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rfc:rfc1841

Network Working Group J. Chapman Request For Comments: 1841 Cisco Systems, Inc. Category: Informational D. Coli

                                                   Cisco Systems, Inc.
                                                             A. Harvey
                                                   Cisco Systems, Inc.
                                                             B. Jensen
                                                   Cisco Systems, Inc.
                                                             K. Rowett
                                                   Cisco Systems, Inc.
                                                        September 1995
          PPP Network Control Protocol for LAN Extension

Status of Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.

Abstract

 Telecommunications infrastructure is improving to offer higher
 bandwidth connections at lower cost. Access to the network is
 changing from modems to more intelligent devices. This informational
 RFC discusses a PPP Network Control Protocol for one such intelligent
 device. The protocol is the LAN extension interface protocol.

Table of Contents

 1.0    Introduction ...........................................    3
    1.1   LAN Extension Interface Topology .....................    4
    1.2   LAN Extension Interface Architecture .................    5
    1.3   LAN Extension Interface Protocol .....................    6
 2.0    LAN Extension Interface Protocol Control Packets........    8
    2.1   Startup Options ......................................    8
    2.2   Remote Command Options ...............................   14
    2.3   Conditions for Sending PPP-LEX Packet ................   17
 3.0    Filter Protocol Type ...................................   18
    3.1   LEX_RCMD_REQUEST - Filter Protocol Type...............   19
    3.2   Response Packets - Filter Protocol Type...............   21
 4.0    Filter MAC Address .....................................   22
    4.1   LEX_RCMD_REQUEST - Filter MAC Address ................   23
    4.2   Response Packets - Filter MAC Address.................   25

Chapman, et al Informational [Page 1] RFC 1841 LAN Extension Interface Protocol September 1995

 5.0    Set Priority ...........................................   27
    5.1   LEX_RCMD_REQUEST - Set Priority ......................   27
    5.2   Response Packets - Set Priority ......................   29
 6.0    Disable LAN Extension Ethernet Interface ...............   30
    6.1   LEX_RCMD_REQUEST - Disable LAN Extension
          Ethernet Interface ...................................   31
    6.2   Response Packets - Disable LAN Extension
          Ethernet Interface ...................................   32
 7.0    Enable LAN Extension Ethernet Interface ................   33
    7.1   LEX_RCMD_REQUEST - Enable LAN Extension
          Ethernet Interface ...................................   33
    7.2   Response Packets - Enable LAN Extension
          Ethernet Interface ...................................   34
 8.0    Reboot LAN Extension Interface Unit ....................   35
    8.1   LEX_RCMD_REQUEST - Reboot LAN Extension Interface
          Unit .................................................   35
    8.2   Response Packets - Reboot LAN Extension
          Interface Unit .......................................   36
 9.0    Request Statistics .....................................   37
    9.1   LEX_RCMD_REQUEST - Request Statistics ................   37
    9.2   LEX_RCMD_ACK - Request Statistics ....................   39
    9.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Request Statistics .......   44
 10.0    Download Request ......................................   45
    10.1   LEX_RCMD_REQUEST - Download Request .................   46
    10.2   Response Packets - Download Request..................   48
 11.0    Download Data .........................................   49
    11.1   LEX_RCMD_REQUEST - Download Request .................   49
    11.2   Response Packets - Download Data ....................   51
 12.0    Download Status .......................................   52
    12.1   LEX_RCMD_REQUEST - Download Status ..................   53
    12.2   LEX_RCMD_ACK - Download Status ......................   54
    12.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Download Status .........   56
 13.0    Inventory Request .....................................   56
    13.1   LEX_RCMD_REQUEST - Inventory Request ................   57
    13.2   LEX_RCMD_ACK - Inventory Request ....................   58
    13.3   LEX_RCMD_NAK/LEX_RCMD_REJ - Inventory Request .......   61
 14.0    LAN Extension Interface Protocol Data Packets .........   62
    14.1   Frame Format ........................................   62
    14.2   Summary Field Descriptions...........................   63

Chapman, et al Informational [Page 2] RFC 1841 LAN Extension Interface Protocol September 1995

