draft-ietf-tcpm-urgent-data-03.txt   draft-ietf-tcpm-urgent-data-04.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 Updates: 793, 1011, 1122 Cisco
Expires: August 23, 2010 February 19, 2010 (if approved) March 3, 2010
Intended status: Standards Track
Expires: September 4, 2010
On the implementation of the TCP urgent mechanism On the implementation of the TCP urgent mechanism
draft-ietf-tcpm-urgent-data-03.txt draft-ietf-tcpm-urgent-data-04.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
skipping to change at page 1, line 44 skipping to change at page 1, line 46
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 August 23, 2010. This Internet-Draft will expire on September 4, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 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
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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(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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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described in the BSD License. described in the BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Specification of the TCP urgent mechanism . . . . . . . . . . 3 2. Specification of the TCP urgent mechanism . . . . . . . . . . 4
2.1. Semantics of urgent inications . . . . . . . . . . . . . . 3 2.1. Semantics of urgent indications . . . . . . . . . . . . . 4
2.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 4 2.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 5
2.3. Allowed length of urgent data . . . . . . . . . . . . . . 4 2.3. Allowed length of urgent data . . . . . . . . . . . . . . 5
3. Current implementation practice of TCP urgent data . . . . . . 4 3. Current implementation practice of TCP urgent data . . . . . . 5
3.1. Semantics of urgent indications . . . . . . . . . . . . . 4 3.1. Semantics of urgent indications . . . . . . . . . . . . . 5
3.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 5 3.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 6
3.3. Allowed length of urgent data . . . . . . . . . . . . . . 5 3.3. Allowed length of urgent data . . . . . . . . . . . . . . 6
3.4. Interaction of middle-boxes with TCP urgent indications . 6 3.4. Interaction of middle-boxes with TCP urgent indications . 7
4. Updating RFC 1122 . . . . . . . . . . . . . . . . . . . . . . 6 4. Updating RFC 793, RFC 1011, and RFC 1122 . . . . . . . . . . . 7
5. Advice to new applications employing TCP . . . . . . . . . . . 6 5. Advice to new applications employing TCP . . . . . . . . . . . 7
6. Advice to applications that make use of the urgent 6. Advice to applications that make use of the urgent
mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 7 mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . . 9
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 . . . 10
A.1. FreeBSD . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.1. FreeBSD . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.2. Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.2. Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.3. NetBSD . . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.3. NetBSD . . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.4. OpenBSD . . . . . . . . . . . . . . . . . . . . . . . . . 10 A.4. OpenBSD . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.5. Cisco IOS software . . . . . . . . . . . . . . . . . . . . 10 A.5. Cisco IOS software . . . . . . . . . . . . . . . . . . . . 11
A.6. Microsoft Windows 2000, Service Pack 4 . . . . . . . . . . 10 A.6. Microsoft Windows 2000, Service Pack 4 . . . . . . . . . . 11
A.7. Microsoft Windows 2008 . . . . . . . . . . . . . . . . . . 10 A.7. Microsoft Windows 2008 . . . . . . . . . . . . . . . . . . 11
A.8. Microsoft Windows 95 . . . . . . . . . . . . . . . . . . . 10 A.8. Microsoft Windows 95 . . . . . . . . . . . . . . . . . . . 12
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) . . . . . . . . . . . . . . 12
B.1. Changes from draft-ietf-tcpm-urgent-data-02 . . . . . . . 11 B.1. Changes from draft-ietf-tcpm-urgent-data-03 . . . . . . . 12
B.2. Changes from draft-ietf-tcpm-urgent-data-01 . . . . . . . 11 B.2. Changes from draft-ietf-tcpm-urgent-data-02 . . . . . . . 12
B.3. Changes from draft-ietf-tcpm-urgent-data-00 . . . . . . . 11 B.3. Changes from draft-ietf-tcpm-urgent-data-01 . . . . . . . 12
B.4. Changes from draft-gont-tcpm-urgent-data-01 . . . . . . . 11 B.4. Changes from draft-ietf-tcpm-urgent-data-00 . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 B.5. Changes from draft-gont-tcpm-urgent-data-01 . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
This document analyzes how some current TCP implementations process This document analyzes how some current TCP implementations process
TCP urgent indications, and how the behavior of some widely-deployed TCP urgent indications, and how the behavior of some widely-deployed
middle-boxes affect the processing of urgent indications by hosts. middle-boxes affect the processing of urgent indications by hosts.
