On 12/06/2020 21:06, [email protected] wrote:
You'll find that VoIP over 4G is very much a 50/50 chance.. Mostly due
to how it's all natted etc,
I've got people working at home fine on 4G. For weeks.
Presume the end device is a SIP desk phone?
Usual suspects (Paul, Peter, Alan already alluded, but I thought i'd
make 1 list)
Gamma a big company, with a lot of customers. Surprised they have
issues, but a lot of steps in the chain.
1) Nat time outs faster than nat refresh in CGnat. (best fix is to move
to SIP over TLS)
2) same device from a different IP address. (suppose, CGnat) Some
mobile devices move IPv4s a lot. So make a call, and the RTP appears
on a different IP address to the SIP just before it. Lots of firewalls
can't cope with this. (Seems to be a common problem in the US as
mobile providers got to 464xlat. )
3) double nat - nat in hotspot, and then nat in the CGnat in the
network (carrier can't cope)
4) SIP ALG in the hotspot. or in the CGnat.
5) Setting the SIP registration timer too fast - so due to a bit of
packet loss, doesn't get a chance to re-register before expiry. And
retry in the phone too slow too.
6) (not gamma) people who use qualify in asterisk. A feature which
should be deleted.
7) Bufferbloat - so get timeouts.
I'd pop out to amazon and buy a Three pre-pay sim. And then set the
APN to 3internet which gives you a public IPv4 address. And try that.
Unless you already have a APN on your existing sims that give a public IP.
Or try an AAISP SIM.
Also worth checking what device he's using for 4G. Lot of people have
a `just for backup` device but it's 7 years old, maybe not a UK version,
doesn't have all the 4G frequency bands, ........ which can cause naff
performance.
And put in a support call with Gamma and see what they say???
--
Tim Bray
Huddersfield, GB
[email protected]
+44 7966479015
