TCP
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... TCP Modification ...
... RFC2414] and updates [RFC2581] and specifies
an increase in the permitted upper bound for TCP's initial window
from one or two segment(s) to between two and four segments ...
... (MSS) of 1460 bytes (assuming no IP or TCP options). Therefore,
limiting the initial window's MSS to 4380 bytes allows the sender ...
... MSS;
This increased initial window is optional: a TCP MAY start with a
larger initial window. However, we expect that most general-purpose
...
... start with a
larger initial window. However, we expect that most general-purpose
TCP implementations would choose to use the larger initial congestion
window given in equation (1) above.
...
... first round trip time (RTT) of data transmission following the TCP
three-way handshake. Neither the SYN ...
... MSS bytes.
TCP implementations use slow start in as many as three different
ways: (1) to start ...
... restart transmission after a retransmit timeout (the loss
window). The change specified in this document affects the value of
the initial window. Optionally, a TCP MAY set the restart window to
the minimum of the value used for the initial window and the current
...
...
The larger initial window specified in this document is not intended
as encouragement for web browsers to open multiple simultaneous TCP
connections, all with large initial windows. When web browsers open
simultaneous TCP connections to the same destination ...
... as encouragement for web browsers to open multiple simultaneous TCP
connections, all with large initial windows. When web browsers open
simultaneous TCP connections to the same destination, they are
working against TCP ...
... TCP connections to the same destination, they are
working against TCP's congestion control mechanisms [FF99],
...
... HTTP/1.1
[RFC2068] (persistent TCP connections and pipelining) as a way to
achieve better performance ...
... will be of particular benefit for high-bandwidth large-
propagation-delay TCP connections, such as those over satellite
links.
...
... router
queues), a TCP connection can sometimes be better off starting with
an initial window of one segment ...
... starting with
an initial window of one segment. There are scenarios where a TCP
connection slow-starting from an initial window of one segment might
...
... segment might
not have segments dropped, while a TCP connection starting with an
initial window of four segments ...
... RFC2309]).
Some TCP connections will receive better performance with the larger
initial window even if the burstiness of the initial window results
...
... initial window even if the burstiness of the initial window results
in premature segment drops. This will be true if (1) the TCP
connection recovers from the segment drop without a retransmit
timeout, and (2) the TCP connection ...
... TCP
connection recovers from the segment drop without a retransmit
timeout, and (2) the TCP connection is ultimately limited to a small
congestion window by either network ...
... network:
How much would the larger initial window for TCP increase the
number of segments on congested links ...
... path.
First, many of the TCP connections will have only one congested
link along the path. Segments ...
... being dropped on subsequent congested links. To the extent that
the drop rate is independent of the initial window used by TCP
segments, the problem of congested links ...
... will be dropped before reaching their destination will be similar
for TCP connections that start by sending four segments or one
...
... For a network with a high segment drop rate, increasing the TCP
initial window could increase the segment drop rate even further.
...
... traffic in times of congestion.
However, given uncorrelated arrivals for TCP connections, the
larger TCP initial window should not significantly increase the
...
... However, given uncorrelated arrivals for TCP connections, the
larger TCP initial window should not significantly increase the
segment drop rate. Simulation-based explorations of these issues
...
... congestion control), there is no such danger to the
network from increasing the TCP initial window to 4K bytes.
...
... low-bandwidth paths, assuming
the standard algorithm for determining the TCP retransmission timeout
(RTO ...
... paths on which the transmission time of a packet is a large portion
of the round-trip time, the small packets used to establish a TCP
connection do not seed the RTO estimator appropriately. When the
first window of data packets ...
... connection establishment, leaving the default RTO in place until TCP
takes a sample from a data segment and the corresponding ACK ...
... RTO is seeded.
The use of limited transmit [RFC3042] to aid a TCP connection in
recovering from loss using fast retransmit rather than the RTO ...
... Larger TCP initial windows would not dramatically increase the
burstiness of TCP traffic in the Internet today, because such traffic ...
... is already fairly bursty. Bursts of two and three segments are
already typical of TCP [Flo97]; a delayed ACK (covering two
...
... segment burst. While not necessarily
typical, bursts of four and five segments for TCP are not rare.
