Vehicle communication problem in vanet-sumo. py

[xiansheng F]

Dear Ramon,

Hope you are doing well.

I found that when a vehicle disconnects from one base station and connects to the next, the vehicle cannot communicate with the vehicle below the previous base station (I have installed flow rules for them).

I have tested it many times and found that as long as it is the base station where the vehicle has driven, the vehicle cannot communicate with the vehicles under these base stations.

How can I solve this problem?

I do appreciate your help.

 

[Ramon Fontes]

> I found that when a vehicle disconnects from one base station and connects to the next, the vehicle cannot communicate with the vehicle below the previous base station (I have installed flow rules for them)

Please describe what you did and why the communication should occur according to your network setup. 

Sent from my android

[xiansheng F]

 I have set up nine base stations and ten cars. I need to measure the packet loss rate and transmission delay of the current vehicle when communicating with other vehicles when the vehicle is running

[xiansheng F]

Do I need to upload my network topology?

在2021年10月19日星期二 UTC+8 下午5:13:20<ramonre...@gmail.com> 写道：

[Ramon Fontes]

Sorry, I see no detailed description here. You said: "I have installed flow rules for them". Could you elaborate on that please? Which commands/rules did you use? Which troubleshooting steps did you try?

[xiansheng F]

I used the Ryu controller, through which I could issue routing rules to each base station, and the base station would forward the packets to the vehicle according to these rules.

I installed routing when the vehicle switched to a new base station (here I found that the vehicle could communicate with vehicles under the base station that had not been through, but not with vehicles under the base station that had been through, I checked my routing rules and it was ok)

I then experimented with a vanet-Sumo.py network topology without any changes. There were two cars, CAR1 and Car2, both under the same base station at first. Then I let Car1 drive and switch to the next base station, and installed routing rules for car1 and CAR2 communication on both base stations. Car1 and CAR2 cannot establish communication.

[xiansheng F]

Here's an example.

Car1 moves from BS1 to BS2 and connects to BS2, and Car9 connects to BS1.

Also, BS1 and BS2 have routing rules for CAR1 and CAR9 (correct rules, but no communication can be established).

[xiansheng F]

The link between BS1 and BS2 is OK

And both CAR1 and CAR9 can communicate with CAR6

[Ramon Fontes]

Does the module you are using for Ryu support mobility? Which troubleshooting steps did you try???

[xiansheng F]

Yes, I designed a routing rule setup module in the Ryu controller for vehicle movement.

In fact, this problem can be reproduced without using an SDN controller.

You can try to place two cars under the same base station, then have one car drive out of the base station and connect to the next one, and then route both of them using the ovs-ofctl add flow....... command.

[Ramon Fontes]

Great, you have used ovs-ofctl add flow... What about the first flow??  Which troubleshooting steps did you try??? :( :(

[xiansheng F]

The problem still exists when I use OVS to manually install routing rules without using SDN controller.

[xiansheng F]

Have you recreated the problem?

[Ramon Fontes]

Sorry, could you please answer the questions?? Which troubleshooting steps did you try???

[xiansheng F]

I used the Wireshark to capture packets, and found that ARP messages did not respond when the link was normal.

[Ramon Fontes]

What about the flow tables??? :(

[xiansheng F]

If the vehicle changes to station, an ARP reply occurs

在2021年10月19日星期二 UTC+8 下午9:11:39<ramonre...@gmail.com> 写道：

[xiansheng F]

Flow tables are routing rules

[Ramon Fontes]

Please provide as much information as possible. Otherwise, I won't be able to help you. Is "Flow tables are routing rules" the only thing you can say about the flow tables???

[xiansheng F]

The ovs-ofctl add-flow command is used to install routing rules.

Two network devices can communicate with each other only by routing rules.

[xiansheng F]

Do you know the ovs-ofctl command?

If you know the command, you can also try to reproduce the problem.

Vehicles passing a base station will not be able to communicate with other vehicles under the base station.

在2021年10月19日星期二 UTC+8 下午9:27:45<ramonre...@gmail.com> 写道：

[Ramon Fontes]

The handover/mobiltiy is a known issue. You argue that your Ryu module supports mobility. I really appreciate if you can show me the flow table and convince me that ping between car1 and car2 should work as you expect.

[xiansheng F]

Thank you for your help.

In fact, the problem has little to do with the mobility management module in the SDN controller. Because the function of the controller is to update the routing rules, so that each network device can communicate normally.

When I discovered this problem, I was curious as to why the routing rules I installed didn't work. If Car1 has not been connected to the base station before, Car1 can establish communication with vehicles or stations under the base station. However, if car1 has previously established a connection with the base station, car1 cannot establish communication with the vehicle or site under the base station (even if the correct routing rules exist).

This problem can be reproduced without the help of the controller, and the controller can be replaced with the ovs-ofctl add-flow command.

Thanks again for your help, I will solve this problem in another way.

[Ramon Fontes]

If you have the following rule:

Match: in_port=1 and Action: output:2

Ryu won't replace the rule with a new one with the same match. You usually have to take a look at the flow timeout since each switch/ap has idle and hard timeouts associated with the flow tables.

Sent from my android

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