We have a network consisting of multiple OpenFlow 1.0 and 1.3 compatible switches, that are interconnected. Each of the switches is connected to one or more switches in a way that there is a route from every switch to every other switch, though not necessarily directly (so the packets might end up having to be passed through multiple switches to reach it's destination).
What I need to do is to get some form of tunneling system, where I can create a flow that passes packets through all these switches to the target machine.
What I know that is possible is to push and pop MPLS labels to the packet. So I figured I might push two labels at the ingress. The outer label identifies the target switch and the inner label identifies the target port. This way I only need flows on each switch to pass packets with matching labels to the target switch first and then to the target port, when it reached the target switch.
The problem here is only that I found no way of matching on MPLS labels. Does anyone know if there is a way to match on these labels? Or is there any other way of doing what I want to do?
Thanks a lot in advance!
yes, you can do
match = parser.OFPMatch(in_port=inPort,eth_type=ether.ETH_TYPE_MPLS,mpls_label=m_label)
that's how you can match mpls labels and give whatever actions you wanna give.
Related
In my current scenario, I'm using NETLIGHT Pin (Pin no. 64) of SIM800 module with my PIC microcontroller to know whether my module is registered or not?
This way I built the circuit. Just I removed LED from VBAT. Then I connect collected of NPN transistor to pic micro input PIN.
I want to know whether any easy way using AT commands to find network registration status of SIM800?
Unfortunalty it's seem not to be really possible (or in fact detecting this state in only one way)
I use SIM800 and let it run for hours and I have seen many cases of network loose, while the AT+CREG? continue telling everything is OK.
Also, even with network down, the SIM800 continue sending you the name of the operator and the strengh of the signal.
The only way I've found is to monitor the serial port: when the SIM800 loose the network, it sends two messages:
+PDP: DEACT and
+SAPBR 1: DEACT
I suggest you to have a look at the document "SIM800 Series_AT Command Manual" and especially the chapter "19.3 Summary of Unsolicited Result Codes". You'll find +PDP and other interesting code (like under-voltage warning, DNS failed...) and see some of these messages are not linked to AT command.
From the manufacturer's documentation:
I am using ryu controller (3.22) to monitor switches (Open vSwitch 2.0.2, supporting Open Flow 1.3), which are a part of virtual network created using mininet (2.1.0). It is a tree topology with depth = 2, and fanout = 5. I am using switch_monitor.py
With the help of controller, I can get port statistics using the EventOFPPortStatsReply decorator. I can get values of rx_packets, rx_bytes, rx_errors, tx_packets, tx_bytes, tx_errors, rx_dropped, tx_dropped etc.
But the values of rx_dropped, tx_dropped come out to be zero always, even when the switches are actually dropping packets, as reported by qdisc (linux command).
How to get packet loss statistics from an Open Flow switch?
a. How to get a non zero value?
b. Is there any alternate way?
qdisc reports what the kernel is dropping, not what the network is dropping. You're getting zero's because the switch isn't dropping frames.
(I don't know if your virtual network system supports simulating frame drops.)
I believe that dropped only cares about packets that are dropped due to actual drop rules or due to buffer overflows.
Another way to calculate packet loss is to compare the packet counts for the two switches on the edge of a link. Suppose you have A <--> B and want to calculate the packet loss rate from A to B. Then you take:
plr(A,B) = (tx_packets(A) - rx_packets(B)) / tx_packets(A))
Beware though that sometimes the counters are reset leading to rx_packets being higher that tx_packets. I am facing this behavior in my SDN software and tend to invalidate the results, if there are strange combinations.
I have LV application, where user can specify input and output channels for connected DAQ device. I want to synchronise both channels using trigger on the input channel, with analog output start as a trigger source (image on this site shows part of what I am trying to do).
My problem is that user specifies only IO channels, but how can I switch from a DAQmx Physical Channel (e.g. cDAQ1Mod4/ao0) line into source for the DAQmx Start Trigger block (probably /cDAQ1Mod4/ao0/StartTrigger in this case, but I am not sure) ?
I've found an answer, but I am not really happy with this way of solving a problem. I have to scan whole devices tree and compare channel or module names available for each device with the name of my selected channel ... simple channel property would be easier, but haven,t found any property which could give me what I need.
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)
This Question is extension of the following
OpenFlow Rule Metadata
I would like to have this clarified, on my question about Metadata
Let us say, I have an Open Flow rules, as below
Cookie=0x8000001, duration=228925.445s, table=17, n_packets=350, n_bytes=32424, priority=10,metadata=0xc000f30000000000/0xffffff0000000000 actions=goto_table:19
I wanted to understand the following
Do we have certain rule/ Algorithm , to determine these Metadata from a Packet.
because the Packet in OVS is actually switched based on Matching Metadata, Is that correct ?? ( At least according to the above flow rule )
And the Packet itself does not carry the Metadata, then how exactly
the packet hitting a flow matched against the Metadata.
So, If I understood it correctly the Packets those are traversed between the flow-tables, are within the OVS application itself or Handled #OVS Application level, until it had determined Egress Port
So in that Case, the MetaData are handled #OVS-Application level, until the Packets is send via Egress Port.
Is this correct??
Finally which Module in ODL is responsible for determine the Metadata, and I would like to understand from the code how exactly it was done.
The OpenFlow metadata field starts with a value of zero for every packets. Tables can then writes to this field and you can match on it in subsequent tables. It is only used to carry information from one table to the next, as explained in the OpenFlow specifications:
Metadata: a maskable register that is used to carry information from one table to the next.
first of all you can try Ryu instead, its code is more easy to read and understand.
Then, I think metadata/instructions/actions.... these things are belong to the processing of OVS forwarding, but these things needs to attach to something and that is the packet that OVS received. About the question "Do we have certain rule/ Algorithm , to determine these Metadata from a Packet. " I think the value of the Metadata is determind by the controller, which means that it depends on 'how do you design your own network instance using some(e.g. RYU) controller application'.