The DNS protocol itself is binary clean. Bytes in labels can have any value. Of course this may cause problems in applications / user interface code or the like. And it is true that leading underscores and such like may, by convention be reserved. And "host" names are nominally supposed to start with a letter or digits and have only letters, digits, and hyphens. etc. The labels are length value encoded on the wire and there are only 6 bits for length so labels are limited to 63 bytes. The label of length zero is reserved for the label of the root node. Labels only "end in a period" in their usual string representation, not on the wire. Thanks, Donald =============================== Donald E. Eastlake 3rd +1-508-333-2270 (cell) 2386 Panoramic Circle, Apopka, FL 32703 USA d3e3e3@xxxxxxxxx On Sat, May 17, 2025 at 10:29 AM Michael Richardson <mcr@xxxxxxxxxxxx> wrote: > > > <#secure method=pgpmime mode=sign> > > David Blacka via Datatracker <noreply@xxxxxxxx> wrote: > > The draft suggests that the names need to conform to the domain name > > rules in RFC 1034. Because of the way these old RFCs are written, it > > isn't clear that RFC 1034 puts many restrictions on domain names. > > There appears to be an *assumption* that domain names are formed from > > the "letters-digits-hyphens" part of the ASCII character set, but the > > only actual requirements are: > > I thought that there more recent restrictions. > For instance labels starting with _ are reserved for infrastructure things. > > > -- > Michael Richardson <mcr+IETF@xxxxxxxxxxxx> . o O ( IPv6 IøT consulting ) > Sandelman Software Works Inc, Ottawa and Worldwide > > > > > -- > last-call mailing list -- last-call@xxxxxxxx > To unsubscribe send an email to last-call-leave@xxxxxxxx -- last-call mailing list -- last-call@xxxxxxxx To unsubscribe send an email to last-call-leave@xxxxxxxx
