The U.N.'s "Code for Trade and Transport Locations" [0] was new to me and its use makes sense in some cases. I was also quite surprised to see on the list two _very small_ towns where I have facilities.
For those who have no gear outside of the U.S., however, CLLI codes [1], common in the telco industry, might be a better fit. Some of the codes on the U.N. list aren't very "intuitive" and the CLLI codes (the six-character "Network Site Codes", specifically) make a bit more sense. The U.N. code for Albin, Wyoming, for example, is "US AQI" while the (geographical portion of the) CLLI code is ALBNWY.
Side note: As seen below, you'll often see CLLI codes in PTR RRs when running traceroutes across the Internet. This can sometimes help when troubleshooting networking issues ("LSANCA" refers to Los Angeles, California).
$ traceroute route-server.ip.att.net
traceroute to route-server.ip.att.net (12.0.1.28), 30 hops max, 60 byte packets
... snip ...
3 ge-0-7-0-24.r04.lsanca03.us.bb.gin.ntt.net (129.250.198.185) 0.691 ms 1.393 ms 1.098 ms
Author here...I hadn't heard of the CLLI codes before, but that's a nice reference, thanks! I do tend to prefer the UN/LOCODE values just because you can almost always get away with using just three letters to define a location, and they work well internationally. I do agree that they're not always the most intuitive though, so that's certainly a trade-off.
One important thing to keep in mind for those who run their own mail systems is that you'll want the A and PTR RRs to match up or you increase the chances of your messages being considered spam.
In addition, you'll want the name used by your users (e.g. "mail.example.com") to match what's on your certificate or (at least some) mail clients will throw up errors (just as browsers do).
Multiple mail servers used by different users? nginx can proxy POP3, IMAP, and SMTP as well, so everyone can use "mail.example.com" and get routed to the correct backend server.
I did add a quick section under "special cases" on making sure to assign usable A records for mail servers and name servers, but you make a good point about ensuring the reverse matches in those scenarios as well (and to pay attention to your certificates).
[+] [-] jlgaddis|12 years ago|reply
For those who have no gear outside of the U.S., however, CLLI codes [1], common in the telco industry, might be a better fit. Some of the codes on the U.N. list aren't very "intuitive" and the CLLI codes (the six-character "Network Site Codes", specifically) make a bit more sense. The U.N. code for Albin, Wyoming, for example, is "US AQI" while the (geographical portion of the) CLLI code is ALBNWY.
Side note: As seen below, you'll often see CLLI codes in PTR RRs when running traceroutes across the Internet. This can sometimes help when troubleshooting networking issues ("LSANCA" refers to Los Angeles, California).
[0]: http://www.unece.org/cefact/locode/service/location.html[1]: https://en.wikipedia.org/wiki/CLLI_code
[+] [-] elasticdog|12 years ago|reply
[+] [-] jlgaddis|12 years ago|reply
In addition, you'll want the name used by your users (e.g. "mail.example.com") to match what's on your certificate or (at least some) mail clients will throw up errors (just as browsers do).
Multiple mail servers used by different users? nginx can proxy POP3, IMAP, and SMTP as well, so everyone can use "mail.example.com" and get routed to the correct backend server.
[+] [-] elasticdog|12 years ago|reply