General :: Netem For Mac OS X To Emulate Network Latency And Dropped Packets?
Aug 9, 2010
I'm looking for an open source/free network emulator tool that I could use on Mac OS X, to simulate a slow network connection, limited bandwidth and other network characteristics such as dropped packets etc for both UDP/TCP connections (or even on the physical layer).
I'm looking for the simplest solution that would allow me to run TCP/UDP servers and have a few clients connect to them on localhost emulating various network connections. I'm mainly wondering if I can use something like Linux's netem on Mac OS X (or even better cross-platform Windows/Linux/Mac). Perhaps I can run VirtualBox and a Linux kernel running netem, has anyone had luck with that?[URL]...
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Sep 12, 2010
I've been receiving a LOT of log cruft ever since I installed my WUSB100V2 (using the rt2870sta community driver from the Linux kernel) and was wondering what it all meant.
Many times when these messages occur it is accompanied by slow network speeds and many DNS queries and outgoing SYNs being dropped. I have searched for documentation for these (error?) messages and have come up empty as far as what they mean or how I can stop them from occurring.
I reside on the opposite side of the building from my WAP. I have taken steps to improve the signal strength, but the signal quality hovers between 50% and 70%, sometimes dropping to 40% for unknown reasons.
My /var/log/messages:
Sep 12 05:04:40 necronomicon -- MARK --
Sep 12 05:29:48 necronomicon kernel: 0:3 LTL=0 , TL=0 L:4284
Sep 12 05:29:53 necronomicon kernel: 0:3 LTL=0 , TL=0 L:4104
Sep 12 05:30:06 necronomicon kernel: 0:3 LTL=0 , TL=0 L:4156
[code]....
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Oct 1, 2010
One of our RHEL 5.3 servers has trouble about 30% of the time with TCP-based communications, but it does not seem to be firewall issues. From another computer on the same switch, you can SSH to the server sometimes and other times the SSH command will just hang. When it hangs, you can often just Ctrl+C and try it again and it works. Same with HTTP connections. You'll get part of a web page and then FireFox will just hang waiting for the rest and eventually time out. Same goes for communication initiated FROM the server. SSH'ing from the server to any outside server or connecting to any web site works sometimes, but most times not. iptables if off. No other firewalls are running. Tcpdump shows communication gets so far and then stops. It does not matter whether tou run tcpdump on that server or the client connecting to it. Either way you see the connection stops working. MEANWHILE, pinging with small or large packets works flawlessly. 10,000 packets, zero drops.
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Jan 11, 2010
I've recently installed Ubunter 9.10 Server Edition to use as a NAT firewall for the lab I run. I'm using iptables to do NAT forwarding and everything works great except that, occasionally, connections seem to break. Ssh connections close with "Connection reset by peer" and HTTP connections just stall out.I believe this has to do with the firewall's internal network interface occasionally dropping packets.
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Feb 13, 2009
I have question regarding netstat? When performing a "netstat -s" I receive the following information regarding dropped packets under IP:
IP:
93978695 total packets received
0 forwarded
0 incoming packets discarded
79472157 incoming packets delivered
65235033 requests sent out
29527 outgoing packets dropped
However if I run a "netstat -i" I have no dropped packets whatsoever: (apologies for the table format):
Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
bond0 1500 0 34326528 0 0 0 72755307 0 0 0 BMmRU
bond0:1 1500 0 - no statistics available - BMmRU
bond1 1500 0 28605491 0 0 0 20948952 0 0 0 BMmRU
eth0 1500 0 34199550 0 0 0 72755278 0 0 0 BMsRU
eth1 1500 0 126978 0 0 0 29 0 0 0 BMsRU
eth2 1500 0 97911 0 0 0 1 0 0 0 BMsRU
eth3 1500 0 28507580 0 0 0 20948951 0 0 0 BMsRU
lo 16436 0 34094225 0 0 0 34094225 0 0 0 LRU
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Mar 13, 2010
I am using ubuntu 9.10. Configuring my firewall using guarddog. I have setup a rule to allow traffic OUT on port 7078 UDP, and just because i'm having problems i added an IN rule.
# Create the filter chains
# Create chain to filter traffic going from 'Internet' to 'Local'
ipchains -N f0to1
[code]....
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Dec 5, 2010
I've run into a of a routing issue pertaining to packets leaving a firewall, traversing and IPSec tunnel, hitting the target and then returning via a different tunnel, finally arriving back on the source firewall but on a different interface from where it started. Once the packet has returned to the firewall it is dropped I've been unable to discover the reason for the drop. Two sides to the system, Firewall A and Firewall B. Each firewall provides the default gateway to its respective side and offers a backup IPSec tunnel to the high capacity tunnel handled internally. The Layer 3 Switch uses OSPF and takes care of the bulk of the behind the scenes routing between the sides. In case of failure the Layer 3 switches direct traffic to use the Firewall tunnels to route traffic.
