diff --git a/experiments/rtp-hdrext/index.md b/experiments/rtp-hdrext/index.md index 2115df2..01e701d 100644 --- a/experiments/rtp-hdrext/index.md +++ b/experiments/rtp-hdrext/index.md @@ -13,5 +13,6 @@ Underneath this page, RTP header extensions are listed. * [abs-send-time](abs-send-time) * [color-space](color-space) * [playout-delay](playout-delay) + * [transport-wide-cc-02](transport-wide-cc-02) * [video-content-type](video-content-type) * [video-timing](video-timing) diff --git a/experiments/rtp-hdrext/transport-wide-cc-02/index.md b/experiments/rtp-hdrext/transport-wide-cc-02/index.md new file mode 100644 index 0000000..5fda1b0 --- /dev/null +++ b/experiments/rtp-hdrext/transport-wide-cc-02/index.md @@ -0,0 +1,66 @@ +--- +layout: default +title: transport-wide-cc-02 +permalink: /experiments/rtp-hdrext/transport-wide-cc-02/ +--- + +This RTP header extension is an extended version of the extension defined in + + +**Name:** "Transport-wide congenstion control 02" + +**Formal name:** + + +**Status:** This extension is defined here to allow for experimentation. Once +experience has shown that it is useful, we intend to make a proposal based on +it for standardization in the IETF. + +The original extension defines a transport-wide sequence number that is used in +feedback packets for congestion control. The original implementation sends these +feedback packets at a periodic interval. The extended version presented here has +two changes compared to the original version: +* Feedback is sent only on request by the sender, therefore, the extension has + two optional bytes that signals that a feedback packet is requested. +* The sender determines if timing information should be included or not in the + feedback packet. The original version always include timing information. + +Contact or for more info. + +## RTP header extension format + +### Data layout overview +Data layout of transport-wide sequence number + 1-byte header + 2 bytes of data: + + 0              1 2  + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ID   | L=1 |transport-wide sequence number | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +Data layout of transport-wide sequence number and optional feedback request + 1-byte header + 4 bytes of data: + + 0              1 2                   3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ID   | L=3 |transport-wide sequence number |T|  seq count | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |seq count cont.| + +-+-+-+-+-+-+-+-+ + +### Data layout details +The data is written in the following order, +* transport-wide sequence number (16-bit unsigned integer) +* feedback request (optional) (16-bit unsigned integer)
+ If the extension contains two extra bytes for feedback request, this means + that a feedback packet should be generated and sent immediately. The feedback + request consists of a one-bit field giving the flag value T and a 15-bit + field giving the sequence count as an unsigned number. + - If the bit T is set the feedback packet must contain timing information. + - seq count specifies how many packets of history that should be included in + the feedback packet. If seq count is zero no feedback should be be + generated, which is equivalent of sending the two-byte extension above. + This is added as an option to allow for a fixed packet header size. +