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3.6. Messages and TLVs for Extensibility

Support for LDP extensibility includes the rules for the U- and F- bits that specify how an LSR handles unknown TLVs and messages.

This section specifies TLVs and messages for vendor-private and experimental use.

3.6.1. LDP Vendor-Private Extensions​

Vendor-private TLVs and messages are used to convey vendor-private information between LSRs.

3.6.1.1. LDP Vendor-Private TLVs​

The Type range 0x3E00 through 0x3EFF is reserved for vendor-private TLVs.

The encoding for a vendor-private TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F|    Type (0x3E00-0x3EFF)   |            Length             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Vendor ID                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
|                           Data....                            |
~                                                               ~
|                                                               |
|                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U-bit Unknown TLV bit. Upon receipt of an unknown TLV, if U is clear (=0), a notification MUST be returned to the message originator and the entire message MUST be ignored; if U is set (=1), the unknown TLV is silently ignored and the rest of the message is processed as if the unknown TLV did not exist.

The determination as to whether a vendor-private message is understood is based on the Type and the mandatory Vendor ID field.

Implementations that support vendor-private TLVs MUST support a user-accessible configuration interface that causes the U-bit to be set on all transmitted vendor-private TLVs; this requirement MAY be satisfied by a user-accessible configuration interface that prevents transmission of all vendor-private TLVs for which the U- bit is clear.

F-bit Forward unknown TLV bit. This bit only applies when the U-bit is set and the LDP message containing the unknown TLV is to be forwarded. If F is clear (=0), the unknown TLV is not forwarded with the containing message; if F is set (=1), the unknown TLV is forwarded with the containing message.

Type Type value in the range 0x3E00 through 0x3EFF. Together, the Type and Vendor ID field specify how the Data field is to be interpreted.

Length Specifies the cumulative length in octets of the Vendor ID and Data fields.

Vendor ID 802 Vendor ID as assigned by the IEEE.

Data The remaining octets after the Vendor ID in the Value field are optional vendor-dependent data.

3.6.1.2. LDP Vendor-Private Messages​

The Message Type range 0x3E00 through 0x3EFF is reserved for Vendor- Private messages.

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|    Msg Type (0x3E00-0x3EFF) |      Message Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     Message ID                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                     Vendor ID                                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+                                                               +
|                     Remaining Mandatory Parameters            |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+                                                               +
|                     Optional Parameters                       |
+                                                               +
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

U-bit Unknown message bit. Upon receipt of an unknown message, if U is clear (=0), a notification is returned to the message originator; if U is set (=1), the unknown message is silently ignored.

The determination as to whether a Vendor-Private message is understood is based on the Msg Type and the Vendor ID parameter.

Implementations that support Vendor-Private messages MUST support a user-accessible configuration interface that causes the U-bit to be set on all transmitted Vendor-Private messages; this requirement MAY be satisfied by a user-accessible configuration interface that prevents transmission of all Vendor-Private messages for which the U-bit is clear.

Msg Type Message Type value in the range 0x3E00 through 0x3EFF. Together, the Msg Type and the Vendor ID specify how the message is to be interpreted.

Message Length Specifies the cumulative length in octets of the Message ID, Vendor ID, Remaining Mandatory Parameters, and Optional Parameters.

Message ID 32-bit integer used to identify this message. Used by the sending LSR to facilitate identifying Notification messages that may apply to this message. An LSR sending a Notification message in response to this message will include this Message ID in the notification message; see Section "Notification Message".

Vendor ID 802 Vendor ID as assigned by the IEEE.

Remaining Mandatory Parameters Variable length set of remaining required message parameters.

Optional Parameters Variable length set of optional message parameters.

3.6.2. LDP Experimental Extensions​

LDP support for experimentation is similar to support for vendor- private extensions with the following differences:

  • The Type range 0x3F00 through 0x3FFF is reserved for experimental TLVs.

  • The Message Type range 0x3F00 through 0x3FFF is reserved for experimental messages.

  • The encodings for experimental TLVs and messages are similar to the vendor-private encodings with the following difference.

    Experimental TLVs and messages use an Experiment ID field in place of a Vendor ID field. The Experiment ID field is used with the Type or Message Type field to specify the interpretation of the experimental TLV or Message.

    Administration of Experiment IDs is the responsibility of the experimenters.