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I installed Rserve in a unix ec2 which has private and public IP. When I try to communicate to it with small dataset, there is no issues.

However, when I do the same with little big more data, the private IP gets connection timed-out (Note: My source/client ec2 is in same subnet).

On the other hand, when I try the same with the public IP from a machine outside this VPC (that is, using internet), Rserve is very quick.

I am wondering, how come intranet gets timed-out but internet is fast. Is there any settings in the unix which restricts something

Can someone shed some light on this please.

(Note: my source/client tool is Tableau)

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I would make sure you are allowing ICMP for MTU path discovery inside of the VPC.

By going through the public internet will limit you to 1500 bytes, but in the VPC you will have Jumbo frames. If there is a there is a difference in the maximum transmission unit (MTU) size in the network path between the two hosts with no PMTU discovery due to blocked ICMP you will see these types of pauses.

This is a fairly common problem in even core AWS services if security groups block ICMP. Here is a link to a page that may be related to redshift but is likely the same problem.

https://docs.aws.amazon.com/redshift/latest/mgmt/connecting-drop-issues.html

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  • Pretty interesting stuff +1 ; in a previous job I had to pester them to not block all ICMP packets exactly because of this. Commented Jan 13, 2018 at 12:52

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