Internet dies if GPS dies?

[Michael Shields]

In message <BAY7-F36LCVYl4maEqx0000bfc8 at hotmail.com>,
"Tyler Durden" <camera_lumina at hotmail.com> wrote:
> But the time stamps for SONET clocks are in the DS1 overhead, so the
> packets in the (other) DS1s/DS3s, etc...never "see" that timestamp,
> unless that timestamp is somehow read by a router and then put into
> the packets. But does a router  even GET timing? (ie, is there a BITS
> interface on a router? I don't think so.)

Routers do not have any ability to take input from a frequency
standard, even if you have one available.  Each interface recovers
clocking from the line, or can use an internal clock.  Some discussion
of this as it applies to routers running PPP over SONET over dark fiber:
http://www.cisco.com/en/US/tech/tk713/tk607/technologies_tech_note09186a0080094bb9.shtml

Those routers will operate independently of any external clock.
Routers that are connected to a mux (which includes anything DS3 and
below) will recover clock from the mux, which will have its own timing
interface or internal clock.

I'm not a SONET guru, but my understanding is that even with the
internal clocks, you would see at worst an occasional error burst for
a few ms.  No credible engineer would make a network that fell over
without GPS anyway, since it's just too easy for someone to
accidentally knock over your antenna while installing another, or nick
the cable with a saw, or who knows what.  In a nutshell, this isn't
something I'd worry about.
-- 
Shields.