draft-ietf-tcpm-urgent-data-01.txt   draft-ietf-tcpm-urgent-data-02.txt 
TCP Maintenance and Minor F. Gont TCP Maintenance and Minor F. Gont
Extensions (tcpm) UTN/FRH Extensions (tcpm) UTN/FRH
Internet-Draft A. Yourtchenko Internet-Draft A. Yourtchenko
Intended status: Standards Track Cisco Intended status: Standards Track Cisco
Expires: May 14, 2010 November 10, 2009 Expires: May 30, 2010 November 26, 2009
On the implementation of the TCP urgent mechanism On the implementation of the TCP urgent mechanism
draft-ietf-tcpm-urgent-data-01.txt draft-ietf-tcpm-urgent-data-02.txt
Abstract Abstract
This document analyzes how current TCP implementations process TCP This document analyzes how current TCP implementations process TCP
urgent indications, and how the behavior of some widely-deployed urgent indications, and how the behavior of some widely-deployed
middle-boxes affect how urgent indications are processed by end middle-boxes affect how urgent indications are processed by end
systems. This document updates the relevant specifications such that systems. This document updates the relevant specifications such that
they accommodate current practice in processing TCP urgent they accommodate current practice in processing TCP urgent
indications, provides advice to applications that make use of the indications, provides advice to applications that make use of the
urgent mechanism, and raises awareness about the reliability of TCP urgent mechanism, and raises awareness about the reliability of TCP
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on May 14, 2010. This Internet-Draft will expire on May 30, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Survey of the processing of TCP urgent Appendix A. Survey of the processing of TCP urgent
indications by some popular TCP implementations . . . 9 indications by some popular TCP implementations . . . 9
A.1. FreeBSD . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.1. FreeBSD . . . . . . . . . . . . . . . . . . . . . . . . . 9
A.2. Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.2. Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 9
A.3. NetBSD . . . . . . . . . . . . . . . . . . . . . . . . . . 10 A.3. NetBSD . . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.4. OpenBSD . . . . . . . . . . . . . . . . . . . . . . . . . 10 A.4. OpenBSD . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.5. Cisco IOS, versions 12.2(18)SXF7, 12.4(15)T7 . . . . . . . 10 A.5. Cisco IOS software . . . . . . . . . . . . . . . . . . . . 10
A.6. Microsoft Windows 2000, Service Pack 4 . . . . . . . . . . 10 A.6. Microsoft Windows 2000, Service Pack 4 . . . . . . . . . . 10
A.7. Microsoft Windows 2008 . . . . . . . . . . . . . . . . . . 11 A.7. Microsoft Windows 2008 . . . . . . . . . . . . . . . . . . 11
A.8. Microsoft Windows 95 . . . . . . . . . . . . . . . . . . . 11 A.8. Microsoft Windows 95 . . . . . . . . . . . . . . . . . . . 11
Appendix B. Changes from previous versions of the draft (to Appendix B. Changes from previous versions of the draft (to
be removed by the RFC Editor before publishing be removed by the RFC Editor before publishing
this document as an RFC) . . . . . . . . . . . . . . 11 this document as an RFC) . . . . . . . . . . . . . . 11
B.1. Changes from draft-ietf-tcpm-urgent-data-00 . . . . . . . 11 B.1. Changes from draft-ietf-tcpm-urgent-data-01 . . . . . . . 11
B.2. Changes from draft-gont-tcpm-urgent-data-01 . . . . . . . 11 B.2. Changes from draft-ietf-tcpm-urgent-data-00 . . . . . . . 11
B.3. Changes from draft-gont-tcpm-urgent-data-01 . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
TCP incorporates an "urgent mechanism" that allows the sending user TCP incorporates an "urgent mechanism" that allows the sending user
to stimulate the receiving user to accept some "urgent data" and to to stimulate the receiving user to accept some "urgent data" and to
permit the receiving TCP to indicate to the receiving user when all permit the receiving TCP to indicate to the receiving user when all
the currently known urgent data has been received by the user. This the currently known urgent data has been received by the user. This
mechanism permits a point in the data stream to be designated as the mechanism permits a point in the data stream to be designated as the
end of urgent information. Whenever this point is in advance of the end of urgent information. Whenever this point is in advance of the
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specified in Section 4 of this document. It does not provide any specified in Section 4 of this document. It does not provide any
sysctl to override this behavior. sysctl to override this behavior.