This document updates RFC 1122 [RFC1122] such that it accommodates This document updates RFC 793 [RFC0793], RFC 1011 [RFC1011], and RFC
current practice in processing TCP urgent indications, provides 1122 [RFC1122] such that they accommodate current practice in
advice to applications using the urgent mechanism, and raises processing TCP urgent indications, provides advice to applications
awareness about the reliability of TCP urgent indications in the using the urgent mechanism, and raises awareness about the
current Internet. reliability of TCP urgent indications in the current Internet.
Section 2 describes what the current IETF secifications state with Section 2 describes what the current IETF specifications state with
respect to TCP urgent indications. Section 3 describes how some respect to TCP urgent indications. Section 3 describes how some
current TCP implementations actually process TCP urgent indications. current TCP implementations actually process TCP urgent indications.
Section 4 updates RFC 1122 [RFC1122] such that it accommodates Section 4 updates RFC 793 [RFC0793], RFC 1011 [RFC1011], and RFC 1122
current practice in processing TCP urgent indications. Section 5 [RFC1122], such that they accommodate current practice in processing
provides advice to to new applications employing TCP, with respect to TCP urgent indications. Section 5 provides advice to to new
the TCP urgent mechanism. Section 6 provides advice to existing applications employing TCP, with respect to the TCP urgent mechanism.
applications that use or rely on the the TCP urgent mechanism. Section 6 provides advice to existing applications that use or rely
on the TCP urgent mechanism.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Specification of the TCP urgent mechanism 2. Specification of the TCP urgent mechanism
2.1. Semantics of urgent inications 2.1. Semantics of urgent indications
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 have been received by the user. the currently known urgent data have been received by the user.
The TCP urgent mechanism permits a point in the data stream to be The TCP urgent mechanism permits a point in the data stream to be
designated as the end of urgent information. Whenever this point is designated as the end of urgent information. Whenever this point is
in advance of the receive sequence number (RCV.NXT) at the receiving in advance of the receive sequence number (RCV.NXT) at the receiving
TCP, that TCP must tell the user to go into "urgent mode"; when the TCP, that TCP must tell the user to go into "urgent mode"; when the
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[RFC0793] states that the Urgent Pointer "communicates the current [RFC0793] states that the Urgent Pointer "communicates the current
value of the urgent pointer as a positive offset from the sequence value of the urgent pointer as a positive offset from the sequence
number in this segment. The urgent pointer points to the sequence number in this segment. The urgent pointer points to the sequence
number of the octet following the urgent data. This field is only be number of the octet following the urgent data. This field is only be
interpreted in segments with the URG control bit set". However, interpreted in segments with the URG control bit set". However,
Section 3.9 (page 56) of RFC 793 [RFC0793] states, when describing Section 3.9 (page 56) of RFC 793 [RFC0793] states, when describing
the processing of the SEND call in the ESTABLISHED and CLOSE-WAIT the processing of the SEND call in the ESTABLISHED and CLOSE-WAIT
states, that "If the urgent flag is set, then SND.UP <- SND.NXT-1 and states, that "If the urgent flag is set, then SND.UP <- SND.NXT-1 and
set the urgent pointer in the outgoing segments". set the urgent pointer in the outgoing segments".
RFC 961 [RFC0961] clarified this ambiguity in RFC 793 stating that RFC 1011 [RFC1011] clarified this ambiguity in RFC 793 stating that
"Page 17 is wrong. The urgent pointer points to the last octet of "Page 17 is wrong. The urgent pointer points to the last octet of
urgent data (not to the first octet of non-urgent data)". RFC 1122 urgent data (not to the first octet of non-urgent data)". RFC 1122
[RFC1122] formally updated RFC 793 by stating, in Section 4.2.2.4 [RFC1122] formally updated RFC 793 by stating, in Section 4.2.2.4
(page 84), that "the urgent pointer points to the sequence number of (page 84), that "the urgent pointer points to the sequence number of
the LAST octet (not LAST+1) in a sequence of urgent data." the LAST octet (not LAST+1) in a sequence of urgent data."