Assuming delayed ACKs, a single dropped ACK ...
... Studies of TCP Connections using that Larger Initial Window ...
...
This section surveys simulations and experiments that explore the
effect of larger initial windows on TCP connections. The first set
of experiments explores performance over satellite links ...
... satellite links. Larger
initial windows have been shown to improve the performance of TCP
connections over satellite channels [All97b ...
... buffer. The study concluded that for the
scenario investigated, the use of larger initial windows was not
harmful to TCP performance.
...
...
This section surveys simulations and experiments investigating the
impact of the larger window on other TCP connections sharing the
path. Experiments in [All97a, AHO98 ...
... four-segment initial windows. The overall conclusions were that
increasing the TCP initial window to three packets (or 4380 bytes)
helps to improve perceived performance.
...
... network with transfers of 20K in size. The loss rate in
networks where all TCP connections use an initial window of four
segments is shown to be 1-2% greater than in a network ...
... connections used an initial window of four segments, TCP connections
spent more time waiting for the retransmit timer (RTO ...
... This document discusses the initial congestion window permitted for
TCP connections. Changing this value does not raise any known new
security issues with TCP ...
...
This document specifies a small change to TCP that will likely be
beneficial to short-lived TCP connections and those over links ...
... This document specifies a small change to TCP that will likely be
beneficial to short-lived TCP connections and those over links with
long RTTs ...
... End-to-End-Interest Mailing List, and members of the IETF TCP
Implementation Working Group for continuing discussions ...
... Mark Allman, Chris Hayes, and Shawn Ostermann, An Evaluation of TCP with Larger Initial Windows, March 1998. ACM Computer Communication Review, 28(3), July 1998. URL "http://roland.lerc.nasa.gov/~mallman/papers/initwin.ps". ...
... Mark Allman. An Evaluation of TCP with Larger Initial Windows. 40th IETF Meeting -- TCP Implementations WG ...
... Mark Allman. An Evaluation of TCP with Larger Initial Windows. 40th IETF Meeting -- TCP Implementations WG. December, 1997. Washington, DC. ...
... Fall, K., and Floyd, S., Simulation-based Comparisons of Tahoe, Reno, and SACK TCP. Computer Communication Review, 26(3), July 1996. ...
... Floyd, S., TCP and Explicit Congestion Notification. Computer Communication Review, 24(5):10-23, October 1994. ...
... Floyd, S., Issues of TCP with SACK. Technical report, January 1996. Available from http://www-nrg.ee.lbl.gov/floyd/ . ...
... Floyd, S., Increasing TCP's Initial Window. Viewgraphs, 40th IETF Meeting - TCP Implementations WG ...
... Floyd, S., Increasing TCP's Initial Window. Viewgraphs, 40th IETF Meeting - TCP Implementations WG. December, 1997. URL "ftp://ftp.ee.lbl.gov/talks/sf-tcp-ietf97.ps ...
... Allman, M., Floyd, S. and C. Partridge, "Increasing TCP's Initial Window", RFC 2414(-> 3390prop), September 1998. ...
... Poduri, K. and K. Nichols, "Simulation Studies of Increased Initial TCP Window Size", RFC 2415, September 1998. ...
... Shepard, T. and C. Partridge, "When TCP Starts Up With Four Packets Into Only Three Buffers", RFC 2416 ...
... Paxson, V. and M. Allman, "Computing TCP's Retransmission Timer", RFC 2988prop, November 2000. ...
... Allman, M., Balakrishnan, H. and S. Floyd, "Enhancing TCP's Loss Recovery Using Limited Transmit", RFC 3042prop, January 2001. ...
... If one segment is dropped from the initial window, there are three
different ways for TCP to recover: (1) Slow-starting from a window of
one segment ...
... one segment, as is done after a retransmit timeout, or after Fast
Retransmit in Tahoe TCP; (2) Fast Recovery without selective
acknowledgments (SACK ...
... acknowledgments (SACK), as is done after three duplicate ACKs in Reno
TCP; and (3) Fast Recovery with SACK, for TCP ...
... segments that have already been received at
the receiver) are transmitted. Note that for a TCP sending four
512-byte segments in the initial window, a single segment ...