Re: [Netconf] xml start directive with ssh

[Andy Bierman <andy at netconfcentral.com>]

WashamFan wrote:
> Hi,
> 
>>  >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.
>>  
>>  Since hello and other messages are individual XML documents, they
>>  MAY being with an XML declaration.
> 
>>From this sentence:
> 
>    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.
> 
> <hello> message with an XML declaration is a MUST.
>

This text is a perfect example of the "CLI mentality" in place
when NETCONF was written.  It was assumed that implementations
would do a normal CLI login, and then magically (or manually)
switch to "NETCONF mode", after a bunch of screen-scraping.
(Wrong!)

IMO, this text should be removed somehow.  NETCONF agents should
expect only a stream of XML instance documents, not garbage text
sometimes.  The replacement text should say the manager MUST send
only complete XML instance documents (PDUs) and nothing else.

I doubt any agents actually support this requirement.
Since a manager has to explicitly start up the 'netconf' subsystem
in its implementation, there is no reason whatsoever for
the manager to send garbage text after that.
The manager knows (regardless of port number) whether it
is connecting to a plain CLI or to a NETCONF session.
At the time 4742 was written, nobody in the WG was aware of how
SSH subsystems actually worked.




> washam

Andy