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rfc:rfc2097

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

Pall Standards Track [Page 1] RFC 2097 NBFCP January 1997

 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.

Pall Standards Track [Page 2] RFC 2097 NBFCP January 1997

 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

Pall Standards Track [Page 3] RFC 2097 NBFCP January 1997

 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

Pall Standards Track [Page 4] RFC 2097 NBFCP January 1997

 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.

Pall Standards Track [Page 5] RFC 2097 NBFCP January 1997

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.

Pall Standards Track [Page 6] RFC 2097 NBFCP January 1997

    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.)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   1st NetBIOS-Name (cont.)    |    Added      |2nd NetBIOS Name...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Type
    1
 Length
    2 + (Number of NetBIOS names * 17)
 NetBIOS-Names
    This group of zero or more sixteen octet NetBIOS-Name fields
    contains a list of all the NetBIOS names the peer wishes to add to
    the remote network if the packet is Configure-Request.  If the
    packet is Configure-Reject, the peer does not support this
    configuration option and it can be assumed that no NetBIOS names
    were added.
    Because the length field is only one octet, only 14 NetBIOS names
    can be added per Name-Projection option.  If more than 14 NetBIOS
    names should be added, then more than one Name-Projection option
    packet will have to be sent in the Configure-Request packet.

Pall Standards Track [Page 7] RFC 2097 NBFCP January 1997

 Added
    This is a one octet field which plays a dual role.  The Added
    field in the Name-Projection Request packet contains the type of
    NetBIOS name added.  A summary of name types is listed below.
       01   Unique Name.
       02   Group Name.
    If the packet is a Configure-Reject the Added field should contain
    the NetBIOS return code for the NetBIOS Add Name or NetBIOS Add
    Group Name command as defined in the NetBIOS 3.0 specification =
    [3].
 A summary of common result codes is listed below in type hex.
       00   Name successfully added.
       0D   Duplicate name in local name table.
       0E   Name table full.
       15   Name not found or cannot specify "*" or null.
       16   Name in use on remote NetBIOS.
       19   Name conflict detected.
       30   Name defined by another environment.
       35   Required system resources exhausted.

3.2. Peer-Information

 Description
    This Configuration Option provides a way for the peer to
    communicate NetBIOS pertinent configuration information. Although
    negotiation of this option is not mandatory, it is suggested.
 A summary of the Peer-Information 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     |         Peer-class            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Peer-version (major)   |       Peer-version(minor)    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Peer-name ....
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Pall Standards Track [Page 8] RFC 2097 NBFCP January 1997

 Type
    2
 Length
    >=3D8
    If the length is 8, there is no Peer-name.  If the length is
    greater than 8, the Peer-name's length is Length - 8.
 Peer-class
    The Peer-class field is one octet. It identifies the sender's
    implementation type.
    Initial values are assigned as follows:
    Value           Class
      1             Reserved for legacy implementations.
      2             PPP NetBIOS Gateway Server.
      3             Reserved for legacy implementations.
      4             PPP Local Access Only Server.
      5             Reserved for legacy implementations.
      6             PPP NBF Bridge.
      7             Reserved for legacy implementations.
      8             PPP End-System.
 Peer-version
    The Peer-version field is four octets and indicates the version of
    the communication peer providing one side of the PPP connection.
    The first two octets are the major version number and the last two
    octets are the minor version number.  The major and minor version
    represent a 16 bit unsigned number sent with the most significant
    octet first.
 Peer-name
    The name of the peer.  A suggested name is the NetBIOS workstation
    name of the peer.  If the length field is 8, no peer name is
    provided.  The peer-name may not be greater than 32 octets in
    length.

Pall Standards Track [Page 9] RFC 2097 NBFCP January 1997

3.3. Multicast-Filtering

 Description
    This Configuration Option provides a way to negotiate the use of
    the Multicast-Forward-Period and the Multicast-Priority.  This
    Configuration Option provides a way to negotiate how to handle
    mulicast packets.  It allows the sender of the Configure-Request
    to state the current handling of multicast packets.  The peer can
    request parameters by NAKing the option, and returning valid
    Multicast-Filtering parameters.
    If negotiation about the remote Multicast-Filtering is required,
    and the peer did not provide the option in its Configure-Request,
    the option SHOULD be appended to a Configure-Nak.
    Controlling the multicast rate is important because some NetBIOS
    applications use multicasts to communicate and withholding
    multicasts may prevent these applications from working.  It is
    also true that other NetBIOS applications do not need to receive
    any multicast packets and therefore it is best to quench the rate
    at which the peer will send multicast packets.
    By default, the peer is pre-configured to an administrator
    assigned Multicast-Forward-Period and Priority.  A Multicast-
    Forward-Period specified as hex type FFFF in a Configure-Request
    is interpreted as requesting the receiving peer to specify a value
    in its Configure-Nak.  A Multicast-Forward-Period value specified
    as hex type FFFF in a Configure-Nak is interpreted as agreement
    that no value exists. A Multicast-Forward-Period of zero indicates
    that all multicast packets SHOULD be forwarded.
    Peers that rely on all multicast packets being forwarded SHOULD
    request a Multicast-Forward-Period of zero and a Multicast-
    Priority of one by NAKing the Configure-Request option and
    appending the proper parameters to a Configure-Nak.
 A summary of the Multicast-Filtering 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     |    Multicast-Forward-Period   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Priority    |
 +-+-+-+-+-+-+-+-+

