I am using tcpreplay and I need to synchronize two or more machines replaying recorded network traffic.
Do You know how can I synchronize replaying pcap file on multiple hosts ?
Maybe there is a better way than using tcpreplay?
Thanks for answer.
Related
I'm trying to implementing tree topology with Cooja/contiky. Finding through examples i've not been able to find an a good example to find what i need.
In short :
I'd need to implementing a topology of this type(picture here under) with cooja end contiky, is there someone that could give me some advice?
Thanks in advance
I don't really use Contiki Operating System, I have only ever used TinyOS but a network topology such as the one you have should be easily achievable.
For TinyOS, the mote-to-mote radio tutorial HERE will show you how to two different sensor nodes can communicate with each other (a gateway is basically just a sensor node connected to a PC) and the mote-to-PC communication tutorial HERE will show you how a gateway node can forward information from itself to the PC it is connected to. When the network is running you basically have a Java application listening to USB port and receiving packets from gateway node. Once the packet has been received on the Java application then you can send it to an external network server.
It may sound difficult if you have never developed on TinyOS but what you want to do is very common and so there will be complete programs in the tutorial section of a typical TinyOS distribution showing you how to achieve most of the things you need you need to achieve. There should also be similar examples in Contiki.
I have two applications (.exe) that are running on the same machine (Windows XP x86) and I know are communicating with eachother (I dont know how, I didn't write them). I would like to find a way to sniff the communication between the applications. Is there a way to do this?
I've done some messing with ProMon and i can probably figure it out from there but I'm wondering if there is something a little more specific to this purpose. ProMon can be a bit intimidating.
First, you could watch your two applications with a system call tracer like StraceNT (or see this question). With some luck, you should be able to figure out whether the processes communicate through a local socket, a TCP connection (via localhost undoubtedly), a pipe, a named file, or shared memory.
You can also run netstat while the applications are running to see if they are opening any network ports.
Once you know what you're looking for, you can choose a more specific monitoring tool. If it's network communication (even over a loopback interface), you could try capturing the data with something like WinDump. If the communication is via shared memory, you could attach a debugger to one of the two processes and inspect the shared memory periodically.
I run a server monitoring site for a video game. It monitors thousands of servers (currently 15,000 or so).
My current setup is a bit janky, and I want to improve it. Currently I use cron to submit every server to a resque job queue. I refill the queue just as soon as it's empty, essentially creating a constantly working queue. The job will then simply try and open a socket connection to the server ip and port in question, and mark it down if it fails to connect.
I have 20 workers, and it gets the job done in about 5 minutes. I feel that this should be able to go MUCH faster.
Is there a better, quicker way of doing this?
So, what you are doing currently I assume is doing a TCP socket connection which pings your game server. The problem with using TCP is obviously that it is a lot slower than UDP.
What I would advise instead is creating a UDP socket that just checks for the game server port.
Here's a nice quote from another question:
> UDP is really faster than TCP, and the simple reason is because
> it's non-existent acknowledge packet (ACK) that permits a continuous
> packet stream, instead of TCP that acknowledges each packet.
Read this question here: UDP vs TCP, how much faster is it?
From my experience with game servers, the majority if not 100% of all modern game servers allow you to query them on a UDP socket. This will then respond with details on the game server. (I used to host a lot of servers myself too).
So basically, make sure that you are using UDP rather than TCP...
Example Query
I'm just searching for this information now and will update my question...when I find some source.. what game is it that you are trying to get information for?
Use typical solutions for typical tasks. This case is about available detection every n seconds - one of daily sysadmin task. It should not be over ICMP, use SNMP over UDP proto. One of complete solution is Nagious/Cacti/Zabbix, which have built-in functionality to combine everything about your servers: LA, HDD, RAM, IO, NET as well as available detection.
You don't mention how you are making the socket connections, but you might want to try using ruby curl bindings: curb instead of net/http.
This will typically be much faster.
How can i make my laptop to act as a multicast router.
I need to stream video content to other computers with in same network. How can i make my laptop to work as a multicast router.
There are some tools like that iou,iou2net.pl
It's simple - write a simple app to recieve multicast on one network card and simply re-send it on another one. One packet in - one packet out. And this way you can make userspace multicast router. Very easy. Just dont forget to register IGMP on these sockets.
This way you can also send it to multiple networks at once, etc etc.
Say you install Cisco IOU on a VM (ubuntu) or directly if you already use ubuntu.
Every instance you run (level 3 bin files for routers and level 2 for switches) is dealt with as a seperate physical machine.
This way you can:
create a network within one machine.
save up on memory as IOUs don't really take that much (64mb by default)
do any type of testing you need locally and for free.
iou2net.pl for instance is a tool you use to link an IOU instance to external networks.
This way you can use a real router/switch or network setting up the IOU either as one or a group or client OR your server itself.
I need to use one logical PGM based multicast address in application while enable such application "seamlessly" running across several different geo-locations (i.e. think US/Europe/Australia).
Application is quite throughput (several million biz. messages a day) and latency demanding whith a lot of small but very frequently send messages. Classical Atom pub will not work here due some external limits of latencies.
I have come up with several options to connect those datacenters but can’t find the best one.
Options which I have considered are:
1) Forward multicast messages via VPN’s (can VPN handle such big load).
2) Translate all multicast messages to “wrapper messages” and forward them via AMQP.
3) Write specialized in-house gate which tunnels multicast messages via TCP to other two locations.
4) Any other solution
I would prefer option 1 as it does not need additional code writes from devs. but I’m afraid it will not be reliable connection.
Are there any rules to apply for such connectivity?
What the best network configuration with regard to the geographical configuration is for above constrains.
Just wanted to say hello :)
As for the topic, we have not much experience with multicasting over WAN, however, my feeling is that PGM + WAN + high volume of data would lead to retransmission storms. VPN won't make this problem disappear as all the Australian receivers would, when confronted with missing packets, send NACKS to Europe etc.
PGM specification does allow for tree structure of nodes for message delivery, so in theory you could place a single node on the receiving side that would in its turn re-multicast the data locally. However, I am not sure whether this kind of functionality is available with MS implementation of PGM. Optionally, you can place a Cisco router with PGM support on the receiving side that would handle this for you.
In any case, my preference would be to convert the data to TCP stream, pass it over the WAN and then convert it back to PGM on the other side. Some code has to be written, but no nasty surprises are to be expected.
Martin S.
at CohesiveFT we ran into a very similar problem when we designed our "VPN-Cubed" product for connecting multiple clouds up to servers behind our own firewall, in one VPN. We wanted to be able to run apps that talked to each other using multicast, but for example Amazon EC2 does not support multicast for reasons that should be fairly obvious if you consider the potential for network storms across a whole data center. We also wanted to route traffic across a wide area federation of nodes using the internet.
Without going into too much detail, the solution involved combining tunneling with standard routing protocols like BGP, and open technologies for VPNs. We used RabbitMQ AMQP to deliver messages in a pubsub style without needing physical multicast. This means you can fake multicast over wide area subnets, even across domains and firewalls, provided you are in the VPN-Cubed safe harbour. It works because it is a 'network overlay' as described in technical note here: http://blog.elasticserver.com/2008/12/vpn-cubed-technical-overview.html
I don't intend to actually offer you a specific solution, but I do hope this answer gives you confidence to try some of these approaches.
Cheers, alexis