GENWiki

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]