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RFC 1841

 
 
 

PPP Network Control Protocol for LAN Extension

Part 2 of 3, p. 22 to 45
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4.0 Filter MAC Address

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x02 to the LAN extension interface unit to configure the LAN
   extension interface unit to filter inbound packets by source MAC
   address. A MAC address filter determines whether or not the LAN
   extension interface unit forwards packets with a specific source MAC

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   address to the host router. A MAC address filter consists of MAC
   address, a MAC address mask, and a permit or deny field. (See the
   "Option-Data Field Descriptions" section later in this section for
   more information on these filter fields.)

   A LEX_RCMD_REQUEST packet can contain 0 to 100 (depending on MTU
   size) MAC address filters. When a LEX_RCMD_REQUEST packet contains
   multiple filters, they are concatenated.

   The LAN extension interface unit applies MAC address filters to each
   inbound packet's source MAC address in the order in which the filters
   exist in the filter entry list. A packet must be permitted by one of
   the filters before the LAN extension interface unit can forward the
   packet across the serial link.

4.1 LEX RCMD_REQUEST - Filter MAC Address

   Figure 7 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for the Filter MAC Address remote command option. The host router
   transmits the fields from left to right.

    Figure 7 LEX_RCMD_REQUEST Packet Frame Format - Filter MAC Address

                            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 Options
<--------------------------------
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      MAC Address (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      MAC Address Mask (48 bits)....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Permit/Deny (16 bits)    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 Options, refer to the "Remote Command Options" section
   earlier in this document. Table 4 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that configures the LAN
   extension interface unit to filter by source MAC address.

   Table 4  Field Values for LEX_RCMD_REQUEST Packet - Filter MAC Address

   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               Minimum length = 12 octets
                        Maximum length = 1412 octets
   Option-Type          0x02 (Filter MAC Address)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets

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                        Maximum length = 1404 octets
   Option-Data          Zero or more filters to be applied at the
                        LAN extension interface unit. See the
                        following "Option-Data Field Description
                        section for details.

   Option-Data Field Descriptions

   The following three Option-Data fields are used in conjunction to
   specify a MAC address filter:

   *  MAC Address

   The MAC Address field contains a 48-bit IEEE 802.3 MAC address in
   canonical format.

   *  MAC Address Mask

   The MAC Address Mask field contains a "wild card" mask. The mask is a
   48-bit hexadecimal number whose ones bits correspond to the MAC
   address bits to be ignored during the comparison. The mask excludes
   bits from the comparison in the MAC address filter.

   *  Permit/Deny

   The Permit/Deny field determines whether or not a MAC address filter
   permits or denies inbound frames of a specific MAC address to pass to
   the host router. A permit value is a non-zero value that allows
   frames of a specific MAC address to pass to the host router. A deny
   value is a zero value that does not allow frames of a specific MAC
   address to pass to the host router.

   Implementation Notes

   Each LEX_RCMD_REQUEST packet is a complete specification of all MAC
   address filters and replaces any previously established filters.

   A LEX_RCMD_REQUEST packet with an Option-Length field equal to four
   (without any filter entries) instructs the LAN extension interface
   unit to turn off filtering. All MAC addresses, except local
   destination addresses cached in the self-learning filter, are
   forwarded.

4.2 Response Packets - Filter MAC Address

   The following packets are valid responses to the Filter MAC Address
   LEX_RCMD_REQUEST packet:

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   *  LEX_RCMD_ACK - Filter MAC Address

   The LAN extension interface unit sends a LEX_RCMD_ACK packet in
   response to a Filter MAC Address LEX_RCMD_REQUEST packet when the LAN
   extension interface unit correctly receives the Filter MAC Address
   remote command option and applies the entries to its filter table.
   All MAC address filter entries are returned in the LEX_RCMD_ACK
   packet.

   *  LEX_RCMD_NAK - Filter MAC Address

   The LAN extension interface unit sends a LEX_RCMD_NAK packet in
   response to the Filter MAC Address LEX_RCMD_REQUEST packet when the
   request contains an incorrect number of bytes in the filter or when
   there are no more filter entries available. The LAN extension
   interface unit continues to use the previous filter table (that is,
   the filter table that existed prior to the receipt of the request).
   The host router should signal an error to the user/network
   administrator. All filter entries are returned in the LEX_RCMD_NAK
   packet.

