I'm talking about http://en.wikipedia.org/wiki/Quality_of_service. With streaming stackoverflow podcasts and downloading the lastest updates to ubuntu, I would like to have QoS working so I can use stackoverflow without my http connections timing out or taking forever.
I'm using an iConnect 624 ADSL modem which has QoS built-in but I can't seem to get it to work. Is it even possible to control the downstream (ie. from ISP to your modem)?
I don't know if this will help you, but I've never been a fan of using the ISP provided box directly. Personally I use a Linksys wrt54gl, with DD-wrt, behind(DMZ) my ISP provided box.
DD-wrt has excellent QoS management.
Sorry I can't be more help with your existing hardware.
You just need the tc command to handle the QoS on Linux boxen. However I wouldn't expect that much from it because of the results I obtained and detailed here.
Related
I've got a proprietary BMS language that is sending it's info over a specific UDP port on the network. The existing interface is not very well made or maintained, and functions poorly.
I have access to the stack for the code, and don't mind creating some interpretation functionality
My question is what is the best way that I should be receiving these raw packets in my program to be interpreted? I'm not finding any good documentation on how to do this, and I wanted to try and do it in a reasonably appropriate way.
Do I basically need to make my program constantly sniff a specific port? and will this be cumbersome to the network or program to be doing this?
You tagged this BACnet. Why don't you try Wireshark, with a capture filter "udp port 47808" and see if wireshark exposes the packets in a way that makes sense to you. (or have you done this). If it is bacnet, then normal UDP sockets, bound to port 47808 is the way to go. Note, that 47808-47823 are the most common BACnet "default" ports. Use cports or something to see exactly what port(s) your application is bound to.
You could use a packet-capture library - but that has security connotations, so instead you can probably (for most part) get away with using a .NET 'UdpClient'.
But! The real challenge is the breaking-down & interpretation of the BACnet packets, which is the hard part.
There is (now!/finally) a NuGet package for BACnet - not that I've used it, but that might be one of the best choices for your case.
But I also suggest you experiment with the (advanced & free) VTS (Visual Test Tool) too.
You could also try using the BACnet stack that YABE uses too.
I've been asked to implement VPN capabilities in an existing software project on an embedded system, in order to make the device available via network to an external server while avoiding trouble with firewalls (no need for encryption, just to make it accessible).
Unfortunately, the embedded system is based on a Cortex-M4 MCU, therefore Linux, which would allow for VPN nearly out of the box, is not an option. All I've got is an RTOS and a working LwIP stack.
I've used VPNs in the past. However, my network knowledge is rather limited concerning implementing VPNs, so I'm rather stumped. As I think, I'd use the current LwIP instance for building up the tunnel connection, and the application would use a second instance for the actual network communication, while the network interface of the second instance is a virtual one (like a tap device on linux), encapsulating its low level data and tranceiving it via the tunnel connection of the first LwIP instance.
Maybe this way I'd be able to create a custom solution for the problem, but the solution should conform to any standards (as the server will be any kind of sophisticated system).
So I wonder if anyone has been confronted with a task like this, and would appreciate any hint what to do, at least a direction where to look at.
Thanks in advance!
I have used a lot of parent control software but none of them is perfect. I am thinking to write my own. I want to use either C++ or java or combination of two. My main issue is how to capture all traffic originating from browser.
I want to do it in a way hack proof way.
I appreciate greatly any help on this.
Thanks in advance.
You can't intercept data transfers from your http/https connections
You will have to build a Packet sniffer and find a way to filter out the packages you are looking for, To my suprise im not getting any solid results when i try to google C++ packet sniffer tutorials, but thats defeneteley the way to go.
For windows you need create filter driver for network adapter. Under linux you can use raw sockets for this purpose. Unfortunately, windows not support full row socket functionality.
Are there any libraries which put a reliability layer on top of UDP broadcast?
I need to broadcast large amounts of data to a large number of machines as quickly as possible, and generally it seems like such a problem must have already been solved many times over, but I wasn't able to find anything except for the Spread toolkit, which has a somewhat viral license (you have to mention it in all materials advertising the end product, which I'm not sure our customer will be willing to do).
I was already going to write such a thing myself (because it would be extremely fun to do!) but decided to ask first.
I looked also at UDT (http://udt.sourceforge.net) but it does not seem to provide a broadcast operation.
