Internet Engineering Task Force Sumitha Bhandarkar
INTERNET DRAFT A. L. Narasimha Reddy
draft-ietf-tcpm-tcp-dcr-03.txt Texas A&M University
Expires : August 2005 Mark Allman
ICIR
Ethan Blanton
Purdue University
February 2005
Improving the Robustness of TCP to Non-Congestion Events
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire in August 2005.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract:
This document specifies Non-Congestion Robustness (NCR) for TCP. In
the absence of explicit congestion notification from the network,
TCP's loss recovery algorithms treat the receipt of three duplicate
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acknowledgments as an implicit indication of congestion in the
network. This is not always correct, notably in the case when
network paths reorder segments (for whatever reason), resulting in
degraded performance. TCP-NCR is designed to mitigate this degraded
performance by increasing the number of duplicate acknowledgments
required to trigger loss recovery, based on the current state of the
connection, in an effort to disambiguate true segment loss from
segment reordering. In addition, we specify a change to TCP's
congestion reaction decision point, as well (but, do not require such
a change to use NCR). This document specifies the changes to TCP, as
well as the costs and benefits of these modifications.
Terminology
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 [RFC2119].
Readers should be familiar with the TCP terminology given in
[RFC2581] and [RFC3517].
1. Introduction
One strength of TCP [RFC793] lies in its ability to adjust its
sending rate according to the perceived congestion in the network
[Jac88,RFC2581]. In the absence of explicit notification of
congestion from the network, TCP uses segment loss as an indication
of congestion (i.e., assuming queue overflow). TCP receivers send
cumulative acknowledgments (ACKs) indicating the next sequence number
expected from the sender for arriving segments [RFC793]. When
segments arrive out of order duplicate ACKs are generated. As
specified in [RFC2581], a TCP sender uses the arrival of three
duplicate ACKs as an indication of segment loss. The TCP sender
retransmits the lost segment and reduces the load imposed on the
network, assuming the segment loss was caused by resource contention
within the network path. The TCP sender does not assume loss on the
first duplicate ACK, but waits for three dupacks to account for mild
reordering. However, the use of this constant number of duplicate
ACKs has a number of implications that can be mitigated if the
duplicate ACK requirement is changed.
The following is an example of TCP's behavior:
+ TCP A is the data sender and TCP B is the data receiver.
+ TCP A sends 10 segments each consisting of a single data byte
(i.e., transmits bytes 1-10 in segments 1-10).
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+ Assume segment 3 is dropped in the network.
+ TCP B cumulatively acknowledges segments 1 and 2, making the
cumulative ACK transmitted to the sender 3 (the next expected
sequence number). (Note: TCP B may generate one or two ACKs,
depending on whether delayed ACKs [RFC1122,RFC2581] are
employed.)
+ The arrival of segments 4-10 at TCP B will each trigger the
transmission of a cumulative ACK for sequence number 3. (Note:
[RFC2581] recommends that delayed ACKs not be used when the ACK
is triggered by an out-of-order segment.)
+ When TCP A receives the third duplicate ACK (or fourth ACK
overall) for sequence number 3, TCP A will retransmit
segment 3 and reduce the sending rate by roughly half (see
[RFC2581] for specifics on the congestion control state
adjustments).
Alternatively, suppose segment 3 was not dropped by the network, but
rather delayed such that segment 3 arrives after segment 10. The
above scenario will play out in precisely the same manner. In other
words, TCP is not capable of disambiguating that level of packet
reordering from loss.
The following is the specific motivation behind making TCP robust to
reordered segments:
* A number of Internet measurement studies have shown that packet
reordering is not a rare phenomenon [Pax97,BPS99,JIDKT03,GPL04].
Further, the reordering can be well beyond that which fast
retransmit can cope with using the arrival of three duplicate
ACKs to disambiguate loss and reordering.
* [BA02,ZKFP03] show the negative performance implications that
packet reordering has on current TCP.