2.3. Allowed length of urgent data 2.3. Allowed length of urgent data
RFC 793 [RFC0793] allows TCP peers to send urgent data of any length, RFC 793 [RFC0793] allows TCP peers to send urgent data of any length,
as the TCP urgent mechanism simply provides a pointer to an as the TCP urgent mechanism simply provides a pointer to an
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allows an application to override the (broken) default processing of allows an application to override the (broken) default processing of
urgent data, so that they are delivered "in band" to the application, urgent data, so that they are delivered "in band" to the application,
thus providing the semantics intended by the IETF specifications. thus providing the semantics intended by the IETF specifications.
3.2. Semantics of the Urgent Pointer 3.2. Semantics of the Urgent Pointer
All the popular implementations that the authors of this document All the popular implementations that the authors of this document
have been able to test interpret the semantics of the TCP Urgent have been able to test interpret the semantics of the TCP Urgent
Pointer as specified in Section 3.1 of RFC 793. This means that even Pointer as specified in Section 3.1 of RFC 793. This means that even
when RFC 1122 officially updated RFC 793 to clarify the ambiguity in when RFC 1122 officially updated RFC 793 to clarify the ambiguity in
the semantics of the Urgent Pointer, this clarification never was the semantics of the Urgent Pointer, this clarification was never
reflected into actual implementations (i.e., virtually all reflected into actual implementations (i.e., virtually all
implementations default to the semantics of the urgent pointer implementations default to the semantics of the urgent pointer
specified in Section 3.1 of RFC 793). specified in Section 3.1 of RFC 793).
Some operating systems provide a system-wide toggle to override this Some operating systems provide a system-wide toggle to override this
behavior, and interpret the semantics of the Urgent Pointer as behavior, and interpret the semantics of the Urgent Pointer as
clarified in RFC 1122. However, this system-wide toggle has been clarified in RFC 1122. However, this system-wide toggle has been
found to be inconsistent. For example, Linux provides the sysctl found to be inconsistent. For example, Linux provides the sysctl
"tcp_stdurg" (i.e., net.ivp4.tcp_stdurg) that, when set, supposedly "tcp_stdurg" (i.e., net.ivp4.tcp_stdurg) that, when set, supposedly
changes the system behavior to interpret the semantics of the TCP changes the system behavior to interpret the semantics of the TCP
skipping to change at page 7, line 26 skipping to change at page 7, line 28
and setting the Urgent Pointer to zero. This causes the "urgent and setting the Urgent Pointer to zero. This causes the "urgent
data" to become "in line" (that is, accessible by the read(2) call or data" to become "in line" (that is, accessible by the read(2) call or
the recv(2) call without the MSG_OOB flag) in the case of those TCP the recv(2) call without the MSG_OOB flag) in the case of those TCP
implementations that implement the urgent mechanism as out-of-band implementations that implement the urgent mechanism as out-of-band
data (as described in Section 3.1). An example of such a middle-box data (as described in Section 3.1). An example of such a middle-box
is the Cisco PIX firewall [Cisco-PIX]. This should discourage is the Cisco PIX firewall [Cisco-PIX]. This should discourage
applications from depending on urgent indications for their correct applications from depending on urgent indications for their correct
operation, as urgent indications may not be not reliable in the operation, as urgent indications may not be not reliable in the
current Internet. current Internet.
4. Updating RFC 1122 4. Updating RFC 793, RFC 1011, and RFC 1122
Considering that as long as both the TCP sender and the TCP receiver Considering that as long as both the TCP sender and the TCP receiver
implement the same semantics for the Urgent Pointer there is no implement the same semantics for the Urgent Pointer there is no
functional difference in having the Urgent Pointer point to "the functional difference in having the Urgent Pointer point to "the
sequence number of the octet following the urgent data" vs. "the last sequence number of the octet following the urgent data" vs. "the last
octet of urgent data", and since all known implementations interpret octet of urgent data", and since all known implementations interpret
the semantics of the Urgent Pointer as pointing to "the sequence the semantics of the Urgent Pointer as pointing to "the sequence
number of the octet following the urgent data", hereby we update RFC number of the octet following the urgent data", we hereby update RFC
1122 [RFC1122] such that "the urgent pointer points to the sequence 793 [RFC0793], RFC 1011 [RFC1011], and RFC 1122 [RFC1122], such that
number of the octet following the urgent data" (in segments with the "the urgent pointer points to the sequence number of the octet
URG control bit set), thus accommodating virtually all existing TCP following the urgent data" (in segments with the URG control bit
implementations. set), thus accommodating virtually all existing TCP implementations.
