[ndnSIM] [EXT] Can we access ns3 packet tags in forwarder.cc

[Atif Rehman]

Hi Sonia,

I am trying to get it using one of the methods mentioned by Junxiao. I don't think only packets with 0 SNR are sent to the upper layers. If the ?SNR value is under the acceptable range (below a threshold value), the packets are accepted and sent to the upper layer.
At the mac layer, I can see all the packets have a certain SNR value, I didn't see any 0 value. Please correct me if I am wrong.

It depends on what physical layer loss model are you using in the simulations. Ideally, it will be 0, however, I agree, in practical scenario and specifically in a wireless channel case, there will extremely small acceptable value (only in the absence of obstacles and if the signal strength is strong) otherwise, IMHO, the packet will be requested again.  So, if you still need those "small values" at network layer, it is fine and depends on your proposed scheme. Looking forward to your solution for sharing tags in ndnSIM.


Regards



Muhammad Atif Ur Rehman (Ph.D. Candidate)

________________________________
From: Sonia <zohanoor67 at gmail.com>
Sent: Friday, June 11, 2021 11:25 AM
To: Atif Rehman <atif_r at outlook.com>
Cc: ndnsim at lists.cs.ucla.edu <ndnsim at lists.cs.ucla.edu>
Subject: Re: [ndnSIM] [EXT] Can we access ns3 packet tags in forwarder.cc

Hi Atif,

Thank you for the explanation. Actually, I want to see the relationship between the life of wireless links (connection) and SNR along with some other parameters among mobile nodes. I need this information to design a forwarding strategy.

Concluding all this, I would say that, may be you will be able to fetch the SNR tag value using Junxiao solution but when you will extract its value, it will be 0 in most of the cases.

I am trying to get it using one of the methods mentioned by Junxiao. I don't think only packets with 0 SNR are sent to the upper layers. If the SNR value is under the acceptable range (below a threshold value), the packets are accepted and sent to the upper layer.
At the mac layer, I can see all the packets have a certain SNR value, I didn't see any 0 value. Please correct me if I am wrong.

Please do share your experience once you done with the experiments.
I will for sure.

Thank you for the help.


On Fri, Jun 11, 2021 at 9:03 AM Atif Rehman via ndnSIM <ndnsim at lists.cs.ucla.edu<mailto:ndnsim at lists.cs.ucla.edu>> wrote:

Hi Sonia,


Just out of curiosity, why do you need physical/MAC layer parameter at network layer. Specifically, in SNR case, do we really need that at network layer or is it even possible that we can fetch SNR value at network layer? In the later case, I might be wrong but I don’t think SNR value will be retained at network layer, at least in the default implementation.


So here is the rationale with an example. Node 1 received a packet let say through wireless medium in this case, and at MAC layer the error in packet (frame) is calculated. Now MAC layer encountered that the SNR is high and the packet has to be fetched again from the forwarding node because there is no other way to reconstruct the original packet. In this case, the MAC layer will not forward the packet to the upper layer but rather wait for the forwarding node to send the packet again.


You may ask why the MAC layer shouldn’t send the packet to the network layer, and for that the rationale is,  if the received packet has many erroneous bits then it is useless to further process the packet.


Finally, if the packet is correctly received, it will be sent to the network layer and at this time there will be either no or extremely small SNR.


Concluding all this, I would say that, may be you will be able to fetch the SNR tag value using Junxiao solution but when you will extract its value, it will be 0 in most of the cases.


Please do share your experience once you done with the experiments. Thanks


Regards


Muhammad Atif Ur Rehman ( Ph.D. Candidate )

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