Movatterモバイル変換

Network Working Group                                         S. BradnerRequest for Comments: 2556                            Harvard UniversityCategory: Informational                                       March 1999OSI connectionless transport services on topof UDP Applicability Statement for Historic StatusStatus 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.AbstractRFC 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 followRFC 1240.  In   addition there is a growing concern over using UDP-based transport   protocols in environments where congestion is a possibility.1. Use ofRFC 1240 Technology   A message was sent to the IETF list in October 1998 seeking any   information on the actual use of the technology described inRFC1240.  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 thatRFC 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.  SeeRFC 896 for a discussion of congestionBradner                      Informational                      [Page 1]

RFC 2556RFC 1240 to Historic                March 1999   collapse.   In the case ofRFC 1240, the authors seemed to assume that if some   level of reliability was needed in anRFC 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 asRFC 2126 describes is the better choice.3. Conclusion   Due to the lack of use of the technology described inRFC 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. ReferencesRFC 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 2556RFC 1240 to Historic                March 19996. Author's Address   Scott Bradner   Harvard University   1350 Mass Ave, rm 876   Cambridge, MA   02138   USA   Phone: +1 617 495 3864   EMail: sob@harvard.eduBradner                      Informational                      [Page 3]

RFC 2556RFC 1240 to Historic                March 19997.  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]