   *  LEX_RCMD-REJ - Filter MAC Address

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

   Table 5 summarizes the field values of Filter MAC Address
   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

      Table 5  Field Values for Response Packets - Filter MAC Address

   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
   Option-Type          0x02 (Filter MAC Address)
   Option-Flags         None
   Option-Length        The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Data          The filter entries sent in the

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                        LEX_RCMD_REQUEST packet

5.0 Set Priority

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x03
   to the LAN extension interface unit to establish the sending priority
   of different protocol type packets from the LAN extension interface
   unit to host router. There are four levels of priority:

      *  High
      *  Medium
      *  Normal
      *  Low

   Packets are classified according to protocol type and then are queued
   to one of four output queues on the LAN extension interface unit that
   correspond to the above priority levels. When the LAN extension
   interface unit is ready to transmit a packet, it scans the priority
   queues in order, from the highest to lowest, to find the highest
   priority packet.

5.1 LEX RCMD_REQUEST - Set Priority

   To establish priority queues for each protocol type, the host router
   sends a Set Priority LEX_RCMD_REQUEST packet. Figure 8 shows a frame
   format summary of such a LEX_RCMD_REQUEST packet. The host router
   transmits the fields from left to right.

       Figure 8 LEX_RCMD_REQUEST Packet Frame Format - Set Priority

                            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 Options
<--------------------------------
 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Protocol Type (16 bits)   |    Protocol Value (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 Options, 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 sets
   priority queuing.

     Table 6  Field Values for LEX_RCMD_REQUEST Packet - Set Priority

   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               Minimum length = 12 octets
                        Maximum length = 1028 octets
   Option-Type          0x03 (Set Priority)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets
                        Maximum length = 1020 octets
   Option-Data          Protocol Type and Priority Value. See the
                        following "Option-Data Field Description"
                        section for details.

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   Option-Data Field Descriptions

   The following Option-Data fields set the priority queuing of
   different protocol type packets.

   *  Protocol Type

   The Protocol Type field contains a 16-bit number that is any Ethernet
   type code. See the most recent "Assigned Numbers" RFC for the correct
   Ethernet type code.

   *  Priority Value

   The Priority Value field specifies the priority queue for the
   protocol type specified in the Protocol Type field. Valid values are
   as follows:

      - 0 - High priority queue
      - 1 - Medium priority queue
      - 2 - Normal priority queue
      - 3 - Low priority queue

   Sending a LEX_RCMD_REQUEST packet with an Option-Length of four (no
   priority entries) disables priority queuing. When disabled, the LAN
   extension interface unit transfers all packets at a normal (2)
   priority level. When a new priority is specified, it overwrites the
   previous setting.

5.2 Response Packets - Set Priority

   The following packets are valid responses to the Set Priority

   LEX_RCMD_REQUEST packet.

   *  LEX_RCMD_ACK - Set Priority

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

   *  LEX_RCMD_NAK - Set Priority

   The LAN extension interface unit sends a LEX_RCMD_NAK packet in
   response to the Set Priority LEX_RCMD_REQUEST packet when the request
   contains an incorrect number of bytes in the message, when necessary
   resources are not available, or when the specified priority is
   invalid.

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   *  LEX_RCMD-REJ - Set Priority

   See the "Conditions for Sending PPP-LEX Packets" section earlier in
   this document for more information on this packet type.  Table 7
   summarizes the field values of Set Priority LEX_RCMD_ACK,
   LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

         Table 7  Field Values for Response Packets - Set Priority

   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           A randomly generated value that aids in
                        matching requests with replies
   Length               Minimum length = 12 octets
                        Maximum length = 1028 octets
   Option-Type          0x03 (Set Priority)
   Option-Flags         None
   Option-Length        Minimum length = 4 octets
                        Maximum length = 1020 octets
   Option-Data          Protocol Type and Priority Value sent
                        in the LEX_RCMD_REQUEST packet

6.0 Disable LAN Extension Ethernet Interface

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x04
   to the LAN extension interface unit to disable the LAN extension
   Ethernet interface. This remote command option stops data traffic
   from the LAN extension interface unit to the host router for
   troubleshooting or for reconfiguring the LAN extension interface
   unit. This remote command option only affects data traffic. PPP-LEX
   control packets can still be transferred over the serial link.

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6.1 LEX RCMD_REQUEST - Disable LAN Extension Ethernet Interface

   Figure 9 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for the Disable LAN Extension Ethernet Interface remote command
   option. The host router transmits the fields from left to right.

