draft-ietf-tcpimpl-cong-control-00.txt   draft-ietf-tcpimpl-cong-control-01.txt 
TCP Implementation Working Group M. Allman
TCP Implementation Working Group W. Stevens INTERNET DRAFT NASA Lewis/Sterling Software
INTERNET DRAFT Consultant File: draft-ietf-tcpimpl-cong-control-01.txt V. Paxson
File: draft-ietf-tcpimpl-cong-control-00.txt M. Allman
NASA Lewis/Sterling Software
V. Paxson
LBNL LBNL
August, 1998 W. Stevens
Consultant
November, 1998
TCP Congestion Control TCP Congestion Control
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
skipping to change at page 2, line 52 skipping to change at page 2, line 52
when a connection is established. when a connection is established.
LOSS WINDOW (LW): LOSS WINDOW (LW):
The loss window is the size of the congestion window after a TCP The loss window is the size of the congestion window after a TCP
sender detects loss using its retransmission timer. sender detects loss using its retransmission timer.
RESTART WINDOW (RW): RESTART WINDOW (RW):
The restart window is the size of the congestion window after a The restart window is the size of the congestion window after a
TCP restarts transmission after an idle period. TCP restarts transmission after an idle period.
FLIGHT SIZE:
The amount of data the has been sent but not yet acknowledged.
3 Congestion Control Algorithms 3 Congestion Control Algorithms
This section defines the four congestion control algorithms: slow This section defines the four congestion control algorithms: slow
start, congestion avoidance, fast retransmit and fast recovery, start, congestion avoidance, fast retransmit and fast recovery,
developed in [Jac88] and [Jac90]. In some situations it may be developed in [Jac88] and [Jac90]. In some situations it may be
beneficial for a TCP sender to be more conservative than the beneficial for a TCP sender to be more conservative than the
algorithms allow, however a TCP MUST NOT be more aggressive than the algorithms allow, however a TCP MUST NOT be more aggressive than the
following algorithms allow (that is, MUST NOT send data when the following algorithms allow (that is, MUST NOT send data when the
value of cwnd computed by the following algorithms would not allow value of cwnd computed by the following algorithms would not allow
the data to be sent). the data to be sent).
skipping to change at page 4, line 15 skipping to change at page 4, line 18
above); or when cwnd reaches rwnd; or when congestion is observed. above); or when cwnd reaches rwnd; or when congestion is observed.
During congestion avoidance, cwnd is incremented by 1 full-sized During congestion avoidance, cwnd is incremented by 1 full-sized
segment per round-trip time (RTT). Congestion avoidance continues segment per round-trip time (RTT). Congestion avoidance continues
until cwnd reaches the receiver's advertised window or congestion is until cwnd reaches the receiver's advertised window or congestion is
detected. One formula commonly used to update cwnd during detected. One formula commonly used to update cwnd during
congestion avoidance is given in equation 2: congestion avoidance is given in equation 2:
cwnd += MSS*MSS/cwnd (2) cwnd += MSS*MSS/cwnd (2)
This provides an acceptable approximation to the underlying This adjustment is executed on every incoming non-duplicate ACK.
Equation (2) provides an acceptable approximation to the underlying
principle of increasing cwnd by 1 full-sized segment per RTT. (Note principle of increasing cwnd by 1 full-sized segment per RTT. (Note
that for a connection in which the receiver acknowledges every data that for a connection in which the receiver acknowledges every data
segment, (2) proves slightly more aggressive than 1 segment per RTT, segment, (2) proves slightly more aggressive than 1 segment per RTT,
and for a receiver acknowledging every-other packet, (2) is less and for a receiver acknowledging every-other packet, (2) is less
aggressive.) aggressive.)
