On 1/24/09, Mark Smith <[email protected]> wrote: > > Does it also mean that leading and trailing underscores will be > > disallowed in usernames? > > I don't see why we'd disallow it?
Cureently, usernames on LJ that start or end with underscores are disallowed, and any that remain do not get a subdomain URL, instead getting a URL under http://users.livejournal.com/ . This is because of the combination of RFCs 1035 and 1123. The BNF syntax in RFC 1035 section 2.3.1 ( http://rfc.sunsite.dk/rfc/rfc1035.html ) stipulated that labels within a subdomain can start only with a letter, and end only with a letter or digit. This restriction was made a bit more liberal in RFC 1123, section 2.1 ( http://rfc.sunsite.dk/rfc/rfc1123.html ) to say that the first character can be either a letter or a digit. Notice, however, that the other allowable character, the hyphen, was *not* allowed. Thus, a subdomain like http://-test.livejournal.com/ or http://test-.livejournal.com/ is invalid according to the RFCs. In spite of this, today's apps still allow you to use them, though they really shouldn't. This is made possible by RFC 2181, section 11 ( http://rfc.sunsite.dk/rfc/rfc2181.html ), which specifies how the syntax of a DNS name. DNS itself doesn't place any restrictions on the content of a label in DNS except for its length (since it's not required that the label in a DNS record be a hostname), so DNS servers are allowed to store such labels and those querying DNS servers are allowed to query for them. However, the restrictions on hostnames still take effect. Thus, we wouldn't want to allow usernames beginning or ending with an underscore unless a means can be figured out of doing so which causes the name to both begin and end with a letter or digit. > > (Hm... will usernames that start with "xn__" be allowed? Then people > > could register, say, xn__lite_9oa as their username, resulting in a > > subdomain of élite.dreamwidth.org.) > > Hmmm, yeah, those should be disallowed. Should they? I can see some great applications of those. I think the point being made was that such names would be quite useful. - Sophie. _______________________________________________ dw-discuss mailing list [email protected] http://lists.dwscoalition.org/cgi-bin/mailman/listinfo/dw-discuss
