[RP-PPPoE] pppoe error code definition

[明]

I look up RFC2516 , but donot find definition of error code.

On windows xp, when dial-up fail, there always pops up error code,
e.g. Error 691 means "Access was denied because the user name and/or
password was invalid on the domain."

is Error 691 a standard error code of pppoe ? if yes, where to find
the specification?
or Error 691 is only apply to windows system? (not linux etc.)