TCPM WG J. Touch
Internet Draft USC/ISI
Intended status: Best Current Practice M. Welzl
Expires: December 2016 S. Islam
University of Oslo
J. You
Huawei
June 27, 2016
TCP Control Block Interdependence
draft-touch-tcpm-2140bis-00.txt
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Abstract
This memo describes interdependent TCP control blocks, where part of
the TCP state is shared among similar concurrent or consecutive
connections. TCP state includes a combination of parameters, such as
connection state, current round-trip time estimates, congestion
control information, and process information. Most of this state is
maintained on a per-connection basis in the TCP Control Block (TCB),
but implementations can (and do) share certain TCB information
across connections to the same host. Such sharing can improve
transient transport performance, while maintaining backward-
compatibility with existing implementations. The sharing described
herein is limited to only the TCB initialization and so has no
effect on the long-term behavior of TCP after a connection has been
established.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................3
3. Terminology....................................................4
4. The TCP Control Block (TCB)....................................4
5. TCB Interdependence............................................5
6. An Example of Temporal Sharing.................................5
7. An Example of Ensemble Sharing.................................7
8. Compatibility Issues...........................................9
9. Implications..................................................10
10. Implementation Observations..................................12
11. Security Considerations......................................13
12. IANA Considerations..........................................14
13. References...................................................14
13.1. Normative References....................................14
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13.2. Informative References..................................15
14. Acknowledgments..............................................16
1. Introduction
TCP is a connection-oriented reliable transport protocol layered
over IP [RFC793]. Each TCP connection maintains state, usually in a
data structure called the TCP Control Block (TCB). The TCB contains
information about the connection state, its associated local
process, and feedback parameters about the connection's transmission
properties. As originally specified and usually implemented, most
TCB information is maintained on a per-connection basis. Some
implementations can (and now do) share certain TCB information
across connections to the same host. Such sharing can lead to better
transient performance, especially for numerous short-lived and
simultaneous connections, as often used in the World-Wide Web
[Be94],[Br02].
This document discusses TCB state sharing that affects only the TCB
initialization, and so has no effect on the long-term behavior of
TCP after a connection has been established. It assumes that TCP
segments having the same host-pair traverse the same bottleneck in
the network, irrespective of TCP port numbers. The observations
about TCB sharing in this document apply similarly to any protocol
with congestion state, including SCTP [RFC4960] and DCCP [RFC4340],
as well as for individual subflows in Multipath TCP [RFC6824].
2. Conventions used in this document
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
In this document, the characters ">>" preceding an indented line(s)
indicates a statement using the key words listed above. This
convention aids reviewers in quickly identifying or finding the
portions of this RFC covered by these keywords.
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3. Terminology
Host - a source or sink of TCP segments associated with a single IP
address
Host-pair - a pair of hosts and their corresponding IP addresses
Path - an Internet path between the IP addresses of two hosts
4. The TCP Control Block (TCB)
A TCB describes the data associated with each connection, i.e., with
each association of a pair of applications across the network. The
TCB contains at least the following information [RFC793]:
Local process state
pointers to send and receive buffers
pointers to retransmission queue and current segment
pointers to Internet Protocol (IP) PCB
Per-connection shared state
macro-state
connection state
timers
flags
local and remote host numbers and ports
micro-state
send and receive window state (size*, current number)
round-trip time and variance
cong. window size (snd_cwnd)*
cong. window size threshold (ssthresh)*
path maximum transmission unit (PMTU)*
max windows seen*
MSS#
round-trip time and variance#
The per-connection information is shown as split into macro-state
and micro-state, terminology borrowed from [Co91]. Macro-state
describes the finite state machine; we include the endpoint numbers
and components (timers, flags) used to help maintain that state.
Macro-state describes the protocol for establishing and maintaining
shared state about the connection. Micro-state describes the
protocol after a connection has been established, to maintain the
reliability and congestion control of the data transferred in the
connection.
We further distinguish two other classes of shared micro-state that
are associated more with host-pairs than with application pairs. One
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class is clearly host-pair dependent (#, e.g., MSS, RTT), and the
other is host-pair dependent in its aggregate (*, e.g., congestion
window information, current window sizes, etc.).