Implementation Note: Since integer arithmetic is usually used in TCP Implementation Note: Since integer arithmetic is usually used in TCP
implementations, the formula given in equation 2 can fail to implementations, the formula given in equation 2 can fail to
increase cwnd when the congestion window is very large (larger than increase cwnd when the congestion window is very large (larger than
MSS*MSS). If the above formula yields 0, the result SHOULD be MSS*MSS). If the above formula yields 0, the result SHOULD be
skipping to change at page 4, line 50 skipping to change at page 4, line 54
Implementation Note: some implementations maintain cwnd in units of Implementation Note: some implementations maintain cwnd in units of
bytes, while others in units of full-sized segments. The latter bytes, while others in units of full-sized segments. The latter
will find equation (2) difficult to use, and may prefer to use the will find equation (2) difficult to use, and may prefer to use the
counting approach discussed in the previous paragraph. counting approach discussed in the previous paragraph.
When a TCP sender detects segment loss using the retransmission When a TCP sender detects segment loss using the retransmission
timer, the value of ssthresh MUST be set to no more than the value timer, the value of ssthresh MUST be set to no more than the value
given in equation 3: given in equation 3:
ssthresh = max (min (cwnd, rwnd) / 2, 2*MSS) (3) ssthresh = max (FlightSize / 2, 2*MSS) (3)
Implementation Note: an easy mistake to make is to forget the inner As discussed above, FlightSize is the amount of outstanding data in
min() operation and simply use cwnd, which in some implementations the network.
may incidentally increase well beyond rwnd.
Implementation Note: an easy mistake to make is to simply use cwnd,
rather than FlightSize, which in some implementations may
incidentally increase well beyond rwnd.
Furthermore, upon a timeout cwnd MUST be set to no more than the Furthermore, upon a timeout cwnd MUST be set to no more than the
loss window, LW, which equals 1 full-sized segment (regardless of loss window, LW, which equals 1 full-sized segment (regardless of
the value of IW). Therefore, after retransmitting the dropped the value of IW). Therefore, after retransmitting the dropped
segment the TCP sender uses the slow start algorithm to increase the segment the TCP sender uses the slow start algorithm to increase the
window from 1 full-sized segment to the new value of ssthresh, at window from 1 full-sized segment to the new value of ssthresh, at
which point congestion avoidance again takes over in a fashion which point congestion avoidance again takes over in a fashion
identical to that for a connection's initial slow start. identical to that for a connection's initial slow start.
3.3 Fast Retransmit/Fast Recovery 3.3 Fast Retransmit/Fast Recovery
A TCP receiver SHOULD send an immediate duplicate ACK when an A TCP receiver SHOULD send an immediate duplicate ACK when an
out-of-order segment arrives. The purpose of this ACK is to inform out-of-order segment arrives. The purpose of this ACK is to inform
the sender that a segment was received out-of-order and which the sender that a segment was received out-of-order and which
sequence number is expected. From the sender's perspective, sequence number is expected. From the sender's perspective,
duplicate ACKs can be caused by a number of network problems. duplicate ACKs can be caused by a number of network problems.
First, they can be caused by dropped segments. In this case, all First, they can be caused by dropped segments. In this case, all
segments after the dropped segment will trigger duplicate ACKs. segments after the dropped segment will trigger duplicate ACKs.
Second, duplicate ACKs can be caused by the re-ordering of data Second, duplicate ACKs can be caused by the re-ordering of data
segments by the network (not a rare event along some network paths). segments by the network (not a rare event along some network paths
Finally, duplicate ACKs can be caused by replication of ACK or data [Pax97]). Finally, duplicate ACKs can be caused by replication of
segments by the network. ACK or data segments by the network. In addition, a TCP receiver
SHOULD send an immediate ACK when the incoming segment fills in all
or part of a gap in the sequence space. This will generate more
timely information for a sender recovering from a loss through a
retransmission timeout, a fast retransmit, or an experimental loss
recovery algorithm, such as NewReno [FH98].
The TCP sender SHOULD use the "fast retransmit" algorithm to detect The TCP sender SHOULD use the "fast retransmit" algorithm to detect
and repair loss, based on incoming duplicate ACKs. The fast and repair loss, based on incoming duplicate ACKs. The fast
retransmit algorithm uses the arrival of 3 duplicate ACKs (i.e., 4 retransmit algorithm uses the arrival of 3 duplicate ACKs (4
identical ACKs) as an indication that a segment has been lost. identical ACKs without the arrival of any other intervening packets)
After receiving 3 duplicate ACKs, TCP performs a retransmission of as an indication that a segment has been lost. After receiving 3
what appears to be the missing segment, without waiting for the duplicate ACKs, TCP performs a retransmission of what appears to be
retransmission timer to expire. the missing segment, without waiting for the retransmission timer to
expire.