* The requirement imposed by TCP for almost in-order packet
delivery places a severe constraint on the design of future
technology. Novel routing algorithms, network components,
link-layer retransmission mechanisms and applications could all
be looked at with a fresh perspective if TCP were to be more
robust to segment reordering. For instance, high speed packet
switches could cause resequencing of packets if TCP were more
robust. There has been work proposed in the literature
explicitly to ensure that packet ordering is maintained in such
switches [KM02]. Also, link-layer mechanisms that attempt to
recover from packet corruption by retransmitting could be
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allowed to reorder packets and, hence, increase the chances of
local loss repair rather than relying on TCP to repair the loss
(and, needlessly reduce its sending rate). Other examples are
multi-path routing, high-delay satellite links and some of the
schemes proposed for differentiated services architecture. By
making TCP more robust to non-congestion events, TCP-NCR may
open the design space of the future Internet components.
In this document we specify a set of sender modifications to provide
Non-Congestion Robustness (NCR) to TCP. In particular, these changes
are built on top of TCP with selective acknowledgments (SACKs)
[RFC2018] and the SACK-based loss recovery scheme given in [RFC3517],
since SACK is widely deployed at this point ([MAF04] indicates that
68% of web servers and 88% of web clients utilize SACK as of spring,
2004).
The remainder of this document is organized as follows. In Section
2, we specify the TCP-NCR algorithm. Section 3 provides a brief
overview of the benefits of TCP-NCR, while Section 4 discusses the
drawbacks of TCP-NCR. Section 5 discusses related work. Section 6
discusses security concerns.
2. Algorithm
The TCP-NCR modifications make two fundamental changes to the way
[RFC3517] currently operates, as follows.
First, the trigger for retransmitting a segment is changed from three
duplicate ACKs [RFC2581,RFC3517] to a congestion window's worth of
duplicate ACKs. This provides more time for packet reordering to
"work itself out" before the TCP sender infers that a segment has
been lost and needs retransmitted. Setting the retransmission point
is a balancing act. On the one hand, if the trigger is too
aggressive (as is sometimes the situation in current TCP stacks using
three duplicate acknowledgments to trigger loss recovery), the TCP
sender cannot accurately disambiguate loss from reordering. On the
other hand, waiting too long to decide to use fast retransmit risks
relying on the costly retransmission timeout (RTO) mechanism
[RFC2988]. Using a congestion window's worth of duplicate ACKs
provides a reasonable tradeoff because the delay involved (roughly
one RTT) is strictly less than the RTO and there is enough data in
the pipe to generate the number of duplicate ACKs required to trigger
a retransmission (given the extended version of Limited Transmit
[RFC3042] specified below).
Second, TCP-NCR decouples initial congestion control decisions from
retransmission decisions, in some cases delaying congestion control
changes relative to TCP's current behavior defined in [RFC2581]. The
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algorithm provides two alternatives for extending Limited Transmit.
The two variants of extended Limited Transmit are:
Careful Limited Transmit:
This variant calls for reducing the sending rate at
approximately the same time [RFC2581] implementations reduce
the congestion window, while at the same time withholding a
retransmission (and the final congestion determination) for
approximately one RTT.
Aggressive Limited Transmit:
This variant calls for maintaining the sending rate in the
face of duplicate ACKs until TCP concludes a segment is lost
and needs to be retransmitted. (which, per the above, TCP-NCR
delays by one RTT when compared with current loss recovery
schemes).
TCP-NCR implementation MUST use either Careful Limited Transmit or
Aggressive Limited Transmit.
A constant MUST be set depending on which variant of extended Limited
Transmit is used, as follows:
Careful Limited Transmit:
LT_F = 2/3
Aggressive Limited Transmit:
LT_F = 1/2
This constant reflects the fraction of outstanding data that must be
ACKed before a retransmission is triggered. Since NCR's goal is to
wait roughly one RTT to retransmit, the fraction reflects the
different number of segments that will be transmitted during extended
Limited Transmit by the two schemes (and therefore their
aggressiveness).
The TCP-NCR modifications specified in this document lend themselves
to incremental deployment. Only the TCP implementation on the sender
side requires modification. The changes themselves are modest.
However, as will be discussed below, availability of additional
buffer space at the receiver will help maximize the benefits of using
TCP-NCR but are not strictly necessary.
