The Echo-Reply is a PPTP control message sent by either peer of a PAC-PNS control connection in response to the receipt of an Echo-Request.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | PPTP Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Magic Cookie |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Control Message Type | Reserved0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result Code | Error Code | Reserved1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LengthTotal length in octets of this PPTP message, including the entire PPTP header.
PPTP Message Type1 for Control Message.
Magic Cookie0x1A2B3C4D.
Control Message Type6 for Echo-Reply.
Reserved0This field MUST be 0.
IdentifierThe contents of the identify field from the received Echo-Request is copied to this field.
Result CodeIndicates the result of the receipt of the Echo-Request. Current valid Result Code values are:
1 (OK) - The Echo-Reply is valid
2 (General Error) - Echo-Request not accepted for the reason indicated in Error Code
Error CodeThis field is set to 0 unless a "General Error" condition exists, in which case Result Code is set to 2 and this field is set to the value corresponding to the general error condition as specified in Section 2.16.
Reserved1This field MUST be 0.