On 13/04/2022 21:25, Liudvikas Bukys wrote:
My company (a SIP equipment manufacturer) has noticed a sudden flurry
of problems related to RTP streams containing some packets with the
wrong number of samples (different from what was negotiated). Our
equipment negotiates 20ms packets, we're seeing the emission of a few
5ms packets with MARK bit set, before the 20ms packets start flowing.
I theorized that some vendor's SBC or Media Gateway has released
software that causes this.
It has erupted at multiple customers. I thought there was no
commonality of carrier or trunk provider, but today I heard a report
that T-Mobile is definitely implicated and reproducible. Other
sources are possible too.
Has anyone else noticed this?
Does anyone have a good contact for SIP-related matters at T-Mobile?
I've seen something similar to this before, this year. I can't remember
exactly when or what. (I'm usually looking at PCAPs over somebody's
shoulder when they need a second opinion.)
It isn't usually a problem, I don't think. Worst that happens is the
first few RTP packets are dropped at the receiver. I've always presumed
just a bit of a race condition between the SIP part and the RTP part.
5ms unusual.
--
Tim Bray
Huddersfield, GB
t...@kooky.org
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