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RFC 1841

 
 
 

PPP Network Control Protocol for LAN Extension

Part 3 of 3, p. 45 to 66
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10.0 Download Request

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x08 to alert the LAN extension interface unit that the host
   router will be issuing a software download to Flash memory. When the
   LAN extension interface unit acknowledges the command, the host
   router starts sending download data.

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10.1 LEX RCMD_REQUEST - Download Request

   Figure 14 shows a summary frame format of a LEX_RCMD_REQUEST packet
   for a Download Request remote command option. The host router
   transmits the fields from left to right.

    Figure 14  LEX_RCMD_REQUEST Packet Frame Format - Download Request

                          PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Block Number (16 bits)    |        File Size (32 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Filename (Max. 64 octets).......
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 17 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that informs the LAN extension
   interface unit of an upcoming software download to Flash memory.

   Table 17  Field Values for LEX_RCMD_REQUEST Packet - Download Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               Variable depending on size of filename in
                        the Filename field. Valid range:
                        Minimum length = 19 octets
                        Maximum length = 82 octets
   Option-Type          0x08 (Download Request)
   Option-Flags         None
   Option-Length        Variable depending on size of filename in
                        the Filename field. Valid range:
                        Minimum length = 11 octets
                        Maximum length = 74 octets
   Option-Data          Block Number, File Size, and Filename of
                        the code/image to be downloaded. See the
                        following "Option-Data Field Descriptions"
                        section for details.

   Option-Data Field Descriptions

   The Option-Data field contains the following fields:

   *  Block Number

   The Block Number field contains a value that identifies a contiguous
   group of code bits to be downloaded to the LAN extension interface
   unit. In the LEX_RCMD_REQUEST packet, the Block Number is always
   zero.

   *  File Size

   The File Size field contains the size (in octets) of the code to be
   downloaded to the LAN extension interface unit.

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   *  Filename

   The Filename field contains the name of the image to be transferred
   to the LAN extension interface unit.

10.2 Response Packets - Download Request

   The following packets are valid responses to a Download Request
   LEX_RCMD_REQUEST packet:

   *  LEX_RCMD_ACK - Download Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for more information on when the LAN extension
   interface unit sends this packet.

   *  LEX_RCMD_NAK - Download Request

   The LAN extension interface unit sends a Download Request
   LEX_RCMD_NAK packet when the LAN Extension interface unit is
   currently programming Flash, when the File Size field value in the
   request is greater than the unit's available Flash bytes, when the
   LAN extension interface unit is out of memory, or when the Block
   Number field value in the request is not zero.

   *  LEX_RCMD_REJ - Download Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for more information on when the LAN extension
   interface unit sends this packet.

   Table 18 summarizes the field values of the Download Request
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

      Table 18  Field Values for Response Packets - Download Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               The same value as that sent by the
                        LEX_RCMD_REQUEST packet

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   Option-Type          0x08 (Download Request)
   Option-Flags         None
   Option-Length        The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Data          Block Number, File Size, and Filename of
                        the code/image to be downloaded.

11.0 Download Data

   Once the host router receives a Download Request LEX_RCMD_ACK packet
   from the LAN extension interface unit, the host router downloads the
   data to be written to Flash memory by sending a LEX_RCMD_REQUEST
   packet with an Option-Type of 0x09. The host router sends multiple
   Download Data LEX_RCMD_REQUEST packets, each with 512 octets of
   Option-Data containing the binary data to be programmed into Flash
   memory.

   A packet containing Option-Data with less than 512 octets signals the
   end of the download data (that is, the end of tile). If the size of
   the file being downloaded is an even multiple of 512 bytes, then the
   last packet transferred should have an Option-Length of 6. That is,
   the last packet transferred should have Option-Data containing the
   Block Number field value but no data. A Block Number field value
   without data alerts the LAN extension interface unit that this is the
   last block to be transmitted.

11.1 LEX RCMD_REQUEST - Download Data

   The frame format for the Download Data LEX_RCMD_REQUEST packet is
   similar to a TFTP frame format. Figure 15 shows a summary frame
   format. The host router transmits the fields from left to right.

