Sonet is used for WAN optical links in the USA. In Europe then we use SDH which is very similar. Sometimes you'll get metro ethernet optical circuits which use ethernet over dark fibre, however these tend to be short haul.
For Q2 then I'm afraid I don't know much about PSTN.
Does sonet connect central offices together in usa?
Central Offices within a region (where traffic is less)conneceted with SONET rings. whereas it is possible that central offices in NY connected to Central office in california over SONET which in turn going over DWDM. When traffic is more than few SONET rings it is better to use DWDM.
2)How does the pstn network in usa connect to pstn in a foreign country?
Here also SONET/DWDM, SONET is used to consoldate small traffic and DWDM is used to carry big pipes.
We are pleased to announce availability of Beta software for 16.6.3.
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looking for early feedback from customers befor...
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