 NOTES ......................................................      65
 REFERENCES .................................................      65
 SECURITY CONSIDERATIONS ....................................      66
 AUTHORS' ADDRESSES .........................................      66

1.0 Introduction

 An increasing number of corporations allow their employees to
 telecommute to work due to local government regulations on traffic
 and air pollution. Additionally, many businesses are run out of
 internetworked home offices and small branch offices. With these
 changes in the workplace, more people and businesses require Internet
 access from small LANs.
 Today, routers serve the LAN-to-LAN traffic using high-speed WAN
 links such as leased lines, ISDN, or Frame Relay. This new breed of
 Internet users from home offices and small branch offices may have a
 different, less network-literate skill set than those connecting up
 to the Internet today. These new users need an alternative to the
 complex and hard-to-configure routers currently employed for
 connectivity. One such alternative is a LAN extension interface unit.
 A LAN extension interface unit is a hardware device installed at
 remote sites (such as a home office or small branch office) that
 connects a LAN across a WAN link to a router at a central site. The
 following sections introduce a LAN extension interface topology,
 architecture, and protocol.

Chapman, et al Informational [Page 3] RFC 1841 LAN Extension Interface Protocol September 1995

1.1 LAN Extension Interface Topology

 Figure 1 shows the topology of LAN extension interfaces. The figure
 shows two LAN extension interface units connected via a WAN link to a
 central or "host router."
               Figure 1 LAN Extension Interface Topology
  1. —————————————-

Router

  1. —————————————-

Virtual Interface Virtual Interface

                      123.123.78.1        123.123.89.1
                .........................................
                         Serial 0           Serial n
                -----------------------------------------
                           |<---- WAN Link ---->|
              ------------------                    ------------------
              | LAN Extension  |                    | LAN Extension  |
              | Interface Unit |                    | Interface Unit |
              ------------------                    ------------------
                      |                                     |
              ------------------                    ------------------
                |                                      |
              ------------                          ------------
              | End node |                          | End node |
              ------------                          ------------
              123.123.78.2                          123.123.46.2
 Each LAN extension interface unit maps to a virtual interface at the
 host router. The virtual interface mirrors the characteristics of the
 LAN extension interface unit. To the routing protocols, the virtual
 interface looks just like a local interface, but with the bandwidth
 of a serial line. The virtual interface keeps the state (up or down)
 of the LAN extension interface unit, and identifies each LAN
 extension interface unit by its MAC address.
 A LAN extension interface protocol transfers MAC frames from the LAN
 extension interface unit across the serial line to the host router.
 At the termination point in the router, the router routes the
 packets. This topology uses only one subnet per remote LAN rather
 than two, as is the case when routers exist on both ends of a WAN
 link. Figure 1 shows this subnetting structure. The IP addresses of
 the virtual interfaces on the router are in the same subnet as the IP
 addresses of the end nodes on the LAN of the LAN extension interface
 unit. The LAN extension interface unit itself has no IP address.

Chapman, et al Informational [Page 4] RFC 1841 LAN Extension Interface Protocol September 1995

 LAN extension interface units resemble bridges, but with the
 following distinct differences:
  • LAN extension interface units always depend on a host router.

They cannot operate standalone or even back-to-back with other

    LAN extension interface units.
  • LAN extension interface units need not employ any spanning tree

algorithm.

  • (LAN extension interface units transfer MAC frames across a

serial line (like bridges), but a router can either route or

    bridge the LAN extension interface data packets.

1.2 LAN Extension Interface Architecture

 Figure 2 shows the basic LAN extension interface architecture.
             Figure 2 LAN Extension Interface Architecture
               Router                        LAN Extension Interface
        -------------------                  -------------------
        |   Network Layer |                  |     MAC Layer   |
        -------------------                  -------------------
                |                                       |
        -------------------                  -------------------
   |    |Virtual Interface|                  |       Filters   |   |
   |    -------------------                  -------------------   |
   |            |                                 |                |
   |    -------------------                  -------------         |
   |    |      PPP        |                  |   RCMD    |         |
   |    |                 |                  |   Handler |         |
   |    -------------------                  -------------         |
   |            |                                 |                |
   |    -------------------                  -------------------   |
   |    |Serial Interface |                  |        PPP      |   |
   |    -------------------                  -------------------   |
   |            |                                      |           |
   |            |                            -------------------   |
   |            |                            | Serial Interface|   |
   |            |                            -------------------   |
   |            |          WAN Link                    |           |
   |            ---------------------------------------            |
   |                                                               |
   |   Outbound                                          Inbound   |
   -------------->                                  <---------------