      Figure 15 LEX_RCMD_REQUEST Packet Frame Format - Download Data

                           PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

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                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Block Number (16 bits)    |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
|       Binary Download Data (Max. 512 octets).....             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. The following table provides a summary of
   these fields when sending a LEX_RCMD_REQUEST packet that download
   software to the LAN extension interface unit.

      Table 19  Field Values for LEX_RCMD_REQUEST Packet - Download Data

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)

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   Identifier           Valid values: 0x01-0xFF
   Length               Minimum length = 14 octets
                        Maximum length = 526 octets
   Option-Type          0x09 (Download Data)
   Option-Flags         None
   Option-Length        Minimum length = 6 octets (signals end of
                        data transfer for a file with a file size
                        of an even multiple of 512 bytes)
                        Maximum length = 518 octets
   Option-Data          Block Number and Download Data. See the
                        following "Option-Data Field Descriptions"
                        section for details.

   Option-Data Field Descriptions

   The following Option-Data fields provide the LAN extension interface
   unit with download data:

   *  Block Number

   The Block Number identifies the contiguous group of code bits to be
   downloaded. The host router automatically generates this number. The
   first Download Data packet gets a block number of one. The host
   router increments this Block Number value by one with every Download
   Data LEX_RCMD_REQUEST packet sent to the LAN extension interface
   unit. The maximum value of the Block Number is dependent on the
   unit's Flash memory size.

   *  Download Data

   The Download Data are the actual code bits being downloaded to the
   LAN extension interface unit. A maximum of 512 octets of download
   data can sent in one Download Data LEX_RCMD_REQUEST packet.

11.2 Response Packets - Download Data

   The following packets are valid responses to a Download Data
   LEX_RCMD_REQUEST packet:

   *  LEX_RCMD_ACK - Download Data

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in the document for more information on this packet.

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   *  LEX_RCMD_NAK - Download Data

   The LAN extension interface unit sends a Download Data LEX_RCMD_NAK
   packet when the LAN extension interface unit is not in the proper
   state or when accepting the data will over-run the download buffer.

   *  LEX_RCMD_REJ - Download Data

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in the document for more information on this packet.

   Table 20 summarizes the field values of the Download Data
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

       Table 20  Field Values for Response Packets - Download Data

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x41 (LEX_RCMD_ACK packet)
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               14 octets
   Option-Type          0x09 (Download Data)
   Option-Flags         None
   Option-Length        6 octets
   Option-Data          Block Number only

12.0 Download Status

   Upon completion of a Download Data sequence, the host router issues a
   LEX_RCMD_REQUEST packet with an Option-Type of 0x0A to request status
   of the success or failure of the download. A bad checksum of the
   image or a malfunctioning Flash memory could cause the download to
   fail.

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12.1 LEX RCMD_REQUEST - Download Status

   Figure 16 shows the frame format summary of a LEX_RCMD_REQUEST packet
   for a Download Status remote command option. The host router
   transmits the fields from left to right.

    Figure 16  LEX_RCMD_REQUEST Packet Frame Format - Download Status

                           PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 21 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests the download
   status of the LAN extension interface unit.

   Table 21  Field Values for LEX_RCMD_REQUEST Packet - Download Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)

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   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

12.2 LEX RCMD_REQUEST - Download Status

   When the LAN extension interface unit correctly receives the Download
   Status LEX_RCMD_REQUEST packet, it returns a LEX_RCMD_ACK packet
   containing the appropriate status information in the Option-Data
   field.

   Figure 17 shows the frame format for the Download Status LEX_RCMD_ACK
   packet. The LAN extension interface unit transmits the fields from
   left to right.

      Figure 17  LEX_RCMD_ACK Packet Frame Format - Download Status

                            PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

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            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Status (16 bits)       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete descriptions of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 22 provides a summary of these fields
   when sending a status information to the host router.