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Apr 4, 2011
I'm running a Debian Squeeze 6.0.1a box that's connected to my ISP via an L2TP connection that's managed by OpenL2TPD. The box is configured to perform NAT from local clients (on eth0) to the internet (on ppp0).
However, I'm having an issue with TCP packets that are sent from the box itself to the internet (packets originally coming from the local clients get sent and received over the internet just fine)
I'm using this Python app to test this:
Code:
#!/usr/bin/env python
import socket, time
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('', 5003))
s.listen(1)
while 1:
conn, addr = s.accept()
[Code]...
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Oct 18, 2010
I am trying to figure out what command to use to show the number of DROPPED and INVALID packets that the firewall is handling.I'm going to put these commands into a log analyzer script which will run every 15 minutes with cron. The firewall is running and operating the way I want it to. I'm running CentOS 5.4.
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Oct 5, 2010
In my Fedora13 machine, while in mobile broadband, i can ping and skype outside, but cannot browse/yum etc. Few output that may be of relevence are here:
$ netstat -s
IP:
149468 total packets received
6 with invalid headers
16174 with invalid addresses
0 forwarded
0 incoming packets discarded
118821 incoming packets delivered
101331 requests sent out
124 outgoing packets dropped
866 dropped because of missing route .....
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Feb 28, 2010
with my other ethernet card problem solved, I suddenly run into this:
Code:
eth1
Link encap:Ethernet HWaddr 00:02:e3:16:37:4c
inet addr:10.0.2.1 Bcast:10.0.2.255 Mask:255.255.255.0
inet6 addr: fe80::202:e3ff:fe16:374c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
[Code]...
This card was working perfectly fine up until....an hour ago and it started doing this. My iptables isn't blocking it somehow, because I didn't change anything. I tried reverting to an older kernel and that didn't help. It's not the network cable, it works fine in any other card. Also, the dropped packets seem to count down? It seems to go down by exactly one every time I run ifconfig, no matter the length of time in between running it.
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Sep 1, 2009
I switched over to Fedora a couple of days ago. I'm using the built-in firewall shipped with it but I can't find out how to enable logging of dropped packets. Among others I'd like to use psad that needs firewall logging. Is there an easy way to do this? I'm not an iptables "expert".
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Sep 15, 2010
As is known, there is a queue lies between the kernel subsystem and the network driver for incoming data. And if data come when this queue has no space for it, the data got dropped by kernel. Is there some way to see how many packets are dropped due to this buff penury? I tried netstat -s but could not find something useful. On the other hand, I found this 12176 packets collapsed in receive queue due to low socket buffer from netstat -s. I think this is something related to the per-socket buffer, but not the incoming queue between the network driver and kernel. Is this right?
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Jul 6, 2011
my NIC drives me crazy and I need some help to gather all relevant informations to file a decent bug report. Maybe someone could guide me through this process.My mainboard is an AsRock Z68 Pro3
[URL]
I use a dual-boot setup with Windows7 installed in parallel to Fedora 15-x64. Whenever I had Windows in use and jjust reboot the system into Fedora, the NIC does not work as expected. Instead it goes in an endless "em1: link up" loop which results in very low bandwith or even complete network timeouts. This happens in Firefox as well as with yum or ping.
Quote:
Originally Posted by dmesg
[ 58.763294] r8169 0000:05:00.0: em1: link up
[ 59.686773] r8169 0000:05:00.0: em1: link up
[ 61.936454] r8169 0000:05:00.0: em1: link up
[code]....
If I directly cold boot into Fedora (after the power cord has been removed and the system got completely re-initialized) there are no problems at alll and I get a fast and stable network conection. This also happens with other linux distributions, for example SysRescCD.
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Aug 30, 2010
i need to write a program in c that can sniff packets from Ethernet and distinguish RTP packets from Non-RTP packets, i have no idea what should i do
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Feb 8, 2011
how to fix this error: I wanna compile a C program which niffs the network for arp packets and prints them out ,I keep getting this error:
undefined reference to `pcap_parse' I have installed every thing new version of pcap ,..
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Jul 25, 2011
I have users using Windows XP, Windows 7, Linux (Fedora) and Mac. They all are in a single private network and all access internet through a Linux (RHEL5) system in which Squid acts as gateway. The same is true with my branch offices too except that private network is different and gateway system uses Fedora 9 instead of RHEL5. All the branch offices are connected through point to point leased lines with the head office for file transfer.