5. Advice to new applications employing TCP 5. Advice to new applications employing TCP
As a result of the issues discussed in Section 3.2 and Section 3.4, As a result of the issues discussed in Section 3.2 and Section 3.4,
new applications SHOULD NOT employ the TCP urgent mechanism. new applications SHOULD NOT employ the TCP urgent mechanism.
However, TCP implementations MUST still include support for the However, TCP implementations MUST still include support for the
urgent mechanism such that existing applications can still use it. urgent mechanism such that existing applications can still use it.
6. Advice to applications that make use of the urgent mechanism 6. Advice to applications that make use of the urgent mechanism
Even though applications SHOULD NOT employ the urgent mechanism, Even though applications SHOULD NOT employ the urgent mechanism,
applications that still decide to employ it MUST set the SO_OOBINLINE applications that still decide to employ it MUST set the SO_OOBINLINE
socket option, such that "urgent data" are delivered inline, as socket option, such that "urgent data" are delivered inline, as
intended by the IETF specifications. intended by the IETF specifications.
7. Security Considerations 7. Security Considerations
Given that there are two different interpretations of the semantics Given that there are two different interpretations of the semantics
of the Urgent Pointer in current implementations (e.g., depnding on of the Urgent Pointer in current implementations (e.g., depending on
the value of the tcp_stdurg sysctl), and that middle-boxes (such as the value of the tcp_stdurg sysctl), and that middle-boxes (such as
packet scrubbers) or the end-systems themselves could cause the packet scrubbers) or the end-systems themselves could cause the
urgent data to be processed "in band", there exists ambiguity in how urgent data to be processed "in band", there exists ambiguity in how
"urgent data" sent by a TCP will be processed by the intended "urgent data" sent by a TCP will be processed by the intended
recipient. This might make it difficult for a Network Intrusion recipient. This might make it difficult for a Network Intrusion
Detection System (NIDS) to track the application-layer data Detection System (NIDS) to track the application-layer data
transferred to the destination system, and thus lead to false transferred to the destination system, and thus lead to false
negatives or false positives in the NIDS [CPNI-TCP]. negatives or false positives in the NIDS [CPNI-TCP].
Probably the best way to avoid the security implications of TCP Probably the best way to avoid the security implications of TCP
skipping to change at page 8, line 40 skipping to change at page 8, line 40
might cause interoperability problems or undesired behavior in the might cause interoperability problems or undesired behavior in the
applications running on top of TCP. applications running on top of TCP.
8. IANA Considerations 8. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
9. Acknowledgements 9. Acknowledgements
The authors of this document would like to thank (in alphabetical The authors of this document would like to thank (in alphabetical
order) David Borman, Wesley Eddy, Alfred Hoenes, Carlos Pignataro, order) David Borman, Wesley Eddy, John Heffner, Alfred Hoenes, Carlos
Anantha Ramaiah, Joe Touch, Michael Welzl, and Dan Wing for providing Pignataro, Anantha Ramaiah, Joe Touch, Michael Welzl, Dan Wing, and
valuable feedback on earlier versions of this document. Alexander Zimmermann for providing valuable feedback on earlier
versions of this document.
Additionally, Fernando would like to thank David Borman and Joe Touch Additionally, Fernando would like to thank David Borman and Joe Touch
for a fruitful discussion about TCP urgent mode at IETF 73 for a fruitful discussion about TCP urgent mode at IETF 73
(Minneapolis). (Minneapolis).
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC1011] Reynolds, J. and J. Postel, "Official Internet protocols",
RFC 1011, May 1987.
[RFC1122] Braden, R., "Requirements for Internet Hosts - [RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989. Communication Layers", STD 3, RFC 1122, October 1989.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References 10.2. Informative References
[CPNI-TCP] [CPNI-TCP]
CPNI, "Security Assessment of the Transmission Control Gont, F., "Security Assessment of the Transmission Control
Protocol (TCP)", (to be published) . Protocol (TCP)", http://www.cpni.gov.uk/Docs/
tn-03-09-security-assessment-TCP.pdf, 2009.
[Cisco-PIX] [Cisco-PIX]
Cisco PIX, "http://www.cisco.com/en/US/docs/security/asa/ Cisco PIX, "http://www.cisco.com/en/US/docs/security/asa/
asa70/command/reference/tz.html#wp1288756". asa70/command/reference/tz.html#wp1288756".
