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Network Working Group S. Bradner
Request for Comments: 2556 Harvard University
Category: Informational March 1999
OSI connectionless transport services on top
of UDP Applicability Statement for Historic Status
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
RFC 1240, "OSI connectionless transport services on top of UDP", was
published as a Proposed Standard in June 1991 but at this time there
do not seem to be any implementations which follow RFC 1240. In
addition there is a growing concern over using UDP-based transport
protocols in environments where congestion is a possibility.
1. Use of RFC 1240 Technology
A message was sent to the IETF list in October 1998 seeking any
information on the actual use of the technology described in RFC
1240. A number of responses were received, including from the
International Organization for Standardization (ISO), the keeper of
the OSI protocols. None of these messages pointed to any current use
for this technology. Most of the messages which made any
recommendation did recommend that RFC 1240 be moved to historic.
2. Responsiveness to Congestion
Since 1991 there has been a great deal of experience with the
complexities of dealing with congestion in the Internet. Congestion
control algorithms have been improved but there is still work
underway to further understand the issues. In this environment any
UDP-based protocol is somewhat worrisome since quite frequently
people who use UDP-based protocols invent their own reliability and
congestion control functions which may not include the results of the
current state of the art. This leads to a dange r of congestion
collapse with potentially quite serious consequences for the network
in which it is run. See RFC 896 for a discussion of congestion
Bradner Informational [Page 1]
RFC 2556 RFC 1240 to Historic March 1999 collapse. In the case of RFC 1240, the authors seemed to assume that if some level of reliability was needed in an RFC 1240 environment that the reliability algorithms and the congestion control algorithms which would then be required would reside in the OSI protocols running over the UDP transport. It is far from clear that any perceived advantages of running over UDP would not be eclipsed by the difficulties experienced in trying to create a reasonable congestion control algorithm. Implementers would likely find that running over TCP as RFC 2126 describes is the better choice. 3. Conclusion Due to the lack of use of the technology described in RFC 1240 and the issues surrounding congestion control in the Internet, RFC 1240 should be reclassified as Historic and its implementation actively discouraged. 4. Security Considerations This type of non-protocol document does not directly effect the security of the Internet. 5. References RFC 896 Nagle, J., "Congestion control in IP/TCP internetworks", RFC 896, January 1984. RFC 1240 Shue, C., Haggerty, W. and K. Dobbins, "OSI connectionless transport services on top of UDP: Version 1.", RFC 1240 June 1991. RFC 2126 Pouffary, Y. and A. Young, "ISO Transport Service on top of TCP (ITOT)", RFC 2126, March 1997. Bradner Informational [Page 2]
RFC 2556 RFC 1240 to Historic March 1999 6. Author's Address Scott Bradner Harvard University 1350 Mass Ave, rm 876 Cambridge, MA 02138 USA Phone: +1 617 495 3864 EMail: sob@harvard.edu Bradner Informational [Page 3]
RFC 2556 RFC 1240 to Historic March 1999 7. Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Bradner Informational [Page 4]