OpenBSD provides the SO_OOBINLINE socket option that, when set, OpenBSD provides the SO_OOBINLINE socket option that, when set,
causes TCP urgent data to remain "in band". That is, they will be causes TCP urgent data to remain "in band". That is, they will be
accessible by the read(2) or recv(2) calls without the MSG_OOB flag. accessible by the read(2) or recv(2) calls without the MSG_OOB flag.
OpenBSD supports only one byte of urgent data. That is, only the OpenBSD supports only one byte of urgent data. That is, only the
byte preceding the Urgent Pointer is considered as "urgent data". byte preceding the Urgent Pointer is considered as "urgent data".
A.5. Cisco IOS, versions 12.2(18)SXF7, 12.4(15)T7 A.5. Cisco IOS software
Cisco IOS, versions 12.2(18)SXF7, 12.4(15)T7 interpret the semantics Cisco IOS Software Releases 12.2(18)SXF7, 12.4(15)T7 interpret the
of the urgent pointer as specified in Section 4 of this document. semantics of the urgent pointer as specified in Section 4 of this
document.
Tests performed with an HTTP server running on Cisco IOS version The behaviour is consistent with having the SO_OOBINLINE socket
12.2(18)SXF7 and 12.4(15)T7 suggest that urgent data is processed "in option turned on, i.e. the data is processed "in band".
band". That is, they are accessible together with "normal" data.
The TCP debugs on the Cisco IOS device do explicitly mention the
presence of urgent data, and thus we infer that the behavior is
different depending on the application.
A.6. Microsoft Windows 2000, Service Pack 4 A.6. Microsoft Windows 2000, Service Pack 4
Microsoft Windows 2000 [Windows2000] interprets the semantics of the Microsoft Windows 2000 [Windows2000] interprets the semantics of the
urgent pointer as specified in Section 4 of this document. It urgent pointer as specified in Section 4 of this document. It
provides the TcpUseRFC1122UrgentPointer system-wide variable to provides the TcpUseRFC1122UrgentPointer system-wide variable to
override this behavior, interpreting the Urgent Pointer as specified override this behavior, interpreting the Urgent Pointer as specified
in RFC 1122 [RFC1122]. in RFC 1122 [RFC1122].
Tests performed with a sample server application compiled using the Tests performed with a sample server application compiled using the
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BSDUrgent system-wide variable to override this behavior, BSDUrgent system-wide variable to override this behavior,
interpreting the Urgent Pointer as specified in RFC 1122 [RFC1122]. interpreting the Urgent Pointer as specified in RFC 1122 [RFC1122].
Windows 95 supports only one byte of urgent data. That is, only the Windows 95 supports only one byte of urgent data. That is, only the
byte preceding the Urgent Pointer is considered as "urgent data". byte preceding the Urgent Pointer is considered as "urgent data".
[Windows95] [Windows95]
Appendix B. Changes from previous versions of the draft (to be removed Appendix B. Changes from previous versions of the draft (to be removed
by the RFC Editor before publishing this document as an by the RFC Editor before publishing this document as an
RFC) RFC)
B.1. Changes from draft-ietf-tcpm-urgent-data-00 B.1. Changes from draft-ietf-tcpm-urgent-data-01
o Fixes reference to Cisco IOS Software (layer 8+ stuff ;-) ).
o Cleaned-up Appendix A.5.
B.2. Changes from draft-ietf-tcpm-urgent-data-00
o Minor editorial changes. o Minor editorial changes.
o Incorporated the specific changes/advice stated in o Incorporated the specific changes/advice stated in
http://www.ietf.org/mail-archive/web/tcpm/current/msg04548.html in http://www.ietf.org/mail-archive/web/tcpm/current/msg04548.html in
different sections (Section 4, Section 5, Section 6). different sections (Section 4, Section 5, Section 6).
B.2. Changes from draft-gont-tcpm-urgent-data-01 B.3. Changes from draft-gont-tcpm-urgent-data-01
o Draft resubmitted as draft-ietf, as a result of wg consensus on o Draft resubmitted as draft-ietf, as a result of wg consensus on
adopting the document as a tcpm wg item. adopting the document as a tcpm wg item.
Authors' Addresses Authors' Addresses
Fernando Gont Fernando Gont
Universidad Tecnologica Nacional / Facultad Regional Haedo Universidad Tecnologica Nacional / Facultad Regional Haedo
Evaristo Carriego 2644 Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706 Haedo, Provincia de Buenos Aires 1706
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