Michael Shields wrote... "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." SONET Synchronization is not a thing that can easily be discussed in any short amount of time. Synch in a SONET network is "provisioned", NE-by-NE, and if its done right then the chances of timing slips are very low. However, in certain cases you can have a big timing "island", and in this case over the course of days you'll start to see more and more slips until that whole Island pretty much disconnects from the rest of the network. (This can happen when the primary reference fails, and when the reamining NEs all get their timing from each other in a big loop, like a snake eating its tail. The whole clock for this island begins to drift wrt the rest of the network, and in some cases there can eventually be enough slips as to cause some NEs to declare AIS. However, if Synch was provisioned correctly this won't be seen.) The existence of possible timing islands, owever, should not be strongly associated with the loss of GPS. Traditionally, SONET networks use Cesium clocks as their primary reference source.GPSs have only started to proliferate in order to simplify synch. So in order for GPS cancellation to do anything at all to the internet, you'd have to have a network that has no access to ANY stratum1 clock (Cesium or GPS), you'd have to have old NEs in that network (ie, with a poor internal SONET clock), AND you'd have to have a timing island. And even then, only this island would be affected. If this island were in the middle of UUNet, you might see some slowdown. As for routers I'll take it that they can read timing out of the Synch Status Byte (S1 in the SONET overhead), so they'll "know" what the problem is at least (ie, that byte will tell them what the quality of the synch is). If the line clock is bad, I'd guess that the big Cisco routers will go into "holdover" (or whatever router heads call holdover), and that's the time they'll use to stamp the flows with. So, no problem I'm 99.9% sure. (And I'm rarely that sure of anything.) -TD _________________________________________________________________ Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail