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initial draft for evaluating Data Channel as the transport protocol. #24

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merged 1 commit into from
Apr 9, 2017
Merged

initial draft for evaluating Data Channel as the transport protocol. #24

merged 1 commit into from
Apr 9, 2017

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schien
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@schien schien commented Mar 29, 2017 •
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address issue #10

mfoltzgoogle
mfoltzgoogle reviewed Apr 3, 2017
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[Data Channel](https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-13)
is a non-media transport protocol in WebRTC framework, designed for exchanging
data from peer to peer. It advertise the following benefits:
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advertises

mfoltzgoogle
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data from peer to peer. It advertise the following benefits:

- Implemented in major browsers (except Safari)
- Support heterogeneous network environment e.g. NAT, firewall.
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Supports

mfoltzgoogle
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- Implemented in major browsers (except Safari)
- Support heterogeneous network environment e.g. NAT, firewall.
- Easily support media transport for remote playback
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Supports

mfoltzgoogle
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# Presentation API functionality

Data Channel is designed to be a non-media transport for WebRTC, with built-in
sub protocol negociation mechanism defined.
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Typo in "negotiation"

mfoltzgoogle
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sub protocol negociation mechanism defined.

A Data Channel is built on top of SCTP/DTLS/UDP protocol stack, which supports
reliable data transmition. Each Data Cahnnel has a unique integer ID and a label.
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Typo in Channel

mfoltzgoogle
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Assume that a single Data Channel is used as a control channel to transmit control
messages between the controller and receiver and one Data Channel is created for each
connected Presentation Connection for trasmitting application data.
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Typo: transmitting

mfoltzgoogle
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connected Presentation Connection for trasmitting application data.

An extra signalling channel and protocol for exchanging ICE candidates is required
to bootstrap the control channel. The bootstraping procedure needs to be executed
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bootstrapping

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1. Send a control message on control channel from the controller to the display
reconnect to a presentation with ID and URL for the initial presentation connection.
2. Receiver spawn a Data Channel on the same RTC connection of control channel, with
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If a second controller wants to initiate connection to the same presentation, would it have a duplicate Data Channel label?

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@schien schien Apr 9, 2017 •
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Generating a unique session Id in Receiver side seems to be a simpler solution for supporting many-to-one presentation.

mfoltzgoogle
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# Latency to establish a new connection

Data on connection establishment latency.
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It sounds like are three sources of latency:

  1. Connecting a reliable channel the first time for for ICE negotiation.
  2. Establishing the first Data Channel (perhaps this is part of [Meta] Write document describing protocol requirements #1).
  3. Adding an additional Data Channel on top of an existing peer-to-peer connection.

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Yes, exactly. I'll add it to this document.

mfoltzgoogle
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# Reliability

WebRTC is designed to be operated on heterogeneous network environment, using
ICE for address discovery and built-in negociation/re-negociation mechanism.
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s/negociation/negotiation/g

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This looks great @schien! Most of my comments are minor typos.

Did you have thoughts about establishing the bootstrap reliable channel for ICE negotation? IIRC Mozilla uses a TCP channel for this. I believe the bootstrap channel needs to remain open in case the network routing changes and ICE renegotiation occurs.

I recently heard from local WebRTC contacts that there is exploratory work to layer RTCDataChannel on top of QUIC, since the functionality is similar. Something to keep an eye on.

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schien commented Apr 4, 2017

Yes, the example protocol we have in current Gecko codebase uses TCP channel for bootstrapping DataChannel. To be more specific, TLS connection is used (with self-generated certificate, fingerprint broadcast on DNSSD).
We might use QUIC to replace the TLS/TCP channel if maintaining a QUIC connection is cheaper.

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anssiko commented Apr 6, 2017

@schien, great work! Feel free to land this. You can keep #10 open to track the remaining TODOs.

@schien schien force-pushed the issue-10-data-channel-transport branch 2 times, most recently from af92d82 to 07d1d55 Compare April 9, 2017 08:26
@schien schien force-pushed the issue-10-data-channel-transport branch from 07d1d55 to 600beba Compare April 9, 2017 08:29
@schien schien merged commit e41ac65 into w3c:gh-pages Apr 9, 2017
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@schien @mfoltzgoogle @anssiko @tomoyukilabs