Pall Standards Track [Page 10] RFC 2097 NBFCP January 1997

 Type
    3
 Length
    5
 Multicast-Forward-Period
    The Multicast-Forward-Period field is two octets and indicates
    the maximum period in seconds at which multicast packets can
    be sent.  The maximum value for this field is 60 (one minute).
    A value of zero indicates that there is no maximum period at
    which multicast packets can be sent.  A value of hex type FFFF
    indicates that the Multicast-Forward-Period is unknown.  A value
    of five indicates that multicast packets will not be sent at a
    rate more frequent than once every five seconds.  This two
    octet value represents a 16 bit unsigned number sent with
    the most significant octet first.
 Priority
    The Priority field is one octet long and indicates if multicast
    packets have priority over other packets when being sent.  A value
    of 0 indicates that directed packets have priority.  A value of 1
    indicates that multicast packets have priority.

3.4. IEEE-MAC-Address-Required

 Description
    This boolean Configuration Option provides a method for the peer
    to require that all NBF datagrams be sent with a 12 octet IEEE MAC
    Address header.  By default, it is assumed that no MAC header is
    required.
 A summary of the IEEE-MAC-Address-Required Boolean Configuration
 Option format is shown below.  The fields are transmitted from left
 to right.
  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Type      |    Length     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Pall Standards Track [Page 11] RFC 2097 NBFCP January 1997

 Type
    4
 Length
    2
 Requirements
    By default the NBF datagram is sent without any MAC header
    information.  The NBF datagram information field is equivalent to
    the data field in 802.3, 802.5, and FDDI frames.
    If this option is negotiated successfully, each NBF datagram is
    sent with a 12 octet IEEE MAC Address header prepended to the
    information field.  A summary of the information field when using
    12 octet IEEE MAC Headers is shown below. The fields are
    transmitted from left to right.  The MAC Address is in non-
    canonical form. This means that the first bit to be transmitted in
    every byte is the most significant bit.
  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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       Destination MAC Address                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Destination MAC Address   |  Source MAC Address           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                       Source MAC Address                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |               802.3/802.5/FDDI data field...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Security Considerations

 Security issues are not discussed in this memo.

References

 [1]   Simpson, W., Editor, "The Point-to-Point Protocol (PPP)",
       STD 51, RFC 1661, July 1994.
 [2]   Reynolds, J., and J. Postel, "Assigned Numbers", STD 2,
       RFC 1700, October 1994.
 [3]   IBM Corp., "IBM Local Area Network Technical Reference",
       Third Edition, Document Number SC30-3383-2, November 4, 1988.

Pall Standards Track [Page 12] RFC 2097 NBFCP January 1997

 [4]   Baker, F., and R. Bowen "PPP Bridging Control Protocol (BCP)",
       Work in Progress.

Acknowledgments

 Some of the text in this document is taken from previous documents
 produced by the Point-to-Point Protocol Working Group of the Internet
 Engineering Task Force (IETF).
 Thomas J. Dimitri (previously at Microsoft Corporation) authored the
 original draft.
 Special thanks go to coworkers at Microsoft, Bill Simpson
 (Daydreamer), Tom Coradetti (DigiBoard), Marty Del Vecchio (Shiva),
 Russ Gocht (Shiva) and several members of the IETF PPP Working Group.

Chair's Address

 The working group can be contacted via the current chair:
    Karl Fox
    Ascend Communications
    3518 Riverside Drive, Suite 101
    Columbus, Ohio 43221
    karl@MorningStar.com
    karl@Ascend.com

Author's Address

 Questions about this memo can also be directed to:
    Gurdeep Singh Pall
    Microsoft Corporation
    1 Microsoft Way
    Redmond, WA 98052-6399
    EMail: gurdeep@microsoft.com

Pall Standards Track [Page 13]

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