Switch Network interfaces while stream is running

[tob...@googlemail.com]

Hi group,

are there any experiences here how GRPC handles a switch of the network interface while a bi-di stream is running?

E.g. I start a connection on a laptop that is using LAN and WLAN.Due to the interface metric I would expect that the channel would prefer the LAN connection.

But what happens to the stream if I pull the network cable?

Now a WLAN only scenario - e.g. I walk with the laptop through a large building with many access points.

What happens to the stream if the WLAN switches to a different accesspoint (still connected to the same network)?

Are there any differences between IPv4 and IPv6?

I would appreciate any thoughts or input on this matter.

Thanks

Tobias

[Carl Mastrangelo]

Replies inline:

On Friday, June 14, 2019 at 12:15:29 AM UTC-7, tob...@googlemail.com wrote:

Hi group,

are there any experiences here how GRPC handles a switch of the network interface while a bi-di stream is running?

Sorry, this is not supported currently.   It is theoretically solvable if using QUIC, which has a separate connection identifier in each packet, but  I don't think gRPC supports it yet.   File an issue on the GitHub tracker if you are interested in it. 

 

E.g. I start a connection on a laptop that is using LAN and WLAN.Due to the interface metric I would expect that the channel would prefer the LAN connection.

But what happens to the stream if I pull the network cable?

It will take a while to realize the packets are not being responded to.  You can set a keep alive timer on the channel to make sure you noticed within some time frame.

 

Now a WLAN only scenario - e.g. I walk with the laptop through a large building with many access points.

What happens to the stream if the WLAN switches to a different accesspoint (still connected to the same network)?

Are there any differences between IPv4 and IPv6?

Not really, at least in the scope of this question.

[Eric Anderson]

Streams are bound to the underlying TCP connection they were "placed on." So the questions are answered by "what happens with TCP in that scenario."

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