     Table 22  Field Values for LEX_RCMD_ACK Packet - Download Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x41 (LEX_RCMD_ACK packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               14 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        6 octets
   Option-Data          Status information. See the following
                        "Option-Data Field Descriptions" section
                        for details.

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   Option-Data Field Descriptions

   The Option-Data field uses the Status field to send the download
   status to the host router. The Status field reports the following
   status information:

      *  1 - Acknowledgment that no errors occurred
      *  3 - Sequence error occurred
      *  6 - Flash write error occurred
      *  7 - Checksum error

12.3 LEX RCMD_NAK/LEX RCMD_REJ - Download Status

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for information on when the LAN extension interface
   unit sends a Download Status LEX_RCMD_NAK packet and Download Status
   LEX_RCMD_REJ packet.

   The frame format for these two response packets mirror the frame
   format of the Download Status LEX_RCMD_REQUEST packet. Table 23
   summarizes the field values of the Download Status LEX_RCMD_NAK and
   LEX_RCMD_REJ packets.

   Table 23  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets - Download
   Status

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x0A (Download Status)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

13.0 Inventory Request

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x0B to the LAN extension interface unit to request inventory
   information. The host router may use this remote command option to
   accomplish the following:

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   *  Distinguish between different versions of the LAN extension
      interface unit for determining their capabilities

   *  Determine whether a new version of Flash code should be downloaded

13.1 LEX RCMD_REQUEST - Inventory Request

   Figure 18 shows the frame format for a LEX_RCMD_REQUEST packet with
   an Inventory Request remote command option. The host router transmits
   the fields from left to right.

   Figure 18  LEX_RCMD_REQUEST Packet Frame Format - Inventory Request

                           PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

            LAN Extension Interface Remote Command Option
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |        Option-Length          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)                    (2)

   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 24 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests inventory
   information.

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   Table 24  Field Values for LEX_RCMD_REQUEST Packet-Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x40 (LEX_RCMD_REQUEST packet)
   Identifier           Valid values: 0x01-0xFF
   Length               12 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

13.2 LEX RCMD_ACK - Inventory Request

   When it correctly receives the Inventory Request remote command
   option and retrieves the inventory information, the LAN extension
   interface unit responds with an acknowledgment. This acknowledgment
   contains the requested inventory information in the Option-Data
   field.

   Figure 19 shows the frame format for the Inventory Request
   LEX_RCMD_ACK packet.

      Figure 19 LEX_RCMD_ACK Packet Frame Format - Inventory Request

                            PPP Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              0xFF03           |          Protocol-Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              (2 octets)                         (2)

                LAN Extension Interface Protocol Header
<-------------------------------------------------------------->
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Code     |   Identifier  |              Length           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        (1)             (1)                     (2)

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            LAN Extension Interface Remote Command Option
<--------------------------------
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option-Type  |  Option-Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         (1)            (1)

                ----------------------------------------------->
                 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        Option-Length          |  Option-Data  |
                -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              (2)

   Where the Option-Data field contains the following fields:

                            (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Flash Size                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Serial Number                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  HW Version   | PROM Major Ver| PROM Minor Ver|Flash Major Ver|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flash Minor Ver|     FLAGS     | RAM Major Ver | RAM Minor Ver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
+   Mac Address (6 octets)      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Summary Field Descriptions

   For a complete description of the fields in the PPP Header, the LAN
   Extension Interface Protocol Header, and the LAN Extension Interface
   Remote Command Option, refer to the "Remote Command Options" section
   earlier in this document. Table 25 provides a summary of these fields
   when acknowledging a LEX_RCMD_REQUEST packet that requests inventory
   information.

    Table 25  Field Values for LEX_RCMD_ACK Packet - Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 0x41 (LEX_RCMD_ACK packet)

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   Identifier           The same value as that sent by
                        LEX_RCMD_REQUEST packet
   Length               34 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        26 octets
   Option-Data          Inventory data. See the following
                        "Option-Data Field Descriptions" section
                        for details.

   Option-Data Field Descriptions

   The Option-Data field of the LEX_RCMD_ACK packet uses the following
   fields to send inventory data to the host router about the LAN
   extension interface unit.

