Internet Security - Dang Thanh Binh's Page

270 INTERNET SECURITY
The Domain of Interpretation field (32 bits) identifies the DOI under which this deletion
is taking place. For ISAKMP this value is zero(0) and for the IPsec DOI it is one (1).
The Protocol-id field (8 bits) specifies that ISAKMP can establish SAs for various protocols,
including ISAKMP and IPsec. This field identifies which SA database to apply the
delete request.
The SPI Size field (8 bits) is the length in octets of the SPI as defined by the Protocol-id.
In the case of ISAKMP, the Initiator and Responder cookie pair is the ISAKMP SPI. In
this case, the SPI Size would be 16 bytes for each SPI being deleted.
The # of SPIs field (16 bits) is the number of SPIs contained in the Delete Payload. The
size of each SPI is defined by the SPI Size field.
The Security Parameter Indexes field (variable length) identifies the specific security
associations to delete. Values for this field are DOI and protocol specific. The length of
this field is determined by the SPI Size and # of SPIs fields.
The Payload type for the Delete Payload is twelve(12).
Vendor ID Payload
The Vendor ID Payload contains a vendor defined constant. The constant is used by vendors
to identify and recognize remote instances of their implementations. This mechanism
allows a vendor to experiment with new features while maintaining backwards compatibility.
However, this is not a general extension facility of ISAKMP.
If a Vendor ID payload is sent, it must be sent during the Phase 1 negotiation. Reception
of a familiar Vendor ID Payload in the Phase 1 negotiation allows an implementation to
make use of Private Use payload numbers for vendor specific extension during Phase 2
negotiation.
The Vendor ID Payload fields are defined as follows:
The Next Payload field (8 bits) is the identifier for the payload type of the next payload
in the message. If the current payload is the last in the message, then this field will be 0.
The Reserved field (8 bits) is unused, but set to 0.
The Payload Length field (16 bits) is the length in octets of the current payload, including
the generic payload header.
The Vendor ID field (variable length) contains the choice of hash and text to hash. Vendors
could generate their vendor-id by taking a keyless hash of a string containing the product
name, and the version of the product.
The Payload type for the Vendor ID Payload is thirteen(13).
(III) ISAKMP Exchanges
TEAMFLY
ISAKMP supplies the basic syntax of a message exchange. ISAKMP allows the creation
of exchanges for SA establishment and key exchange. There are currently five default
Exchange Types defined for ISAKMP. Exchanges define the content and ordering of
Team-Fly ®