My requirement is this: I have a web server located at head office. Presently I am able to access this server from my branch offices through internet. I would like to access this server from branch offices through leased lines. This too I am able to access if I do routing in users system. The file transfer is taking place through one to one system at two ends by creating static routing in those systems.
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Dec 15, 2010
I'm experiencing massive latency/unreachable problems on my Linux machine. It's true for all network connections, here's an example of me trying to ping my router:
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=15115 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=14107 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=13107 ms
64 bytes from 192.168.0.1: icmp_req=4 ttl=64 time=12107 ms
64 bytes from 192.168.0.1: icmp_req=5 ttl=64 time=11108 ms
[Code]...
I've tried now with both the maverick default kernel and 2.6.37-rc5 kernel (both 64 bit), same result. If I take the card up and down (ifup, ifdown) performance is restored for a little while, then it's back. I've tried changing cable, network card and router port but no luck.
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Aug 6, 2011
My LAN has 2 PCs installed, Ubuntu 10.04 and Windows XP. I run the server on Ubuntu, and client on Windows XP. Because I am doing stress test, so the client will keep sending tons of packets to server.
The strange thing is: After few seconds, the client program crash because of insufficient network buffer, the server is still ok. But after that I cant connect Ubuntu PC anymore until I restart it. And I check the router, the led for the Ubuntu PC is always ON (not blinking), look like it is jam already.
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Mar 9, 2011
I am using tcp for data transmission between 2pcs running linux.During transmission, I have noticed that if I unplug the network cable and reinsert it quickly,connection is not lost(same as i expect)and the sender start to resend the packet after 5s(what i expect is that network packets sent immediately after quick physical disconnect and reconnect).My question is can i reduce 5s to 0s(resend immediately after network cable reconnect)?Any parameters(tcp rto,txqueuelength,..) can be modified to achieve this condition?
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Feb 10, 2011
Recommend open source tools that can help in figuring out if we are experiencing a network latency due to the newly installed firewall on our server.
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Oct 11, 2010
my laptop running 10.10 and a dell. the college is witch i attend's unsecured wireless network keep disconnecting me from every on average 45 minutes to an hour ands will not re connect for about 10-15 minutes. it works fine anywhere else i go but here i get dropped.
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Jun 1, 2011
I have been noticing a trend on boxes running 11.4 getting RX dropped packets where prior to 11.4 they did not get them. Basically every box running 11.4 now logs dropped RX packets. Have tried changing cables, and in one case replaced the NIC with a different brand (and driver) nic. Also played with receive buffers and yet the counters still increment. In addition to OpenSUSE, I run several operating systems to include Centos, Scientific Linux, Debian, OpenIndiana, HP-UX, VMS and so forth. So far this anomaly has only shown up on machines running OpenSUSE 11.4. Any one else noticing this on your OS 11.4 machines? If so, were you able to resolve?
[code]....
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Sep 4, 2010
How do I find out the memory bandwidth/latency to RAM of the machine?
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Feb 28, 2010
How can I emulate a mouse click on a keyboard on linux, e.g. by defining that my right CTRL-key should behave as if I clicked the right mouse button?
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Feb 19, 2011
I predominantly use Ubuntu at home, which means I am used to "highlight 'copies' and center click 'pastes'" (I believe this is true for all X-windows-sever machines, but I don't know). Unfortunately, that is not the behavior on the machines I use at work (I have a Mac and Win 7.). Is there an application which would let me imitate this mouse behavior for either of those OS's?
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Jan 3, 2011
What is the equivalent for inetadm -M command in Linux ?
-M option gives as below
-M {name=value}...
Change the values of the specified inetd default properties. Properties are specified as whitespace-separated
name=value pairs.
whether service command in Linux can achieve this . if so what option I need to give with service to emulate inetadm -M command in solaris?
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Apr 3, 2010
I've been trying for a couple days now to get netem rate limiting to work on a Fedora 12 i686 virtual machine (both on VMware Fusion and KVM), and have had no success.In order to do outbound rate limiting, I want to use the netem token bucket filter (TBF), as described here:[URL]Unfortunately, attempting to use the TBF results in this error:
Code:
[root@f12-build ~]# tc qdisc add dev eth1 parent 1:1 handle 10: tbf rate 256kbit buffer 1600 limit 3000
[code]...
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Feb 17, 2011
I have a four-cores machine (core1,core2, core3, core4 ). I want to test the communication or latency between two cores (for example, core1 and core2; core3 and core4). Does anyone know how to write a code to test it under linux operating system?
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Apr 22, 2010
Program code as how to measure interrupt latency..
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