rfc1841.txt

<VC++网络游戏建摸与实现>源代码

              LAN Extension Interface Startup 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x01     |               0x03            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length

                                  ------------------------------>
                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                               0x01             |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                             Option-Data











Chapman, et al               Informational                     [Page 12]

RFC 1841           LAN Extension Interface Protocol       September 1995


 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x03     |               0x08            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length        |

                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                    0A  0A  0A  0A  0B  0C      |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 ---------- Option-Data --------|

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      0x05     |               0x03            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Option-Type             Option-Length

                                  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                0x01            |
                                 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                           Option-Data

   In Figure 4, the Address field always contains 0xFF, and the Control
   field always contains 0x03. The Protocol-Type field value is 0x8041
   because the startup options packet is a LAN extension interface
   control packet. The Code field value is 0x01 because the LAN
   extension interface unit is sending an LCP Configure-Request packet
   to configure or negotiate PPP-LEX. The Identifier field contains a
   randomly generated number. The Length field gives the total length of
   the entire packet.

   The first startup option is the MAC Type startup option. The Option-
   Type value for MAC Type is 0x01. The Option-Length field value for
   the MAC type startup option is 3 octets. The Option-Data field value
   is 0x01 because, in this example, the LAN extension interface unit
   connects to an Ethernet LAN using 802.3 canonical addresses.

   The next startup option transmitted is the MAC Address. Its Option-
   Type field value is 0x03, its Option-Length field value is 8 octets,
   and its Option-Data field value is the actual MAC address.

   Lastly, the LAN Extension startup option is transmitted. Its Option-
   Type field value is 0x05, its Option-Length field value is 3 octets,
   and its Option-Data field value is the LAN extension interface
   protocol version number (0x01).




Chapman, et al               Informational                     [Page 13]

RFC 1841           LAN Extension Interface Protocol       September 1995


   The host router responds to this LCP Configure-Request packet with an
   LCP Configure-Ack packet, Configure-Nak packet, or Configure-Rej
   packet. For more information on these packets, refer to "The Point-
   to-Point Protocol (PPP) for the Transmission of Multi-protocol
   Datagrams over Point-to-Point Links" RFC. (References, [1])

2.2 Remote Command Options

   Once the host router responds to the startup options Configure-
   Request packet with a Configure-Ack packet, the PPP-LEX NCP is in an
   "opened" state, and the LAN extension interface unit and the host
   router freely exchange PPP-LEX data packets and remote command
   options packets.

   The host router initiates PPP-LEX remote command options packets to
   control the configuration of the LAN extension interface unit and to
   gather statistics. There are 11 types of remote command options that
   the host router can send in a LEX_RCMD_REQUEST packet to the LAN
   extension interface unit. The LAN extension interface unit responds
   to a LEX_RCMD_REQUEST packet with a LEX_RCMD_ACK, LEX_RCMD_NAK, or
   LEX_RCMD_REJ packet.

   Frame Format

   Figure 5 shows a summary of the frame format for a remote command
   options packet. These fields are transmitted from left to right.

               Figure 5 Remote Command Options Frame Format

                        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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    Address    |     Control   |          Protocol Type        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     (1 octet)          (1)                      (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 octet)          (1)                      (2)







Chapman, et al               Informational                     [Page 14]

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 octet)          (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)

   Address

   This PPP-specified field is a single octet and contains the binary
   sequence 11111111 (hexadecimal 0xFF), the All-Stations address. PPP
   does not assign individual station addresses. The All-Stations
   address must be recognized and received by all devices. For more
   information on this field, refer to "The Point-to-Point Protocol
   (PPP) for the Transmission of Multi-protocol Datagrams over Point-
   to-Point Links." (References, [1])

   Control

   This PPP-specified field is a single octet and contains the binary
   sequence 00000011 (hexadecimal 0x03), the Unnumbered Information (UI)
   command with the P/F bit set to zero.

   For more information on this field, refer to "The Point-to-Point
   Protocol (PPP) for the Transmission of Multi-protocol Datagrams over
   Point-to Point Links." (References, [1])

   Note:  Hereafter the Address and Control fields will be represented
   together as a 2-octet field containing "0xFF03".

