[CentOS] Centos 7: UPD packet checksum verification?

Wed Jan 29 07:53:50 UTC 2020
Simon Matter <simon.matter at invoca.ch>

> On Tuesday, January 28, 2020 1:50:57 PM CET Stephen John Smoogen wrote:
>> On Sun, 26 Jan 2020 at 20:45, hw <hw at gc-24.de> wrote:
>> > > I'm not sure I understand what you are asking.
>> >
>> > It is about VOIP calls via SRTP being interrupted at irregular
>> intervals.
>> > The intervals appear to depend on the time of day:  Such phone calls
>> can
>> > last for a duration of about 5--25 minutes during the day to up to 1.5
>> > hours at around 3am before being interrupted.
>> UDP is called Unreliable Datagram Protocol for a reason. It can be
>> dropped at all kinds of places in between the two users depending on
>> how busy the routers/firewalls between 2 users can be.
> How would packets being dropped explain the replay errors and
> authentication
> failures?
>> Packets can get
>> out of order or a dozen other things which then relies on the
>> application layer to put the things back in 'order'.
> libsrtp seems to have provisions to deal with packets arriving out of
> order.
>> For voice, that
>> usually means a drop or other ugliness because it is assumed that if
>> the quality is too bad, the people would just call each other again.
> That's a funny idea.  Phone calls just worked fine and were good quality
> 25
> years ago, and mostly long before that.  I have never expected to have to
> call
> anyone back because of poor quality in over 40 years, and I'm not going to
> start to expect that now.

Just wait another 10 or 20 years and everybody will tell you it's normal
and nothing to worry. They won't believe you if you tell them there was a
time long ago when telephony just worked.

I remember in around 1999, when a lot of companies started to hear about
VoIP and wanted to implement it to save money and welcome the future, I
had lot's of discussion about it in the company I was working back then.
Those who new a bit more from the technology side said this can be done in
a company but not widely as a replacement for (public) telephony
infrastructure. Now that whole countries went all IP, just listen to
police and emergency services what they think about it: only now they
start to realize that having telephony which just works is a thing of the

But hey, don't worry, they will fix it with "the Cloud" :-)

> It's unacceptable, and it's not feasible, either.  For example, try to
> call
> paypal to solve some issue with your account.  It can take an hour before
> they
> call you back because everyone is busy.  Finally you talk to someone and
> just
> after you explained the problem, the call is interrupted.  Good luck
> calling
> the same person back.  You won't get anywhere because your next try will
> only
> result in another interrupted call.
>> For the most part this works pretty well but all it takes is a
>> firewall to get busy on something else and you have a bunch of UDP
>> packets out of order and people's calls dropping.
> VOIP calls are worlds away from what phone calls used to be.  Dropping
> calls
> has never been an option and is not an option now.

Telephony is like operating systems these days: a lot of things improve
but not everything...