Merge pull request #3807 from quicwg/define-preferred-address

Define preferred_address

draft-ietf-quic-transport.md

@@ -5041,13 +5041,21 @@ disable_active_migration (0x0c):
 preferred_address (0x0d):
 
 : The server's preferred address is used to effect a change in server address at
-  the end of the handshake, as described in {{preferred-address}}.  The format
-  of this transport parameter is shown in {{fig-preferred-address}}.  This
-  transport parameter is only sent by a server. Servers MAY choose to only send
+  the end of the handshake, as described in {{preferred-address}}.  This
+  transport parameter is only sent by a server.  Servers MAY choose to only send
   a preferred address of one address family by sending an all-zero address and
   port (0.0.0.0:0 or ::.0) for the other family. IP addresses are encoded in
   network byte order.
 
+: The preferred_address transport parameter contains an address and port for
+  both IP version 4 and 6.  The four-byte IPv4 Address field is followed by the
+  associated two-byte IPv4 Port field.  This is followed by a 16-byte IPv6
+  Address field and two-byte IPv6 Port field.  After address and port pairs,
+  a Connection ID Length field describes the length of the following Connection
+  ID field.  Finally, a 16-byte Stateless Reset Token field includes the
+  stateless reset token associated with the connection ID.  The format of this
+  transport parameter is shown in {{fig-preferred-address}}.
+
 : The Connection ID field and the Stateless Reset Token field contain an
   alternative connection ID that has a sequence number of 1; see {{issue-cid}}.
   Having these values bundled with the preferred address ensures that there will