             Figure 9  LEX_RCMD_REQUEST Packet Frame Format -
                 Disable LAN Extension Ethernet Interface

                            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 Options
<-------------------------------------------------------------->
 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 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 disables the
   LAN extension interface unit.

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           Table 8  Field Values for LEX_RCMD_REQUEST Packet -
                 Disable LAN Extension Ethernet Interface

   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          0x04 (Disable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

6.2 Response Packets - Disable LAN Extension Ethernet Interface

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Disable LAN Extension Ethernet Interface
   LEX_RCMD_REQUEST packet. 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 each of these response
   packets. Note that the LAN extension interface unit sends the
   LEX_RCMD_ACK packet after shutting down the interface.

   Table 9 summarizes the field values of Disable LAN Extension Ethernet
   Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

               Table 9  Field Values for Response Packets -
                 Disable LAN Extension Ethernet Interface

   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               12 octets
   Option-Type          0x04 (Disable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

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7.0 Enable LAN Extension Ethernet Interface

   The host router sends a LEX_RCMD_ REQUEST with an Option-Type of 0x05
   to the LAN extension interface unit to enable the LAN extension
   Ethernet interface. This remote command option allows LAN traffic to
   flow into the LAN extension interface unit after the interface has
   been disabled.

7.1 LEX RCMD_REQUEST - Enable LAN Extension Ethernet Interface

   Figure 10 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for an Enable LAN Extension Ethernet Interface remote command option.
   The host router transmits the fields from left to right.

   Figure 10 LEX_RCMD_REQUEST Packet Frame Format - Enable LAN Extension
   Ethernet Interface

                            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 Options
<-------------------------------------------------------------->
 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 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 10 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that enables the LAN extension

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   Ethernet interface.

           Table 10  Field Values for LEX_RCMD_REQUEST Packet -
                  Enable LAN Extension Ethernet Interface

   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               12octets
   Option-Type          0x05 (Enable LAN Extension Ethernet
                        Interface)
   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

7.2 Response Packets - Enable LAN Extension Ethernet Interface

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Enable LAN Extension Ethernet Interface
   LEX_RCMD_REQUEST packet. 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 each of these response
   packets. Note that the LAN extension interface unit sends the
   LEX_RCMD_ACK packet after enabling the interface.

   The frame format of the response packets mirrors that of the request.
   Table 11 summarizes the field values of Enable LAN Extension Ethernet
   Interface LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.

              Table 11  Field Values for Response Packets -
                  Enable LAN Extension Ethernet Interface

   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               12 octets
   Option-Type          0x05 (Enable LAN Extension Ethernet
                        Interface)

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   Option-Flags         None
   Option-Length        4 octets
   Option-Data          None

8.0 Reboot LAN Extension Interface Unit

   The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x06 to the LAN extension interface unit to cause the LAN
   extension interface unit to reboot itself. The Option-Flags field
   specifies the boot mode for the LAN extension interface unit. There
   are two boot modes:

   * The first boot mode (Option-Flag 0x00) is the default. The
     default boot mode causes the LAN extension interface unit to
     check for a valid Flash image and to boot from it if it exists.
     If a valid Flash image does not exist, the default boot mode
     causes the LAN extension interface unit to boot from the PROM
     image. Similarly, if the Flash image is bad, then the LAN
     extension interface unit recovers by booting from the PROM image.

   * The second boot mode (Option-Flag 0x01) forces the LAN extension
     interface unit to boot from the PROM image.

8.1 LEX RCMD_REQUEST - Reboot LAN Extension  Interface Unit

   Figure 11 shows a frame format summary of a LEX_RCMD_REQUEST packet
   for a Reboot LAN Extension Interface Unit remote command option. The
   host router transmits the fields from left to right.

             Figure 11 LEX_RCMD_REQUEST Packet Frame Format -
                    Reboot LAN Extension Interface Unit

                            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 Options
<-------------------------------------------------------------->
 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 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 12 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that instructs the LAN
   extension interface unit to reboot.