Chapman, et al Informational [Page 5] RFC 1841 LAN Extension Interface Protocol September 1995

 In the inbound direction (from the remote LAN, to the LAN extension
 interface unit, across the WAN link, to the host router), the LAN
 extension interface unit can filter received frames to optimize WAN
 utilization. The LAN extension interface unit can filter frames by
 protocol type or by MAC address. Frames that pass through the LAN
 extension interface filters go to the WAN protocol state machine. In
 Figure 2, this state machine is PPP. The LAN extension interface unit
 adds PPP encapsulation and forwards the packet to the router via the
 WAN serial link.
 Upon receiving the frame, the host router decapsulates the PPP header
 and passes the packet to the virtual interface. From there the
 virtual interface handles the packet like any packet received on a
 local interface -- by routing or bridging the packet to another
 interface, depending on configuration.
 In the outbound direction (from the host router, across the WAN link,
 to the LAN extension interface unit, to the LAN), the host router's
 virtual interface builds the full MAC header, before adding PPP
 encapsulation. The router then sends the packet across the WAN serial
 link to the LAN extension interface unit. The LAN extension interface
 unit strips the PPP header and forwards the packet directly onto the
 LAN. The host router has already determined that the packet needs to
 be forwarded to the LAN extension interface unit, hence there is no
 need for additional filtering or processing at that end.
 Embedded in the data stream is a control stream for configuring and
 managing the LAN extension interface unit from the host router. The
 virtual interface makes the remote LAN extension interface unit
 appear like a local router interface to the routing protocols.
 Configuration commands and statistics gathering commands are issued
 on the router to the virtual interface. The virtual interface formats
 the LAN extension interface remote commands into encoded messages and
 transfers them in-band with the data packets. The LAN extension
 interface unit decodes the remote commands and executes them.
 Responses are similarly formatted messages sent by the LAN extension
 interface unit to the host router. The remote command messages use a
 different encapsulation type than the data packets, as described
 later in this document in the "LAN Extension Interface Protocol
 Control Packets" and "LAN Extension Interface Protocol Data Packets"
 sections.

1.3 LAN Extension Interface Protocol

 To accommodate this LAN extension interface architecture, a new
 Network Control Protocol (NCP) for PPP exists. This NCP is called
 PPP-LEX. The basic functionality of PPP-LEX is to encapsulate LAN

Chapman, et al Informational [Page 6] RFC 1841 LAN Extension Interface Protocol September 1995

 extension interface control and data packets. The IETF has assigned
 two new protocol types for these functions, as shown in Table 1.
               Table 1  IETF Protocol Types for PPP-LEX
 Protocol Type       Function
 0x8041              Encapsulates control packets
 0x0041              Encapsulates data packets (MAC frames)
 PPP is a natural choice for a LAN extension interface protocol
 because it allows for negotiating a specific control protocol and
 options at connection time. This means that network administrators do
 not have to statically configure the router interface for remote
 interfaces. Rather, remote interfaces negotiate the link at
 connection time.
 The LAN extension interface protocol employs PPP link operation as
 described in RFC 1331, which reads as follows:
    In order to establish communications of a point-to-point link,
    each end of the PPP link must first send [Link Control Protocol]
    LCP packets to configure and test the data link. After the link
    has been established,the peer may be authenticated. Then PPP must
    send NCP packets to choose and configure one or more network layer
    protocols. Once each of the chosen network-layer protocols has
    been configured, datagrams from each network layer protocol can be
    sent over the link.
    The link will remain configured for communications until explicit
    LCP or NCP packets close the link down, or until some external
    event occurs (an inactivity timer expires or network administrator
    intervention). (References, [1])
 Thus, the LAN extension interface unit and the host router exchange
 PPP-LCP packets at connection time to dynamically configure and test
 the WAN serial link. Once the link reaches an "opened" state, the LAN
 extension interface unit and host router exchange PPP-LEX NCP packets
 to configure the LAN extension interface protocol. Once it is
 configured, the NCP (PPP-LEX) reaches an "opened" state, and PPP
 carries the PPP-LEX control and data packets across the serial link.
 At this point, link traffic is a any combination of LCPs, PPP-LEX
 NCPs, PPP-LEX control packets, and PPP-LEX data packets.
 Note that the LAN extension interface protocol is not a bridging
 protocol. The only similarity to the PPP Bridging Control Protocol
 (References. [2]) is that the LAN extension interface protocol also
 encapsulates MAC frames.

