[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]
Versions: (draft-gont-tcpm-urgent-data) 00 01
02 03 04 05 06 07 RFC 6093
TCP Maintenance and Minor F. Gont
Extensions (tcpm) UTN/FRH
Internet-Draft A. Yourtchenko
Updates: 793, 1011, 1122 Cisco
(if approved) October 16, 2010
Intended status: Standards Track
Expires: April 19, 2011
On the implementation of the TCP urgent mechanism
draft-ietf-tcpm-urgent-data-07.txt
Abstract
This document analyzes how current TCP implementations process TCP
urgent indications, and how the behavior of some widely-deployed
middle-boxes affect how urgent indications are processed by end
systems. This document updates the relevant specifications such that
they accommodate current practice in processing TCP urgent
indications, raises awareness about the reliability of TCP urgent
indications in the Internet and recommends against the use of the
urgent indications (but provides advice to applications in case that
they do).
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 19, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Gont & Yourtchenko Expires April 19, 2011 [Page 1]
Internet-Draft On the TCP urgent mechanism October 2010
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Specification of the TCP urgent mechanism . . . . . . . . . . 4
2.1. Semantics of urgent indications . . . . . . . . . . . . . 4
2.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 5
2.3. Allowed length of urgent data . . . . . . . . . . . . . . 5
3. Current implementation practice of TCP urgent data . . . . . . 6
3.1. Semantics of urgent indications . . . . . . . . . . . . . 6
3.2. Semantics of the Urgent Pointer . . . . . . . . . . . . . 6
3.3. Allowed length of urgent data . . . . . . . . . . . . . . 7
3.4. Interaction of middle-boxes with TCP urgent indications . 7
4. Updating RFC 793, RFC 1011, and RFC 1122 . . . . . . . . . . . 7
5. Advice to new applications employing TCP . . . . . . . . . . . 8
6. Advice to applications that make use of the urgent
mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Survey of the processing of TCP urgent
indications by some popular TCP implementations . . . 10
A.1. FreeBSD . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.2. Linux . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.3. NetBSD . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.4. OpenBSD . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.5. Cisco IOS software . . . . . . . . . . . . . . . . . . . . 12
A.6. Microsoft Windows 2000, Service Pack 4 . . . . . . . . . . 12
A.7. Microsoft Windows 2008 . . . . . . . . . . . . . . . . . . 12
A.8. Microsoft Windows 95 . . . . . . . . . . . . . . . . . . . 12
Appendix B. Changes from previous versions of the draft (to
be removed by the RFC Editor before publishing
this document as an RFC) . . . . . . . . . . . . . . 12
B.1. Changes from draft-ietf-tcpm-urgent-data-06 . . . . . . . 12
B.2. Changes from draft-ietf-tcpm-urgent-data-05 . . . . . . . 13
B.3. Changes from draft-ietf-tcpm-urgent-data-04 . . . . . . . 13
B.4. Changes from draft-ietf-tcpm-urgent-data-03 . . . . . . . 13
Gont & Yourtchenko Expires April 19, 2011 [Page 2]
Internet-Draft On the TCP urgent mechanism October 2010
B.5. Changes from draft-ietf-tcpm-urgent-data-02 . . . . . . . 13
B.6. Changes from draft-ietf-tcpm-urgent-data-01 . . . . . . . 13
B.7. Changes from draft-ietf-tcpm-urgent-data-00 . . . . . . . 13
B.8. Changes from draft-gont-tcpm-urgent-data-01 . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
Gont & Yourtchenko Expires April 19, 2011 [Page 3]
Internet-Draft On the TCP urgent mechanism October 2010
1. Introduction
This document analyzes how some current TCP implementations process
TCP urgent indications, and how the behavior of some widely-deployed
middle-boxes affect the processing of urgent indications by hosts.
This document updates RFC 793 [RFC0793], RFC 1011 [RFC1011], and RFC
1122 [RFC1122] such that they accommodate current practice in
processing TCP urgent indications, provides advice to applications
using the urgent mechanism, and raises awareness about the
reliability of TCP urgent indications in the current Internet.
Given the above issues and potential interoperability issues with
respect to the currently common default mode operation, it is
strongly recommended that applications do not employ urgent
indications. Nevertheless, urgent indications are still retained as
a mandatory part of the TCP protocol to support the few legacy
applications that employ them. However, it is expected that even
these applications will have difficulties in environments with
middle-boxes.
