I have executed this "ls /lib/modules/uname -r/kernel/net/ipv4/" in my linux 2.16.36 . There i can see a list of algorithms.tcp_westwood is listed in that list . is that tcp_westwood or tcp_westwood+ ?
This suggests that westwood now refers to westwood+.
Related
I installed Ubuntu 18.04 on Hyper-V Win Server 2016.
And network performance of the Ubuntu is bad: I'm hosting few sites (Apache + PHP) and sometime response time is > 10 seconds. Sometimes it is fast.
As I troubleshooted, I see this netstat results:
# netstat -s | egrep -i 'loss|retran'
3447700 segments retransmitted
226 times recovered from packet loss due to fast retransmit
Detected reordering 6 times using reno fast retransmit
TCPLostRetransmit: 79831
45 timeouts after reno fast retransmit
6247 timeouts in loss state
2056435 fast retransmits
107095 retransmits in slow start
TCPLossProbes: 220607
TCPLossProbeRecovery: 3753
TCPSynRetrans: 90564
What can be cause of such high "segments retransmitted" number? And how to fix it?
Few notes:
- VMQ is disabled for Ubuntu VM
- The host system Network adapter is Intel I210
- I disabled IPv6 both on host and in VM
Here is WireShark showing, that it takes ~7 seconds to connect (just initial connection) to my site Propovednik.com:
Sep 20: So far, the issue seems to be caused by OVH / SoYouStart bad network:
This command shows 20-30% packets loss:
sudo ping us.soyoustart.com -c 10 -i 0.2 -p 00 -s 1200 -l 5
The problem could be anywhere along the network, including the workstation where you work from. I suggest you check the network as retransmissions and packetloss means that either something is malfunctioning or misconfigured. If this is on a wireless network, you could be out of range of your router.
I am pinging the website you noted from my computer and there is no packetloss.
I'm trying to get sipp communicate with Asterisk in order to perform
performance tests:
I've been through these steps:
1) In sip.conf
[sippuac]
type=friend
username=sippuac
host=127.0.0.1
port=5061
context=test
dtmfmode=rfc2833
insecure=very
canreinvite=no
nat=yes
[sippuas]
type=friend
username=sippuas
host=127.0.0.1
port=5062
context=test
dtmfmode=rfc2833
insecure=very
canreinvite=no
nat=yes
2) In extensions.conf
[test]
exten=>s,1,Dial(SIP/sippuas,20)
3) Running SIPp
sipp -sn uas -rsa 127.0.0.1:5060 -p 5062 -i 127.0.0.1 -mp 6001
sipp -sn uac 127.0.0.1:5060 -s s -p 5061 -i 127.0.0.1
Finally I get on Asterisk :
[Jun 14 07:36:56] WARNING[2600][C-00000120]: app_dial.c:2437
dial_exec_full: Unable to create channel of type 'SIP' (cause 20 -
Subscriber absent)
How can I solve this and make the UAS receive the calls ?
Thanks for your help !
I think in sip.conf should be type=peer for sippuas.
It is bad idea to run performance test from localhost. SIPP will impact performance of Asterisk. Additionally it make seance to run scenario with audio and I will recommend just answer a call on Asterisk and play some sound, it is not so important to send call out to second sipp.
For receiving calls from asterisk, SIPp user(s) should be registered first to it. You can see if your user is registered or not by using the command:
sip show peers
in the asterisk CLI. If your uas is not registered and you are trying to tell asterisk to dial to a client and not giving the address of it. There are simple xml examples in this link for how to register and make calls to asterisk. Please follow the scenario you want.
It is strange that when i nmap -sS Target,I take longer timer than when I namp -sT Target.(both I have root).In the namp docs, the namp sS option send a syn packet should take less time than sT option which tend to complete a TCP connection with target.
It there any reason for this?I use nmap 6.40 on Ubuntu14.04.
I'm trying to write the linux client script for a simple port knocking setup. My server has iptables configured to require a certain sequence of TCP SYN's to certain ports for opening up access. I'm able to successfully knock using telnet or manually invoking netcat (Ctrl-C right after running the command), but failing to build an automated knock script.