Chapman, et al Informational [Page 7] RFC 1841 LAN Extension Interface Protocol September 1995

 The following sections detail PPP-LEX control packets and data
 packets.

2.0 LAN Extension Interface Protocol Control Packets

 There are two types of PPP-LEX control packets, as follows:
  • Startup options packet
  • Remote command options packets
 The startup options packet is the first PPP-LEX NCP packet that the
 LAN extension interface unit sends to the host router after the LCP
 has reached an "opened" state. This required startup options packet
 configures the LAN extension interface protocol and puts the PPP-LEX
 NCP in an "opened" state.
 Remote command options are the PPP-LEX NCP packets that control the
 functioning and statistics gathering of the LAN extension interface
 protocol.

2.1 Startup Options

 The LAN extension interface unit sends a startup options packet to
 the host router to negotiate the following startup options:
  • MAC Type
  • MAC Address
  • LAN Extension
 The MAC Type startup option informs the host router of the type of
 media that the LAN extension interface unit is connected to. For
 example, the LAN extension interface unit may be connected to an
 Ethernet LAN or a Token Ring LAN. Currently, only Ethernet is
 supported. The MAC type tells the host router what type of traffic
 the LAN extension interface unit is prepared to receive. If the host
 router rejects the MAC type, the LAN extension interface unit sends
 the Configure-Request again.
 The MAC Address startup option sends the MAC address of the LAN
 extension interface unit to the host router to authenticate the LAN
 extension interface unit and bind it to the corresponding virtual
 interface at the host router. The host router also inserts the MAC
 address in outbound packets. The MAC address is represented in IEEE
 802.3 canonical format.
 The LAN Extension startup option establishes the network layer
 protocol (NCP) as PPP-LEX and provides the host router with the LAN
 extension interface protocol version number.

Chapman, et al Informational [Page 8] RFC 1841 LAN Extension Interface Protocol September 1995

 Each startup option is transmitted in a series of three fields:
 Option-Type, Option-Length, and Option-Data fields. The fields are
 concatenated in the startup options Configure-Request packet.
 Frame Format
 Figure 3 shows a summary of the frame format for the startup options
 packet. The LAN extension interface unit sends this startup options
 packet to the host router. The LAN extension interface unit transmits
 these fields from left to right.
      Figure 3  Startup Options Frame Format (Configure-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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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)
          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 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Type Option-Length Option-Data

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   (1 octet)          (1)
 Address
 This PPP-specified field is one 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])

Chapman, et al Informational [Page 9] RFC 1841 LAN Extension Interface Protocol September 1995

 Control
 This PPP-specified field is one 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])
 Protocol-Type
 The Protocol-Type field is two octets and contains the IETF-assigned
 protocol type value. Valid LAN extension interface protocol type
 values are as follows:
  • 0x8041 (for control packets)
  • 0x0041 (for data packets)
 Because the startup 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 LCP packet
 that the LAN extension interface packet is sending. Valid values are
 as follows:
  • 0x01 - Configure-Request
  • 0x02 - Configure-Ack
  • 0x03 - Configure-Nak
  • 0x04 - Configure-Rej
 The LAN extension interface unit initiates the startup options
 packet; therefore, the valid value for this field is 1.
 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.