           Table 12  Field Values for LEX_RCMD_REQUEST Packet -
                    Reboot LAN Extension Interface Unit

   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          0x06 (Reboot LAN Extension Interface Unit)
   Option-Flags         Valid values:
                        * 0x00 - Reboot from Flash image if it
                          exists. If not, reboot from PROM. (This
                          value does not force the LAN extension
                          interface unit to reboot from PROM.)
                        * 0x01 - Reboot from PROM explicitly.
   Option-Length        4 octets
   Option-Data          None

8.2 Response Packets - Reboot LAN Extension Interface Unit

   LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD-REJ packets are valid
   responses to the Reboot LAN Extension Interface Unit LEX_RCMD_REQUEST
   packet. 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 each of these response packets. Note
   that the LAN extension interface unit reboots after sending the
   LEX_RCMD_ACK packet.

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   The frame format for the response packets mirrors that of the
   request. Table 13 summarizes the field values for Reboot LAN
   Extension Interface Unit LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ
   packets.

              Table 13  Field Values for Response Packets -
                    Reboot LAN Extension Interface Unit

   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 in the
                        LEX_RCMD_REQUEST packet
   Length               12 octets
   Option-Type          0x06 (Reboot LAN Extension Interface Unit)
   Option-Flags         Valid values:
                        * 0x00 - Reboot from Flash image if it
                          exists. If not, reboot from PROM. (This
                          value does not force the LAN extension
                          interface unit to reboot from PROM.)
                        * 0x01 - Reboot from PROM explicitly.
   Option-Length        4 octets
   Option-Data          None

9.0 Request Statistics

   The host router issues a LEX_RCMD_REQUEST packet with an Option-Type
   of 0x07 to obtain statistics information from the LAN extension
   interface unit. The host router may want statistics information about
   the following:

      *  Serial interface only
      *  LAN interface only
      *  Both the serial and LAN interfaces

   The host router may also send a Statistics Request LEX_RCMD_REQUEST
   packet to reset statistics in the LAN extension interface unit.

9.1 LEX RCMD_REQUEST - Request Statistics

   Figure 12 shows a summary frame format of a LEX_RCMD_REQUEST packet
   for a Statistics Request remote command option. The host router
   transmits the fields from left to right.

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    Figure 12 LEX_RCMD_REQUEST Packet Frame Format - Request Statistics

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

Summary Field Descriptions

   For 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 14 provides a summary of these fields
   when sending a LEX_RCMD_REQUEST packet that requests statistics of
   the LAN extension interface unit.

           Table 14  Field Values for LEX_RCMD_REQUEST Packet -
                            Request Statistics

   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          0x07 (Request Statistics)
   Option-Flags         Valid values:
                        * 0x01 - Resets serial statistics in the LAN

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                          extension interface unit
                        * 0x02 - Returns serial statistics from the
                          LAN extension interface unit
                        * 0x04 - Returns LAN statistics from the LAN
                          extension interface unit
                        * 0x08 - Resets LAN statistics in the LAN
                        * extension interface unit
                        If both serial and LAN statistics are
                        desired, the corresponding bits of this
                        field should be set (that is, 0x06). The
                        serial interface statistics appear in the
                        response packet before the LAN statistics.
   Option-Length        4 octets
   Option-Data          None

9.2 LEX RCMD_ACK - Request Statistics

   The normal response to a Statistics Request LEX_RCMD_REQUEST packet
   is a LEX_RCMD_ACK packet. This acknowledgment packet has an Option-
   Type, an Option-Flags, and an Option-Length field followed by one or
   two blocks of statistics data. The value in the Option-Flags field
   indicates whether the packet has one or two blocks of statistics. For
   more information on these values, see the following "Summary Field
   Descriptions" section.

   The frame format for the Statistics Request LEX_RCMD_ACK packet
   follows. The LAN extension interface unit transmits the fields from
   left to right.

      Figure 13 LEX_RCMD_ACK Packet Frame Format - Request Statistics

                            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 Options
<--------------------------------
 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 fields contains one or both of the following
   statistics blocks:

   Serial Interface Statistics Block:

                       (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Received                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of CRC Erros                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Framing Errors                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Overruns                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Frame Aborts                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets in Error                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to Lack of   |
| Buffer Descriptors                                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Time of Last Packet Received               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Data Rate                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Average Packet Rate                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Octets Received                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Input, Number of Packets Dropped Due to No Buffers|