5. TCB Interdependence
There are two cases of TCB interdependence. Temporal sharing occurs
when the TCB of an earlier (now CLOSED) connection to a host is used
to initialize some parameters of a new connection to that same host,
i.e., in sequence. Ensemble sharing occurs when a currently active
connection to a host is used to initialize another (concurrent)
connection to that host.
6. An Example of Temporal Sharing
The TCB data cache is accessed in two ways: it is read to initialize
new TCBs and written when more current per-host state is available.
New TCBs are initialized using context from past connections as
follows; snd_cwnd reuse is not yet implemented:
TEMPORAL SHARING - TCB Initialization
Cached TCB New TCB
----------------------------------------
old_PMTU old_PMTU
old_MSS old_MSS
old_RTT old_RTT
old_RTTvar old_RTTvar
old_ssthresh old_ssthresh
old_snd_cwnd old_snd_cwnd (not yet impl.)
Most cached TCB values are updated when a connection closes. Two
exceptions are PMTU, which is updated after Path MTU Discovery
[RFC4821], and MSS, which is updated whenever the MSS option is
received in a TCP header.
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TEMPORAL SHARING - Cache Updates
Cached TCB Current TCB when? New Cached TCB
----------------------------------------------------------------
old_PMTU curr_PMTU PMTUD current (cur)_PMTU
old_MSS curr_MSS MSSopt cur_MSS
old_RTT curr_RTT CLOSE old += (cur - old) >> 2
old_RTTvar curr_RTTvar CLOSE old += (cur - old) >> 2
old_ssthresh curr_ssthresh CLOSE old += (cur - old) >> 2
old_snd_cwnd curr_snd_cwnd CLOSE cur_snd_cwnd (not yet impl.)
Caching PMTU and MSS is trivial; reported values are cached, and the
most recent values are used. The cache is updated when the MSS
option is received or after PMTUD (i.e., when an ICMPv4
Fraqmentation Needed [RFC1191] or ICMPv6 Packet Too Big message is
received [RFC1981] or the equivalent is inferred, e.g. as from
PLMTUD [RFC4821]), respectively, so the cache always has the most
recent values from any connection. For MSS, the cache is consulted
only at connection establishment and not otherwise updated, which
means that MSS options do not affect current connections. The
default MSS is never saved; only reported MSS values update the
cache, so an explicit override is required to reduce the MSS.
RTT values are updated by a more complicated mechanism
[RFC1644][Ja86]. Dynamic RTT estimation requires a sequence of RTT
measurements. As a result, the cached RTT (and its variance) is an
average of its previous value with the contents of the currently
active TCB for that host, when a TCB is closed. RTT values are
updated only when a connection is closed. Further, the method for
averaging the RTT values is not the same as the method for computing
the RTT values within a connection, so that the cached value may not
be appropriate.
The updates for RTT, RTTvar and ssthresh rely on existing
information, i.e., old values. Should no such values exist, the
current values are cached instead.
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7. An Example of Ensemble Sharing
Sharing cached TCB data across concurrent connections requires
attention to the aggregate nature of some of the shared state.
Although MSS and RTT values can be shared by copying, it may not be
appropriate to copy congestion window or ssthresh information. At
this point, we present only the PMTU, MSS and RTT rules:
ENSEMBLE SHARING - TCB Initialization
Cached TCB New TCB
----------------------------------
old_PMTU old_PMTU
old_MSS old_MSS
old_RTT old_RTT
old_RTTvar old_RTTvar
ENSEMBLE SHARING - Cache Updates
Cached TCB Current TCB when? New Cached TCB
-----------------------------------------------------------
old_PMTU curr_PMTU PMTUD/PLPMTUD new_PMTU
old_MSS curr_MSS MSSopt curr_MSS
old_RTT curr_RTT update rtt_update(old,cur)
old_RTTvar curr_RTTvar update rtt_update(old,cur)
For ensemble sharing, TCB information should be cached as early as
possible, sometimes before a connection is closed. Otherwise,
opening multiple concurrent connections may not result in TCB data
sharing if no connection closes before others open. The amount of
work involved in updating the aggregate average should be minimized,
but the resulting value should be equivalent to having all values
measured within a single connection. The function "rtt_update" in
the ensemble sharing table indicates this operation, which occurs
whenever the RTT would have been updated in the individual TCP
connection. As a result, the cache contains the shared RTT
variables, which no longer need to reside in the TCB [Ja86].
