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3.11. Delete Payload

3.11. Delete Payload​

The Delete payload, denoted as D in this document, contains a protocol-specific Security Association identifier that the sender has removed from its Security Association database and is, therefore, no longer valid. Figure 17 shows the format of the Delete payload. It is possible to send multiple SPIs in a Delete payload; however, each SPI MUST be for the same protocol. Mixing of protocol identifiers MUST NOT be performed in the Delete payload. It is permitted, however, to include multiple Delete payloads in a single INFORMATIONAL exchange where each Delete payload lists SPIs for a different protocol.

Deletion of the IKE SA is indicated by a protocol ID of 1 (IKE) but no SPIs. Deletion of a Child SA, such as ESP or AH, will contain the IPsec protocol ID of that protocol (2 for AH, 3 for ESP), and the SPI is the SPI the sending endpoint would expect in inbound ESP or AH packets.

The Delete payload is defined as follows:

                    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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload  |C|  RESERVED   |         Payload Length        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol ID   |   SPI Size    |          Num of SPIs          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
~               Security Parameter Index(es) (SPI)              ~
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 17: Delete Payload Format

  • Protocol ID (1 octet) - Must be 1 for an IKE SA, 2 for AH, or 3 for ESP.

  • SPI Size (1 octet) - Length in octets of the SPI as defined by the protocol ID. It MUST be zero for IKE (SPI is in message header) or four for AH and ESP.

  • Num of SPIs (2 octets, unsigned integer) - The number of SPIs contained in the Delete payload. The size of each SPI is defined by the SPI Size field.

  • Security Parameter Index(es) (variable length) - Identifies the specific Security Association(s) to delete. The length of this field is determined by the SPI Size and Num of SPIs fields.

The payload type for the Delete payload is forty-two (42).

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