Network Working Group S. Bensley
Internet-Draft Microsoft
Intended status: Informational L. Eggert
Expires: May 18, 2017 NetApp
D. Thaler
P. Balasubramanian
Microsoft
G. Judd
Morgan Stanley
November 14, 2016
Datacenter TCP (DCTCP): TCP Congestion Control for Datacenters
draft-ietf-tcpm-dctcp-03
Abstract
This informational memo describes Datacenter TCP (DCTCP), an
improvement to TCP congestion control for datacenter traffic. DCTCP
uses improved Explicit Congestion Notification (ECN) processing to
estimate the fraction of bytes that encounter congestion, rather than
simply detecting that some congestion has occurred. DCTCP then
scales the TCP congestion window based on this estimate. This method
achieves high burst tolerance, low latency, and high throughput with
shallow-buffered switches. This memo also discusses deployment
issues related to the coexistence of DCTCP and conventional TCP, the
lack of a negotiating mechanism between sender and receiver, and
presents some possible mitigations. DCTCP as described in this draft
is applicable to deployments in controlled environments like
datacenters but it MUST NOT be deployed over the public Internet
without additional measures, as detailed in Section 5.
Status of This Memo
This Internet-Draft is submitted 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 May 18, 2017.
Bensley, et al. Expires May 18, 2017 [Page 1]
Internet-Draft DCTCP November 2016
Copyright Notice
Copyright (c) 2016 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
(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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DCTCP Algorithm . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Marking Congestion on the L3 Switches and Routers . . . . 4
3.2. Echoing Congestion Information on the Receiver . . . . . 4
3.3. Processing Congestion Indications on the Sender . . . . . 6
3.4. Handling of SYN, SYN-ACK, RST Packets . . . . . . . . . . 8
4. Implementation Issues . . . . . . . . . . . . . . . . . . . . 8
5. Deployment Issues . . . . . . . . . . . . . . . . . . . . . . 9
6. Known Issues . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
Large datacenters necessarily need many network switches to
interconnect their many servers. Therefore, a datacenter can greatly
reduce its capital expenditure by leveraging low-cost switches.
However, such low-cost switches tend to have limited queue capacities
and are thus more susceptible to packet loss due to congestion.
Network traffic in a datacenter is often a mix of short and long
flows, where the short flows require low latencies and the long flows
require high throughputs. Datacenters also experience incast bursts,
where many servers send traffic to a single server at the same time.
Bensley, et al. Expires May 18, 2017 [Page 2]
Internet-Draft DCTCP November 2016
For example, this traffic pattern is a natural consequence of
MapReduce workload: The worker nodes complete at approximately the
same time, and all reply to the master node concurrently.
These factors place some conflicting demands on the queue occupancy
of a switch:
o The queue must be short enough that it does not impose excessive
latency on short flows.
o The queue must be long enough to buffer sufficient data for the
long flows to saturate the path capacity.
o The queue must be long enough to absorb incast bursts without
excessive packet loss.
Standard TCP congestion control [RFC5681] relies on packet loss to
detect congestion. This does not meet the demands described above.
First, short flows will start to experience unacceptable latencies
before packet loss occurs. Second, by the time TCP congestion
control kicks in on the senders, most of the incast burst has already
been dropped.
[RFC3168] describes a mechanism for using Explicit Congestion
Notification (ECN) from the switches for detection of congestion.
However, this method only detects the presence of congestion, not its
extent. In the presence of mild congestion, the TCP congestion
window is reduced too aggressively and this unnecessarily reduces the
throughput of long flows.
Datacenter TCP (DCTCP) improves traditional ECN processing by
estimating the fraction of bytes that encounter congestion, rather
than simply detecting that some congestion has occurred. DCTCP then
scales the TCP congestion window based on this estimate. This method
achieves high burst tolerance, low latency, and high throughput with
shallow-buffered switches.
It is recommended that DCTCP be only deployed in a datacenter
environment where the endpoints and the switching fabric are under a
single administrative domain. This protocol is not meant for
uncontrolled deployment in the global Internet. Refer to Section 5
for more details.
2. 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]. Normative
Bensley, et al. Expires May 18, 2017 [Page 3]
Internet-Draft DCTCP November 2016
language is used to describe how necessary the various aspects of the
Microsoft implementation are for interoperability, but even compliant
implementations without the measures in sections 4-6 would still only
be safe to deploy in controlled environments.