After the fast retransmit sends what appears to be the missing After the fast retransmit sends what appears to be the missing
segment, the "fast recovery" algorithm governs the transmission of segment, the "fast recovery" algorithm governs the transmission of
new data until a non-duplicate ACK arrives. The reason for not new data until a non-duplicate ACK arrives. The reason for not
performing slow start is that the receipt of the duplicate ACKs not performing slow start is that the receipt of the duplicate ACKs not
only tells the TCP that a segment has been lost, but also that only indicates that a segment has been lost, but also that segments
segments are leaving the network. In other words, since the are most likely leaving the network (although a massive segment
receiver can only generate a duplicate ACK when a segment has duplication by the network can invalidate this conclusion). In
arrived, that segment has left the network and is in the receiver's other words, since the receiver can only generate a duplicate ACK
buffer, so we know it is no longer consuming network resources. when a segment has arrived, that segment has left the network and is
Furthermore, since the ACK "clock" [Jac88] is preserved, the TCP in the receiver's buffer, so we know it is no longer consuming
sender can continue to transmit new segments (although transmission network resources. Furthermore, since the ACK "clock" [Jac88] is
must continue using a reduced cwnd). preserved, the TCP sender can continue to transmit new segments
(although transmission must continue using a reduced cwnd).
The fast retransmit and fast recovery algorithms are usually The fast retransmit and fast recovery algorithms are usually
implemented together as follows. implemented together as follows.
1. When the third duplicate ACK is received, set ssthresh to no 1. When the third duplicate ACK is received, set ssthresh to no
more than the value given in equation 3. more than the value given in equation 3.
2. Retransmit the lost segment and set cwnd to ssthresh plus 3*MSS. 2. Retransmit the lost segment and set cwnd to ssthresh plus 3*MSS.
This artificially "inflates" the congestion window by the number This artificially "inflates" the congestion window by the number
of segments (three) that have left the network and which the of segments (three) that have left the network and which the
skipping to change at page 6, line 19 skipping to change at page 6, line 33
5. When the next ACK arrives that acknowledges new data, set cwnd 5. When the next ACK arrives that acknowledges new data, set cwnd
to ssthresh (the value set in step 1). This is termed to ssthresh (the value set in step 1). This is termed
"deflating" the window. "deflating" the window.
This ACK should be the acknowledgment elicited by the This ACK should be the acknowledgment elicited by the
retransmission from step 1, one RTT after the retransmission retransmission from step 1, one RTT after the retransmission
(though it may arrive sooner in the presence of significant (though it may arrive sooner in the presence of significant
out-of-order delivery of data segments at the receiver). out-of-order delivery of data segments at the receiver).
Additionally, this ACK should acknowledge all the intermediate Additionally, this ACK should acknowledge all the intermediate
segments sent between the lost segment and the receipt of the segments sent between the lost segment and the receipt of the
first duplicate ACK, if none of these were lost. third duplicate ACK, if none of these were lost.
Implementing fast retransmit/fast recovery in this manner can lead
to a phenomenon which allows the fast retransmit algorithm to repair
multiple dropped segments from a single window of data [Flo94].
However, in doing so, the size of cwnd is also reduced multiple
times, which reduces performance. The following steps MAY be taken
to reduce the impact of successive fast retransmits on performance.
A. After the third duplicate ACK is received follow step 1 above,
but also record the highest sequence number transmitted
(send_high).
B. Instead of reducing cwnd to ssthresh upon receipt of the first
non-duplicate ACK received (step 5), the sender should wait
until an ACK covering send_high is received. In addition, each
duplicate ACK received should continue to artificially inflate
cwnd by 1 MSS.
C. A non-duplicate ACK that does not cover send_high, followed by 3 Note: This algorithm is known to generally not recover very
duplicate ACKs should not reduce ssthresh or cwnd but SHOULD efficiently from multiple losses in a single flight of packets. One
trigger a retransmission. A non-duplicate ACK that does not proposed set of modifications to it to address this problem can be
cover send_high SHOULD NOT cause any adjustment in cwnd. found in [FH98].
