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6.1.6. Map-Register Message Format

6.1.6. Map-Register Message Format​

The usage details of the Map-Register message can be found in specification [RFC6833]. This section solely defines the message format.

The message is sent in UDP with a destination UDP port of 4342 and a randomly selected UDP source port number.

The Map-Register message format is:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Type=3 |P|            Reserved               |M| Record Count  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Nonce . . .                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         . . . Nonce                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Key ID             |  Authentication Data Length   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

~ Authentication Data ~

   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |                          Record TTL                           |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

R | Locator Count | EID mask-len | ACT |A| Reserved |

   e   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

c | Rsvd | Map-Version Number | EID-Prefix-AFI |

   o   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

r | EID-Prefix |

   d   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  /|    Priority   |    Weight     |  M Priority   |   M Weight    |
   | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | o |        Unused Flags     |L|p|R|           Loc-AFI             |
   | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  \|                             Locator                           |
   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Packet field descriptions:

Type: 3 (Map-Register)

P: This is the proxy Map-Reply bit. When set to 1, an ETR sends a Map-Register message requesting the Map-Server to proxy a Map-Reply. The Map-Server will send non-authoritative Map-Replies on behalf of the ETR. Details on this usage can be found in [RFC6833].

Reserved: This field MUST be set to 0 on transmit and MUST be ignored on receipt.

M: This is the want-map-notify bit. When set to 1, an ETR is requesting a Map-Notify message to be returned in response to sending a Map-Register message. The Map-Notify message sent by a Map-Server is used to acknowledge receipt of a Map-Register message.

Record Count: This is the number of records in this Map-Register message. A record is comprised of that portion of the packet labeled 'Record' above and occurs the number of times equal to Record Count.

Nonce: This 8-octet 'Nonce' field is set to 0 in Map-Register messages. Since the Map-Register message is authenticated, the 'Nonce' field is not currently used for any security function but may be in the future as part of an anti-replay solution.

Key ID: This is a configured ID to find the configured Message Authentication Code (MAC) algorithm and key value used for the authentication function. See Section 14.4 for codepoint assignments.

Authentication Data Length: This is the length in octets of the 'Authentication Data' field that follows this field. The length of the 'Authentication Data' field is dependent on the MAC algorithm used. The length field allows a device that doesn't know the MAC algorithm to correctly parse the packet.

Authentication Data: This is the message digest used from the output of the MAC algorithm. The entire Map-Register payload is authenticated with this field preset to 0. After the MAC is computed, it is placed in this field. Implementations of this specification MUST include support for HMAC-SHA-1-96 [RFC2404], and support for HMAC-SHA-256-128 [RFC4868] is RECOMMENDED.

The definition of the rest of the Map-Register can be found in Section 6.1.4.

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