Congestion window size and ssthresh aggregation are more complicated
in the concurrent case. When there is an ensemble of connections, we
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need to decide how that ensemble would have shared these variables,
in order to derive initial values for new TCBs.
Any assumption of this sharing can be incorrect, including this one,
because identical endpoint address pairs may not share network
paths. In current implementations, new congestion windows are set at
an initial value of 4-10 segments [RFC3390][RFC6928], so that the
sum of the current windows is increased for any new connection. This
can have detrimental consequences where several connections share a
highly congested link.
There are several ways to initialize the congestion window in a new
TCB among an ensemble of current connections to a host, as shown
below. Current TCP implementations initialize it to four segments as
standard [rfc3390] and 10 segments experimentally [RFC6928] and
T/TCP hinted that it should be initialized to the old window size
[RFC1644]. In the former cases, the assumption is that new
connections should behave as conservatively as possible. In the
latter T/TCP case, no accommodation is made for concurrent aggregate
behavior.
In either case, the sum of window sizes can increase, rather than
remain constant. A different approach is to give each pending
connection its "fair share" of the available congestion window, and
let the connections balance from there. The assumption we make here
is that new connections are implicit requests for an equal share of
available link bandwidth, which should be granted at the expense of
current connections. This may or may not be the appropriate
function; we propose that it be examined further.
ENSEMBLE SHARING - TCB Initialization
Some Options for Sharing Window-size
Cached TCB New TCB
-----------------------------------------------------------------
old_snd_cwnd (current) one segment
(T/TCP hint) old_snd_cwnd
(proposed) old_snd_cwnd/(N+1)
subtract old_snd_cwnd/(N+1)/N
from each concurrent
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ENSEMBLE SHARING - Cache Updates
Cached TCB Current TCB when? New Cached TCB
----------------------------------------------------------------
old_snd_cwnd curr_snd_cwnd update (adjust sum as appropriate)
8. Compatibility Issues
For the congestion and current window information, the initial
values computed by TCB interdependence may not be consistent with
the long-term aggregate behavior of a set of concurrent connections
between the same endpoints. Under conventional TCP congestion
control, if a single existing connection has converged to a
congestion window of 40 segments, two newly joining concurrent
connections assume initial windows of 10 segments [RFC6928], and the
current connection's window doesn't decrease to accommodate this
additional load and connections can mutually interfere. One example
of this has been seen in the past on trans-Atlantic links, where
concurrent connections supporting Web traffic collided because their
initial windows were too large, even when set at one segment.
Under TCB interdependence, all three connections could change to use
a congestion window of 12 (rounded down to an even number from
13.33, i.e., 40/3). This would include both increasing the initial
window of the new connections (vs. current recommendations
[RFC6928]) and decreasing the congestion window of the current
connection (from 40 down to 12). Most current implementations focus
on the impact to new connections and do not address the impact to
ongoing connections, however.
Because this proposal attempts to anticipate the aggregate steady-
state values of TCB state among a group or over time, it should
avoid the transient effects of new connections. In addition, because
it considers the ensemble and temporal properties of those
aggregates, it should also prevent the transients of short-lived or
multiple concurrent connections from adversely affecting the overall
network performance. There have been ongoing analysis and
experiments to validate these assumptions. For example, [Ph12]
recommends to only cache ssthresh for temporal sharing when flows
are long.
Due to mechanisms like ECMP and LAG [RFC7424], TCP connections
sharing the same host-pair may not always share the same path. When
TCB information is shared across different SYN destination ports,
the sharing calculation can be incorrect; however, the impact of
this error is potentially diminished if (as discussed here) TCB
sharing affects only the transient event of a connection start or if
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TCB information is shared only within connections to the same SYN
destination port. In case of Temporal Sharing, TCB information could
also become invalid over time. Because this is similar to the case
when a connection becomes idle, mechanisms that address idle TCP
connections (e.g., [RFC7661]) could also be applied to TCB cache
management.
There may be additional considerations to the way in which TCB
interdependence rebalances congestion feedback among the current
connections, e.g., it may be appropriate to consider the impact of a
connection being in Fast Recovery [RFC5861] or some other similar
unusual feedback state, e.g., as inhibiting or affecting the
calculations described herein.