4 Additional Considerations 4 Additional Considerations
4.1 Re-starting Idle Connections 4.1 Re-starting Idle Connections
A known problem with the TCP congestion control algorithms described A known problem with the TCP congestion control algorithms described
above is that they allow a potentially inappropriate burst of above is that they allow a potentially inappropriate burst of
traffic to be transmitted after TCP has been idle for a relatively traffic to be transmitted after TCP has been idle for a relatively
long period of time. After an idle period, TCP cannot use the ACK long period of time. After an idle period, TCP cannot use the ACK
clock to strobe new segments into the network, as all the ACKs have clock to strobe new segments into the network, as all the ACKs have
skipping to change at page 7, line 29 skipping to change at page 7, line 26
persistent HTTP connections [HTH98]. In this case, a WWW server persistent HTTP connections [HTH98]. In this case, a WWW server
receives a request before transmitting data to the WWW browser. The receives a request before transmitting data to the WWW browser. The
reception of the request makes the test for an idle connection fail, reception of the request makes the test for an idle connection fail,
and allows the TCP to begin transmission with a possibly and allows the TCP to begin transmission with a possibly
inappropriately large cwnd. inappropriately large cwnd.
Therefore, a TCP SHOULD reduce cwnd to no more than RW before Therefore, a TCP SHOULD reduce cwnd to no more than RW before
beginning transmission if the TCP has not sent data in an interval beginning transmission if the TCP has not sent data in an interval
exceeding the retransmission timeout. exceeding the retransmission timeout.
4.2 Acknowledgment Mechanisms 4.2 Generating Acknowledgments
The delayed ACK algorithm specified in [Bra89] SHOULD be used by a The delayed ACK algorithm specified in [Bra89] SHOULD be used by a
TCP receiver. When used, a TCP receiver MUST NOT excessively delay TCP receiver. When used, a TCP receiver MUST NOT excessively delay
acknowledgments. Specifically, an ACK MUST be generated for every acknowledgments. Specifically, an ACK SHOULD be generated for at
second full-sized segment. (This "MUST" is listed in [Bra89] in one least every second full-sized segment, and MUST be generated within
place as a SHOULD and another as a MUST; here we unambiguously state 500 ms of the arrival of the first unacknowledged packet.
it is a MUST.) Furthermore, an ACK SHOULD be generated for every
second segment regardless of size. Finally, an ACK MUST NOT be The requirement that an ACK "SHOULD" be generated for at least every
delayed for more than 500 ms waiting on a second full-sized segment second full-sized segment is listed in [Bra89] in one place as a
to arrive. Out-of-order data segments SHOULD be acknowledged SHOULD and another as a MUST. Here we unambiguously state it is a
immediately, in order to trigger the fast retransmit algorithm. SHOULD. We also emphasize that this is a "strong" SHOULD, meaning
that an implementor should indeed only deviate from this requirement
after careful consideration of the implications. See the discussion
of "Stretch ACK violation" in [PAD+98] and the references therein
for a discussion of the possible performance problems with
generating ACKs less frequently than every second full-sized
segment.
In some cases, the sender and receiver may not agree on what what
constitutes a full-sized segment. An implementation is deemed to
comply with this requirement if it sends at least one acknowledgment
every time it receives 2*MSS bytes of new data from the sender,
where MSS is the Maximum Segment Size specified by the receiver to
the sender (or the default value of 536 bytes, per [Bra89], if the
receiver does not specify an MSS option during connection
establishment). Finally, we repeat that an ACK MUST NOT be delayed
for more than 500 ms waiting on a second full-sized segment to
arrive. Out-of-order data segments SHOULD be acknowledged
immediately, in order to accelerate loss recovery. To trigger the
fast retransmit algorithm, the receiver SHOULD send an immediate
duplicate ACK when it receives a data segment above a gap in the
sequence space. To provide feedback to senders recovering from
losses, the receiver SHOULD send an immediate ACK when it receives a
data segment that fills in all or part of a gap in the sequence
space.
