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janus: Tailscale has 1280 MTU actually #326

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Merged
mdevaev merged 1 commit into from
Mar 10, 2026
Merged

janus: Tailscale has 1280 MTU actually #326

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6 changes: 3 additions & 3 deletions janus/src/rtp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,13 +27,13 @@

// Max RTP size for WebRTC is 1200 bytes:
// - https://stackoverflow.com/questions/47635545/why-webrtc-chose-rtp-max-packet-size-to-1200-bytes
// But(!) Tailscale has 1200 MTU. So to fit it required to substract:
// But(!) Tailscale has 1280 MTU. So to fit it required to subtract:
// 1. possible RTP extensions (see sdp.c)
// 2. additional SRTP fields (>= 10 bytes)
// 3. UDP header (8 bytes)
// 4. IPv6 header (40 bytes)
// Finally it looks like 100 bytes for all above should be enough
#define US_RTP_TOTAL_SIZE (1200 - 100)
// Finally it looks like below value should be good enought for all cases
#define US_RTP_TOTAL_SIZE 1150
#define US_RTP_HEADER_SIZE 12
#define US_RTP_PAYLOAD_SIZE (US_RTP_TOTAL_SIZE - US_RTP_HEADER_SIZE)

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