3. DCTCP Algorithm
There are three components involved in the DCTCP algorithm:
o The switches (or other intermediate devices in the network) detect
congestion and set the Congestion Encountered (CE) codepoint in
the IP header.
o The receiver echoes the congestion information back to the sender,
using the ECN-Echo (ECE) flag in the TCP header.
o The sender computes a congestion estimate and reacts, by reducing
the TCP congestion window accordingly (cwnd).
3.1. Marking Congestion on the L3 Switches and Routers
The L3 switches and routers in a datacenter fabric indicate
congestion to the end nodes by setting the CE codepoint in the IP
header as specified in Section 5 of [RFC3168]. For example, the
switches may be configured with a congestion threshold. When a
packet arrives at a switch and its queue length is greater than the
congestion threshold, the switch sets the CE codepoint in the packet.
For example, Section 3.4 of [DCTCP10] suggests threshold marking with
a threshold K > (RTT * C)/7, where C is the link rate in packets per
second. However, the actual algorithm for marking congestion is an
implementation detail of the switch and will generally not be known
to the sender and receiver. Therefore, sender and receiver should
not assume that a particular marking algorithm is implemented by the
switching fabric.
3.2. Echoing Congestion Information on the Receiver
According to Section 6.1.3 of [RFC3168], the receiver sets the ECE
flag if any of the packets being acknowledged had the CE code point
set. The receiver then continues to set the ECE flag until it
receives a packet with the Congestion Window Reduced (CWR) flag set.
However, the DCTCP algorithm requires more detailed congestion
information. In particular, the sender must be able to determine the
number of bytes sent that encountered congestion. Thus, the scheme
described in [RFC3168] does not suffice.
One possible solution is to ACK every packet and set the ECE flag in
the ACK if and only if the CE code point was set in the packet being
Bensley, et al. Expires May 18, 2017 [Page 4]
Internet-Draft DCTCP November 2016
acknowledged. However, this prevents the use of delayed ACKs, which
are an important performance optimization in datacenters. If the
delayed ACK frequency is m, then an ACK is generated every m packets.
The typical value of m is 2 but it could be affected by ACK
throttling or packet coalescing techniques designed to improve
performance.
Instead, DCTCP introduces a new Boolean TCP state variable, "DCTCP
Congestion Encountered" (DCTCP.CE), which is initialized to false and
stored in the Transmission Control Block (TCB). When sending an ACK,
the ECE flag MUST be set if and only if DCTCP.CE is true. When
receiving packets, the CE codepoint MUST be processed as follows:
1. If the CE codepoint is set and DCTCP.CE is false, send an ACK for
any previously unacknowledged packets and set DCTCP.CE to true.
2. If the CE codepoint is not set and DCTCP.CE is true, send an ACK
for any previously unacknowledged packets and set DCTCP.CE to
false.
3. Otherwise, ignore the CE codepoint.
The immediate ACK generated SHOULD NOT acknowledge any data in the
received packet that changes the DCTCP.CE state.
Receiver handling of the "Congestion Window Reduced" (CWR) bit is
also per [RFC3168] including [RFC3168-ERRATA3639]. That is, on
receipt of a segment with both the CE and CWR bits set, CWR is
processed first and then ECE is processed.
Send immediate
ACK with ECE=0
.----. .-------------. .---.
Send 1 ACK / v v | | \
for every | .------. .------. | Send 1 ACK
m packets | | CE=0 | | CE=1 | | for every
with ECE=0 | '------' '------' | m packets
\ | | ^ ^ / with ECE=1
'---' '------------' '----'
Send immediate
ACK with ECE=1
Figure 1: ACK generation state machine. DCTCP.CE abbreviated as CE.
Bensley, et al. Expires May 18, 2017 [Page 5]
Internet-Draft DCTCP November 2016
3.3. Processing Congestion Indications on the Sender
The sender estimates the fraction of bytes sent that encountered
congestion. The current estimate is stored in a new TCP state
variable, DCTCP.Alpha, which is initialized to 1 and SHOULD be
updated as follows:
DCTCP.Alpha = DCTCP.Alpha * (1 - g) + g * M
where
o g is the estimation gain, a real number between 0 and 1. The
selection of g is left to the implementation. See Section 4 for
further considerations.
o M is the fraction of bytes sent that encountered congestion during
the previous observation window, where the observation window is
chosen to be approximately the Round Trip Time (RTT). In
particular, an observation window ends when all bytes in flight at
the beginning of the window have been acknowledged.
