Sync speed question

[#1]

No - the router is connected to the exchange, not to us. The exchange equipment routes that connection according to the realm on the line.
Hence the disconnect packet is sent to the exchange itself.
With regard to why the DLM equipment needs to know, well it doesn't really - but the DLM equipment isn't the sum total of the exchange equipment. The bit that makes the connection to the router needs to know in order to drop the connection

[#2]

Perhaps I'm being thick but normal advice is not to reboot the modem too much as the DLM will see this as instability. But if the PPP session is stopped first before a resync then it's not.
So if I was a designer of modems I would make sure that the reboot function disconnect the PPP session first.

[#3]

More interesting is when I do a resync using DMT or Routerstats do they send the disconnect packet first and if not why not

[#4]

I've never noticed a loss/change of sync on routerstats when doing a PPP disco/reconnect to get on to another gateway.
Getting confused,so do you have to do a reboot after and during the change in the PPP session before the PPP session reconnects?

[#5]

If you disconnect first you can then reboot or resync the router without the exchange seeing it as a fault