The following algorithms depend on the notions provided by [RFC3517]
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and we assume the reader is familiar with the terminology given in
[RFC3517]. The TCP-NCR algorithm can be adapted to alternate SACK-
based loss recovery schemes. [BR04,BSRV04] outline non-SACK-based
algorithms, however, we do not specify those algorithms in this
document and do not recommend them due to both the complexity and
security implications of having only a gross understanding of the
number of outstanding segments in the network.
A TCP connection using the Nagle algorithm [RFC896,RFC1122] MAY
employ the TCP-NCR algorithm. If a TCP implementation does implement
TCP-NCR the implementation MUST follow the various specifications
provides in sections 2.1 - 2.4. If the Nagle algorithm is not being
used there is no way to accurately calculate the number of
outstanding segments in the network (and, therefore, no good way to
derive an appropriate duplicate ACK threshold). A TCP connection
that does not employ the Nagle algorithm MAY use TCP-NCR if the TCP
implementation tracks the sequence numbers transmitted in each
segment and the following algorithm is carefully adapted.
2.1. Initialization
When entering a period of loss / reordering detection and Extended
Limited Transmit a TCP-NCR MUST initialize several state variables.
A TCP MUST enter Extended Limited Transmit upon receiving the first
ACK with a SACK block after the reception of an ACK that (a) did not
contain SACK information and (b) did increase the connection's
cumulative ACK point. The initializations are:
(I.1) Save the current FlightSize.
FlightSizePrev = FlightSize
(I.2) Set a variable for tracking the number of segments for which
an ACK does not trigger a transmission during Careful Limited
Transmit.
Skipped = 0
(I.3) Set DupThresh (from [RFC3517]) based on the size of the
current FlightSize.
DupThresh = max (LT_F * (FlightSize / SMSS),3)
Note: We keep the lower bound of DupThresh = 3 from
[RFC2581,RFC3517].
In addition to the above steps, the incoming ACK MUST be processed
with the E series of steps in section 2.3.
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2.2. Terminating Extended Limited Transmit and Preventing Bursts
Extended Limited Transmit MUST be terminated at the start of loss
recovery as outlined in section 2.4.
The arrival of an ACK that advances the cumulative ACK point before
loss recovery is triggered signals that the series of duplicate ACKs
were caused by reordering and not congestion. Therefore, the receipt
of an ACK that extends the cumulative ACK point MUST terminate
Extended Limited Transmit. As described below, an ACK that also
contains SACK information will also trigger the beginning of a new
Extended Limited Transmit phase. Upon the termination of Extended
Limited Transmit, and especially when using the Careful variant, TCP-
NCR may be in a situation where the entire cwnd is not being utilized
and therefore TCP-NCR will be prone to transmitting a burst of
segments into the network. Therefore, upon exiting Extended Limited
Transmit the following steps MUST be taken.
When a TCP-NCR in the Extended Limited Transmit phase receives an ACK
that updates the cumulative ACK point (regardless of whether the ACK
contains SACK information), the following steps MUST be taken:
(T.1) cwnd = min (FlightSize + SMSS,FlightSizePrev)
This step ensures that cwnd is not grossly larger than the
amount of data outstanding --- a situation that would cause a
line rate burst.
(T.2) ssthresh = FlightSizePrev
This step provides TCP-NCR with a sense of "history". If step
(T.1) reduces cwnd below FlightSizePrev this step ensures that
TCP-NCR will slow start back to operating point in effect
before Extended Limited Transmit.
(T.3) Transmit previously unsent data as allowed by cwnd,
FlightSize, application data availability and the receiver's
advertised window.
(T.4) When the cumulative ACK also contains SACK information, the
initializations in steps (I.2) and (I.3) from section
2.1 MUST be taken (but, not step (I.1)) to re-start Extended
Limited Transmit. In addition, the series of steps in section
2.3 (the "E" steps) MUST be taken.
2.3. Extended Limited Transmit
On each ACK containing SACK information that arrives after TCP-NCR
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has entered the Extended Limited Transmit phase (as outlined in
section 2.1) and before Extended Limited Transmit terminates, the
sender MUST use the following procedure.
(E.1) Use the SetPipe () procedure from [RFC3517] to set the "pipe"
variable (which represents the number of bytes still considered
"in the network").
(E.2) If the following comparison holds and there are SMSS bytes of
previously unsent data available for transmission then
transmit one segment of SMSS bytes.