In order to update DCTCP.Alpha, the TCP state variables defined in
[RFC0793] are used, and three additional TCP state variables are
introduced:
o DCTCP.WindowEnd: The TCP sequence number threshold for beginning a
new observation window; initialized to SND.UNA.
o DCTCP.BytesAcked: The number of sent bytes acknowledged during the
current observation window; initialized to zero.
o DCTCP.BytesMarked: The number of bytes sent during the current
observation window that encountered congestion; initialized to
zero.
The congestion estimator on the sender SHOULD process acceptable ACKs
as follows:
1. Compute the bytes acknowledged (TCP SACK options [RFC2018] are
ignored for this computation):
BytesAcked = SEG.ACK - SND.UNA
2. Update the bytes sent:
DCTCP.BytesAcked += BytesAcked
3. If the ECE flag is set, update the bytes marked:
Bensley, et al. Expires May 18, 2017 [Page 6]
Internet-Draft DCTCP November 2016
DCTCP.BytesMarked += BytesAcked
4. If the acknowledgment number is less than or equal to
DCTCP.WindowEnd, stop processing. Otherwise, the end of the
observation window has been reached, so proceed to update the
congestion estimate as follows:
5. Compute the congestion level for the current observation window:
M = DCTCP.BytesMarked / DCTCP.BytesAcked
6. Update the congestion estimate:
DCTCP.Alpha = DCTCP.Alpha * (1 - g) + g * M
7. Determine the end of the next observation window:
DCTCP.WindowEnd = SND.NXT
8. Reset the byte counters:
DCTCP.BytesAcked = DCTCP.BytesMarked = 0
Rather than always halving the congestion window as described in
[RFC3168], when the sender receives an indication of congestion
(ECE), the sender SHOULD update cwnd as follows:
cwnd = cwnd * (1 - DCTCP.Alpha / 2)
Thus, when no bytes sent experienced congestion, DCTCP.Alpha equals
zero, and cwnd is left unchanged. When all sent bytes experienced
congestion, DCTCP.Alpha equals one, and cwnd is reduced by half.
Lower levels of congestion will result in correspondingly smaller
reductions to cwnd.
Just as specified in [RFC3168], DCTCP does not react to congestion
indications more than once for every window of data. The setting of
the "Congestion Window Reduced" (CWR) bit is also as per [RFC3168].
This is required for interop with classic ECN receivers due to
potential misconfigurations.
A DCTCP sender MUST deal with loss episodes in the same way as
conventional TCP. In case of a timeout or fast retransmit or any
change in delay (for delay based congestion control), the cwnd and
other state variables like ssthresh must be changed in the same way
that a conventional TCP would have changed them.
Bensley, et al. Expires May 18, 2017 [Page 7]
Internet-Draft DCTCP November 2016
3.4. Handling of SYN, SYN-ACK, RST Packets
The switching fabric can drop TCP packets that do not have the ECT
set in the IP header. If SYN and SYN-ACK packets for DCTCP
connections do not have ECT set, they will be dropped with high
probability. For DCTCP connections, the sender SHOULD set ECT for
SYN, SYN-ACK and RST packets.
4. Implementation Issues
As noted in Section 3.3, the implementation will need to choose a
suitable estimation gain. [DCTCP10] provides a theoretical basis for
selecting the gain. However, it may be more practical to use
experimentation to select a suitable gain for a particular network
and workload. The Microsoft implementation of DCTCP in Windows
Server 2012 uses a fixed estimation gain of 1/16.
The implementation must also decide when to use DCTCP. Datacenter
servers may need to communicate with endpoints outside the
datacenter, where DCTCP is unsuitable or unsupported. Thus, a global
configuration setting to enable DCTCP will generally not suffice.
DCTCP provides no mechanism for negotiating its use. Thus, there is
additional management and configuration overhead required to ensure
that DCTCP is not used with non-DCTCP endpoints.