Chapman, et al Informational [Page 10] RFC 1841 LAN Extension Interface Protocol September 1995

 Length
 The Length field is two octets and indicates the length of the entire
 packet in octets, including the Code, Identifier, Length, and startup
 options fields.
 Option-Type
 The Option-Type field is one octet and identifies the startup option
 being negotiated. Valid values are as follows:
  • 0x01 - MAC Type
  • 0x03 - MAC Address
  • 0x05 - LAN Extension
 Option-Length
 The Option-Length field is one octet and specifies the length of the
 startup option fields, including the Option-Type, Option-Data, and
 Option-Length fields.
 Option-Data
 The Option-Data field contains the data relating to the value
 specified in the Option-Type field. That is, if the Option-Type field
 specifies MAC type (0x01), then the Option-Data field contains the
 MAC type (Ethernet, Token Ring, and so on). If the Option-Type field
 specifies MAC address (0x03), then the Option-Data field contains the
 actual MAC address. If the Option-Type field specifies LAN Extension
 (0x05), then the Option-Data field contains LAN extension interface
 software information. The following table defines the contents of the
 Option-Data field for each possible Option-Type field value:
 Option-Type Field Value   Option-Data
 0x01 (MAC Type)           The most up-to-date value of the MAC type as
                           specified in the most recent "Assigned
                           Numbers" RFC. The current valid value from
                           that RFC follows:
                           *  0x01: IEEE 802.3/Ethernet with canonical
                              addresses
 0x03 (MAC Address)        The burned-in MAC address in IEEE 802.3
                            canonical format.
 0x05 (LAN Extension)      The LAN extension interface protocol version
                           number. 0x01 is the current protocol version
                           supported.

Chapman, et al Informational [Page 11] RFC 1841 LAN Extension Interface Protocol September 1995

 Example
 In the Configure-Request packet that it sends to the host router, the
 LAN extension interface unit concatenates the Option-Type, Option-
 Data, and Option-Length fields for each startup option, as shown in
 Figure 4. The LAN extension interface unit transmits these fields
 from left to right.
       Figure 4 Sample Startup Options Configure-Request Packet
                       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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0xFF 0x03 0x8041

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Address          Control             Protocol-Type
              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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0x01 0x09 0x12

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 Option-Type      Identifier               Length
            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
  1. —————————–>

4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0x01 |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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)
  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
 messages from the LAN extension interface unit.

3.0 Filter Protocol Type

 The host router sends a LEX_RCMD_REQUEST packet with an Option-Type
 of 0x01 to the LAN extension interface unit to configure the LAN
 extension interface unit to filter inbound packets by protocol type.
 A protocol type filter determines whether or not the LAN extension
 interface unit forwards packets of a specific protocol type to the
 host router. A protocol type filter consists of a 16-bit value, 16-
 bit mask, and a permit or deny field. (See the "Option-Data Field
 Descriptions" section for more information on these filter fields.)
 A LEX_RCMD_REQUEST packet can contain 0 to 200 (depending on MTU
 size) protocol type filters. When a LEX_RCMD_REQUEST packet contains
 multiple filters, they are concatenated.
 The LAN extension interface unit applies the protocol type filters to
 each inbound packet's protocol type field in the order in which the
 filters exist in the filter table. A packet must be permitted by one
 of the filters before the LAN extension interface unit can forward
 the packet across the serial link.
 The following example is a filtering algorithm:
 if (protocol_type_field & (~filter_mask)) == filter_value)
  if (permit/deny_field == PERMIT) <forward packet on serial LAN>
 else <DROP PACKET>
 The protocol type filter should also be applied to the DIX type code
 field of Ethernet II frames as well as to IEEE 802.2 SNAP packets.