Section 2 describes what the current IETF specifications state with
respect to TCP urgent indications. Section 3 describes how some
current TCP implementations actually process TCP urgent indications.
Section 4 updates RFC 793 [RFC0793], RFC 1011 [RFC1011], and RFC 1122
[RFC1122], such that they accommodate current practice in processing
TCP urgent indications. Section 5 provides advice to to new
applications employing TCP, with respect to 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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Specification of the TCP urgent mechanism
2.1. Semantics of urgent indications
TCP incorporates an "urgent mechanism" that allows the sending user
to stimulate the receiving user to accept some "urgent data" and to
permit the receiving TCP to indicate to the receiving user when all
the currently known urgent data have been received by the receiving
user.
The TCP urgent 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 receive sequence number (RCV.NXT) at the receiving
Gont & Yourtchenko Expires April 19, 2011 [Page 4]
Internet-Draft On the TCP urgent mechanism October 2010
TCP, that TCP must tell the user to go into "urgent mode"; when the
receive sequence number catches up to the urgent pointer, the TCP
must tell user to go into "normal mode" [RFC0793]. This means, for
example, that data that was received as "normal data" might become
"urgent data" if an urgent indication is received in some successive
TCP segment before that data is consumed by the TCP user.
The URG control flag indicates that the "Urgent Pointer" field is
meaningful and must be added to the segment sequence number to yield
the urgent pointer. The absence of this flag indicates that there is
no urgent data outstanding [RFC0793].
The TCP urgent mechanism is NOT a mechanism for sending "out-of-band"
data: the so-called "urgent data" should be delivered "in-line" to
the TCP user.
2.2. Semantics of the Urgent Pointer
There is some ambiguity in RFC 793 [RFC0793] with respect to the
semantics of the Urgent Pointer. Section 3.1 (page 17) of RFC 793
[RFC0793] states that the Urgent Pointer "communicates the current
value of the urgent pointer as a positive offset from 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
interpreted in segments with the URG control bit set". However,
Section 3.9 (page 56) of RFC 793 [RFC0793] states, when describing
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
set the urgent pointer in the outgoing segments".
RFC 1011 [RFC1011] clarified this ambiguity in RFC 793 stating that
"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
[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
the LAST octet (not LAST+1) in a sequence of urgent data."
2.3. Allowed length of urgent data
RFC 793 [RFC0793] allows TCP peers to send urgent data of any length,
as the TCP urgent mechanism simply provides a pointer to an
interesting point in the data stream. In this respect, Section
4.2.2.4 (page 84) of RFC 1122 explicitly states that "A TCP MUST
support a sequence of urgent data of any length".
Gont & Yourtchenko Expires April 19, 2011 [Page 5]
Internet-Draft On the TCP urgent mechanism October 2010
3. Current implementation practice of TCP urgent data
3.1. Semantics of urgent indications
As discussed in Section 1, the TCP urgent mechanism simply permits a
point in the data stream to be designated as the end of urgent
information, but does NOT provide a mechanism for sending out of band
data.
Unfortunately, virtually all TCP implementations process TCP urgent
data differently. By default, the last byte of "urgent data" is
delivered "out of band" to the application. That is, it is not
delivered as part of the normal data stream. For example, the "out
of band" byte is read by an application when a recv(2) system call
with the MSG_OOB flag set is issued.
Most implementations provide a socket option (SO_OOBINLINE) that
allows an application to override the (broken) default processing of
urgent data, so that it is delivered "in band" to the application,
thus providing the semantics intended by the IETF specifications.
3.2. Semantics of the Urgent Pointer
All the popular implementations that the authors of this document
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
when RFC 1122 officially updated RFC 793 to clarify the ambiguity in
the semantics of the Urgent Pointer, this clarification was never
reflected into actual implementations (i.e., virtually all
implementations default to the semantics of the urgent pointer
specified in Section 3.1 of RFC 793).
Some operating systems provide a system-wide toggle to override this
behavior, and interpret the semantics of the Urgent Pointer as
clarified in RFC 1122. However, this system-wide toggle has been
found to be inconsistent. For example, Linux provides the sysctl
"tcp_stdurg" (i.e., net.ipv4.tcp_stdurg) that, when set, supposedly
changes the system behavior to interpret the semantics of the TCP
Urgent Pointer as specified in RFC 1122. However, this sysctl
changes the semantics of the Urgent Pointer only for incoming
segments, but not for outgoing segments. This means that if this
sysctl is set, an application might be unable to interoperate with
itself if both the TCP sender and the TCP receiver are running on the
same host.
