1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/mtransport/README Wed Dec 31 06:09:35 2014 +0100
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1.4 +This is a generic media transport system for WebRTC.
1.5 +
1.6 +The basic model is that you have a TransportFlow which contains a
1.7 +series of TransportLayers, each of which gets an opportunity to
1.8 +manipulate data up and down the stack (think SysV STREAMS or a
1.9 +standard networking stack). You can also address individual
1.10 +sublayers to manipulate them or to bypass reading and writing
1.11 +at an upper layer; WebRTC uses this to implement DTLS-SRTP.
1.12 +
1.13 +
1.14 +DATAFLOW MODEL
1.15 +Unlike the existing nsSocket I/O system, this is a push rather
1.16 +than a pull system. Clients of the interface do writes downward
1.17 +with SendPacket() and receive notification of incoming packets
1.18 +via callbacks registed via sigslot.h. It is the responsibility
1.19 +of the bottom layer (or any other layer which needs to reference
1.20 +external events) to arrange for that somehow; typically by
1.21 +using nsITimer or the SocketTansportService.
1.22 +
1.23 +This sort of push model is a much better fit for the demands
1.24 +of WebRTC, expecially because ICE contexts span multiple
1.25 +network transports.
1.26 +
1.27 +
1.28 +THREADING MODEL
1.29 +There are no thread locks. It is the responsibility of the caller to
1.30 +arrange that any given TransportLayer/TransportFlow is only
1.31 +manipulated in one thread at once. One good way to do this is to run
1.32 +everything on the STS thread. Many of the existing layer implementations
1.33 +(TransportLayerPrsock, TransportLayerIce, TransportLayerLoopback)
1.34 +already run on STS so in those cases you must run on STS, though
1.35 +you can do setup on the main thread and then activate them on the
1.36 +STS.
1.37 +
1.38 +
1.39 +EXISTING TRANSPORT LAYERS
1.40 +The following transport layers are currently implemented:
1.41 +
1.42 +* DTLS -- a wrapper around NSS's DTLS [RFC 6347] stack
1.43 +* ICE -- a wrapper around the nICEr ICE [RFC 5245] stack.
1.44 +* Prsock -- a wrapper around NSPR sockets
1.45 +* Loopback -- a loopback IO mechanism
1.46 +* Logging -- a passthrough that just logs its data
1.47 +
1.48 +The last three are primarily for debugging.
1.49 +
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