The IESG has approved the Internet-Draft 'STUN - Simple Traversal of UDP Through Network Address Translators' <draft-ietf-midcom-stun-05.txt> as a Proposed Standard. This document is the product of the Middlebox Communication Working Group. The IESG contact persons are Allison Mankin and Scott Bradner. Technical Summary This document describes Simple Traversal of UDP Through NATs (STUN). STUN is a lightweight protocol that allows applications to discover the presenceand types of Network Address Translators (NATs) and firewalls between them and the public Internet. It also provides the ability for applications to determine the public IP addresses allocated to them by the NAT. STUN works with many existing types of NATs, and does not require any special behavior from them. As a result, it allows a wide variety of applications to work through existing NAT infrastructure. This protocol is not a cure-all for the problems associated with NATs. It does not enable incoming TCP connections through NAT. It allows incoming UDP packets through NAT, but only through a subset of existing NAT types. In particular, STUN does not enable incoming UDP packets through symmetric NATs, which are common in large enterprises. STUN's discovery procedures are based on assumptions on NAT treatment of UDP; such assumptions may prove invalid down the road as new NAT devices are deployed. STUN is a simple client-server protocol. A client sends a request to a server on the Internet, and the server returns a response. The server examines the source IP address and port of the request, and copies them into a response that is sent back to the client. Working Group Summary The midcom working group supported publication of this document. Security issues raised during IETF last call have been addressed in the current revision of the document. Protocol Quality This document was review for the IESG by Scott Bradner and Eric Rescorla. The area directors know of recent interoperability testing among several servers and clients in pre-commercial state, where the functions of STUN were successfully tested against each of the NAT varieties currently targeted. RFC Editor Note: Please add the following sentence to the IANA Considerations section: "Any future extensions will establish any needed regsteries."