(pipe + Skipped) <= (FlightSizePrev - SMSS)
If the comparison does not hold or no new data can be
transmitted (due to lack of data from the application or the
advertised window limit), skip to step (E.6).
(E.3) Increment pipe by SMSS bytes.
(E.4) If using Careful Limited Transmit, increment Skipped by SMSS
bytes to ensure that the next SMSS bytes of SACKed data
processed do not trigger a Limted Transmit transmission (since
the goal of Careful Limited Transmit is to send upon the
reception of every second duplicate ACK).
(E.5) Return to step (E.2) to ensure that as many bytes as
appropriate are transmitted. This provides robustness to ACK
loss that can be (largely) compensated for using SACK
information.
(E.6) Reset DupThresh via:
DupThresh = max (LT_F * (FlightSize / SMSS),3)
where FlightSize is the total number of bytes that have not
been cumulatively acknowledged.
2.4 Entering Loss Recovery
When a segment is deemed lost via the algorithms in [RFC3517],
Extended Limited Transmit MUST be terminated, leaving the
algoritms in [RFC3517] to govern TCP's behavior. One slight
change to [RFC3517] MUST be made, however. In section 5, step
(2) of [RFC3517] MUST be changed to:
(2) ssthresh = cwnd = (FlightSizePrev / 2)
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This ensures that the congestion control modifications are made
with respect to the amount of data in the network before
FlightSize was increased by Extended Limited Transmit.
3. Advantages
The major advantages of TCP-NCR are two-fold. As discussed in
section 1, TCP-NCR will open up the design space for network
applications and components that are currently constrained by TCP's
lack of robustness to packet reordering. The second advantage is in
terms of an increase in TCP performance.
[BR04] presents ns-2 [NS-2] simulations of a pre-cursor to the TCP-
NCR algorithm specified in this document, called TCP-DCR (Delayed
Congestion Response). The paper shows that TCP-DCR aids performance
in comparison to unmodified TCP in the presence of packet reordering.
In addition, the extended version of [BR04] presents results based on
emulations involving Linux (kernel 2.4.24). These results show that
the performance of TCP-DCR is similar to Linux's native
implementation that seeks to "undo" wrong decisions based on DSACK
[RFC2883] feedback (similar to the schemes outlined in [ZKFP03]) when
packets are reordered by less than one RTT. The advantages of using
TCP-DCR over the DSACK-based scheme is that the DSACK-based scheme
tries to estimate the exact amount of reordering in the network using
fairly complex algorithms, whereas TCP-DCR achieves similar results
with less complicated modifications.
In addition, [BR04,BSRV04] illustrate the ability of TCP-DCR to allow
for the improvement of other parts of the system. For example, these
papers show that increasing TCP's robustness to packet reordering
allows for a novel wireless ARQ mechanism to be added at the link-
layer. The added robustness of the link-layer to channel errors, in
turn, increases TCP performance by not requiring TCP to retransmit
packets that were dropped due to corruption (and, hence, also
prevents TCP from needlessly reducing the sending rate when
retransmitting these segments).
4. Disadvantages
While we note that all of the changes outlined above are implemented
in the sender, the receiver also potentially has a part to play. In
particular, TCP-NCR increases the receiver's buffering requirement by
up to an extra cwnd -- in the case of the TCP sender using Aggressive
Limited Transmit and actual loss occurring in the network.
Therefore, to maximize the benefits from TCP-NCR receivers should
advertise a large window to absorb the extra out-of-order traffic. In
the case that the additonal buffer requirements are not met, the use
of the above algorithm takes into account the reduced advertised
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window, resulting in slighlty reduced robustness to reordering. (The
worst case robustness of cwnd/2 still offers an improvement over
existing [RFC2581] implementations.)
In addition, using TCP-NCR could delay the delivery of data to the
application by up to one RTT because the fast retransmission point is
delayed by roughly one RTT in TCP-NCR. Applications that are
sensitive to such delays should turn off the TCP-NCR option.
Finally, the use of TCP-NCR makes the recovery from congestion events
sluggish. While the simulation study presented in [BR04,BSRV04] shows
that this does not have a significant impact further experimentation
on the real Internet is required to verify that result.