Chapman, et al Informational [Page 18] RFC 1841 LAN Extension Interface Protocol September 1995

3.1 LEX RCMD_REQUEST-Filter Protocol Type

 Figure 6 shows a frame format summary of a LEX_RCMD_REQUEST packet
 for the Filter Protocol Type remote command option. The host router
 transmits the fields from left to right.
 Figure 6 LEX_RCMD_REQUEST Packet Frame Format - Filter Protocol Type
                            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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Type Option-Flags

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       (1)            (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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Value (16 bits) Value (16 bits)

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Permit/Deny (16 bits)

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Chapman, et al Informational [Page 19] RFC 1841 LAN Extension Interface Protocol September 1995

 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. The following table provides a summary of
 these fields when sending a LEX_RCMD_REQUEST packet that configures
 the LAN extension interface unit to filter by protocol type.
 Table 2  Field Values for LEX_RCMD_REQUEST Packet-Filter Protocol Type
 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 = 1212 octets
 Option-Type         0x01 (Filter Protocol Type)
 Option-Flags        None
 Option-Length       Minimum length = 4 octets
                     Maximum length = 1204 octets
 Option-Data         Zero or more filters to be applied at
                     the LAN extension interface unit. See the
                     following "Option-Data Field Descriptions"
                     for details.
 Option-Data Field Descriptions
 The following three Option-Data fields are used in conjunction to
 specify a protocol type filter:
  • Value
 The Value field contains a 16-bit value that is any Ethernet type
 code. Refer to the "Assigned Numbers" RFC for valid Ethernet type
 codes. (References, [4]).
  • Mask
 The Mask field contains a 16-bit "wild card" mask. That is, this
 field contains a 16-bit number whose ones bits correspond to the type
 code bits to be ignored during the comparison. Thus, the mask
 excludes bits from the comparison in the protocol type filter.

Chapman, et al Informational [Page 20] RFC 1841 LAN Extension Interface Protocol September 1995

  • Permit/Deny
 The Permit/Deny field determines whether a protocol type filter
 permits or denies inbound frames to pass to the host router. A permit
 value is a non-zero value that allows frames of a specific protocol
 type to pass to the host router. A deny value is a zero value that
 does not allow frames of a specific protocol type to pass to the host
 router.
 Implementation Notes
 Each LEX_RCMD_REQUEST packet is a complete specification of all
 protocol type filters and replaces any previously established
 filters.
 Note the following special cases:
  • 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 protocol type filtering. All MAC
    protocol types are forwarded.
  • A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the

Value field, 0xFFFF in the Mask field, and a positive value in the

    Permit/Deny field means that if previous filters in the filter list
    do not permit the inbound packet then this filter entry will. This
    filter entry is typically the last filter in a list of filters
    contained within the Option-Data field.
  • A LEX_RCMD_REQUEST packet with a filter entry of 0x0000 in the

Value field, 0xFFFF in the Mask field, and a zero in the

    Permit/Deny field, means that the LAN extension interface unit must
    deny all protocol types. This filter is typically the last filter in
    a list of filters contained within the Option-Data field.

3.2 Response Packets - Filter Protocol Type

 The following packets are valid responses to the Filter Protocol Type
 LEX_RCMD_REQUEST packet:
  • LEX_RCMD_ACK - Filter Protocol Type
 The LAN extension interface unit sends a LEX_RCMD_ACK packet in
 response to the Filter Protocol Type LEX_RCMD_REQUEST packet when the
 LAN extension interface unit correctly receives the Filter Protocol
 Type remote command option and applies all filter entries to its
 filter table. All filter entries are returned to the host router in
 the LEX_RCMD_ACK packet.

Chapman, et al Informational [Page 21] RFC 1841 LAN Extension Interface Protocol September 1995

  • LEX_RCMD_NAK - Filter Protocol Type
 The LAN extension interface unit sends a LEX_RCMD_NAK packet in
 response to the Filter Protocol Type 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 to the host router in
 the LEX_RCMD_NAK packet.
  • LEX_RCMD-REJ - Filter Protocol Type
 See the "Conditions for Sending PPP-LEX Packets" section earlier in
 this document for more information on this packet type.
 Table 3 summarizes the field values of Filter Protocol Type
 LEX_RCMD_ACK, LEX_RCMD_NAK, and LEX_RCMD_REJ packets.
   Table 3  Field Values for Response Packets - Filter Protocol Type
 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          0x01 (Filter Protocol Type)
 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
                      LEX_RCMD_REQUEST packet

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

Chapman, et al Informational [Page 22] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 23] 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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

(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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

Chapman, et al Informational [Page 24] 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:

Chapman, et al Informational [Page 25] 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

Chapman, et al Informational [Page 26] 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)

Chapman, et al Informational [Page 27] 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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

(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.

