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<div>Thanks for the feedback. I have a lot more learning ahead. I will try to concisely post questions, only when needed, in future. I appreciate your collective help.<br></div><div><br></div><div>Sincerely,<br></div><div>Joseph</div><div><br></div><div><br></div><div>23 Nov 2020, 10:14 am by talk@gtalug.org:<br></div><blockquote class="tutanota_quote" style="border-left: 1px solid #93A3B8; padding-left: 10px; margin-left: 5px;"><div>On Mon, 23 Nov 2020 09:20:57 -0500 (EST)<br></div><div>"D. Hugh Redelmeier via talk" <talk@gtalug.org> wrote:<br></div><blockquote><div>I have no time for a careful answer. But it is important that you <br></div><div>understand these points:<br></div></blockquote><div>I can also spend a few minutes to add to the points below, if<br></div><div>that helps anyone...<br></div><blockquote><div>- DNS is a distributed tree, with nodes that are authoritative for <br></div><div> particular domains.<br></div></blockquote><div>Yes, and not at all - names = not so much, possibly, a little like a<br></div><div>one or two branch tree - Numbers = always four or six "branches"<br></div><div><br></div><div>DNS is mostly a fixed single easy thing. (although you do get weird<br></div><div>'trees' like de.li.cio.us (or whatever that was)<br></div><div><br></div><div>For names it could resemble a tree with one sometimes two or thee<br></div><div>branches, hardly ever more than that... (in theory it could have<br></div><div>millions of branches - but IRL (in real life) two or three...<br></div><div><br></div><div>An example - would be example.com<br></div><div>.com says which NS server(s) is/are authorative for example<br></div><div><br></div><div>That NS server(s) may further say where is www.example.com<br></div><div><br></div><div>but not often do you find www.www.www.www.example.com<br></div><div>(although you could, in theory, have a "tree", I guess...)<br></div><div><br></div><div>for numbers though, the delegation is only 4 "branches" deep for ipv4<br></div><div>and 6 "branches" deep for ipv6 - unless you count the main .in-addr.arpa<br></div><div>as another two?<br></div><div><br></div><div>So, DNS may be a bit like a very small bonsai? hehehehe<br></div><div> <br></div><blockquote><div>- there is caching (recursive servers) if you trust them (almost<br></div><div>always one does). Unless you are using DNSSec, the caching server<br></div><div>can lie, sometimes usefully.<br></div><div><br></div><div>- the forward domain is technically unrelated to the reverse domain.<br></div></blockquote><div>yes, reverse and forward lookup is not related, but when they match, as<br></div><div>in for use as an email server, this is another layer in the onion of<br></div><div>trust.<br></div><div><br></div><div>and, technically - it is ALL forward lookups (even a reverse lookup :) <br></div><div>the 'reverse' is actually you/inquirer 'reversing' the number and<br></div><div>adding .in-addr.arpa )<br></div><blockquote><div>The forward domain lookup uses a conventional domain name as the<br></div><div> key.<br></div></blockquote><div><br></div><div>You can have 192.168.1.100.com - so the only 'convention' is that<br></div><div>forward and reverse both has 'sub domains'<br></div><div><br></div><div>it is all really 'forward' lookups :)<br></div><div><br></div><div>forward works from the back<br></div><div>123 -> com for 123.com<br></div><div><br></div><div>reverse works by "reversing the number" and adding .in-addr.arpa<br></div><div><br></div><div>192.168.1.1 -> 192 for 168<br></div><div>so: 1.2.168.192.in-addr.arpa<br></div><div><br></div><div>for example: dig NS 136.100.in-addr.arpa tells you how 136.100 is<br></div><div>delegated, etc etc.<br></div><blockquote><div>The reverse lookup uses the IP address (in a funny format) as the<br></div><div> key.<br></div></blockquote><div>not so funny, just the normal ip number format<br></div><div><br></div><div>but the reverse is from the start of the number and not the end<br></div><blockquote><div>- Reverse example: to lookup the reverse for IPv4 address 1.2.3.4,<br></div><div> your system actually queries 4.3.2.1.in-addr.arpa. I think you can<br></div><div> see how that is constructed.<br></div></blockquote><div>yes, this is all it is :) <br></div><blockquote><div>- the reverse domain is a mystery to most people (because it mostly <br></div><div> doesn't matter to most users). If you run a mail server, it does <br></div><div> matter.<br></div><div>- whoever provided you with your IP address controls the reverse<br></div><div> domain for that IP address. Generally, if you pay for a static IP<br></div><div> address, they will let you specify what you want them to put in the<br></div><div> reverse domain for that IP address. Most ordinary consumers don't<br></div><div> have static addresses and are not given a say in what the reverse<br></div><div> says.<br></div></blockquote><div>if whomever provided you with the number did not hijack it from<br></div><div>somewhere and it is in fact properly delegated, then they could, in<br></div><div>their own auth NS, add whatever 'name' you like to the IP number :)<br></div><blockquote><div>- if your provider provides you with a CIDR of network addresses,<br></div><div> static, they may delegate the reverse domain for that CIDR to a DNS<br></div><div> of your choosing. This is not the normal home case.<br></div></blockquote><div><br></div><div>---<br></div><div>Post to this mailing list talk@gtalug.org<br></div><div>Unsubscribe from this mailing list https://gtalug.org/mailman/listinfo/talk<br></div></blockquote><div><br></div> </body>
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