I have to work on Mininet, Python, SDN and my objective is to do a simple task: create a network with some switches connected randomly (so the topology is not important), every one with a host connected. In the network I have to do load balancing and I have to be able to monitor if the load balancing is working.
This is a project and so the load balancing has to be simple and it has to something like this: H1 wants to ping H2 and from H1 to H2 there exactly 2 paths with the same number of hops (for example H1 connected so S1 and H2 connected to S2. Then S1 is connected to S3 and S4, that are also connected to S2). The two paths are: H1-S1-S3-S2-H2 and H1-S1-S4-S2-H2. I want to do load balancing in a way that if H1 sends 2 ping, 1 goes throws the first path and the second one goes to the second path. In this way when H1 sends some traffic to H2, the traffic goes 50% on the first path and 50% on the second.
How can I implement something like this in a really simple network (4 switches like in the example)? I've searched a lot for some references but I've found nothing useful. In theory I have to use NOX, but if I have to use POX to understand the topic I'll do it ;)
Thanks in advice to everyone who will try to help me :)
I know you can load balance the connections between switch and controllers but not sure about the switch-switch paths .
Apparently, in openflow a type of group called "select groups". I think based on the wigth assigned to that buckets you can distribute packets. The bucket’s share of the traffic processed by the group is defined by the individual bucket’s weight divided by the sum of the bucket weights in the group. I'm not totally sure about this though.
There are ways around it too. You could set it so that a host is receiving packets from one of the paths and sending packets from the other one.
Another trick could be distributing loads based on packet protocols or other factors. For example you could say send all TCP packets from this path and all UDP packets from different path.
Related
I am working on a video-conferencing application. We have a pool of servers where rooms are created, a room can have n number of users. I was exploring HAProxy and several other load balancers, but couldn't find any solution for what I was looking for.
My requirements are as follows
A room should be created on the server with the lowest load at the time of creation.
All users of that room should join on the same server.
I have tried url_param balance logic with consistent hashing, but it is distributing load randomly. Is it even possible with modern L7 load balancers or do I need to write some custom logic (in some load balancer) or a separate application for this scenario?
Is there any way of balancing load based on connections or CPU usage while maintaining the session stickiness?
balance documentation says you can choose algorithm like leastconn and that this only applies when no persistence information is available, or when a connection is redispatched to another server.
So the second part of the answer are stick tables. Read docs about stick match and other stick keywords
So with stick table it looks like this:
backend foo
mode http
balance leastconn
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:8080
server s2 192.168.1.2:8080
There are more examples in the docs.
What you need to figure out (or tell us) is how can we know the room client wants based on the request and make such stick table and rules. If it's in URL or http header then it is perfectly doable in haproxy.
If leastconn is not good enough, then there is an option of dynamically adjusting servers' weights with haproxy's unix socket CLI and use roundrobin algorithm. Also agent options can be configured for servers to dynamically set servers' weights.
I want to configure IP Load Balancing service for our VPS. I have got the documentation at http://docs.ovh.ca/en/products-iplb.html#presentation where I can integrate it.
I want to limit the number of requests on each server (S1, S2). How can I achieve this?
Suppose, I want S1 should handle all requests if requests sent to load balancer are less than 3500 per minute.
If requests are greater than 3500 (per minute), then load balancer should forward all extra requests to S2.
Regards,
Just had a look and I believe you won't be able to achieve what you are looking for with the available load balancing algorithm.
If you look at the available ones, you can see five ldb algorithm. I would say from my experience with load balancers (not from OVH) that they should do the following:
First: probably the first real server to reply (with health monitor) will get the query
leastcon: this distributes connections to the server that is currently managing the fewest open connections at the time the new connection request is received.
roundrobin: next connection is given to the next real server in line
source: not sure about this one but I believe you load-balance per src ip. Eg if request is coming from 143.32.Y.Z, send it to server A etc.
uri: I believe it load balances by URI. Typical if you are hosting different webservers.
I would advise to check with OVH what you can do. Typically in those scenario with an F5 load balancer for example, you can configure a simple script for this. Or groups, if the first group fail, we sent the traffic to the second one.
Now a ratio (also called weighted) ldb algo can do the job, not exactly what you want indeed.
Cheers
I have a weird problem. I have a successfully working C++ (boost asio) P2P application which works on most of the NAT. The problem is when I give the initial start port number as 1000 it checks if 1000 is free else increment by one and chooses a port and starts handshaking. But when I have 10000, 20000, or any other huge port number the hole punching doesn't work on port restricted cone NAT.
How is that possible? I am pretty sure it nothing to do with the code. and recently it doesn't work on one of my friends' full cone NAT as well, but it has worked in many other full cone NATs. What could be the reason? Is there something I am missing about how a NAT behaves?
