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 11:10 -0400, Greg Troxel wrote:
>> 
>> The point I've been trying to make is that an "outage" of 10 minutes
>> because the phone is doing power save is not really an outage, and
>> loss
>> recovery mechanisms are not designed to deal with this.
>
> I'm not sure I see a phone power saving any different than a network
> link between two routers suffering backhoe damage and needing hours or
> days to repair.  TCP is supposed to survive that.

It's different in that it has known characteristics and a system design
can take those into account.

I don't agree that TCP is supposed to survive a multiple day outage.  It
seems that timeout timers are almost always configured to give up long
before 48h.

>> It is an intentional loss of connectivity, and it's reasonable to
>> treat it as such in the overall system design.
>
> Sure.  But current SIP over TCP cannot handle it.  SIP over UDP handles
> it just fine.

SIP over TCP on your phone, which has aggressive power saving, which may
be doing things wrong in terms of dropping packets rather than just
having late delivery.   We really don't know.

I suspect if SIP/UDP had retransmission rules adjusted to be "TCP
friendly" in terms of congestion avoidance, it wouldn't work as well for
you.  In situations with congestion avoidance, local greedy behavior
almost always wins, even if everyone doing that leads to collapse.

I think there's something bad going on in terms of packet loss and
perhaps otherwise in your case.