[189309] in North American Network Operators' Group
Re: Cost-effectivenesss of highly-accurate clocks for NTP
daemon@ATHENA.MIT.EDU (Lamar Owen)
Mon May 16 12:16:17 2016
X-Original-To: nanog@nanog.org
Date: Mon, 16 May 2016 12:16:13 -0400
From: Lamar Owen <lowen@pari.edu>
To: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <20160515191626.GE15061@besserwisser.org>
Errors-To: nanog-bounces@nanog.org
On 05/15/2016 03:16 PM, M=E5ns Nilsson wrote:
> ...If you think the IP implementations in IoT devices are na=EEve, wait=
=20
> until you've seen what passes for broadcast quality network=20
> engineering. Shoving digital audio samples in raw Ethernet frames is=20
> at least 20 years old, but the last perhaps 5 years has seen some=20
> progress in actually using IP to carry audio streams. (this is=20
> close-to-realtime audio, not file transfers, btw.)=20
Close to realtime is a true statement. Using an IP STL=20
(studio-transmitter link) has enough latency that the announcer can no=20
longer use the air signal as a monitor.
And the security side of things is a pretty serious issue; just ask a=20
major IP STL appliance vendor about the recent hijacking of some of=20
their customers' IP STL devices.... yeah, a random intruder on the=20
internet hijacked several radio stations' IP STL's and began=20
broadcasting their content over the radio. Not pretty. I advise any of=20
my remaining broadcast clients that if they are going to an IP STL that=20
they put in a dedicated point to point IP link without publicly routable=20
IP addresses.
Digital audio for broadcast STL's is old tech; we were doing G.722/G.723=20
over switched-56 in the early 90's. But using a public-facing internet=20
connection with no firewalling for an IP STL appliance like the Barix=20
boxes and the Tieline boxes and similar? That borders on networking=20
malpractice.
> ... But, to try to return to "relevant for NANOG", there are actual=20
> products requiring microsecond precision being sold. And used. And=20
> we've found that those products don't have a very good holdover. ...=20
Television broadcast is another excellent example of timing needs; thanks=
=2E
Valdis mentioned the scariest thing.... the scariest thing I've seen=20
recently? Windows NT 3.5 being used for a transmitter control system,=20
within the past five years. I will agree with Valdis on the scary=20
aspects of the public safety communications Mel mentioned. Thanks, Mel,=20
for the educational post.
