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Network Working Group                                  L. McLaughlin IIIRequest for Comments: 1088                                           TWG                                                           February 1989A Standard for the Transmission of IP Datagrams over NetBIOS NetworksStatus 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.COMMcLaughlin                                                      [Page 3]