specification extends basic CoAP with a pair of ""Block"" options for transferring multiple blocks of information from a resource representation in multiple request-response pairs. In many important cases@ the Block options enable a server to be truly stateless: the server can handle each block transfer separately@ with no need for a connection setup or other server-side memory of previous block transfers. Essentially@ the Block options provide a minimal way to transfer larger representations in a block-wise fashion. A CoAP implementation that does not support these options generally is limited in the size of the representations that can be exchanged@ so there is an expectation that the Block options will be widely used in CoAP implementations. Therefore@ this specification updates RFC 7252. "