Gont & Yourtchenko Expires April 19, 2011 [Page 6]
Internet-Draft On the TCP urgent mechanism October 2010
3.3. Allowed length of urgent data
While Section 4.2.2.4 (page 84) of RFC 1122 explicitly states that "A
TCP MUST support a sequence of urgent data of any length", in
practice all those implementations that interpret TCP urgent
indications as a mechanism for sending out-of-band data keep a buffer
of a single byte for storing the "last byte of urgent data". Thus,
if successive indications of urgent data are received before the
application reads the pending "out of band" byte, that pending byte
will be discarded (i.e., overwritten by the new byte of urgent data).
In order to avoid urgent data from being discarded, some
implementations queue each of the received "urgent bytes", so that
even if another urgent indication is received before the pending
urgent data are consumed by the application, those bytes do not need
to be discarded. Some of these implementations have been known to
fail to enforce any limits on the amount of urgent data that they
queue, thus resulting vulnerable to trivial resource exhaustion
attacks [CPNI-TCP].
It should be reinforced that the aforementioned implementations are
broken. The TCP urgent mechanism is not a mechanism for delivering
out-of-band data.
3.4. Interaction of middle-boxes with TCP urgent indications
As a result of the publication of Network Intrusion Detection (NIDs)
evasion techniques based on TCP urgent indications [phrack], some
middle-boxes clear the urgent indications by clearing the URG flag
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
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
data (as described in Section 3.1). An example of such a middle-box
is the Cisco PIX firewall [Cisco-PIX]. This should discourage
applications from depending on urgent indications for their correct
operation, as urgent indications may not be reliable in the current
Internet.
4. Updating RFC 793, RFC 1011, and RFC 1122
Considering that as long as both the TCP sender and the TCP receiver
implement the same semantics for the Urgent Pointer there is no
functional difference in having the Urgent Pointer point to "the
sequence number of the octet following the urgent data" vs. "the last
octet of urgent data", and since all known implementations interpret
the semantics of the Urgent Pointer as pointing to "the sequence
Gont & Yourtchenko Expires April 19, 2011 [Page 7]
Internet-Draft On the TCP urgent mechanism October 2010
number of the octet following the urgent data", we hereby update RFC
793 [RFC0793], RFC 1011 [RFC1011], and RFC 1122 [RFC1122], such that
"the urgent pointer points to the sequence number of the octet
following the urgent data" (in segments with the URG control bit
set), thus accommodating virtually all existing TCP implementations.
5. Advice to new applications employing TCP
As a result of the issues discussed in Section 3.2 and Section 3.4,
new applications SHOULD NOT employ the TCP urgent mechanism.
However, TCP implementations MUST still include support for the
urgent mechanism such that existing applications can still use it.
6. Advice to applications that make use of the urgent mechanism
Even though applications SHOULD NOT employ the urgent mechanism,
applications that still decide to employ it MUST set the SO_OOBINLINE
socket option, such that "urgent data" is delivered inline, as
intended by the IETF specifications.
Additionally, applications that still decide to use the urgent
mechanism need to be designed for correct operation even when the URG
flag is cleared by middleboxes.
7. Security Considerations
Multiple factors can affect the data flow that is actually delivered
to an application when the TCP urgent mechanism is employed; namely,
the two possible interpretations of the semantics of the Urgent
Pointer in current implementations (e.g., depending on the value of
the tcp_stdurg sysctl), the possible implementation of the urgent
mechanism as an Out-Of-Band (OOB) facility (vs. in-band as intenteded
by the IETF specifications), and middle-boxes (such as packet
scrubbers) or the end-systems themselves that could cause the "urgent
data" to be processed "in band". This might make it difficult for a
Network Intrusion Detection System (NIDS) to track the application-
layer data transferred to the destination system, and thus lead to
false negatives or false positives in the NIDS [CPNI-TCP] [phrack].