Potential solutions rely on either configuration or heuristics.
Heuristics need to allow endpoints to individually enable DCTCP, to
ensure a DCTCP sender is always paired with a DCTCP receiver. One
approach is to enable DCTCP based on the IP address of the remote
endpoint. Another approach is to detect connections that transmit
within the bounds a datacenter. For example, Microsoft Windows
Server 2012 (and later versions) supports automatic selection of
DCTCP if the estimated RTT is less than 10 msec and ECN is
successfully negotiated, under the assumption that if the RTT is low,
then the two endpoints are likely in the same datacenter network.
[RFC3168] forbids the ECN-marking of pure ACK packets, because of the
inability of TCP to mitigate ACK-path congestion. RFC 3168 also
forbids ECN-marking of retransmissions, window probes and RSTs.
However, dropping all these control packets - rather than ECN marking
them - has considerable performance disadvantages. It is RECOMMENDED
that an implementation provide a configuration knob that will cause
ECT to be set on such control packes, which can be used in
environments where such concerns do not apply.
It would be useful to implement DCTCP as additional actions on top of
an existing congestion control algorithm like NewReno. The DCTCP
Bensley, et al. Expires May 18, 2017 [Page 8]
Internet-Draft DCTCP November 2016
implementation MAY also allow configuration of resetting the value of
DCTCP.Alpha as part of processing any loss episodes.
The DCTCP.Alpha calculation as per the formula in Section 3.3
involves fractions. An efficient kernel implementation MAY scale the
DCTCP.Alpha value for efficient computation using shift operations.
For example, if the implementation chooses g as 1/16, multiplications
of DCTCP.Alpha by g become right-shifts by 4. A scaling
implementation SHOULD ensure that DCTCP.Alpha is able to reach zero
once it falls below the smallest shifted value (16 in the above
example). At the other extreme, a scaled update MUST also ensure
DCTCP.Alpha does not exceed the scaling factor, which would be
equivalent to greater than 100% congestion. So, DCTCP.Alpha MUST be
clamped after an update.
This results in the following computations replacing steps 5 and 6 in
Section 3.3, where SCF is the chosen scaling factor (65536 in the
example) and SHF is the shift factor (4 in the example):
1. Compute the congestion level for the current observation window:
ScaledM = SCF * DCTCP.BytesMarked / DCTCP.BytesAcked
2. Update the congestion estimate:
if (DCTCP.Alpha >> SHF) == 0 then DCTCP.Alpha = 0
DCTCP.Alpha += (ScaledM >> SHF) - (DCTCP.Alpha >> SHF)
if DCTCP.Alpha > SCF then DCTCP.Alpha = SCF
5. Deployment Issues
DCTCP and conventional TCP congestion control do not coexist well in
the same network. In DCTCP, the marking threshold is set to a very
low value to reduce queueing delay, and a relatively small amount of
congestion will exceed the marking threshold. During such periods of
congestion, conventional TCP will suffer packet loss and quickly and
drastically reduce cwnd. DCTCP, on the other hand, will use the
fraction of marked packets to reduce cwnd more gradually. Thus, the
rate reduction in DCTCP will be much slower than that of conventional
TCP, and DCTCP traffic will gain a larger share of the capacity
compared to conventional TCP traffic traversing the same path. If
the traffic in the datacenter is a mix of conventional TCP and DCTCP,
it is RECOMMENDED that DCTCP traffic be segregated from conventional
TCP traffic. [MORGANSTANLEY] describes a deployment that uses the IP
DSCP bits to segregate the network such that AQM is applied to DCTCP
traffic, whereas TCP traffic is managed via drop-tail queueing.
Bensley, et al. Expires May 18, 2017 [Page 9]
Internet-Draft DCTCP November 2016
Deployments should take into account segregation of non-TCP traffic
as well. Today's commodity switches allow configuration of different
marking/drop profiles for non-TCP and non-IP packets. Non-TCP and
non-IP packets should be able to pass through such switches, unless
they really run out of buffer space.
Since DCTCP relies on congestion marking by the switches, DCTCP's
potential can only be realized in datacenters where the entire
network infrastructure supports ECN. The switches may also support
configuration of the congestion threshold used for marking. The
proposed parameterization can be configured with switches that
implement RED. [DCTCP10] provides a theoretical basis for selecting
the congestion threshold, but as with the estimation gain, it may be
more practical to rely on experimentation or simply to use the
default configuration of the device. DCTCP will degrade to loss-
based congestion control when transiting a congested drop-tail link.
