4.5. ISAKMP Header Initialization

Unlike ISAKMP or IKE, the cookie pair is completely determined by the GCKS. The cookie pair in the GDOI ISAKMP header identifies the Re-key SA to differentiate the secure groups managed by a GCKS. Thus, GDOI uses the cookie fields as an SPI.

Next Payload identifies an ISAKMP or GDOI payload (see Section 5.0).

Major Version is 1 and Minor Version is 0 according to ISAKMP [RFC2408, Section 3.1].

The Exchange Type has value 33 for the GDOI GROUPKEY-PUSH message.

Flags MUST have the Encryption bit set according to [RFC2408, Section 3.1]. All other bits MUST be set to zero.

Message ID MUST be set to zero.

Length is according to ISAKMP [RFC2408, Section 3.1].