I have a Cisco small business switch and I am wondering what I will gain (or lose) by enabling "TCP congestion avoidance". I read the definition of it but how does one know when one should use it?
I have problem with oracle solaris 10 running on oracle sparc T4-2 server.
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Output from tcpstat.d script
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I have noticed that the initial congestion window in my traces is 8920bytes~=6*1448. rfc3390 states the initial cwand should be max 4000 bytes(around 3*1448).
At first i thought it might be because i'm running my server on mac os x, so apple might have modified the tcp stack. Therefore I tried... (2 Replies)
I was looking at differnt types of TCP Congestion Avoidance algorithms and realized that they are almost all tailored toward "high speed networks with high latency" (aka. LFN)
Anybody know of a Congestion Avoidance algorithm used in low-latency networks? (3 Replies)
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Hello everybody,
It's me again, i need your help!
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I have written a TCP/IP client and server program. The client sends a message to the server and then the server sends a file back to the client. The client reads the buffer and stores it another file in the client side.
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Hello ,
I need to convert X.25 packets to IP packets how should i proceed .......... Please help me , regarding this matter or atleast suggest me some material which can be read regarding this .
Bye (2 Replies)
CC_CDG(4) BSD Kernel Interfaces Manual CC_CDG(4)NAME
cc_cdg -- CDG Congestion Control Algorithm
DESCRIPTION
CAIA-Delay Gradient (CDG) is a hybrid congestion control algorithm which reacts to both packet loss and inferred queuing delay. It attempts
to operate as a delay-based algorithm where possible, but utilises heuristics to detect loss-based TCP cross traffic and will compete effec-
tively as required. CDG is therefore incrementally deployable and suitable for use on shared networks.
During delay-based operation, CDG uses a delay-gradient based probabilistic backoff mechanism, and will also try to infer non congestion
related packet losses and avoid backing off when they occur. During loss-based operation, CDG essentially reverts to cc_newreno(4)-like be-
haviour.
CDG switches to loss-based operation when it detects that a configurable number of consecutive delay-based backoffs have had no measurable
effect. It periodically attempts to return to delay-based operation, but will keep switching back to loss-based operation as required.
MIB Variables
The algorithm exposes the following variables in the net.inet.tcp.cc.cdg branch of the sysctl(3) MIB:
version Current algorithm/implementation version number.
beta_delay Delay-based window decrease factor as a percentage (on delay-based backoff, w = w * beta_delay / 100). Default is 70.
beta_loss Loss-based window decrease factor as a percentage (on loss-based backoff, w = w * beta_loss / 100). Default is 50.
exp_backoff_scale Scaling parameter for the probabilistic exponential backoff. Default is 2.
smoothing_factor Number of samples used for moving average smoothing (0 means no smoothing). Default is 8.
loss_compete_consec_cong
Number of consecutive delay-gradient based congestion episodes which will trigger loss-based CC compatibility. Default is
5.
loss_compete_hold_backoff
Number of consecutive delay-gradient based congestion episodes to hold the window backoff for loss-based CC compatibility.
Default is 5.
alpha_inc If non-zero, this enables an experimental mode where CDG's window increase factor (alpha) is increased by 1 MSS every
alpha_inc RTTs during congestion avoidance mode. (Setting alpha_inc to 1 results in the most aggressive growth of the
window increase factor over time. Use higher alpha_inc values for slower growth.) Default is 0.
SEE ALSO cc_chd(4), cc_cubic(4), cc_hd(4), cc_htcp(4), cc_newreno(4), cc_vegas(4), h_ertt(4), mod_cc(4), tcp(4), khelp(9), mod_cc(9)
D. A. Hayes and G. Armitage, "Revisiting TCP Congestion Control using Delay Gradients", Networking 2011 Proceedings, Part II, 328-341, May
2011.
N. Khademi and G. Armitage, Minimising RTT across homogeneous 802.11 WLANs with CAIA Delay-Gradient TCP (v0.1), CAIA Technical Report
121113A, http://caia.swin.edu.au/reports/121113A/CAIA-TR-121113A.pdf, November 2012.
ACKNOWLEDGEMENTS
Development and testing of this software were made possible in part by grants from the FreeBSD Foundation and The Cisco University Research
Program Fund, a corporate advised fund of Silicon Valley Community Foundation.
HISTORY
The cc_cdg congestion control module first appeared in FreeBSD 9.2.
The module was first released in 2011 by David Hayes whilst working on the NewTCP research project at Swinburne University of Technology's
Centre for Advanced Internet Architectures, Melbourne, Australia. More details are available at:
http://caia.swin.edu.au/urp/newtcp/
AUTHORS
The cc_cdg congestion control module was written by David Hayes <david.hayes@ieee.org>. This manual page was written by Lawrence Stewart
<lstewart@FreeBSD.org> and Grenville Armitage <garmitage@swin.edu.au>.
BUGS
The underlying algorithm and parameter values are still a work in progress and may not be optimal for some network scenarios.
BSD July 2, 2013 BSD