DCTCP requires changes on both the sender and the receiver, so both
endpoints must support DCTCP. Furthermore, DCTCP provides no
mechanism for negotiating its use, so both endpoints must be
configured through some out-of-band mechanism to use DCTCP. A
variant of DCTCP that can be deployed unilaterally and only requires
standard ECN behavior has been described in [ODCTCP][BSDCAN], but
requires additional experimental evaluation.
6. Known Issues
DCTCP relies on the sender's ability to reconstruct the stream of CE
codepoints received by the remote endpoint. To accomplish this,
DCTCP avoids using a single ACK packet to acknowledge segments
received both with and without the CE codepoint set. However, if one
or more ACK packets are dropped, it is possible that a subsequent ACK
will cumulatively acknowledge a mix of CE and non-CE segments. This
will, of course, result in a less accurate congestion estimate.
There are some potential considerations:
o Even with an inaccurate congestion estimate, DCTCP may still
perform better than [RFC3168].
o If the estimation gain is small relative to the packet loss rate,
the estimate may not be too inaccurate.
o If packet loss mostly occurs under heavy congestion, most drops
will occur during an unbroken string of CE packets, and the
estimate will be unaffected.
However, the effect of packet drops on DCTCP under real world
conditions has not been analyzed.
Bensley, et al. Expires May 18, 2017 [Page 10]
Internet-Draft DCTCP November 2016
DCTCP provides no mechanism for negotiating its use. The effect of
using DCTCP with a standard ECN endpoint has been analyzed in
[ODCTCP][BSDCAN]. Furthermore, it is possible that other
implementations may also modify [RFC3168] behavior without
negotiation, causing further interoperability issues.
Much like standard TCP, DCTCP is biased against flows with longer
RTTs. A method for improving the RTT fairness of DCTCP has been
proposed in [ADCTCP], but requires additional experimental
evaluation.
7. Implementation Status
This section documents the implementation status of the specification
in this document, as recommended by [RFC7942].
This document describes DCTCP as implemented in Microsoft Windows
Server 2012. Since publication of the first versions of this
document, the Linux [LINUX] and FreeBSD [FREEBSD] operating systems
have also implemented support for DCTCP in a way that is believed to
follow this document.
8. Security Considerations
DCTCP enhances ECN and thus inherits the security considerations
discussed in [RFC3168]. The processing changes introduced by DCTCP
do not exacerbate these considerations or introduce new ones. In
particular, with either algorithm, the network infrastructure or the
remote endpoint can falsely report congestion and thus cause the
sender to reduce cwnd. However, this is no worse than what can be
achieved by simply dropping packets.
[RFC3168] requires that a compliant TCP must not set ECT on SYN or
SYN-ACK packets. [RFC5562] proposes setting ECT on SYN-ACK packets,
but maintains the restriction of no ECT on SYN packets. Both these
RFCs prohibit ECT in SYN packets due to security concerns regarding
malicious SYN packets with ECT set. These RFCs, however, are
intended for general Internet use, and do not directly apply to a
controlled datacenter environment. The security concerns addressed
by both these RFCs might not apply in controlled environments like
datacenters, and it might not be necessary to account for the
presence of non-ECN servers. Since most servers run virtualized in
datacenters, additional security can be imposed in the physical
servers to intercept and drop traffic resembling an attack.
Bensley, et al. Expires May 18, 2017 [Page 11]
Internet-Draft DCTCP November 2016
9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgements
The DCTCP algorithm was originally proposed and analyzed in [DCTCP10]
by Mohammad Alizadeh, Albert Greenberg, Dave Maltz, Jitu Padhye,
Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari
Sridharan.
We would like to thank Andrew Shewmaker for identifying the problem
of clamping DCTCP.Alpha and proposing a solution for it.
Lars Eggert has received funding from the European Union's Horizon
2020 research and innovation program 2014-2018 under grant agreement
No. 644866 ("SSICLOPS"). This document reflects only the authors'
views and the European Commission is not responsible for any use that
may be made of the information it contains.
