Why are Google Cloud Compute Engine WAN speeds less than what Google has documented?

Solution 1:

As per the documentation, "All caps are meant as maximum possible performance between two VM instances in the same zone, both using internal IP addresses." I verified running two instances running Centos 7 with 1vCPU and 3.75GB RAM in same zone using the "iperf" [1][2] (sudo yum install iperf) and received 1.64 Gbps.

On the GCE VM machine (with iperf install) in the same zone, run the 
command:
iperf -s 

On egress test GCE VM machine (with iperf install) run the command 
iperf -c xx.xx.xx.xx     (where xx.xx.xx.xx is internal IP of the other VM- 
instance)

output:
[ID] Interval       Transfer     Bandwidth
[3]  0.0-10.0 sec  1.91 GBytes  1.64 Gbits/sec

I verified running instance with 4 vCPUs as well and received 7.67 Gbits/sec as bandwidth which is very close to 8 Gbps as defined in the documentation. I would suggest you to verify the same.

Moreover, as Google does not have any control over ISP network and other factors involved (eg: routing etc.) over internet traffic, Google cannot guarantee the egress throughput for the egress network traffic from a virtual machine over the ISP network.

[1] https://iperf.fr/

[2] https://www.linode.com/docs/networking/diagnostics/diagnosing-network-speed-with-iperf