[Netconf] xml start directive with ssh

[David Reid <reid at snmp.com>]

From rfc4742 page 3:

   Once the SSH session has been established, the user (or application)
   will invoke NETCONF as an SSH subsystem called "netconf".  Subsystem
   support is a feature of SSH version 2 (SSHv2) and is not included in
   SSHv1.  Running NETCONF as an SSH subsystem avoids the need for the
   script to recognize shell prompts or skip over extraneous
   information, such as a system message that is sent at shell start-up.
   However, even when a subsystem is used, some extraneous messages may
   be printed by the user's start-up scripts.  Implementations MUST skip
   over these messages by searching for an 'xml' start directive, which
   MUST be followed by a <hello> element in the 'NETCONF' namespace.


I want to make sure I understand this correctly. Does this mean:

Both the netconf client and server MUST send an xml start directive before
the <hello> message and MAY send an xml start directive before any other
message when running over SSH.

When not running over SSH, the xml start directive is always optional.

Anything sent by either the client or server before the xml start directive
MUST be ignored when running over SSH.

When not running over SSH, any extraneous data results in a parse error.

-David Reid