11. References
11.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP
Selective Acknowledgment Options", RFC 2018,
DOI 10.17487/RFC2018, October 1996,
<http://www.rfc-editor.org/info/rfc2018>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<http://www.rfc-editor.org/info/rfc5681>.
Bensley, et al. Expires May 18, 2017 [Page 12]
Internet-Draft DCTCP November 2016
[RFC5562] Kuzmanovic, A., Mondal, A., Floyd, S., and K.
Ramakrishnan, "Adding Explicit Congestion Notification
(ECN) Capability to TCP's SYN/ACK Packets", RFC 5562,
DOI 10.17487/RFC5562, June 2009,
<http://www.rfc-editor.org/info/rfc5562>.
11.2. Informative References
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<http://www.rfc-editor.org/info/rfc7942>.
[DCTCP10] Alizadeh, M., Greenberg, A., Maltz, D., Padhye, J., Patel,
P., Prabhakar, B., Sengupta, S., and M. Sridharan, "Data
Center TCP (DCTCP)", DOI 10.1145/1851182.1851192, Proc.
ACM SIGCOMM 2010 Conference (SIGCOMM 10), August 2010,
<http://dl.acm.org/citation.cfm?doid=1851182.1851192>.
[ODCTCP] Kato, M., "Improving Transmission Performance with One-
Sided Datacenter TCP", M.S. Thesis, Keio University,
2014, <http://eggert.org/students/kato-thesis.pdf>.
[BSDCAN] Kato, M., Eggert, L., Zimmermann, A., van Meter, R., and
H. Tokuda, "Extensions to FreeBSD Datacenter TCP for
Incremental Deployment Support", BSDCan 2015, June 2015,
<https://www.bsdcan.org/2015/schedule/events/559.en.html>.
[ADCTCP] Alizadeh, M., Javanmard, A., and B. Prabhakar, "Analysis
of DCTCP: Stability, Convergence, and Fairness",
DOI 10.1145/1993744.1993753, Proc. ACM SIGMETRICS Joint
International Conference on Measurement and Modeling of
Computer Systems (SIGMETRICS 11), June 2011,
<https://dl.acm.org/citation.cfm?id=1993753>.
[LINUX] Borkmann, D. and F. Westphal, "Linux DCTCP patch", 2014,
<https://git.kernel.org/cgit/linux/kernel/git/davem/net-
next.git/
commit/?id=e3118e8359bb7c59555aca60c725106e6d78c5ce>.
[FREEBSD] Kato, M. and H. Panchasara, "DCTCP (Data Center TCP)
implementation", 2015,
<https://github.com/freebsd/freebsd/
commit/8ad879445281027858a7fa706d13e458095b595f>.
Bensley, et al. Expires May 18, 2017 [Page 13]
Internet-Draft DCTCP November 2016
[MORGANSTANLEY]
Judd, G., "Attaining the Promise and Avoiding the Pitfalls
of TCP in the Datacenter", Proc. 12th USENIX Symposium on
Networked Systems Design and Implementation (NSDI 15), May
2015, <https://www.usenix.org/conference/nsdi15/technical-
sessions/presentation/judd>.
[RFC3168-ERRATA3639]
Scheffenegger, R., "RFC3168 Errata ID 3639", 2013,
<http://www.rfc-editor.org/
errata_search.php/doc/html/rfc3168&eid=3639>.
Authors' Addresses
Stephen Bensley
Microsoft
One Microsoft Way
Redmond, WA 98052
USA
Phone: +1 425 703 5570
Email: sbens@microsoft.com
Lars Eggert
NetApp
Sonnenallee 1
Kirchheim 85551
Germany
Phone: +49 151 120 55791
Email: lars@netapp.com
URI: http://eggert.org/
Dave Thaler
Microsoft
Phone: +1 425 703 8835
Email: dthaler@microsoft.com
Praveen Balasubramanian
Microsoft
Phone: +1 425 538 2782
Email: pravb@microsoft.com
Bensley, et al. Expires May 18, 2017 [Page 14]
Internet-Draft DCTCP November 2016
Glenn Judd
Morgan Stanley
Phone: +1 973 979 6481
Email: glenn.judd@morganstanley.com
Bensley, et al. Expires May 18, 2017 [Page 15]