Chapman, et al Informational [Page 28] RFC 1841 LAN Extension Interface Protocol September 1995

 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:
  1. 0 - High priority queue
  2. 1 - Medium priority queue
  3. 2 - Normal priority queue
  4. 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.

Chapman, et al Informational [Page 29] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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.

Chapman, et al Informational [Page 30] RFC 1841 LAN Extension Interface Protocol September 1995

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.

Chapman, et al Informational [Page 31] RFC 1841 LAN Extension Interface Protocol September 1995

         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

Chapman, et al Informational [Page 32] RFC 1841 LAN Extension Interface Protocol September 1995

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

Chapman, et al Informational [Page 33] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 34] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 35] 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 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.

Chapman, et al Informational [Page 36] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 37] RFC 1841 LAN Extension Interface Protocol September 1995

  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

Chapman, et al Informational [Page 38] RFC 1841 LAN Extension Interface Protocol September 1995

                        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)

Chapman, et al Informational [Page 39] 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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(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

Chapman, et al Informational [Page 40] RFC 1841 LAN Extension Interface Protocol September 1995

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Chapman, et al Informational [Page 41] RFC 1841 LAN Extension Interface Protocol September 1995

 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

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Chapman, et al Informational [Page 42] RFC 1841 LAN Extension Interface Protocol September 1995

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

Chapman, et al Informational [Page 43] RFC 1841 LAN Extension Interface Protocol September 1995

                        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.

Chapman, et al Informational [Page 44] RFC 1841 LAN Extension Interface Protocol September 1995

    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

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.

Chapman, et al Informational [Page 45] RFC 1841 LAN Extension Interface Protocol September 1995

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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(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)

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Chapman, et al Informational [Page 46] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 47] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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

Chapman, et al Informational [Page 48] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 49] RFC 1841 LAN Extension Interface Protocol September 1995

              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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(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)

Chapman, et al Informational [Page 50] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 51] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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.

Chapman, et al Informational [Page 52] RFC 1841 LAN Extension Interface Protocol September 1995

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)

Chapman, et al Informational [Page 53] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 54] RFC 1841 LAN Extension Interface Protocol September 1995

          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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(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.

Chapman, et al Informational [Page 55] RFC 1841 LAN Extension Interface Protocol September 1995

 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:

Chapman, et al Informational [Page 56] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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.

Chapman, et al Informational [Page 57] RFC 1841 LAN Extension Interface Protocol September 1995

 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)

Chapman, et al Informational [Page 58] RFC 1841 LAN Extension Interface Protocol September 1995

          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)
  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

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option-Length | Option-Data |

  1. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

(2)

 Where the Option-Data field contains the following fields:
                          (32 bits)

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Flash Size

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Serial Number

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

HW Version PROM Major Ver PROM Minor VerFlash 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)

Chapman, et al Informational [Page 59] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 60] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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:
  1. 0x01 - Running PROM image
  2. 0x02 - Running Flash image
  3. 0x04 - PROM image passed checksum
  4. 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

Chapman, et al Informational [Page 61] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 62] RFC 1841 LAN Extension Interface Protocol September 1995

              Figure 20  PPP-LEX Data Packet Frame Format
  (8 bits)         (8 bits)      (8 bits)         (8 bits)

+-+-+-+-+-+-+-+-+

HDLC FLAG

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0xFF 0x03 0x0041

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

FIZ0 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:

Chapman, et al Informational [Page 63] RFC 1841 LAN Extension Interface Protocol September 1995

  • 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.

Chapman, et al Informational [Page 64] RFC 1841 LAN Extension Interface Protocol September 1995

 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.

Chapman, et al Informational [Page 65] RFC 1841 LAN Extension Interface Protocol September 1995

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

Chapman, et al Informational [Page 66]

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