%% You should probably cite rfc9175 instead of this I-D. @techreport{ietf-core-echo-request-tag-00, number = {draft-ietf-core-echo-request-tag-00}, type = {Internet-Draft}, institution = {Internet Engineering Task Force}, publisher = {Internet Engineering Task Force}, note = {Work in Progress}, url = {https://datatracker.ietf.org/doc/draft-ietf-core-echo-request-tag/00/}, author = {Christian Amsüss and John Preuß Mattsson and Göran Selander}, title = {{Echo and Request-Tag}}, pagetotal = 17, year = 2017, month = oct, day = 30, abstract = {This document defines two optional extensions to the Constrained Application Protocol (CoAP): the Echo option and the Request-Tag option. Each of these options when integrity protected, such as with DTLS or OSCORE, protects against certain attacks on CoAP message exchanges. The Echo option enables a CoAP server to verify the freshness of a request by requiring the CoAP client to make another request and include a server-provided challenge. The Request-Tag option allows the CoAP server to match message fragments belonging to the same request message, fragmented using the CoAP Block-Wise Transfer mechanism. This document also specifies additional processing requirements on Block1 and Block2 options.}, }