A TCP receiver MUST NOT generate more than one ACK for every A TCP receiver MUST NOT generate more than one ACK for every
incoming segment. incoming segment, other than to update the offered window as the
receiving application consumes new data.
TCP implementations that implement the selective acknowledgment 4.4 Loss Recovery Mechanisms
(SACK) option [MMFR96] are able to determine which segments have not
arrived at the receiver. Consequently, they can retransmit the lost A number of loss recovery algorithms that augment fast retransmit
segments more quickly than TCPs without SACKs. This allows a TCP and fast recovery have been suggested by TCP researchers. While
sender to repair multiple losses in roughly one RTT after detecting some of these algorithms are based on the TCP selective
loss [FF96,MM96a,MM96b]. While no specific SACK-based recovery acknowledgment (SACK) option [MMFR96], such as [FF96,MM96a,MM96b],
algorithm has yet been standardized, any SACK-based algorithm should others do not require SACKs [Hoe96,FF96,FH98]. The non-SACK
follow the general principles embodied by the above algorithms. algorithms use ``partial acknowledgments'' (ACKs which cover new
First, as soon as loss is detected, ssthresh should be decreased per data, but not all the data outstanding when loss was detected) to
equation (3). Second, in the RTT following loss detection, the trigger retransmissions. While this document does not standardize
number of segments sent should be no more than half the number any of the specific algorithms that may improve fast retransmit/fast
transmitted in the previous RTT (i.e., before loss occurred). recovery, these enhanced algorithms are implicitly allowed, as long
Third, after the recovery period is finished, cwnd should be set to as they follow the general principles of the basic four algorithms
the reduced value of ssthresh. The SACK-based algorithms outlined outlined above.
in [FF96,MM96a,MM96b] adhere to these guidelines.
Therefore, when the first loss in a window of data is detected,
ssthresh MUST be set to no more than the value given by equation
(3). Second, until all lost segments in the window of data in
question are repaired, the number of segments transmitted in each
RTT MUST be no more than half the number of outstanding segments
when the loss was detected. Finally, after all loss in the given
window of segments has been successfully retransmitted, cwnd MUST be
set to no more than ssthresh and congestion avoidance MUST be used
to further increase cwnd. Loss in two successive windows of data,
or the loss of a retransmission, should be taken as two indications
of congestion and, therefore, cwnd (and ssthresh) MUST be lowered
twice in this case. The algorithms outlined in
[Hoe96,FF96,MM96a,MM6b] follow the principles of the basic four
congestion control algorithms outlined in this document.
5. Security Considerations 5. Security Considerations
This document requires a TCP to diminish its sending rate in the This document requires a TCP to diminish its sending rate in the
presence of retransmission timeouts and the arrival of duplicate presence of retransmission timeouts and the arrival of duplicate
acknowledgments. An attacker can therefore impair the performance acknowledgments. An attacker can therefore impair the performance
of a TCP connection by either causing data packets or their of a TCP connection by either causing data packets or their
acknowledgments to be lost, or by forging excessive duplicate acknowledgments to be lost, or by forging excessive duplicate
acknowledgments. Causing two congestion control events back-to-back acknowledgments. Causing two congestion control events back-to-back
will often cut ssthresh to its minimum value of 2*MSS, causing the will often cut ssthresh to its minimum value of 2*MSS, causing the
skipping to change at page 8, line 39 skipping to change at page 9, line 21
The four algorithms that are described were developed by Van The four algorithms that are described were developed by Van
Jacobson. Jacobson.
Some of the text from this document is taken from "TCP/IP Some of the text from this document is taken from "TCP/IP
Illustrated, Volume 1: The Protocols" by W. Richard Stevens Illustrated, Volume 1: The Protocols" by W. Richard Stevens
(Addison-Wesley, 1994) and "TCP/IP Illustrated, Volume 2: The (Addison-Wesley, 1994) and "TCP/IP Illustrated, Volume 2: The
Implementation" by Gary R. Wright and W. Richard Stevens Implementation" by Gary R. Wright and W. Richard Stevens
(Addison-Wesley, 1995). This material is used with the permission (Addison-Wesley, 1995). This material is used with the permission
of Addison-Wesley. of Addison-Wesley.
