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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_note09186a0080... 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.