TCP is sometimes used in situations where packets of the same host-
pair always take the same path. Because ECMP and LAG examine TCP
port numbers, they cannot always operate when TCP segments are
encapsulated, encrypted, or altered - for example, some Virtual
Private Networks (VPNs) are known to use proprietary UDP
encapsulation methods. Similarly, they cannot operate when the TCP
header is encrypted, e.g., when using IPsec ESP. TCB interdependence
among the entire set sharing the same endpoint IP addresses should
work without problems under these circumstances. Moreover, measures
to increase the probability that connections use the same path could
be applied: e.g., the connections could be given the same IPv6 flow
label. TCB interdependence can also be extended to sets of host IP
address pairs that share the same network path conditions, such as
when a group of addresses is on the same LAN (see Section 9).
9. Implications
There are several implications to incorporating TCB interdependence
in TCP implementations. First, it may prevent the need for
application-layer multiplexing for performance enhancement
[RFC7231]. Protocols like HTTP/2 [RFC7540] avoid connection
reestablishment costs by serializing or multiplexing a set of per-
host connections across a single TCP connection. This avoids TCP's
per-connection OPEN handshake and also avoids recomputing MSS, RTT,
and congestion windows. By avoiding the so-called, "slow-start
restart," performance can be optimized. TCB interdependece can
provide the "slow-start restart avoidance" of multiplexing, without
requiring a multiplexing mechanism at the application layer.
TCB interdependence pushes some of the TCP implementation from the
traditional transport layer (in the ISO model), to the network
layer. This acknowledges that some state is in fact per-host-pair or
can be per-path as indicated solely by that host-pair. Transport
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protocols typically manage per-application-pair associations (per
stream), and network protocols manage per-host-pair and path
associations (routing). Round-trip time, MSS, and congestion
information is more appropriately handled in a network-layer
fashion, aggregated among concurrent connections, and shared across
connection instances.
An earlier version of RTT sharing suggested implementing RTT state
at the IP layer, rather than at the TCP layer [Ja86]. Our
observations are for sharing state among TCP connections, which
avoids some of the difficulties in an IP-layer solution. One such
problem is determining the associated prior outgoing packet for an
incoming packet, to infer RTT from the exchange. Because RTTs are
still determined inside the TCP layer, this is simpler than at the
IP layer. This is a case where information should be computed at the
transport layer, but shared at the network layer.
Per-host-pair associations are not the limit of these techniques. It
is possible that TCBs could be similarly shared between hosts on a
subnet or within a cluster, because the predominant path can be
subnet-subnet, rather than host-host. Additionally, TCB
interdependence can be applied to any protocol with congestion
state, including SCTP [RFC4960] and DCCP [RFC4340], as well as for
individual subflows in Multipath TCP [RFC6824].
There may be other information that can be shared between concurrent
connections. For example, knowing that another connection has just
tried to expand its window size and failed, a connection may not
attempt to do the same for some period. The idea is that existing
TCP implementations infer the behavior of all competing connections,
including those within the same host or subnet. One possible
optimization is to make that implicit feedback explicit, via
extended information associated with the endpoint IP address and its
TCP implementation, rather than per-connection state in the TCB.
Like its initial version in 1997, this document's approach to TCB
interdependence focuses on sharing a set of TCBs by updating the TCB
state to reduce the impact of transients when connections begin or
end. Other mechanisms have since been proposed to continuously share
information between all ongoing communication (including
connectionless protocols), updating the congestion state during any
congestion-related event (e.g., timeout, loss confirmation, etc.)
[RFC3124]. By dealing exclusively with transients, TCB
interdependence is more likely to exhibit the same behavior as
unmodified, independent TCP connections.
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10. Implementation Observations
The observation that some TCB state is host-pair specific rather
than application-pair dependent is not new and is a common
engineering decision in layered protocol implementations. A
discussion of sharing RTT information among protocols layered over
IP, including UDP and TCP, occurred in [Ja86]. Although now
deprecated, T/TCP proposed using caches to maintain TCB information
across instances (temporal sharing), e.g., smoothed RTT, RTT
variance, congestion avoidance threshold, and MSS [RFC1644]. These
values were in addition to connection counts used by T/TCP to
accelerate data delivery prior to the full three-way handshake
during an OPEN. The goal was to aggregate TCB components where they
reflect one association - that of the host-pair, rather than
artificially separating those components by connection.
