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Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." While many common Internet applications will operate cleanly in the presence of Network Address Translators, others suffer from a variety of problems when crossing these devices. This document discusses those things that application designers might wish to consider when designing new protocols. Guidelines are presented herein to help ensure new protocols and applications will, to the extent possible, be compatible with NAT.