rfc1841.txt

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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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RFC 1841           LAN Extension Interface Protocol       September 1995


                   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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RFC 1841           LAN Extension Interface Protocol       September 1995


                        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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RFC 1841           LAN Extension Interface Protocol       September 1995


   *  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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RFC 1841           LAN Extension Interface Protocol       September 1995


                        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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RFC 1841           LAN Extension Interface Protocol       September 1995


                   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-