Let me repeat again, the restriction is octet(ToASCII(X)) <= 63 (sorry, forget the =).
The length restriction of a domain name (incidently, UTF-8 encoded string which looks like domain name is not a domain name) in a DNS UDP packet is something beyond this working group. Please bring it to the DNSEXT working group. -James Seng > What I request is confirmation and clarification about that restriction. > > If UTF8-encoded, that valid 8bit label will exceed 63 octets limits (up > to 168 octets or more) > which is imposed by RFC1035 even upon non-ASCII 8bit labels . > IDNA section 6.3 does not rule out that utf8 encoded labels may be used > in DNS wire protocols in the future. And that will affect UDP based > DNS protocols > which suffers from lack of space in the UDP packet length limits (512). > Packet truncation or protcol errors are inevitable. > > That is why i suggest that some separate length restriction on utf8 > (other encoding) IDN labels > be needed. Or clarifications about those problems, at least. > > Soobok Lee > > > > >-James Seng > > > > > > > >>That is true only in protocols predating IDNA draft. > >>IDN labels can be typed in/ displayed/ copy&pasted/ or exchanged in > >> UTF8 (or other) encoding > >>in now and future applications or protocols slots as described in IDNA > >>draft itself. > >>See enclosed excerpts from IDNA draft ( "SEE HERE"). > >> > >>I think some length restriction in code points is needed, rather than in > >>octets .... > >>IDNA is the right place to put such things.. > >> > >>Soobok Lee > >> > >>6.3 DNS servers > >> > >>Domain names stored in zones follow the rules for "stored strings" from > >>[STRINGPREP]. > >> > >>For internationalized labels that cannot be represented directly in > >>ASCII, DNS servers MUST use the ACE form produced by the ToASCII > >>operation. All IDNs served by DNS servers MUST contain only ASCII > >>characters. > >> > >>If a signaling system which makes negotiation possible between old and > >>new DNS clients and servers is standardized in the future, the encoding > >>of the query in the DNS protocol itself can be changed from ACE to > >>something else, such as UTF-8. The question whether or not this should > >> > >> > >(SEE HERE) > > > > > >>be used is, however, a separate problem and is not discussed in this > >>memo. > >> > >> > >> > >>6.1 Entry and display in applications > >> > >>(snip) > >> > >>In protocols and document formats that define how to handle > >>specification or negotiation of charsets, labels can be encoded in any > >>charset allowed by the protocol or document format. If a protocol or > >>document format only allows one charset, the labels MUST be given in > >>that charset. > >> > >>In any place where a protocol or document format allows transmission of > >>the characters in internationalized labels, internationalized labels > >>SHOULD be transmitted using whatever character encoding and escape ( SEE > >> > >> > >HERE ) > > > > > >>mechanism that the protocol or document format uses at that place. > >> > >>All protocols that use domain name slots already have the capacity for > >>handling domain names in the ASCII charset. Thus, ACE labels > >>(internationalized labels that have been processed with the ToASCII > >>operation) can inherently be handled by those protocols. > >> > >> > >>6. Implications for typical applications using DNS > >> > >>In IDNA, applications perform the processing needed to input > >>internationalized domain names from users, display internationalized > >>domain names to users, and process the inputs and outputs from DNS and > >>other protocols that carry domain names. > >> > >>The components and interfaces between them can be represented > >>pictorially as: > >> > >> +------+ > >> | User | > >> +------+ > >> ^ > >> | Input and display: local interface methods > >> | (pen, keyboard, glowing phosphorus, ...) > >> +-------------------|-------------------------------+ > >> | v | > >> | +-----------------------------+ | > >> | | Application | | > >> | | (ToASCII and ToUnicode | | > >> | | operations may be | | > >> | | called here) | | > >> | +-----------------------------+ | > >> | ^ ^ | End system > >> | | | | > >> | Call to resolver: | | Application-specific | > >> | ACE | | protocol: | > >> | v | ACE unless the | > >> | +----------+ | protocol is updated | > >> | | Resolver | | to handle other | > >> | +----------+ | encodings | (SEE HERE) > >> | ^ | | > >> +-----------------|----------|----------------------+ > >> DNS protocol: | | > >> ACE | | > >> v v > >> +-------------+ +---------------------+ > >> | DNS servers | | Application servers | > >> +-------------+ +---------------------+ > >> > >> > >> > >> > >> > >> > >> > > > >