[FreeBSD] The FreeBSD project, "http://www.freebsd.org". [FreeBSD] The FreeBSD project, "http://www.freebsd.org".
[Linux] The Linux Project, "http://www.kernel.org". [Linux] The Linux Project, "http://www.kernel.org".
[NetBSD] The NetBSD project, "http://www.netbsd.org". [NetBSD] The NetBSD project, "http://www.netbsd.org".
[OpenBSD] The OpenBSD project, "http://www.openbsd.org". [OpenBSD] The OpenBSD project, "http://www.openbsd.org".
[RFC0961] Reynolds, J. and J. Postel, "Official ARPA-Internet
protocols", RFC 961, December 1985.
[UNPv1] Stevens, W., "UNIX Network Programming, Volume 1. [UNPv1] Stevens, W., "UNIX Network Programming, Volume 1.
Networking APIs: Sockets and XTI", Prentice Hall PTR , Networking APIs: Sockets and XTI", Prentice Hall PTR ,
1997. 1997.
[Windows2000] [Windows2000]
Microsoft Windows 2000, "http://technet.microsoft.com/ Microsoft Windows 2000, "http://technet.microsoft.com/
en-us/library/bb726981(printer).aspx". en-us/library/bb726981(printer).aspx".
[Windows95] [Windows95]
Microsoft Windows 95, Microsoft Windows 95,
skipping to change at page 11, line 27 skipping to change at page 11, line 30
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 software A.5. Cisco IOS software
Cisco IOS Software Releases 12.2(18)SXF7, 12.4(15)T7 interpret the Cisco IOS Software Releases 12.2(18)SXF7, 12.4(15)T7 interpret the
semantics of the urgent pointer as specified in Section 4 of this semantics of the urgent pointer as specified in Section 4 of this
document. document.
The behaviour is consistent with having the SO_OOBINLINE socket The behavior is consistent with having the SO_OOBINLINE socket option
option turned on, i.e. the data is processed "in band". turned on, i.e. the data is processed "in band".
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
cygwin environment, has shown that the default behavior is to return cygwin environment has shown that the default behavior is to return
the urgent data "in band". the urgent data "in band".
A.7. Microsoft Windows 2008 A.7. Microsoft Windows 2008
Microsoft Windows 2008 interprets the semantics of the urgent pointer Microsoft Windows 2008 interprets the semantics of the urgent pointer
as specified in Section 4 of this document. as specified in Section 4 of this document.
A.8. Microsoft Windows 95 A.8. Microsoft Windows 95
Microsoft Windows 95 interprets the semantics of the urgent pointer Microsoft Windows 95 interprets the semantics of the urgent pointer
skipping to change at page 12, line 4 skipping to change at page 12, line 11
Microsoft Windows 2008 interprets the semantics of the urgent pointer Microsoft Windows 2008 interprets the semantics of the urgent pointer
as specified in Section 4 of this document. as specified in Section 4 of this document.
A.8. Microsoft Windows 95 A.8. Microsoft Windows 95
Microsoft Windows 95 interprets the semantics of the urgent pointer Microsoft Windows 95 interprets the semantics of the urgent pointer
as specified in Section 4 of this document. It provides the as specified in Section 4 of this document. It provides the
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-02 B.1. Changes from draft-ietf-tcpm-urgent-data-03
o Addresses feedback sent by David Borman, and nit pointed out by
John Heffner.
B.2. Changes from draft-ietf-tcpm-urgent-data-02
o Addresses WGLC feedback submitted by Michael Welzl, Anantha o Addresses WGLC feedback submitted by Michael Welzl, Anantha
Ramaiah, and Wesley Eddy. Ramaiah, and Wesley Eddy.
B.2. Changes from draft-ietf-tcpm-urgent-data-01 B.3. Changes from draft-ietf-tcpm-urgent-data-01
o Fixes reference to Cisco IOS Software (layer 8+ stuff ;-) ). o Fixes reference to Cisco IOS Software (layer 8+ stuff ;-) ).
o Cleaned-up Appendix A.5. o Cleaned-up Appendix A.5.
B.3. Changes from draft-ietf-tcpm-urgent-data-00 B.4. 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.4. Changes from draft-gont-tcpm-urgent-data-01 B.5. 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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