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rfc:rfc1088

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.

McLaughlin [Page 1] 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.

McLaughlin [Page 2] 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: ljm@TWG.COM

McLaughlin [Page 3]

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