Probably the best way to avoid the security implications of TCP
urgent data is to avoid having applications use the TCP urgent
mechanism altogether. Packet scrubbers could probably be configured
to clear the URG bit, and set the Urgent Pointer to zero. This would
basically cause the urgent data to be put "in band". However, this
might cause interoperability problems or undesired behavior in those
Gont & Yourtchenko Expires April 19, 2011 [Page 8]
Internet-Draft On the TCP urgent mechanism October 2010
applications that rely on the TCP urgent mechanism, such as Telner
[RFC0854] and FTP [RFC0959].
8. IANA Considerations
This document has no actions for IANA.
9. Acknowledgements
The authors of this document would like to thank (in alphabetical
order) Jari Arkko, Ron Bonica, David Borman, Dave Cridland, Ralph
Droms, Wesley Eddy, John Heffner, Alfred Hoenes, Alexey Melnikov,
Keith Moore, Carlos Pignataro, Tim Polk, Anantha Ramaiah, Joe Touch,
Michael Welzl, Dan Wing, and Alexander Zimmermann for providing
valuable feedback on earlier versions of this document.
Additionally, Fernando would like to thank David Borman and Joe Touch
for a fruitful discussion about TCP urgent mode at IETF 73
(Minneapolis).
10. References
10.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC1011] Reynolds, J. and J. Postel, "Official Internet protocols",
RFC 1011, May 1987.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[CPNI-TCP]
Gont, F., "Security Assessment of the Transmission Control
Protocol (TCP)", http://www.cpni.gov.uk/Docs/
tn-03-09-security-assessment-TCP.pdf, 2009.
[Cisco-PIX]
Cisco PIX, "http://www.cisco.com/en/US/docs/security/asa/
Gont & Yourtchenko Expires April 19, 2011 [Page 9]
Internet-Draft On the TCP urgent mechanism October 2010
asa70/command/reference/tz.html#wp1288756".
[FreeBSD] The FreeBSD project, "http://www.freebsd.org".
[Linux] The Linux Project, "http://www.kernel.org".
[NetBSD] The NetBSD project, "http://www.netbsd.org".
[OpenBSD] The OpenBSD project, "http://www.openbsd.org".
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, May 1983.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[UNPv1] Stevens, W., "UNIX Network Programming, Volume 1.
Networking APIs: Sockets and XTI", Prentice Hall PTR ,
1997.
[Windows2000]
Microsoft Windows 2000, "http://technet.microsoft.com/
en-us/library/bb726981(printer).aspx".
[Windows95]
Microsoft Windows 95,
"ftp://ftp.demon.co.uk/pub/mirrors/win95netfaq/
faq-c.html".
[phrack] Ko, Y., Ko, S., and M. Ko, "NIDS Evasion Method named
"SeolMa"", Phrack Magazine, Volume 0x0b, Issue 0x39, Phile
#0x03 of 0x12 http://www.phrack.org/
issues.html?issue=57&id=3#article, 2001.
Appendix A. Survey of the processing of TCP urgent indications by some
popular TCP implementations
A.1. FreeBSD
FreeBSD 8.0 [FreeBSD] interprets the semantics of the urgent pointer
as specified in Section 4 of this document. It does not provide any
sysctl to override this behavior.
FreeBSD provides the SO_OOBINLINE socket option that, when set,
causes TCP "urgent data" to remain "in band". That is, it will be
accessible by the read(2) call or the recv(2) call without the
MSG_OOB flag.
Gont & Yourtchenko Expires April 19, 2011 [Page 10]
Internet-Draft On the TCP urgent mechanism October 2010
FreeBSD supports only one byte of urgent data. That is, only the
byte preceding the Urgent Pointer is considered as "urgent data".
A.2. Linux
Linux 2.6.15-53-386 [Linux] interprets the semantics of the urgent
pointer as specified in Section 4 of this document. It provides the
net.ipv4.tcp_stdurg sysctl to override this behavior to interpret the
Urgent Pointer as specified in RFC 1122 [RFC1122]. However, this
sysctl only affects the processing of incoming segments (the Urgent
Pointer in outgoing segments will still be set as specified in
Section 4 of this document).
Linux provides the SO_OOBINLINE socket option that, when set, causes
TCP "urgent data" to remain "in band". That is, it will be
accessible by the read(2) call or the recv(2) call without the
MSG_OOB flag.
Linux supports only one byte of urgent data. That is, only the byte
preceding the Urgent Pointer is considered as "urgent data".
A.3. NetBSD
NetBSD 5.0.1 [NetBSD] interprets the semantics of the urgent pointer
as specified in Section 4 of this document. It does not provide any
sysctl to override this behavior.