5. Related Work
Over the past few years, several solutions have been proposed to
improve the performance of TCP in the face of segment reordering.
These schemes generally fall into one of two categories (with some
overlap): mechanisms that try to prevent spurious retransmits from
happening and mechanisms that try to detect spurious retransmits and
"undo" the needless congestion control state changes that have been
taken.
[BA02,ZKFP03] attempt to prevent segment reordering from triggering
spurious retransmits by using various algorithms to approximate the
duplicate ACK threshold required to disambiguate loss and reordering
over the given network path. TCP-NCR similarly tries to prevent
spurious retransmits. However, TCP-NCR takes a simplified approach
compared to those in [BA02,ZKFP03] in that TCP-NCR simply delays
retransmission by a fixed amount (in comparison to standard TCP),
while the other schemes use relatively complex algorithms in an
attempt to derive a more precise value for DupThresh that depends on
the network conditions. While TCP-NCR offers simplicity the other
schemes may offer more precision such that applications would not be
forced to wait as long for their retransmissions.
On the other hand, several schemes have been developed to detect and
mitigate needless retransmissions after the fact.
[RFC3522,RFC3708,BA02,LG04,SK04] present algorithms to detect
spurious retransmits and mitigate the changes these events made to
the congestion control state. TCP-NCR could be used in conjunction
with these algorithms, with TCP-NCR attempting to prevent spurious
retransmits and some other scheme kicking in if the prevention
failed. In addition, we note that TCP-NCR is concentrated on
preventing spurious fast retransmits and some of the above algorithms
also attempt to detect and mitigate spurious timeout-based
retransmits.
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6. Security Considerations
We do not believe there are security implications involved with TCP-
NCR over and above those for general TCP congestion control
[RFC2581]. In particular, the Extended Limited Transmit algorithms
have been specifically designed to not be susceptible to the sorts of
ACK splitting attacks TCP's general TCP congestion control is
vulnerable to (as discussed in [RFC3465].
8. Acknowledgements
Sally Floyd, Nauzad Sadry and Nitin Vaidya as well as feedback from
from the TCPM working group have contributed significantly to this
document. Our thanks to all!
9. Normative References
[RFC793] J. Postel, "Transmission Control Protocol", RFC 793,
September 1981.
[RFC2018] M. Mathis, J. Mahdavi, S. Floyd and A. Romanow, "TCP
selective acknowledgment options," Internet RFC 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2581] M. Allman, V. Paxson, and W. Stevens, "TCP Congestion
Control", RFC 2581, April 1999.
[RFC3042] M. Allman, H. Balakrishnan and S. Floyd, "Enhancing TCP's
Loss Recovery Using Limited Transmit", RFC 3042, January 2001.
[RFC3517] E. Blanton, M. Allman, K. Fall and L. Wang, "A Conservative
Selective Acknowledgment (SACK)-based Loss Recovery Algorithm for
TCP", RFC 3517, April 2003.
9. Informative References
[BA02] E. Blanton and M. Allman, "On Making TCP More Robust to Packet
Reordering," ACM Computer Communication Review, January 2002.
[BPS99] J. Bennett, C. Partridge, and N. Shectman, "Packet reordering
is not pat hological network behavior," IEEE/ACM Transactions on
Networking, December 1999.
[BR04] Sumitha Bhandarkar and A. L. Narasimha Reddy, "TCP-DCR: Making
TCP Robust to Non-Congestion Events", In the Proceedings of
Networking 2004 conference, May 2004. Extended version available as
Bhandarkar/et. al. Expires August 2005 [Page 11]
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tech report TAMU-ECE-2003-04.
[BSRV04] Sumitha Bhandarkar, Nauzad Sadry, A. L. Narasimha Reddy and
Nitin Vaidya, "TCP-DCR: A Novel Protocol for Tolerating Wireless
Channel Errors", To appear in IEEE Transactions on Mobile Computing
[GPL04] Ladan Gharai, Colin Perkins and Tom Lehman, "Packet
Reordering, High Speed Networks and Transport Protocol Performance",
ICCCN 2004, October 2004.