In many NAT implementations, there are protection rules in place which prevent one host from tying up a large percentage of ports on the WAN interface, e.g. like described here.
Depending on the router, the NAT table entries have different lifetimes, and there are always limits on how many ports can be allocated to a single client (I've seen numbers from 128 to 4096).
So I think when you get to the point where you need to use high ports, the NAT table for your source IP address is already full (or almost full) with entries from old connections, or connections from other apps, so the router either decides to decline or can't fit the new NAT entry for your port.
However, to be sure, I would try to repeat that on a controlled environment collecting Wireshark dumps on both sides of the NAT and analyze the packets. If possible, it would also be helpful to enable router logs and peek into them.
I understand this is not a "magic bullet", but hope it somehow helps you.
Don't try to choose the port number yourself. The operating system can do this faster and better than your code can.
Bind your socket to port 0 and let the OS choose an available port number for you. You didn't specify what programming language, but it usually involves a call to getsockname() after the bind() call is made to discover what local port is going to be used. Java and .NET have equivalent APIs for doing the same thing.
Then follow all the other steps here:
https://stackoverflow.com/a/8524609/104458
Not sure if this'll help but have you tried having one instance of the client application starting at 1001 and the other starting at 1000, then both increment by 1.
While the 1000 will fail on client B, client A has already tried 1001 and so punched that hole, so hopefully it'll work, right? In theory, it sounds OK in my head.
Can I receive data from network by some processes simultaneously?
For instance, I have two computes in the LAN. One computer send udp packet to other computer on port 5200. In computer number two I want to receive this packet by two processes. Can I create two sockets on same ip and port?
I forget to say that Process A I can't modify. In other words, I want to create application that receive same data as Process A. (Proccess A and Proccess B locate on the computer number two that receive data)
Yes! You can. Open the socket and set setsockopt with REUSE_PORT and REUSE_ADDRESS.
How about you create process A to act as middleware between the two processes B and C. And then add extra data to the packets sent to process A which will be used to determine the final destination of the data - process B or process C.
EDIT:
To answer your question exactly "no", for TCP/IP
"You can only have one application listening on a single port at one time."
Actually you question has been asked by someone else before, and I have only just cited the answer. The full answer can be found -> here.
If I understand the parallel port right, sending data from (D0 to D7) simultaneous, but that it can control the sticks individually?
example:
D0 = Input
D1 = Input
D2 = Output
...
...
...
D7 = Input
would it work?
what I want to do is to both send and receive data simultaneously.
Data wires (D0-D7) are being read or set simultaneously. For various tecniques for bidirectional I/O read the attached articles:
Standard parallel port: http://www.beyondlogic.org/spp/parallel.htm
EPP: http://www.beyondlogic.org/epp/epp.htm
ECP: http://www.beyondlogic.org/ecp/ecp.htm
This site is a good source for programming the parallel port.
The basic idea is that you need a DLL, add-on or library that allows you to access the I/O Ports of the PC. For Windows XP on up you need a specific driver that will allow you do this as the OS doesn't offer access out of the box.
The Parallel port will generally reside at one of three address 278,378, 3BC. This port. have the bytes you are reading or writing.
The (base)+1 port allows access to the status bytes. IE. 279,379, 3BD
The (base)+2 port allows access to the control bytes. IE. 27A,37A,3BE
The parallel port documentation will tell not only how to implement the common modes (like bi-directional) but how to control the port at the byte level to implement your own custom.
Back in the day there was only the standard mode available. You pump out your bytes at the (base) port. Some application, like mine, manipulated individual bits of that ports as form of cheap Digital I/O Controller. We did use the status and control bytes as additional inputs and outputs. There were commands you can send to the Parallel Port chip configure the modes precisely.
Today there are are hundreds of sites with example of using the Parallel Port to solve all kinds of problems. I would be surprised that one of doesn't have something you can use for you specific application.
Again the book I recommend starting with is Parallel Port complete. It tells just about everything you need to start with. If your application is too esoteric for that book it will give a springboard from which you can find the exact setup you need.
Of course by sending a number that has just the required bit set (2n) you'd get the expected result.
I'm not sure about bidirectional access though. I guess it's achieved by using control pins along with the data pins but that's just a guess.
Parallel ports doing EPP or ECP only allow D0-D7 to be all input or all output. Trying to do otherwise may fry your hardware.
See http://www.nor-tech.com/solutions/dox/ieee1284_parallel_ports.pdf, page 6.
However, parallel ports have several control lines that may be useful if you only need a small amount of input/output in the "other" direction.
I believe its bit 5 in the port's control register (base address + 2) that switches direction. (no hardware line attached)