Sally Floyd devised the algorithm presented in section 3.3 for Neal Cardwell, Sally Floyd, Craig Partridge and Joe Touch
avoiding multiple cwnd cutbacks in the presence of multiple packets
lost from the same flight. Craig Partridge and Joe Touch
contributed a number of helpful suggestions. contributed a number of helpful suggestions.
References References
[AFP98] M. Allman, S. Floyd, C. Partridge, Increasing TCP's Initial [AFP98] M. Allman, S. Floyd, C. Partridge, Increasing TCP's Initial
Window Size, Internet-Draft draft-floyd-incr-init-win-03.txt. Window Size, September 1998. RFC 2414.
May, 1998. (Work in progress).
[Bra89] B. Braden, ed., "Requirements for Internet Hosts -- [Bra89] B. Braden, ed., "Requirements for Internet Hosts --
Communication Layers," RFC 1122, Oct. 1989. Communication Layers," RFC 1122, Oct. 1989.
[Bra97] S. Bradner, "Key words for use in RFCs to Indicate [Bra97] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[FF96] Kevin Fall and Sally Floyd. Simulation-based Comparisons of [FF96] K. Fall, S. Floyd. Simulation-based Comparisons of Tahoe,
Tahoe, Reno and SACK TCP. Computer Communication Review, July Reno and SACK TCP. Computer Communication Review, July 1996.
1996. ftp://ftp.ee.lbl.gov/papers/sacks.ps.Z. ftp://ftp.ee.lbl.gov/papers/sacks.ps.Z.
[FH98] S. Floyd, T. Henderson. The NewReno Modification to TCP's
Fast Recovery Algorithm. Internet-Draft
draft-ietf-tcpimpl-newreno-00.txt, November 1998. (Work in
progress).
[Flo94] S. Floyd, TCP and Successive Fast Retransmits. Technical [Flo94] S. Floyd, TCP and Successive Fast Retransmits. Technical
report, October 1994. report, October 1994.
ftp://ftp.ee.lbl.gov/papers/fastretrans.ps. ftp://ftp.ee.lbl.gov/papers/fastretrans.ps.
[HTH98] Amy Hughes, Joe Touch, John Heidemann. Internet-Draft [Hoe96] J. Hoe, Improving the Start-up Behavior of a Congestion
Control Scheme for TCP. In ACM SIGCOMM, August 1996.
[HTH98] A. Hughes, J. Touch, J. Heidemann. Issues in TCP Slow-Start
Restart After Idle. Internet-Draft
draft-ietf-tcpimpl-restart-00.txt, March 1998. (Work in draft-ietf-tcpimpl-restart-00.txt, March 1998. (Work in
progress). progress).
[Jac88] V. Jacobson, "Congestion Avoidance and Control," Computer [Jac88] V. Jacobson, "Congestion Avoidance and Control," Computer
Communication Review, vol. 18, no. 4, pp. 314-329, Aug. 1988. Communication Review, vol. 18, no. 4, pp. 314-329, Aug. 1988.
ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z. ftp://ftp.ee.lbl.gov/papers/congavoid.ps.Z.
[Jac90] V. Jacobson, "Modified TCP Congestion Avoidance Algorithm," [Jac90] V. Jacobson, "Modified TCP Congestion Avoidance Algorithm,"
end2end-interest mailing list, April 30, 1990. end2end-interest mailing list, April 30, 1990.
ftp://ftp.isi.edu/end2end/end2end-interest-1990.mail. ftp://ftp.isi.edu/end2end/end2end-interest-1990.mail.
