A new IETF non-working group email list has been created. List address: spud@ietf.org Archive: http://www.ietf.org/mail-archive/web/spud/ To subscribe: https://www.ietf.org/mailman/listinfo/spud Purpose: The deployment of new transport protocols as well as the extension of existing IETF-defined transport protocols faces the continuing challenge of how to make these protocols robust against packet and flow modification in the Internet at the hands of middleboxes. The increasing deployment of these packet modifications have made expectations about packet handling behaviors implicit. For example, a TCP packet with the SYN and ACK flags set not only synchronizes sequence numbers and set up state on both endpoints for a TCP connection (its explicit meaning), it also confirms network address translation (NAT) mappings along the path as well as signifying to any firewalls along the path that the endpoint has accepted the connection (implicit meanings). One strategy to resolve this tussle, identified and discussed during the recent IAB workshop on Stack Evolution in a Middlebox Internet (SEMI), would be to provide a mechanism for applications at the end as well as boxes along the path to explicitly declare their assumptions and intentions. This list is for discussion of the definition of such a mechanism, as part of a pre-WG activity to determine what can be done. For additional information, please contact the list administrators.