rfc2097.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                                            G. Pall
Request for Comments: 2097                               Microsoft Corp.
Category: Standards Track                                   January 1997


            The PPP NetBIOS Frames Control Protocol (NBFCP)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The Point-to-Point Protocol (PPP) [1] provides a standard method for
   transporting multi-protocol datagrams over point-to-point links.  PPP
   defines an extensible Link Control Protocol, and proposes a family of
   Network Control Protocols for establishing and configuring different
   network-layer protocols.

   The NBF protocol [3] was originally called the NetBEUI protocol. This
   document defines the Network Control Protocol for establishing and
   configuring the NBF protocol over PPP.

   The NBFCP protocol is only applicable for an end system to connect to
   a peer system or the LAN that peer system is connected to.  It is not
   applicable for connecting two LANs together due to NetBIOS name
   limitations and NetBIOS name defense mechanisms.

Table of Contents

   1.     Introduction ..........................................    2
      1.1       Specification of Requirements ...................    2
      1.2       Terminology .....................................    3
   2.     A PPP Network Control Protocol for NBF ................    3
      2.1       Sending NBF Datagrams ...........................    4
      2.2       Bridging NBF Datagrams...........................    5
      2.3       NetBIOS Name Defense.............................    5
   3.     NBFCP Configuration Options ...........................    6
      3.1       Name-Projection..................................    6
      3.2       Peer-Information.................................    8
      3.3       Multicast-Filtering..............................   10
      3.4       IEEE-MAC-Address-Required........................   11
   SECURITY CONSIDERATIONS ......................................   12
   REFERENCES ...................................................   12



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   ACKNOWLEDGEMENTS .............................................   13
   CHAIR'S ADDRESS ..............................................   13
   AUTHOR'S ADDRESS .............................................   13

1.  Introduction

   PPP has three main components:

      1. A method for encapsulating multi-protocol datagrams.

      2. A Link Control Protocol (LCP) for establishing, configuring,
         and testing the data-link connection.

      3. A family of Network Control Protocols for establishing and
         configuring different network-layer protocols.

   In order to establish communications over a point-to-point link, each
   end of the PPP link must first send LCP packets to configure and test
   the data link.  After the link has been established and optional
   facilities have been negotiated as needed by the LCP, PPP must send
   NBFCP packets to choose and configure the NBF network-layer protocol.
   Once NBFCP has reached the Opened state, NBF datagrams can be sent
   over the link.

   The link will remain configured for communications until explicit LCP
   or NBFCP packets close the link down, or until some external event
   occurs (an inactivity timer expires or network administrator
   intervention).

1.1.  Specification of Requirements

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.

   MUST      This word, or the adjective "required", means that the
             definition is an absolute requirement of the specification.

   MUST NOT  This phrase means that the definition is an absolute
             prohibition of the specification.

   SHOULD    This word, or the adjective "recommended", means that there
             may exist valid reasons in particular circumstances to
             ignore this item, but the full implications should be
             understood and carefully weighed before choosing a
             different course.






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   MAY       This word, or the adjective "optional", means that this
             item is one of an allowed set of alternatives.  An
             implementation which does not include this option MUST be
             prepared to interoperate with another implementation which
             does include the option.

1.2.  Terminology

   This document frequently uses the following terms:

   peer      The other end of the point-to-point link.

   silently discard
            This means the implementation discards the packet without
            further processing.  The implementation SHOULD provide the
            capability of logging the error, including the contents of
            the silently discarded packet, and SHOULD record the event
            in a statistics counter.

   end-system
            A user's machine.  It only sends packets to servers and
            other end-systems.  It doesn't pass any packets through
            itself.

   router    Allows packets to pass through, usually from one ethernet
             segment to another.  Sometimes these are called
             "intermediate-systems".

   bridge    Allows packets to pass through with the data field
             unmodified.  Usually from one ethernet segment to another
             or from one ethernet segment to a token-ring segment.

   gateway   Allows packets to be sent from one network protocol to
             the same or different network protocol.  For example,
             NetBIOS packets from an NBF network to a TCP/IP network
             which has implemented RFC 1001 and RFC 1002.

   local access only server A server which does not pass any packets
             through itself to other servers.

2.  A PPP Network Control Protocol for NBF

   The NBF Control Protocol (NBFCP) is responsible for configuring,
   enabling, and disabling the NBF protocol modules on both ends of the
   point-to-point link.  NBFCP uses the same packet exchange mechanism
   as the Link Control Protocol.  NBFCP packets MUST NOT be exchanged
   until PPP has reached the Network-Layer Protocol phase.  NBFCP
   packets received before this phase is reached should be silently



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   discarded.

   The NBF Control Protocol is exactly the same as the Link Control
   Protocol [1] with the following exceptions:

   Frame Modifications

      The packet may utilize any modifications to the basic frame format
      which have been negotiated during the Link Establishment phase.

   Data Link Layer Protocol Field

      Exactly one NBFCP packet is encapsulated in the Information field
      of a PPP Data Link Layer frame where the Protocol field indicates
      type hex 803f (NBF Control Protocol).

   Code field

     Only Codes 1 through 7 (Configure-Request, Configure-Ack,
     Configure-Nak, Configure-Reject, Terminate-Request, Terminate-Ack
     and Code-Reject) are used.  Other Codes should be treated as
     unrecognized and should result in Code-Rejects.

