Re: [Uri-review] URI scheme registration request

[John Wason <[e-mail]>]

I have prepared a more detailed description of the transports and URI 
request.  Please let me know if you need further specific details:

Robot Raconteur URI Scheme Improvement

John Wason

Wason Technology, LLC

[e-mail]

11/20/15

*Introduction*

Robot Raconteur is being improved to better comply with web standards by 
adding support for WebSocket transports and implementing a new URI 
scheme that can be registered with IANA.The URIs for Robot Raconteur use 
the following basic format:

rr+transport://hostname:port/path/to/endpoint?service=servicename&nodename=targetnodename&nodeid=targetnodeuuid

The scheme is “rr”, “+”, and then the transport type.For instance for 
TCP the scheme is “rr+tcp”. If TLS is used, “rr” is replaced with “rrs” 
to indicate the extra security.For TCP a secure transport would use the 
scheme “rrs+tcp”. The following schemes are used and will each be 
discussed in detail in the following sections:

·rr+tcp

·rrs+tcp

·rr+local

·rr+usb

·rr+pci

·rr

·rr+cloud

·rr+ws

·rrs+ws

·rr+wss

·rrs+wss

Each of these schemes corresponds to a different selection of transports 
and security options.

The hostname and port correspond to the hostname and port of the target 
machine.If no port is specified the default is used.For rr+local, 
rr+tcp, rr+usb, rr+pci, rr, and rr+cloud the port must not be included 
as these do not use ports to find the target.

The absolute path (/path/to/endpoint) in the example is only used for 
WebSockets with HTTP to identify the WebSocket target and must be empty 
or “/” for all other transport types.

The query contains the name of the service to connect to.It may also 
contain the nodeid and nodename if desired to help find the node.The 
same endpoint can provide connection to multiple nodes so this provides 
a way to select the target node. The query string can also be used to 
pass extra parameters to the WebSocket HTTP server if desired.The query 
string is passed unmodified to the server.

All nodes can be secured with username and credential pairs.

A functional example of a Robot Raconteur URI is:

rr+tcp://192.168.2.3:48653/?nodeid= 
a7aa5f85-dfa7-41fe-89a1-1ebff43b9580&service=create

The following sections will describe the exact transports and how they 
create connections to the target nodes.

*TCP Transport*

·rr+tcp – Standard TCP communication

·rrs+tcp – TLS TCP communication

The TCP Transport operates by connecting to a remote port and then using 
the Robot Raconteur protocol to communicate.The official listen port is 
48653. The path must be “/” or empty. The first handshake contains the 
target nodeid and/or nodename to identify which node should be 
connected.Both can be blank to connect to the default node on the 
endpoint.The communication can be wrapped in TLS using Start TLS 
semantics.The first message contains the target nodeid and/or nodename 
and a flag to start using TLS.The server node then provides a 
certificate signed by Wason Technology, LLC issued to the UUID (nodeid) 
of the node.The client can also provide a signed certificate to provide 
certificate based authentication.

Discovery for TCP is accomplished through UDP packets that are broadcast 
periodically on port 48653.The packets contain the nodeid, nodename, the 
connection URI, and some additional metadata to help identify the 
capabilities.The information is generally only used to connect to the 
“Service Index” that runs on all nodes.This index provides detailed 
information about the services available and how to connect.The clients 
will interrogate the nodes through the Service Index to determine if the 
node matches the search criteria.During this process it will also verify 
the TLS certificates if appropriate.

*WebSocket Transport*

The WebSocket transport is an extension to the TCP transport and in the 
software is directly integrated into the TCP transport.It works by 
wrapping the TCP transport data into WebSocket binary frames. The frame 
boundaries are ignored as the stream is reassembled on the receiving 
end.The frames however shall be equal to or less than 4 KB of data per 
frame.

The transport also implements the HTTP handshake to start the WebSocket 
protocol using the subprotocol “robotraconteur”. The URI contains the 
path to the WebSocket and query information, both of which are passed 
unmodified to the server. The URI must contain a query parameter named 
“service” to identify the name of the service to connect.

All nodes that listen for TCP connections shall also be capable of 
detecting and accepting an HTTP WebSocket connection to the root file 
path “/” on the same port that listens for standard Robot Raconteur 
connections. This allows for standard web browsers to connect without 
additional plugins. (Note that HTTPS (wss) is not possible in this 
configuration. See below.)