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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Transmitted             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets with Error Transmissions|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Under-run Errors                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Low Priority Queue   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Low Priority Queue                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Low Priority |
| Queue                                                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Normal Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Normal Priority Queue             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in Normal       |
| Priority Queue                                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in Medium Priority Queue|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of Medium Priority Queue             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in              |
| Medium Priority Queue                                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets in High Priority Queue  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Size of High Priority Queue               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Packets Dropped in High         |
| Priority Queue                                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Time of Last Packet Transmitted           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Carrier Transitions             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Transmitted Data Rate                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial Line Output, Number of Octets Transmitted              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Lan Interface Statistics Block:

                        (32 bits)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with CRC Errors         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Framing Errors     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Overruns                                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Congestion        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Frame Aborts                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Broadcast Packets Received               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Received with Errors             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffer    |
| Descriptors                                                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Runts (Too Small Packets) Received       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Time of Last Packet Received                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Data Rate                                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Average Packet Rate                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Octets Received                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Input, Number of Packets Dropped Due to Lack of Buffers   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted                     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Transmitted with Errors         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Under-runs                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Collisions (Ethernet)                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets in Queue                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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| LAN Output, Queue Size                                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Packets Dropped in Queue                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Time of Last Packet Transmitted                   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Data Rate                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Transmit Packet Rate                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN Output, Number of Octets Transmitted                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LAN, Number of Interface Resets                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note:  Counts are cumulative since last counter reset. Time stamps
   are in milliseconds since last given event. Packet rates are in
   packets per second (averaged).

   Summary Field Descriptions

   For complete descriptions of the fields in the PPP Header, the LAN
   Extension Protocol Header, and the LAN Extension Remote Command
   Option, refer to the "Remote Command Options" section earlier in this
   document. The following table provides a summary of these fields for
   a LEX_RCMD_ACK packet that sends statistics to the host router.

    Table 15  Field Values for LEX_RCMD_ACK Packet - Request Statistics

   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               Minimum length = 120 octets
                        Maximum length = 140 octets
   Option-Type          0x07 (Request Statistics)
   Option-Flags         The LAN extension interface unit always sets
                        this field to reflect the actions taken in
                        response to the LEX_RCMD_ACK packet. Valid
                        values:
                        * 0x01 - Reset serial statistics in the LAN
                          extension interface unit
                        * 0x02 - Return serial statistics from the
                          LAN extension interface unit
                        * 0x04 - Return LAN statistics from the LAN

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                          extension interface unit
                        * 0x08 - Reset LAN statistics in the LAN
                          extension interface unit
                          If both serial and LAN statistics are
                          returned, the corresponding bits of this
                          field should are set (that is, 0x06). The
                          serial interface statistics appear in the
                          response packet before the LAN statistics.
   Option-Length        Minimum length = 116 octets
                        Maximum length = 136 octets
   Option-Data          The Serial Interface Statistics Block, the
                        LAN Interface Statistics Block, or both the
                        Serial Interface and LAN Interface
                        Statistics blocks. When the Option-Data
                        contains both blocks, the Serial Interface
                        Block precedes the LAN Interface Block.
                        Statistics values that the LAN extension
                        interface unit does not collect/support
                        are retuned with a value of zero.

   Implementation Notes

   If the LAN extension interface unit does not implement the capability
   of sending the serial and LAN interface statistics blocks separately,
   the implementation may always return both statistics blocks (with the
   Option-Flags and Option-Length fields containing the appropriate
   corresponding values).

   An implementation, such as a Token Ring LAN implementation, can
   collect a different set of statistics than shown above by defining a
   new statistics request type remote command option.

9.3 LEX RCMD_NAK/LEX RCMD_REJ - Request Statistics

   The LAN extension interface unit sends a LEX_RCMD_NAK packet when the
   Statistics Request LEX_RCMD_REQUEST packet did not specify the type
   of statistics the host router wants. That is, the request's Option-
   Flags field equals zero.

   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 Request Statistics LEX_RCMD_REJ packet.

   The frame format for the LEX_RCMD_NAK and LEX_RCMD_REJ packets is the
   same as that of the Statistics Request LEX_RCMD_REQUEST packet. Table
   16 summarizes the appropriate field values for the Statistics Request
   LEX_RCMD_NAK and LEX_RCMD_REJ packets.

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      Table 16  Field Values for LEX_RCMD_NAK/LEX_RCMD_REJ Packets -
                            Request Statistics

   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          0x07 (Request Statistics)
   Option-Flags         The same value as that sent by the
                        LEX_RCMD_REQUEST packet
   Option-Length        4 octets
   Option-Data          None



(page 45 continued on part 3)

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