PS I'm looking at something as lightweight as a library - no infrastructure changes.
How about UDP multicast? Have a look at the PGM protocol for which there are several commercial and open source implementations.
Disclaimer: I'm the author of OpenPGM, an open source implementation of said protocol.
Though some research has been done on reliable UDP multicasting, I haven't yet used anything like that. You should take into consideration that this might not be as trivial as it first sounds.
If you don't have a list of nodes in the target network you have no idea when and to whom to resend, even if active nodes receiving your messages can acknowledge them. Sending to a large number of nodes, expecting acks from all of them might also cause congestion problems in the network.
I'd suggest to rethink the network architecture of your application, e.g. using some kind of centralized solution, where you submit updates to a server, and it sends this message to all connected clients. Or, if the original sender node's address is known a priori, then just let clients connect to it, and let the sender push updates via these connections.
Have a look around the IETF site for RFCs on Reliable Multicast. There is an entire working group on this. Several protocols have been developed for different purposes. Also have a look around Oracle/Sun for the Java Reliable Multicast Service project (JRMS). It was a research project of Sun, never supported, but it did contain Java bindings for the TRAM and LRMS protocols.
So I want to learn all about networks. Well below the socket, down to raw sockets and stuff. And I want to understand hubs, routers, access points, etc. For example, I'd like to be able to write my own software to do this kind of stuff.* Is there a great source for this kind of information?
I know that I'm asking a LOT here, and that to fully explain it all requires from high level down to low level. I guess I'm looking for a source similar in scope and depth to Applied Cryptography, but about networks.
Thanks to anyone who can help to point me (and others like me?) in the right direction.
* Yes, I realize using any of my hand-crafted network stack code would be a huge security issue, and am only looking to do it to learn :)
Similar Question: here. However I'm looking for more than just 'what's below TCP/UDP sockets?'.
Edited for Clarification: The depth I'm talking about is above the driver level. So assuming that the bits can make it to and from the other end of the wire, what next?
I learned IP networking from TCP/IP Illustrated. Highly recommended.
This may not help you learn it, but a packet sniffer like Wireshark will give you some insight into what the data looks like at a pretty low-level protocol (TCP/IP).
As you have obviously recognised, the universe does not start and end with the IP Protocol. Take a look at the OSI 7 Layer Model where IP is a Layer 3 (Network) protocol. Common IP Routers will operate at this level, but there is more complexity you probably should understand in the Data Link and Physical layers before you start coding your own network stacks.
Start with the fundamentals of data communications in all its myriad forms and work your way up the stack until you get to where you need to stop. Data Communications, Computer Networking and Open Systems is a good foundation text, and then look for more detail on each area you need to focus on. Previous answers include good links for IP and TCP/IP, and as mentioned Wireshark will let you look down through some of the layers
CISCO CCNA materials contain a great network fundamentals, but does not affect programming aspect. I'm not sure that there is an official free link, but you can try to find them.
You should equip yourself with a c compiler and the necessary libs and headers for your OS and play around. You may want to read for example:
http://snap.nlc.dcccd.edu/learn/fuller3/chap13/chap13.html
I had some more links in my delicious account, but they all went down the digital drain ;-)
Have you any embedded programming experience ? If so I recommend you buy one of these development boards. They are cheap and allow you work on every part of the networking stack plus all the software tools required are free.
Note that getting going on it isn't easy and I ended up reading the CS8900 IC datasheet to learn how to make it communicate with the ARM7 based processor. But if you enjoy that sort of thing (as I do) then they are great fun.
Hmmm ... have you looked into Computer Networks by Tanenbaum ?
The TCP/IP Guide
I have found the networking chapter in "understanding the linux kernel" and "understanding linux network internals" from oreilly to be very helpful.
The TCP/IP stack is a very good start but there is a lot more and a good understanding of how ethernet works and how ethernet != IP != the-interweb will go a long way.
books on network security often do a decent if not goos job explaining how networks work in a concise context.
what really did the trick for me was taking a job implementing NAT :)
This course worked for me: COS 461 at Princeton. Note that it assumes system-level programming experience with C.
Pretty much all the readings and lectures are available online under "Syllabus". And you can try the assignments too (unfortunately, you won't have access to the Virtual Network System).
Check this.. it is a good collection of information:
http://www.tcpipguide.com/free/t_toc.htm