   *  Flash Size

   This field contains the LAN extension interface unit's Flash size in
   bytes.

   *  Serial Number

   This field provides the LAN extension interface unit's serial number.
   This is an unassigned, 32-bit number.

   *  HW Version

   This field contains the version number of the LAN extension interface
   hardware unit.

   *  PROM Major Ver

   This field contains part of the version number of the PROM image.
   "Major" indicates which major software release this revision belongs
   to. For example, if the PROM version number is 1.2, then the major
   version number is 1.

   *  PROM Minor Ver

   This field contains part of the version number of the PROM image.
   "Minor" indicates which minor software release this revision belongs
   to. For example, if the PROM version number is 1.2, then the minor
   version number is 2.

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   *  Flash Major Ver

   This field contains the "major" version number of the Flash image.
   For example, if the Flash image version number is 1.2, then the major
   version number is 1.

   *  Flash Minor Ver

   This field contains the "minor" version number of the Flash image.
   For example, if the Flash image version number is 1.2, then the minor
   version number is 2.

   *  FLAGS

   FLAGS report the boot status of the LAN extension interface unit. The
   flags are as follows:

   - 0x01 - Running PROM image
   - 0x02 - Running Flash image
   - 0x04 - PROM image passed checksum
   - 0x08 - Flash image passed checksum

   *  RAM Major Ver

   This field contains the "major" version number of the running image
   in RAM. For example, if the RAM image version number is 1.2, then the
   major version number is 1.

   *  RAM Minor Ver

   This field contains the "minor" version number of the running image
   in RAM. For example, if the RAM image version number is 1.2, then the
   minor version number is 2.

   *  MAC Address

   The MAC Address is the LAN extension interface unit's burned-in MAC
   address in canonical format. This field is six octets.

13.3 LEX RCMD_NAK/LEX RCMD_REJ - Inventory Request

   Refer to the "Conditions for Sending PPP-LEX Packets" section earlier
   in this document for information on when the LAN extension interface
   unit sends an Inventory Request LEX_RCMD_NAK packet and Inventory
   Request LEX_RCMD_REJ packet.

   The frame format of these two response packets mirrors that of the
   request. Table 26 summarizes the field values for such Inventory

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   Request LEX_RCMD_NAK/LEX_RCMD_REJ packets.

      Table 26  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
                             Inventory Request

   Field                Value
   Address/Control      0xFF03 (Broadcast address/Unnumbered
                        information)
   Protocol-Type        0x8041 (Control packet)
   Code                 Valid values:
                        * 0x42 (LEX_RCMD_NAK packet)
                        * 0x43 (LEX_RCMD_REJ packet)
   Identifier           The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x0B (Inventory Request)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

14.0 LAN Extension Interface Protocol Data Packets

   When the PPP-LEX NCP is in an "opened" state, the LAN extension
   interface unit and the host router also exchange PPP-LEX data packets
   (as well as control packets). There is only one type of PPP-LEX data
   packet. This data packet is a subset of the PPP-BCP packet format.

   The format subsetting is such that a PPP-BCP implementation will
   successfully process a LAN extension interface protocol packet. The
   differences are as follows:

      *  LAN ID field will not be present.
      *  LAN FCS field will never be present (that is, the F flag will
         always be off [=0]).
      *  LAN ID flag (I) will always be off.
      *  Pad field for the serial link will never be present, and the
         count field will be 0.

   For detailed information on PPP-BCP packets, refer to the "PPP
   Bridging Control Protocol (BCP)" RFC. (References, [2])

14.1 Frame Format

   Figure 20 shows the frame format for a PPP-LEX data packet. The MAC
   frame is transferred except for the FCS field. The LAN extension
   interface unit computes the FCS for packets transferred to the LAN
   and strips the FCS for packets destined for the host router.