   Timeouts

     NBFCP packets MUST NOT be exchanged until PPP has reached the
     Network-Layer Protocol phase.  An implementation should be
     prepared to wait for Authentication and Link Quality Determination
     to finish before timing out waiting for a Configure-Ack or other
     response.  It is suggested that an implementation give up only
     after user intervention or a configurable amount of time.  Also,
     because NetBIOS name defense takes time (typically a minimum of
     3 seconds if names are added in parallel), it is suggested that
     if Name-Projection is negotiated, the timeouts are increased to 10
     seconds.

   Configuration Option Types

     NBFCP has a distinct set of Configuration Options.

2.1.  Sending NBF Datagrams

   Before any NBF packets may be communicated, PPP must reach the
   Network-Layer Protocol phase, and the NBF Control Protocol must reach
   the Opened state.

   Unless otherwise negotiated, exactly one NBF packet is encapsulated
   in the Information field of a PPP Data Link Layer frame where the



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   Protocol field indicates type hex 003f (NBF datagram).

   Since NBF datagrams for PPP do not contain a datagram length field,
   the encapsulated NBF packet MUST NOT contain any extra octet padding
   except when Self-Defining-Padding is negotiated.

   The maximum length of an NBF datagram transmitted over a PPP link is
   the same as the maximum length of the Information field of a PPP data
   link layer frame.  Since there is no standard method for fragmenting
   and reassembling NBF datagrams, PPP links supporting NBF MUST allow
   at least 576 octets in the information field of a data link layer
   frame.  It is recommended that an implementation allow 1500 octets in
   the information field unless the IEEE-MAC-Address-Required boolean
   option is negotiated (see below).

2.2   Bridging NBF Datagrams

   There exist at least four different MAC header implementations for
   NBF packets: 802.3 Ethernet, 802.5 Token-Ring, DIX Ethernet, and
   FDDI.  Because NBF is not a routable protocol, some PPP
   implementations may require IEEE MAC addresses to properly route or
   bridge NBF packets.  Some PPP implementations may require the entire
   MAC media header in order to properly route or bridge NBF packets.
   Other smarter implementations may only require the IEEE MAC addreses,
   and still other implementations (such as NetBIOS gateways) may not
   require any MAC address fields.  NBFCP implementations which require
   IEEE Addresses should negotiate the NBFCP IEEE-MAC-Address-Required
   boolean configuartion option so that the MAC header can be provided
   in the NBF packet.

   If IEEE-MAC-Address-Required boolean configuration option is
   negotiated, all NBF datagrams MUST be sent with the specified 12
   octet IEEE MAC address header.  Since negotiation of this option
   occurs after the LCP phase, NBF packets MAY exceed the negotiated PPP
   MRU size.  A PPP implementation which negotiates this option MUST
   allow reception of PPP NBF packets 12 octets larger than the
   negotiated MRU size.

2.3   NetBIOS Name Defense

   In order to guarantee uniqueness of NetBIOS Names on the network,
   NBFCP requires that end-system implementations MUST negotiate the
   Name-Projection configuration option.








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3.  NBFCP Configuration Options

   NBFCP Configuration Options allow modifications to the standard
   characteristics of the network-layer protocol to be negotiated.  If a
   Configuration Option is not included in a Configure-Request packet,
   the default value for that Configuration Option is assumed.

   NBFCP uses the same Configuration Option format defined for LCP [1],
   with a separate set of Options.

   Up-to-date values of the NBFCP Option Type field are specified in the
   most recent "Assigned Numbers" RFC [2].  Current values are assigned
   as follows:

      1       Name-Projection
      2       Peer-Information
      3       Multicast-Filtering
      4       IEEE-MAC-Address-Required

3.1.  Name-Projection

   Description

      This Configuration Option provides a method for the peer to
      provide the NetBIOS names registered on its network.  The sender
      of the Configure-Request states which NetBIOS names should be
      added by the remote peer.  More than one Name-Projection option
      MAY appear in a single Configure-Request.

      Implementations which do not attempt to add any NetBIOS names MUST
      Configure-Reject the Name-Projection Configuration Option.

      If the Name-Projection Configuration Option is not offered by the
      remote peer, but is required by the local peer, the local peer
      should Configure-Nak the request and indicate that it wishes the
      remote peer to add zero NetBIOS names because it is the only known
      acceptable value.  The remote peer may then terminate NBFCP,
      attempt to add zero NetBIOS names, or attempt add one or more
      NetBIOS names.

      When the receiving peer cannot add all the requested names, it
      MUST Configure-Nak with the complete list of names requested.
      Those names which could be added should have the Added field set
      to zero. Those names which could not be added should have the
      Added field set to an appropriate non-zero return code.  The
      sender of this Configuration Option SHOULD then resend the
      Configure-Request with the successfully added names.




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      The implementation may choose to fail configuration if the
      complete list of NetBIOS names is not accepted.  By failing, the
      implementation should terminate NBFCP by sending a Terminate-
      Request packet.

      Because adding NetBIOS names can take time (usually 3 seconds) and
      because PPP may default the restart timer to 3 seconds, the
      restart timer SHOULD default to 10 seconds when configuring
      NetBIOS names.

   A summary of the Name-Projection Configuration Option format is shown
   below.  The fields are transmitted from left to right.

    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |      1st NetBIOS-Name
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   1st NetBIOS-Name (cont.)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   1st NetBIOS-Name (cont.)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   1st NetBIOS-Name (cont.)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+