Re: [Linphone-users] Why Android (Oreo) phones, are actually less reliable with TCP vs. UDP

[Greg Troxel]

"Brian J. Murrell" <address@hidden> writes:

> On Sat, 2019-03-30 at 08:47 -0400, Greg Troxel wrote:
>> 
>> Or perhaps it is Android's fault, for trying to push people into GCM,
>
> As I stated in my original description, FCM (GCM) doesn't actually
> resolve this problem since the TCP retry backoff timer will cause the
> TCP packets delivery to be delayed regardless of FCM or not.

The FCM way is, I think, for the client to reconnect and query, with the
server not having pushed anything.

>> with linphone not adequately mitigating the Android problems.
>
> Well, the only problem that I really see is people being led to believe
> that UDP is so unreliable that it cannot be used for SIP.  It's been
> used for SIP for many years successfully and QUIC proves that UDP is
> not so unreliable on the Internet even that it cannot be used.

I agree that UDP ought to be workable, and with your comments on
retransmission being handled differently but also acceptably.   But in
this case I think it's about working around a system that isn't
processing packets correctly in a way that none of this was designed to
handle.

I see the TCP/UDP connection issue as having two larger points:

  TCP can and should use TLS, to hide the username and password in
  register messages

  TCP seems more likely to traverse possibly multiple layers of perhaps
  broken firewall and NAT devices.  Yes, UDP ought to work, but I think
  it's more likely to lose with broken devices, and that's part of the
  source of the notion