[MM96a] M. Mathis, J. Mahdavi, "Forward Acknowledgment: Refining TCP [MM96a] M. Mathis, J. Mahdavi, "Forward Acknowledgment: Refining TCP
Congestion Control," Proceedings of SIGCOMM'96, August, 1996, Congestion Control," Proceedings of SIGCOMM'96, August, 1996,
Stanford, CA. Available from Stanford, CA. Available from
http://www.psc.edu/networking/papers/papers.html http://www.psc.edu/networking/papers/papers.html
skipping to change at page 9, line 37 skipping to change at page 10, line 23
Stanford, CA. Available from Stanford, CA. Available from
http://www.psc.edu/networking/papers/papers.html http://www.psc.edu/networking/papers/papers.html
[MM96b] M. Mathis, J. Mahdavi, "TCP Rate-Halving with Bounding [MM96b] M. Mathis, J. Mahdavi, "TCP Rate-Halving with Bounding
Parameters" Available from Parameters" Available from
http://www.psc.edu/networking/papers/FACKnotes/current. http://www.psc.edu/networking/papers/FACKnotes/current.
[MMFR96] M. Mathis, J. Mahdavi, S. Floyd, A. Romanow, "TCP Selective [MMFR96] M. Mathis, J. Mahdavi, S. Floyd, A. Romanow, "TCP Selective
Acknowledgement Options", RFC 2018, October 1996. Acknowledgement Options", RFC 2018, October 1996.
[PAD+98] V. Paxson, M. Allman, S. Dawson, J. Griner, I. Heavens, [PAD+98] V. Paxson, M. Allman, S. Dawson, W. Fenner, J. Griner,
K. Lahey, J. Semke, B. Volz. Internet-Draft I. Heavens, K. Lahey, J. Semke, B. Volz. Internet-Draft
draft-ietf-tcpimpl-prob-04.txt, August 1998. (Work in draft-ietf-tcpimpl-prob-05.txt, October 1998. (Work in
progress). progress).
[Pax97] V. Paxson, "End-to-End Internet Packet Dynamics,"
Proceedings of SIGCOMM '97, Cannes, France, Sep. 1997.
[Pos81] J. Postel, Transmission Control Protocol, September 1981. [Pos81] J. Postel, Transmission Control Protocol, September 1981.
RFC 793. RFC 793.
[Ste94] W. R. Stevens, "TCP/IP Illustrated, Volume 1: The [Ste94] W. R. Stevens, "TCP/IP Illustrated, Volume 1: The
Protocols", Addison-Wesley, 1994. Protocols", Addison-Wesley, 1994.
[Ste97] W. R. Stevens, "TCP Slow Start, Congestion Avoidance, Fast [Ste97] W. R. Stevens, "TCP Slow Start, Congestion Avoidance, Fast
Retransmit, and Fast Recovery Algorithms", RFC 2001, January Retransmit, and Fast Recovery Algorithms", RFC 2001, January
1997. 1997.
[WS95] G. R. Wright, W. R. Stevens, "TCP/IP Illustrated, Volume 2: [WS95] G. R. Wright, W. R. Stevens, "TCP/IP Illustrated, Volume 2:
The Implementation", Addison-Wesley, 1995. The Implementation", Addison-Wesley, 1995.
Author's Address: Author's Address:
W. Richard Stevens
1202 E. Paseo del Zorro
Tucson, AZ 85718
520-297-9416
rstevens@kohala.com
http://www.kohala.com/~rstevens
Mark Allman Mark Allman
NASA Lewis Research Center/Sterling Software NASA Lewis Research Center/Sterling Software
21000 Brookpark Rd. MS 54-2 21000 Brookpark Rd. MS 54-2
Cleveland, OH 44135 Cleveland, OH 44135
216-433-6586 216-433-6586
mallman@lerc.nasa.gov mallman@lerc.nasa.gov
http://gigahertz.lerc.nasa.gov/~mallman http://gigahertz.lerc.nasa.gov/~mallman
Vern Paxson Vern Paxson
Network Research Group Network Research Group
Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory
Berkeley, CA 94720 Berkeley, CA 94720
USA USA
510-486-7504 510-486-7504
vern@ee.lbl.gov vern@ee.lbl.gov
W. Richard Stevens
1202 E. Paseo del Zorro
Tucson, AZ 85718
520-297-9416
rstevens@kohala.com
http://www.kohala.com/~rstevens
 End of changes. 24 change blocks. 
94 lines changed or deleted 132 lines changed or added

This html diff was produced by rfcdiff 1.33. The latest version is available from http://tools.ietf.org/tools/rfcdiff/