TLS is somewhat complicated with WebSockets due to the handshake 
behavior.There are four flavors of WebSocket connections:

·rr+ws – No encryption (HTTP)

·rrs+ws – Encryption using the TLS Robot Raconteur transport.This does 
not encrypt the HTTP handshake.For local network use connecting to a 
device this should be sufficient as the handshake only contains the 
target nodeid/service information which is not considered secret data. 
Just after the handshake the Robot Raconteur TLS layer is activated 
protecting any secret data. (HTTP)

·rr+wss – Encrypted HTTPS transport but no Robot Raconteur 
encryption.Not recommended because the target node identity is not 
verified. (HTTPS)

·rrs+wss – Encryption HTTPS transport and TLS Robot Raconteur 
transport.This will encrypt the HTTP handshake and allow for identity 
verification of the node.Note that this is only possible when the target 
node has an official HTTPS certificate which is not available for IoT 
type devices.In those cases rrs+ws should be used as it is designed for 
such scenarios. rrs+wss should only be used when it is determined to be 
truly necessary.

*Local Transport*

·rr+local

The local transport uses UNIX sockets or Named Pipes to communicate 
between nodes on the same machine.The nodeid and/or nodename are used to 
identify the target nodes.The host is always “localhost”.A username can 
be used to specify which user owns the desired node, ie 
“username@localhost”.The port is never used and must be left out of the 
URI. Access control is accomplished through file permissions and 
standard username/credential access control. Untrusted software shall 
not be allow local transport access. The path must be “/” or empty.

*Hardware Transport*

·rr+usb

·rr+pci

Hardware device drivers are implemented through a userspace daemon 
service.This service provides UNIX socket / Named Pipe connections that 
allow nodes to access the devices.Access control is accomplished through 
file permissions.Generally only admin or equivalent users are given 
access. Untrusted software shall not be allow local transport access. 
The path must be “/” or empty.

*Cloud Transport*

·rr

·rr+cloud

The cloud transport is a transport based on WebRTC.The signaling as 
accomplished through the Robot Raconteur server.Nodes are identified by 
the Robot Raconteur username and nodeid/nodname pair.The hostname for 
each user is “username.cloud.robotraconteur.com”, where username is 
replaced with the registered username.For instance, 
“johnw.cloud.robotraconteur.com” would be the hostname “johnw”. The port 
must not be included. Nodes connecting to the cloud service must all 
have issued certificates tied to the uuid of the node (nodeid). This 
communication is always secured through DTLS at the WebRTC 
layer.Security of the overall cloud is managed by the Robot Raconteur 
server. The hostnames for each user are only relevant within the 
signaling server and do not have any general use DNS meaning. “rr” and 
“rr+cloud” are equivalent. The path must be “/” or empty.



On 11/14/2015 6:37 PM, Dave Thaler wrote:
>
> Short answer: unfortunately no
>
> This was the subject of issue #16:
>
> http://trac.tools.ietf.org/wg/appsawg/trac/ticket/16
>
> It was discussed at IETF 89 and then again at IETF 90. In both cases, 
> and as confirmed on the list,
>
> the consensus of the WG was to not allow a notion of wildcards.   
> Instead you have to individually
>
> register each such scheme.  I see “svn+ssh” is not currently 
> registered, but it sounds like it ought to be.
>
> Dave
>
> *From:*John Wason [mailto:[e-mail]]
> *Sent:* Saturday, November 14, 2015 2:21 PM
> *To:* Dave Thaler <[e-mail]>; Roy T. Fielding 
> <[e-mail]>
> *Cc:* [e-mail]
> *Subject:* Re: [Uri-review] URI scheme registration request
>
> Is it possible to register a "wildcard" or have an understanding that 
> the scheme can be appended with the transport type?  Subversion uses 
> "svn+ssh" to specify an ssh tunnel.  This format seems to be used 
> occasionally in practice.  Because the different transports can point 
> to completely different resources on the same host I am not sure 
> having the transport in the query portion is the correct solution.
>
> On 11/14/2015 3:07 PM, Dave Thaler wrote:
>
>     Roy T. Fielding wrote:
>
>     >A URI scheme should define what it names and how that naming maps
>     to the URI syntax.
>
>     >There is nothing wrong with using separate schemes for different
>     transports if those transports
>
>     >are essential parts of the name (e.g., if something named Fred at
>     TCP:80 is different from something
>
>     >named Fred at UDP:89898).  (I prefer using dots, like rr.tcp and
>     rr.udp and rr.tcp.tls.)
>
>     Careful… RFC 7595 states:
>
>        Furthermore, to prevent collisions with private-use scheme
>     names, new
>
>        scheme names registered MUST NOT contain a "." unless actually
>
>        constructed from a reversed domain name.
>
>     So rr.tcp should only be done if you register rr as a TLD, and
>     since rr is 2 letters, it’s reserved for a country code.
>
>     Dave
>
>
>
>
> -- 
> John Wason, Ph.D.
> Wason Technology, LLC
> PO Box 669
> Tuxedo, NY 10987
> [phone]
> [e-mail] <mailto:[e-mail]>


-- 
John Wason, Ph.D.
Wason Technology, LLC
PO Box 669
Tuxedo, NY 10987
[phone]
[e-mail]