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Monthly Archives: May 2010
Forward RTO-Recovery (F-RTO) defined in RFC4138
$cat /proc/sys/net/ipv4/tcp_frto 2 $ Enables Forward RTO-Recovery (F-RTO) defined in RFC4138. F-RTO is an enhanced recovery algorithm for TCP retransmission timeouts. It is particularly beneficial in wireless environments where packet loss is typically due to random radio interference rather than intermediate router congestion. F-RTO is sender-side only modification. Therefore it does not require any support …
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grep … no matching data -I
$grep -r deactivates * grep: trash4: No such file or directory grep: warning: X11/X11: recursive directory loop Binary file X11/zile matches grep: X11/trash4: No such file or directory Binary file zile matches $grep -I -r deactivates * grep: trash4: No such file or directory grep: warning: X11/X11: recursive directory loop grep: X11/trash4: No such file …
how long to keep sockets in the state FIN-WAIT-2
$cat /proc/sys/net/ipv4/tcp_fin_timeout 60 $ The tcp_fin_timeout variable tells kernel how long to keep sockets in the state FIN-WAIT-2 if you were the one closing the socket. This is used if the other peer is broken for some reason and don’t close its side, or the other peer may even crash unexpectedly. Each socket left in …
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grep -Z
from grep manual in debian. Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name $grep -Z FACK * proc.c SNMP_MIB_ITEM(“TCPFACKReorder”, LINUX_MIB_TCPFACKREORDER), sysctl_net_ipv4.c .ctl_name = NET_TCP_FACK, tcp_input.c * Packet counting of FACK is based on in-order assumptions, therefore TCP tcp_input.c mib_idx = LINUX_MIB_TCPFACKREORDER; tcp_input.c * A”. Its …
Enable FACK congestion avoidance
$cat /proc/sys/net/ipv4/tcp_fack 1 $ tcp_fack Enable FACK congestion avoidance and fast retransmission. The value is not used, if tcp_sack is not enabled. http://www.psc.edu/networking/ftp/papers/Fack.9608.ps grepping through the linux kernel source 2.6.32 proc.c:210: SNMP_MIB_ITEM(“TCPFACKReorder”, LINUX_MIB_TCPFACKREORDER), sysctl_net_ipv4.c:475: .procname = “tcp_fack”, tcp_input.c:847: * Packet counting of FACK is based on in-order assumptions, therefore TCP tcp_input.c:1029: * A”. Its FACK …
explicit congestion notification
$cat /proc/sys/net/ipv4/tcp_ecn 2 $ The tcp_ecn variable turns on Explicit Congestion Notification in TCP connections. This is used to automatically tell the host when there are congestions in a route to a specific host or a network. This can be used to throttle the transmitters to send packets in a slower rate over that specific …
grep –color
$cat textdomain.c #include #include main() { char *textd; textd=textdomain(“iam happy”); printf(“\n %s \n”,textd); } $grep –color=auto hello textdomain.c $grep –color=auto happy textdomain.c textd=textdomain(“iam happy”); $
grep options and fgrep
$grep -V GNU grep 2.6.3 Copyright (C) 2009 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. $ GREP -F or fgrep $grep -F H hello.txt Hello $grep -F helloKello …
grep -n ,-v , -c, -i
$grep -n root /etc/passwd 1:root:x:0:0:root:/root:/bin/bash $ $cat hello.txt hello world $grep -v hello hello.txt world $ $cat hello.txt hello world helloo $grep -c hello hello.txt 2 $grep -c helloo hello.txt 1 $ $cat hello.txt hello world helloo Hello $grep hello hello.txt hello helloo $grep -i hello hello.txt hello helloo Hello $