   Protocol-Type

   The Protocol-Type field is two octets and contains the IETF-assigned
   protocol type value. Valid LAN extension interface protocol type
   values follow:

      *  0x8041 (for control packets)
      *  0x0041 (for data packets)





Chapman, et al               Informational                     [Page 15]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Because the remote command options packet encapsulates LAN extension
   interface control data, the valid value for this field is 0x8041.

   Code

   The Code field is one octet and identifies the type of PPP-LEX
   packet. Valid values are as follows:

      *  0x40 - LEX_RCMD_REQUEST packet
      *  0x41 - LEX_RCMD_ ACK packet
      *  0x42 - LEX_RCMD_NAK packet
      *  0x43 - LEX_RCMD_REJ packet

   The host router sends the LEX_RCMD_REQUEST packet, and the LAN
   extension interface unit sends the LEX_RCMD_ACK, LEX_RCMD_NAK, and
   LEX_RCMD_REJ packets.

   Identifier

   The Identifier field is one octet and contains a randomly generated
   value. The value aids matching requests and replies. It is
   recommended that a non-zero value be used for the identifier. That
   is, zero could be used in the future for unsolicited messages from
   the LAN extension interface unit. Valid values are 0x01-0xFF.

   Length

   The Length field is two octets and indicates the length in octets of
   the entire packet, including the Code, Identifier, Length, and remote
   command options fields.

   Option-Type

   The Option-Type field is one octet and identifies the remote command
   option being transmitted. Valid values are as follows:

      *  0x01 - Filter Protocol Type
      *  0x02 - Filter MAC Address
      *  0x03 - Set Priority
      *  0x04 - Disable LAN Extension Ethernet Interface
      *  0x05 - Enable LAN Extension Ethernet Interface
      *  0x06 - Reboot LAN Extension Interface Unit
      *  0x07 - Request Statistics
      *  0x08 - Download Request
      *  0x09 - Download Data
      *  0x0A - Download Status
      *  0x0B- Inventory Request




Chapman, et al               Informational                     [Page 16]

RFC 1841           LAN Extension Interface Protocol       September 1995


   Each remote command option is discussed in detail in its own section
   later in this document.

   Option-Flags

   This field is one octet and further specifies the remote command
   option, containing specific actions that must be followed.

   Option-Length

   The Option-Length field is two octets and specifies the length in
   octets of the remote command option fields, including the Option-
   Type, Option-Flags, Option-Length, and Option-Data fields.

   Option-Data

   Option-Data field contains data relating to the remote command option
   specified in the Option-Type field.

2.3 Conditions for Sending PPP-LEX Packet

   This section describes the general conditions under which PPP-LEX
   packet types are sent. For specific information by remote command,
   refer to the appropriate remote command section later in this
   document.

   LEX RCMD_REQUEST Packet

   The host router sends LEX_RCMD_REQUEST packets to the LAN extension
   interface unit to initiate a remote command request. Until the host
   router receives a LEX_RCMD_ACK, LEX_RCMD_NAK, or LEX_RCMD_REJ packet
   from the LAN extension interface unit, the host router continues to
   send the LEX_RCMD_REQUEST packet a default number of times, at which
   point the host router times out.

   LEX_RCMD_ACK Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_ACK packet when it correctly receives the
   request and is able to perform the request.

   LEX RCMD_NAK Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_NAK packet when the LAN extension interface
   unit recognizes all the elements of the remote command option, but
   some elements are not acceptable. Upon receipt of a LEX_RCMD_NAK
   packet, the host router immediately stops sending the request.



Chapman, et al               Informational                     [Page 17]

RFC 1841           LAN Extension Interface Protocol       September 1995


   LEX RCMD_REJ Packet

   The LAN extension interface unit responds to a LEX_RCMD_REQUEST
   packet with a LEX_RCMD_REJ packet when the Option-Type value in the
   request packet is invalid. Invalid Option-Type values are those less
   than 0x01 or greater than 0x0B. Currently, this is the only condition
   under which the LAN extension interface unit sends a LEX_RCMD_REJ
   packet. Upon receipt of a LEX_RCMD_REJ packet, the host router
   immediately stops sending the request.

   The following sections detail each of the 11 remote command options.
   The sections provide a general description of the option and then
   specify the option's Option-Type, Option-Flags, Option-Length, and
   Option-Data fields. In addition, the sections describe the return