[Jac88] V. Jacobson, "Congestion Avoidance and Control", Computer
Communication Review, vol. 18, no. 4, pp. 314-329, Aug. 1988.
ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z.
[JIDKT03] S. Jaiswal, G. Iannaccone, C. Diot, J. Kurose, and D.
Towsley, "Measurement and Classification of Out-of-Sequence Packets
in a Tier-1 IP Backbone," Proceedings of IEEE INFOCOM, 2003.
[KM02] I. Keslassy and N. McKeown, "Maintaining packet order in
twostage switche s," Proceedings of the IEEE Infocom, June 2002
[LG04] R. Ludwig, A. Gurtov, "The Eifel Response Algorithm for TCP",
Internet-Draft draft-ietf-tsvwg-tcp-eifel-response-06.txt (work in
progress). September 2004.
[MAF04] A. Medina, M. Allman, S. Floyd. Measuring Interactions
Between Transport Protocols and Middleboxes. ACM SIGCOMM/USENIX
Internet Measurement Conference, Taormina, Sicily, Italy, October
2004.
[NS-2] ns-2 Network Simulator. http://www.isi.edu/nsnam/
[Pax97] V. Paxson, "End-to-End Internet Packet Dynamics," Proceedings
of ACM SIGCOMM, September 1997.
[RFC896] J. Nagle, "Congestion Control in IP/TCP Internetworks", RFC
896, January 1984.
[RFC1122] R. Braden, "Requirements for Internet Hosts - Communication
Layers", RFC 1122, October 1989.
[RFC2883] Sally Floyd, Jamshid Mahdavi, Matt Mathis and Matt
Podolsky, "An Extension to the Selective Acknowledgement (SACK)
Option for TCP," RFC 2883, July 2000.
[RFC2988] V. Paxson and M. Allman, "Computing TCP's Retransmission
Timer", RFC 2988, November 2000.
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[RFC3465] M. Allman. TCP Congestion Control with Appropriate Byte
Counting (ABC), February 2003. RFC 3465.
[RFC3522] R. Ludwig and M. Meyer, "The Eifel Detection Algorithm for
TCP," RFC 3522, April 2003.
[RFC3708] E. Blanton and M. Allman, "Using TCP Duplicate Selective
Acknowledgement (DSACKs) and Stream Control Transmission Protocol
(SCTP) Duplicate Transmission Sequence Numbers (TSNs) to Detect
Spurious Retransmissions", RFC 3708, February 2004.
[SK04] P. Sarolahti, M. Kojo, "Forward RTO-Recovery (F-RTO): An
Algorithm for Detecting Spurious Retransmission Timeouts with TCP and
SCTP", Internet-Draft draft-ietf-tcpm-frto-02.txt (work in progress).
November 2004.
[ZKFP03] M. Zhang, B. Karp, S. Floyd, L. Peterson, RR-TCP: A
Reordering-Robust TCP with DSACK, in Proceedings of the Eleventh IEEE
International Conference on Networking Protocols (ICNP 2003),
Atlanta, GA, November, 2003.
13. Author's Addresses
Sumitha Bhandarkar
Dept. of Elec. Engg.
214 ZACH
College Station, TX 77843-3128
Phone: (512) 468-8078
Email: sumitha@tamu.edu
URL : http://students.cs.tamu.edu/sumitha/
A. L. Narasimha Reddy
Professor
Dept. of Elec. Engg.
315C WERC
College Station, TX 77843-3128
Phone : (979) 845-7598
Email : reddy@ee.tamu.edu
URL : http://ee.tamu.edu/~reddy/
Mark Allman
ICSI Center for Internet Research
1947 Center Street, Suite 600
Berkeley, CA 94704-1198
Phone: (216) 243-7361
Email: mallman@icir.org
URL: http://www.icir.org/mallman/
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Ethan Blanton
Purdue University Computer Sciences
1398 Computer Science Building
West Lafayette, IN 47907
EMail: eblanton@cs.purdue.edu
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Acknowledgment
Bhandarkar/et. al. Expires August 2005 [Page 14]
draft-ietf-tcpm-tcp-dcr-03 February 2005
Funding for the RFC Editor function is currently provided by the
Internet Society.
Bhandarkar/et. al. Expires August 2005 [Page 15]