At least one T/TCP implementation saved the MSS and aggregated the
RTT parameters across multiple connections, but omitted caching the
congestion window information [Br94], as originally specified in
[RFC1379]. Some T/TCP implementations immediately updated MSS when
the TCP MSS header option was received [Br94], although this was not
addressed specifically in the concepts or functional specification
[RFC1379][RFC1644]. In later T/TCP implementations, RTT values were
updated only after a CLOSE, which does not benefit concurrent
sessions.
Temporal sharing of cached TCB data was originally implemented in
the SunOS 4.1.3 T/TCP extensions [Br94] and the FreeBSD port of same
[FreeBSD]. As mentioned before, only the MSS and RTT parameters were
cached, as originally specified in [RFC1379]. Later discussion of
T/TCP suggested including congestion control parameters in this
cache [RFC1644].
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The table below describes the current implementation status for some
TCB information in Linux kernel version 4.6 and FreeBSD 10.
TCB data Status
-----------------------------------------------------------
old_MSS Cached and shared in FreeBSD
old_RTT Cached and shared in FreeBSD
old_RTTvar Cached and shared in FreeBSD
old_snd_cwnd Not shared
old_ssthresh Cached and shared in FreeBSD and Linux:
FreeBSD: arithmetic
mean of ssthresh and previous value if
a previous value exists;
Linux: depending on state,
max(cwnd/2, ssthresh) in most cases
11. Security Considerations
These suggested implementation enhancements do not have additional
ramifications for explicit attacks. These enhancements may be
susceptible to denial-of-service attacks if not otherwise secured.
For example, an application can open a connection and set its window
size to zero, denying service to any other subsequent connection
between those hosts.
TCB sharing may be susceptible to denial-of-service attacks,
wherever the TCB is shared, between connections in a single host, or
between hosts if TCB sharing is implemented within a subnet (see
Implications section). Some shared TCB parameters are used only to
create new TCBs, others are shared among the TCBs of ongoing
connections. New connections can join the ongoing set, e.g., to
optimize send window size among a set of connections to the same
host.
Attacks on parameters used only for initialization affect only the
transient performance of a TCP connection. For short connections,
the performance ramification can approach that of a denial-of-
service attack. E.g., if an application changes its TCB to have a
false and small window size, subsequent connections would experience
performance degradation until their window grew appropriately.
The solution is to limit the effect of compromised TCB values. TCBs
are compromised when they are modified directly by an application or
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transmitted between hosts via unauthenticated means (e.g., by using
a dirty flag). TCBs that are not compromised by application
modification do not have any unique security ramifications. Note
that the proposed parameters for TCB sharing are not currently
modifiable by an application.
All shared TCBs MUST be validated against default minimum parameters
before used for new connections. This validation would not impact
performance, because it occurs only at TCB initialization. This
limits the effect of attacks on new connections to reducing the
benefit of TCB sharing, resulting in the current default TCP
performance. For ongoing connections, the effect of incoming packets
on shared information should be both limited and validated against
constraints before use. This is a beneficial precaution for existing
TCP implementations as well.
TCBs modified by an application SHOULD NOT be shared, unless the new
connection sharing the compromised information has been given
explicit permission to use such information by the connection API.
No mechanism for that indication currently exists, but it could be
supported by an augmented API. This sharing restriction SHOULD be
implemented in both the host and the subnet. Sharing on a subnet
SHOULD utilize authentication to prevent undetected tampering of
shared TCB parameters. These restrictions limit the security impact
of modified TCBs both for connection initialization and for ongoing
connections.
Finally, shared values MUST be limited to performance factors only.
Other information, such as TCP sequence numbers, when shared, are
already known to compromise security.
12. IANA Considerations
There are no IANA implications or requests in this document.
This section should be removed upon final publication as an RFC.
13. References
13.1. Normative References
[RFC793] Postel, Jon, "Transmission Control Protocol," Network
Working Group RFC-793/STD-7, ISI, Sept. 1981.
[RFC1191] Mogul, J., Deering, S., "Path MTU Discovery," RFC 1191,
Nov. 1990.
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[RFC1981] McCann, J., Deering. S., Mogul, J., "Path MTU Discovery
for IP version 6," RFC 1981, Aug. 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4821] Mathis, M., Heffner, J., "Packetization Layer Path MTU
Discovery," RFC 4821, Mar. 2007.