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                Figure 20  PPP-LEX Data Packet Frame Format

    (8 bits)         (8 bits)      (8 bits)         (8 bits)
+-+-+-+-+-+-+-+-+
|   HDLC FLAG   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     0xFF      |      0x03     |             0x0041            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| F|I|Z|0| Pad  |    Mac Type   |    Destination MAC Address    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                        Destination MAC Address                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Source MAC Address                    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       Source MAC Address      |           Length/Type         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           LLC Data                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       ...                                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       (Serial) HDLC CRC       |  HDLC FLAG    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

14.2 Summary Field Descriptions

   HDLC FLAG

   HDLC Frame delimiter.

   0xFF

   This Address field contains the broadcast address.

   0x03

   This Control field contains unnumbered information.

   0x0041

   This field contains the IETF-assigned protocol type value for a
   PPP-LEX data packet. In this case this field will always contain
   0x0041.

   Flags

   The flags F, I, Z, 0 have the following meanings:

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      * F: Set bit F if the LAN FCS field is present. Because PPP-LEX
        data packets do not contain the LAN FCS field, this bit should
        not be set (field=0).

      * I: Set bit I if the LAN ID field is present. Because PPP-LEX
        data packets do not contain the field, this bit should not be
        set (field=0).

      * Z: Set bit Z if IEEE 802.3 Pad must be zero filled to minimum
        size.

      * 0: Reserved, must be zero.

   Pad

   Any PPP frame may have padding inserted in the Optional Data Link
   Layer Padding field. The value tells the receiving system how many
   pad octets to strip off. The LAN extension interface protocol does
   not support the Optional Data Link Layer Padding field, so the
   value of this field should be zero.

   MAC Type

   This field contains the most up-to-date value of the MAC type as
   specified in the most recent "Assigned Numbers" RFC. The current
   value is as follows:

      *  1: IEEE 802.3/Ethernet with canonical addresses

   Destination MAC Address

   This field is 6 octets and contains the MAC address of the
   destination system as defined by IEEE. The MAC Type field defines
   the bit ordering.

   Source MAC Address

   This field is 6 octets and contains the MAC address of the
   destination system as defined by IEEE. The MAC Type field defines
   the bit ordering.

   Length/Type

   This field is any Ethernet protocol type (See RFC 1700 in the
   references "Assigned Numbers").  For IEEE 802.3 frames, this is a
   length field.

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   LLC Data

   This field is the remainder of the MAC frame which is (or would be
   if it were present) protected by the LAN FCS.

   (Serial) HDLC CRC

   This is a 16 bit Cyclic Redundancy Check field.

   For complete information on the above fields and their relationship
   to PPP-BCP packets, refer to the "PPP Bridging Control Protocol
   (BCP)" RFC. (References, [2])

Notes

   1. The LAN extension interface protocol does allow the segmentation
      of individual LAN packets across the serial link. Each LAN
      packet must be transmitted across the serial link as one PPP-LEX
      encapsulation.

   2. MAC addresses in PPP-LEX packets should be in canonical format.

References

   [1] Simpson, W., "The Point-To-Point Protocol (PPP) for the
       Transmission of Multi-protocol Datagrams over Point-To-Point
       Links", RFC 1331, Daydreamer, May 1992.

   [2] Baker, F., and R. Bowen, "PPP Bridging Control Protocol (BCP)",
       RFC 1638, ACC, IBM, June 1994.

   [3] Lloyd, B., and W. Simpson, "PPP Authentication Protocols", RFC
       1334, Lloyd & Associates, Daydreamer, October 1992.

   [4] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1700,
       USC/Information Sciences Institute, October 1994.

   [5] Reynolds, J., and J. Postel, "Standard for the transmission of IP
       datagrams over IEEE 802 networks", RFC 1042, USC/Information
       Sciences Institute, February 1988.

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Security Considerations

   Security issues are not discussed in this memo.

Authors' Addresses

   Joelle Bafile Chapman, Technical Writer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: joelle@cisco.com


   Dave Coli, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: dcoli@cisco.com


   Andy Harvey, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: agh@cisco.com


   Bent Jensen, Engineering Manager
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: bent@cisco.com


   Kevin Rowett, Software Engineer
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706

   EMail: krowett@cisco.com