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comparison: media/mtransport/README
media/mtransport/README
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| 1 This is a generic media transport system for WebRTC. | |
| 2 | |
| 3 The basic model is that you have a TransportFlow which contains a | |
| 4 series of TransportLayers, each of which gets an opportunity to | |
| 5 manipulate data up and down the stack (think SysV STREAMS or a | |
| 6 standard networking stack). You can also address individual | |
| 7 sublayers to manipulate them or to bypass reading and writing | |
| 8 at an upper layer; WebRTC uses this to implement DTLS-SRTP. | |
| 9 | |
| 10 | |
| 11 DATAFLOW MODEL | |
| 12 Unlike the existing nsSocket I/O system, this is a push rather | |
| 13 than a pull system. Clients of the interface do writes downward | |
| 14 with SendPacket() and receive notification of incoming packets | |
| 15 via callbacks registed via sigslot.h. It is the responsibility | |
| 16 of the bottom layer (or any other layer which needs to reference | |
| 17 external events) to arrange for that somehow; typically by | |
| 18 using nsITimer or the SocketTansportService. | |
| 19 | |
| 20 This sort of push model is a much better fit for the demands | |
| 21 of WebRTC, expecially because ICE contexts span multiple | |
| 22 network transports. | |
| 23 | |
| 24 | |
| 25 THREADING MODEL | |
| 26 There are no thread locks. It is the responsibility of the caller to | |
| 27 arrange that any given TransportLayer/TransportFlow is only | |
| 28 manipulated in one thread at once. One good way to do this is to run | |
| 29 everything on the STS thread. Many of the existing layer implementations | |
| 30 (TransportLayerPrsock, TransportLayerIce, TransportLayerLoopback) | |
| 31 already run on STS so in those cases you must run on STS, though | |
| 32 you can do setup on the main thread and then activate them on the | |
| 33 STS. | |
| 34 | |
| 35 | |
| 36 EXISTING TRANSPORT LAYERS | |
| 37 The following transport layers are currently implemented: | |
| 38 | |
| 39 * DTLS -- a wrapper around NSS's DTLS [RFC 6347] stack | |
| 40 * ICE -- a wrapper around the nICEr ICE [RFC 5245] stack. | |
| 41 * Prsock -- a wrapper around NSPR sockets | |
| 42 * Loopback -- a loopback IO mechanism | |
| 43 * Logging -- a passthrough that just logs its data | |
| 44 | |
| 45 The last three are primarily for debugging. | |
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