add more markdown, more content on AXFR/IXFR/ANY

auth.md

@@ -1,4 +1,41 @@
-# Intro
+                <meta charset="utf-8" emacsmode="-*- markdown -*-">
+                            **A warm welcome to DNS**
+
+
+# Authoritative servers
+
+The basics of DNS Authoritative operation have already been described in the
+[Basic DNS](index.html) document.  In this file, we delve deeper into zone
+transfers and and notifications.
+
+This document covers RFCs 1982, 1995, 1996, 4592, 5936, 7766.
+
+# Incoming queries
+An authoritative server ignores the value of the Recursion Desired (RD) bit
+in the DNS header. On any responses it generates, the Recursion Available
+bit is set to zero.
+
+Take special care not to send answers to what is already a DNS answer. This
+leads to tight loops and denial of service attacks. In other words, QR must
+be 0 on incoming packets.
+
+# The algorithm
+As noted before, DNS is fundamentally a tree and hierarchical in nature.
+This means that when a query comes in to an authoritative nameserver, it
+first needs to find the most applicable zone to answer from. And in fact,
+the same name may be present in multiple zones on the name server, and may
+very well have different types and even record contents.
+
+The most specific zone is located for a query name (qname). If no zone can
+be found, set RCODE to 'REFUSED' and send out the response. This is unlike
+many example responses shown in RFCs and other documents listing 'root
+referrals' and other things. Just send 'REFUSED'.
+
+Within the most specific zone, see if the entire qname can be matched. If
+so, determine if that name has the type the query asked for ('qtype'). If
+yes, send out that RRSET.
+
+
 
 xxx
 RFC1982
@@ -37,3 +74,5 @@ This is not a popular feature.
 The final number, 86400, denotes that if a response says a name or RRSET
 does not exist, it will continue to not exist for the next day, and that
 this knowledge may be cached.
+
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