Please see the
Transmission Control Protocol article, section "Segment fields". You'll have to look at it in edit mode to see what I'm trying to do, but, essentially, the source of the material I want to paste is an "ASCII picture". I am guessing that at least some combination of nowiki and code will make this happen, and I hit one random combination that got the latter part to display correctly -- but could not get it to work for the entire graphic.
Protocol field diagrams of this type are a standard convention in IETF specifications, which are public domain. There are other places where I really would like to cut, paste, and issue a few metacommands, rather than have to build the graphic in a draw package, produce a PNG, upload, and then go through the image sizing and positioning details.
Help!