NetBSD provides the SO_OOBINLINE socket option that, when set, causes
TCP "urgent data" to remain "in band". That is, it will be
accessible by the read(2) call or the recv(2) call without the
MSG_OOB flag.
NetBSD supports only one byte of urgent data. That is, only the byte
preceding the Urgent Pointer is considered as "urgent data".
A.4. OpenBSD
OpenBSD 4.2 [OpenBSD] interprets the semantics of the urgent pointer
as specified in Section 4 of this document. It does not provide any
sysctl to override this behavior.
OpenBSD provides the SO_OOBINLINE socket option that, when set,
causes TCP urgent data to remain "in band". That is, it will be
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
byte preceding the Urgent Pointer is considered as "urgent data".
Gont & Yourtchenko Expires April 19, 2011 [Page 11]
Internet-Draft On the TCP urgent mechanism October 2010
A.5. Cisco IOS software
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
document.
The behavior is consistent with having the SO_OOBINLINE socket option
turned on, i.e. the data is processed "in band".
A.6. Microsoft Windows 2000, Service Pack 4
Microsoft Windows 2000 [Windows2000] interprets the semantics of the
urgent pointer as specified in Section 4 of this document. It
provides the TcpUseRFC1122UrgentPointer system-wide variable to
override this behavior, interpreting the Urgent Pointer as specified
in RFC 1122 [RFC1122].
Tests performed with a sample server application compiled using the
cygwin environment has shown that the default behavior is to return
the urgent data "in band".
A.7. Microsoft Windows 2008
Microsoft Windows 2008 interprets the semantics of the urgent pointer
as specified in Section 4 of this document.
A.8. Microsoft Windows 95
Microsoft Windows 95 interprets the semantics of the urgent pointer
as specified in Section 4 of this document. It provides the
BSDUrgent system-wide variable to override this behavior,
interpreting the Urgent Pointer as specified in RFC 1122 [RFC1122].
Windows 95 supports only one byte of urgent data. That is, only the
byte preceding the Urgent Pointer is considered as "urgent data".
[Windows95]
Appendix B. Changes from previous versions of the draft (to be removed
by the RFC Editor before publishing this document as an
RFC)
B.1. Changes from draft-ietf-tcpm-urgent-data-06
o Addresses Jari Arkko's and Tim Polk's DISCUSSes, and various
COMMENTs by members of the IESG.
o Addresses IETF LC comments.
Gont & Yourtchenko Expires April 19, 2011 [Page 12]
Internet-Draft On the TCP urgent mechanism October 2010
B.2. Changes from draft-ietf-tcpm-urgent-data-05
o Draft resubmitted (with no changes) because it was close to the
expiration day.
B.3. Changes from draft-ietf-tcpm-urgent-data-04
o Fixes grammar errors wrt the term "data" (thanks to David Borman,
once again ;-) )
B.4. Changes from draft-ietf-tcpm-urgent-data-03
o Addresses feedback sent by David Borman, and nit pointed out by
John Heffner.
B.5. Changes from draft-ietf-tcpm-urgent-data-02
o Addresses WGLC feedback submitted by Michael Welzl, Anantha
Ramaiah, and Wesley Eddy.
B.6. 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.7. Changes from draft-ietf-tcpm-urgent-data-00
o Minor editorial changes.
o Incorporated the specific changes/advice stated in
http://www.ietf.org/mail-archive/web/tcpm/current/msg04548.html in
different sections (Section 4, Section 5, Section 6).
B.8. Changes from draft-gont-tcpm-urgent-data-01
o Draft resubmitted as draft-ietf, as a result of wg consensus on
adopting the document as a tcpm wg item.
Gont & Yourtchenko Expires April 19, 2011 [Page 13]
Internet-Draft On the TCP urgent mechanism October 2010
Authors' Addresses
Fernando Gont
Universidad Tecnologica Nacional / Facultad Regional Haedo
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fernando@gont.com.ar
URI: http://www.gont.com.ar
Andrew Yourtchenko
Cisco
De Kleetlaan, 7
Diegem B-1831
Belgium
Phone: +32 2 704 5494
Email: ayourtch@cisco.com
Gont & Yourtchenko Expires April 19, 2011 [Page 14]
Html markup produced by rfcmarkup 1.101, available from
http://tools.ietf.org/tools/rfcmarkup/