digital servo communication protocol

i have many years experience in sorts of electronics interested in controlling servos.  seems there analog, understand (repeating 50 hz pulse width 1 ms or 2.5 ms moves servo arm 0 180).

then stumbled across concept of digital servos, makes far more sense in digital world , allows far more features of motion control (movement rate, continuous rotation, feedback device, etc.)

i have done fair search don't see consensus on protocol digital servo control.  i2c nice, example.  see there "openservo" organization "digital-izing" analog servo, seems still have native analog servo inherent limitations (could wrong here . . . didn't spend tons of time on web site).

i did come across references controller area network, nothing specific there standard protocol.

i came across these parts, might make starting point digital servo

http://www.ebay.com/itm/4-pcs-mg995-metal-gear-high-speed-torque-digital-servo-futaba-jr-rc-helicopter-/321334915031?pt=radio_control_parts_accessories&hash=item4ad10dafd7

but can't find specifics on how talk servo.

questions . . .

1) there common electrical +/- software protocol 'digital servos'?
2) can recommend general purpose metal gear, high torque servo has known electrical (serial, i2c, can, etc) plus known commands documentation?

thanks . . .

by way, let me clear i'm not talking sending digital signal means shield or interface board sends analog pulse width control analog servo.  there several videos , blogs calling digital servo.  i'm looking servo can go on directly on digital bus other servos on same bus, example.

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