Protocol

An international agreement linked to an existing convention, but is a separate and additional agreement which must be signed and ratified by the Parties to the convention concerned. Protocols typically strengthen a convention by adding new, more detailed commitments (i.e. supplements), but they could also make amendments to a treaty. An illustrative example is the Kyoto Protocol which is linked to the UNFCCC, but needs to be signed and ratified by states (see Kyto Protocol). The term can also refer to diplomacy. That is, the set of rules, procedures, conventions and ceremonies related to state relations; representing recognized and accepted norms of international courtesy (by governments, individuals or cultures).


Sources:
unfccc.int (general source)
Wikipedia.org (Protocol diplomacy)

Read more on:
www.protocolinternational.org (protocol as diplomacy)
www.globalnegotiator.com (protocal as diplomacy related to international business)
Wikipedia.org (A list of international environmental agreements)