My attempt at an automated port knocking script consists simply of "nc -w 1 x.x.x.x 1234" commands, which connect to x.x.x.x port 1234 and timeout after one second. The problem, however, seems to be the kernel(?) doing automated SYN retries. Most of the time more than one SYN is being send during the 1 second nc tries to connect. I've checked this with tcpdump.
So, does anyone know how to prevent the SYN retries and make netcat simply send only one SYN per connection/knock attempt? Other solutions which do the job are also welcome.
Yeah, I checked that you may use nc too!:
$ nc -z example.net 1000 2000 3000; ssh example.net
The magic comes from (-z: zero-I/O mode)...
You may use nmap for port knocking (SYN). Just exec:
for p in 1000 2000 3000; do
nmap -Pn --max-retries 0 -p $p example.net;
done
try this (as root):
echo 1 > /proc/sys/net/ipv4/tcp_syn_retries
or this:
int sc = 1;
setsockopt(sock, IPPROTO_TCP, TCP_SYNCNT, &sc, sizeof(sc));
You can't prevent the TCP/IP stack from doing what it is expressly designed to do.
OK, we all know how to use PING to test connectivity to an IP address. What I need to do is something similar but test if my outbound request to a given IP Address as well as a specif port (in the present case 1775) is successful. The test should be performed preferably from the command prompt.
Here is a small site I made allowing to test any outgoing port. The server listens on all TCP ports available.
http://portquiz.net
telnet portquiz.net XXXX
If there is a server running on the target IP/port, you could use Telnet. Any response other than "can't connect" would indicate that you were able to connect.
To automate the awesome service portquiz.net, I did write a bash script :
NB_CONNECTION=10
PORT_START=1
PORT_END=1000
for (( i=$PORT_START; i<=$PORT_END; i=i+NB_CONNECTION ))
do
iEnd=$((i + NB_CONNECTION))
for (( j=$i; j<$iEnd; j++ ))
do
#(curl --connect-timeout 1 "portquiz.net:$j" &> /dev/null && echo "> $j") &
(nc -w 1 -z portquiz.net "$j" &> /dev/null && echo "> $j") &
done
wait
done
If you're testing TCP/IP, a cheap way to test remote addr/port is to telnet to it and see if it connects. For protocols like HTTP (port 80), you can even type HTTP commands and get HTTP responses.
eg
Command IP Port
Telnet 192.168.1.1 80
The fastest / most efficient way I found to to this is with nmap and portquiz.net described here: http://thomasmullaly.com/2013/04/13/outgoing-port-tester/ This scans to top 1000 most used ports:
# nmap -Pn --top-ports 1000 portquiz.net
Starting Nmap 6.40 ( http://nmap.org ) at 2017-08-02 22:28 CDT
Nmap scan report for portquiz.net (178.33.250.62)
Host is up (0.072s latency).
rDNS record for 178.33.250.62: electron.positon.org
Not shown: 996 closed ports
PORT STATE SERVICE
53/tcp open domain
80/tcp open http
443/tcp open https
8080/tcp open http-proxy
Nmap done: 1 IP address (1 host up) scanned in 4.78 seconds
To scan them all (took 6 sec instead of 5):
# nmap -Pn -p1-65535 portquiz.net
The bash script example of #benjarobin for testing a sequence of ports did not work for me so I created this minimal not-really-one-line (command-line) example which writes the output of the open ports from a sequence of 1-65535 (all applicable communication ports) to a local file and suppresses all other output:
for p in $(seq 1 65535); do curl -s --connect-timeout 1 portquiz.net:$p >> ports.txt; done
Unfortunately, this takes 18.2 hours to run, because the minimum amount of connection timeout allowed integer seconds by my older version of curl is 1. If you have a curl version >=7.32.0 (type "curl -V"), you might try smaller decimal values, depending on how fast you can connect to the service. Or try a smaller port range to minimise the duration.
Furthermore, it will append to the output file ports.txt so if run multiple times, you might want to remove the file first.