Network Working Group                                  L. McLaughlin III
Request for Comments: 1088                                           TWG
                                                          February 1989


A Standard for the Transmission of IP Datagrams over NetBIOS Networks

Status of this Memo

  This document specifies a standard method of encapsulating the
  Internet Protocol [1] (IP) datagrams on NetBIOS [2] networks.
  Distribution of this memo is unlimited.

Introduction

  The goal of this specification is to allow compatible and
  interoperable implementations for transmitting IP datagrams over
  NetBIOS networks.

  NetBIOS is a standard which specifies a means of creating virtual
  circuits and of transmitting and receiving point-to-point, multicast,
  and broadcast datagrams.  This specification uses only the datagram
  services.

  Previous versions of this memo specified the use of the NetBIOS
  broadcast datagram services instead of the NetBIOS group name
  services to implement IP broadcasting.  These versions are now
  obsolete.

Description

  NetBIOS networks may be used to support IP networks and subnets [3]
  of any class.  By means of encapsulating IP datagrams within NetBIOS
  datagrams and assigning IP numbers to the hosts on a NetBIOS network,
  IP-based applications are supported on these hosts.  The addition of
  a router capable of encapsulating IP packets within ordinary data-
  link protocols (such as 802.3 [4]) as well as within NetBIOS
  datagrams allows these NetBIOS hosts to communicate with the Internet
  at large.

Address Mappings

  In general, NetBIOS names may be any series of 16 bytes, however, a
  few values are reserved or used by common networking packages.
  NetBIOS names for the IP applications on each host are chosen on the
  basis of the internet number of that host.  Since NetBIOS names are a
  mapping of IP addresses, no physical address query mechanism (e.g.,
  ARP [5]) is required.



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RFC 1088                IP over NetBIOS networks           February 1989


  For these internet protocol applications, IP.XX.XX.XX.XX is the
  NetBIOS name for any IP over NetBIOS host where XX represents the
  ascii hexadecimal representation of that byte of the internet
  address.

  This addressing scheme allows for the multiplexing of standard
  datagram protocols over NetBIOS as well as easy visual confirmation
  of the correctness of a given packet's address.

Broadcast and Multicast Addresses

  Broadcast Internet addresses are represented by the NetBIOS group
  name IP.FF.FF.FF.FF.  Currently, no attempt is made to provide
  support of IP multicast addresses using NetBIOS group names.

Maximum Transmission Unit

  The maximum data size of a NetBIOS datagram, and therefore the
  Maximum Transmission Unit (MTU) for IP over NetBIOS networks, is 512
  bytes.  Therefore, any hosts communicating with a host on a NetBIOS
  network may be required to reassemble fragmented datagrams.

Implementation

  To support IP on a NetBIOS host for any given IP address the
  initialization code must:

      1) Add IP.XX.XX.XX.XX to the host's NetBIOS name table.

      2) Add IP.FF.FF.FF.FF to the host's NetBIOS group name table.

      3) Submit a receive datagram request for the reception of NetBIOS
         datagrams destined for IP.XX.XX.XX.XX.

      4) Submit a receive datagram request for the reception of NetBIOS
         datagrams destined for IP.FF.FF.FF.FF.

  When a NetBIOS datagram to either address is received, it is
  processed by the protocol stack and another receive datagram request
  is submitted.

  When an IP datagram is sent, it is considered to be NetBIOS datagram
  data and sent by a send datagram request to either IP.XX.XX.XX.XX or
  IP.FF.FF.FF.FF.

  Optionally, the IP software may desire to make adapter status queries
  of the NetBIOS network.  As support for SNMP becomes a requirement
  for IP hosts, these adapter status queries may become mandatory.



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RFC 1088                IP over NetBIOS networks           February 1989


  Finally, when the IP support for a given NetBIOS host is
  discontinued, a cancel command request should be submitted for every
  pending receive datagram, and a delete name request should be
  submitted for both the IP.XX.XX.XX.XX and IP.FF.FF.FF.FF address
  added during initialization.

Acknowledgements

  This document would not have been possible without the efforts of
  John Bartas, James Davidson, and Dan Ladermann in the early design
  and implementation of IP over NetBIOS.

References

    [1]  Postel, J., "Internet Protocol", RFC-791, September 1981.

    [2]  IBM PC Network Technical Reference, Document Number 6322916,
         September 1984.

    [3]  Mogul, J., and J. Postel, "Internet Standard Subnetting
         Procedure", RFC-950, August 1985.

    [4]  Postel, J., and J. Reynolds, "A Standard for the Transmission
         of IP datagrams over IEEE 802 Networks", RFC-1042,
         February 1988.

    [5]  Plummer, D., "An Ethernet Address Resolution Protocol",
         RFC-826, November 1982.

Author's Address:

  Leo J. McLaughlin III
  The Wollongong Group
  1129 San antonio Road
  Palo Alto, CA 94303

  Phone: (415) 962-7100

  EMail: [email protected]












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