oberman@amazon.llnl.gov (03/03/91)
In article <9103022255.AA04928@ucbvax.Berkeley.EDU>, dmbarton@ralvmm.vnet.ibm.com ("Daniel M. Barton") writes: > RFC 821 and 822 weren't very clear on what characters a hostname could > contain. RFC 952, "DOD Internet Host Table Specification" clarifies > what characters are legal. The legal characters are letters, numbers, > and the hyphen, and the hostname must begin with a letter, and end with > a letter or digit. The exact syntax is: This is out of date information RFC 1122 removes the prohibition of numeric first characters in host names. Other than that, I know of no changes fron 952. As far as I can tell, underscores remain a no-no. That stated, they are quite common and most implementation will allow them. The only problem is when you hit a system that doesn't. So, please follow the rules and don't use them. I would also recommend against numeric first characters as many implementation have not been changed since 1122/1123 were issued. R. Kevin Oberman Lawrence Livermore National Laboratory Internet: oberman@icdc.llnl.gov (415) 422-6955 Disclaimer: Don't take this too seriously. I just like to improve my typing and probably don't really know anything useful about anything.
mdb@bridge2.UUCP (Mark D. Baushke) (03/12/91)
On 2 Mar 91 23:16:51 GMT, oberman@amazon.llnl.gov said: Kevin> In article <9103022255.AA04928@ucbvax.Berkeley.EDU>, Kevin> dmbarton@ralvmm.vnet.ibm.com ("Daniel M. Barton") writes: > RFC 821 and 822 weren't very clear on what characters a hostname could > contain. RFC 952, "DOD Internet Host Table Specification" clarifies > what characters are legal. The legal characters are letters, numbers, > and the hyphen, and the hostname must begin with a letter, and end with > a letter or digit. The exact syntax is: [...and RFC 1123 in section 2.1 modifies RFC 952 to allow leading digits...] Kevin> That stated, they are quite common and most implementation will Kevin> allow them. The only problem is when you hit a system that Kevin> doesn't. So, please follow the rules and don't use them. I Kevin> would also recommend against numeric first characters as many Kevin> implementation have not been changed since 1122/1123 were Kevin> issued. Our site (3Com.COM) has a fair amount of experience with numeric first characters :-). I can say from experience that there are still hosts running software which rejects our domain as illegal. For the most part, these machines are either DEC-20 machines (like NIC.DDN.MIL) or IBM mainframes (typically BITNET sites). There are upgrades for each kind floating around, but it is sometimes difficult to fight intertia and get the system administrators to install the new software. If you have a choice, avoid using illegal characters in your names. You will save yourself a large hassle. Also, if you are designing software which checks names, be liberal in what you accept...the rules may change again. -- Mark D. Baushke Internet: mdb@ESD.3Com.COM UUCP: ...!{3comvax,auspex,sun}!bridge2!mdb