explain why 512 is enough

diff --git a/pdns/recursordist/docs/appendices/FAQ.rst b/pdns/recursordist/docs/appendices/FAQ.rst
index b49ea41fdbc4f58ae56557fe2ec16a446ab1219e..035889fb79734874c396d2d5bd546f1ce881e5ce 100644 (file)
--- a/pdns/recursordist/docs/appendices/FAQ.rst
+++ b/pdns/recursordist/docs/appendices/FAQ.rst
@@ -35,6 +35,7 @@ The EDNS buffer size in a DNS packet, generated by side A, tells the recipient o
 So, when the Recursor talks to an Authoritative, the Recursor reports the buffer size the Authoritative is allowed to use to it - usually 1232 (:ref:`setting-edns-outgoing-bufsize`).
 But the example above is the Recursor responding to a client, and it is telling the client 'from you, I accept packets of up to 512 bytes'.
 Or, to say it differently, the Recursor is telling the client that *questions* must fit in 512 bytes.
+This is fine for the Recursor - unlike an Authoritative, that might need to handle big UPDATE requests, the Recursor really only answers simple questions from clients, and those always comfortably fit in 512 bytes, because the maximum length of a DNS name is 256 bytes.
 
 Similarly, the maximum size of a response from the Recursor to a client is governed by the buffer size reported by the client, and the :ref:`setting-udp-truncation-threshold` setting in the Recursor configuration.
 
@@ -42,3 +43,4 @@ To see the buffer size the Recursor is reporting to authoritatives, ask an autho
 
   $ dig txt header.lua.powerdns.org +short @9.9.9.9
   "id: 52938, aa: false, rd: false, ad: false, cd: false, do: true, ednsbufsiz: 1232, tcp: false"
+