13.2. Informative References
[Br02] Brownlee, N. and K. Claffy, "Understanding Internet
Traffic Streams: Dragonflies and Tortoises", IEEE
Communications Magazine p110-117, 2002.
[Be94] Berners-Lee, T., et al., "The World-Wide Web,"
Communications of the ACM, V37, Aug. 1994, pp. 76-82.
[Br94] Braden, B., "T/TCP -- Transaction TCP: Source Changes for
Sun OS 4.1.3,", Release 1.0, USC/ISI, September 14, 1994.
[Co91] Comer, D., Stevens, D., Internetworking with TCP/IP, V2,
Prentice-Hall, NJ, 1991.
[FreeBSD] FreeBSD source code, Release 2.10, http://www.freebsd.org/
[Ja86] Jacobson, V., (mail to public list "tcp-ip", no archive
found), 1986.
[Ph12] Hurtig, P., Brunstrom, A., "Enhanced metric caching for
short TCP flows," 2012 IEEE International Conference on
Communications (ICC), Ottawa, ON, 2012, pp. 1209-1213.
[RFC1644] Braden, R., "T/TCP -- TCP Extensions for Transactions
Functional Specification," RFC-1644, July 1994.
[RFC1379] Braden, R., "Transaction TCP -- Concepts," RFC-1379,
September 1992.
[RFC3390] Allman, M., Floyd, S., Partridge, C., "Increasing TCP's
Initial Window," RFC 3390, Oct. 2002.
[RFC7231] Fielding, R., J. Reshke, Eds., "HTTP/1.1 Semantics and
Content," RFC-7231, June 2014.
[RFC3124] Balakrishnan, H., Seshan, S., "The Congestion Manager,"
RFC 3124, June 2001.
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[RFC4340] Kohler, E., Handley, M., Floyd, S., "Datagram Congestion
Control Protocol (DCCP)," RFC 4340, Mar. 2006.
[RFC4960] Stewart, R., (Ed.), "Stream Control Transmission
Protocol," RFC4960, Sept. 2007.
[RFC5861] Allman, M., Paxson, V., Blanton, E., "TCP Congestion
Control," RFC 5861, Sept. 2009.
[RFC6824] Ford, A., Raiciu, C., Handley, M., Bonaventure, O., "TCP
Extensions for Multipath Operation with Multiple
Addresses," RFC 6824, Jan. 2013.
[RFC6928] Chu, J., Dukkipati, N., Cheng, Y., Mathis, M., "Increasing
TCP's Initial Window," RFC 6928, Apr. 2013.
[RFC7424] Krishnan, R., Yong, L., Ghanwani, A., So, N., Khasnabish,
B., "Mechanisms for Optimizing Link Aggregation Group
(LAG) and Equal-Cost Multipath (ECMP) Component Link
Utilization in Networks", RFC 7424, Jan. 2015
[RFC7540] Belshe, M., Peon, R., Thomson, M., "Hypertext Transfer
Protocol Version 2 (HTTP/2)", RFC 7540, May 2015.
[RFC7661] Fairhurst, G., Sathiaseelan, A., Secchi, R., "Updating TCP
to Support Rate-Limited Traffic", RFC 7661, Oct. 2015
14. Acknowledgments
This work has received funding from a collaborative research project
between the University of Oslo and Huawei Technologies Co., Ltd.
This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses
Joe Touch
USC/ISI
4676 Admiralty Way
Marina del Rey, CA 90292-6695
USA
Phone: +1 (310) 448-9151
Email: touch@isi.edu
Touch Expires December 27, 2016 [Page 16]
Internet-Draft TCP Control Block Interdependence June 2016
Michael Welzl
University of Oslo
PO Box 1080 Blindern
Oslo N-0316
Norway
Phone: +47 22 85 24 20
Email: michawe@ifi.uio.no
Safiqul Islam
University of Oslo
PO Box 1080 Blindern
Oslo N-0316
Norway
Phone: +47 22 84 08 37
Email: safiquli@ifi.uio.no
Jianjie You
Huawei
101 Software Avenue, Yuhua District
Nanjing 210012
China
Email: youjianjie@huawei.com
Touch Expires December 27, 2016 [Page 17]