[ros-users] The future of ROS 2.0 protocol changes

Valerio De Carolis vd63 at hw.ac.uk
Tue Sep 16 20:31:18 UTC 2014

On 15/09/14 16:27, Jonathan Bohren wrote:
> On Mon, Sep 15, 2014 at 11:11 AM, Brian Gerkey <gerkey at osrfoundation.org
> <mailto:gerkey at osrfoundation.org>> wrote:
>     Now, we're under no illusion that the community will switch
>     wholesale to ROS 2.0 next year when it's ready.  To the contrary, we
>     committed with the release of Indigo as our first LTS distro to
>     support ROS as it exists today for 5 years.  ROS 2.0 won't replace
>     ROS 1.0, but rather will live alongside it, with tools in place to
>     allow the two systems to communicate (through bridges and/or library
>     shims), and to assist with porting existing code to new APIs.
> What I gathered from Aaron's initial post is that an open question is
> whether or not ROS 1.x will continue to be enhanced and/or if OSRF has
> the bandwidth to organize contributions which enhance it in the ways he
> described. Over in ros-sig-ng-ros, I mentioned that there are currently
> a bunch of enhancements floating around which either not been fully
> fleshed out or have not been integrated into the ROS 1.x core. These
> include, but are not limited to UDP Multicast Support [1] and a
> ZeroMQ-based backend which improves performance [2].
> [1] http://wiki.ros.org/ethzasl_message_transport
> [2] https://github.com/esteve/ros_comm/tree/zeromq_thrift

The UDP support and the ZeroMQ transport is really a good combination 
that we use successfully in our projects. Unfortunately the ROS 2.0 
plans seems to diverge on these topics. Hope one can easily plug 
different systems like it was possible with the ROS 1.x version.

JSON and msgpack serialization is way more efficient than the 1.x one.

> On Tue, Sep 16, 2014 at 1:43 PM, Hai Nguyen <haidai at gmail.com> wrote:
>     I'm not particularly familiar with DDS, but does it work nicely with browsers? either through some sort of translation or better yet, natively? I'm interested as the current ROS to WebSockets bridge is particularly ugly: the bridge has to subscribe to all the messages that any web client would need to listen to and then rebroadcast them, which introduces additional delays making it horribly painful to use for things like teleop with large messages like images or point clouds.
> This looks promising:
> http://www.prismtech.com/blog/dds-web-programming-dscript

I fear this suffers of the same problem, cause once you want to play 
with the browser side JSON format is really a must have as you can pass 
your messages without parsing and serializing them twice. There is a 
trade-off one has to choose between having checks on static typed 
messages or embrace the dynamic nature of the web. ;)

Valerio De Carolis - PhD Student
Ocean Systems Laboratory
Heriot-Watt University
EH14 4AS, Edinburgh, UK

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