The TCP-IMPL working group has documented a number of TCP implementation problems [PADHV98]. However, a significant number still have not been fully described and documented in the form used in [PADHV98]. This memo briefly describes a number of these, including commentary as to the authors' opinions regarding the importance of documenting the problem. This memo is *not* intended to ever see light as an RFC of some form; its sole function is to facilitate working group discussion of which problems are more pressing to document than others, and to aid in arriving at a decision as to when [PADHV98] will be sufficiently complete to merit its publication as an Informational RFC. We divide the descriptions into ''serious'' problems, meaning those we think should be included in [PADHV98] prior to its publication; ''security'' problems, which might not be viewed as implementation problems per se, but represent significant security problems of which TCP implementors should be aware; and ''less serious'' problems, those that, if the working group fails to find volunteers to document them, should not hold up [PADHV98]. It might be worthwhile to separate the security problems out into their own document. We particularly solicit working group input on this subject.