Does Global Accellerator before and ALB have a concurrent connection limit from single source IP

Question

Hi

We have deployed a global accellerator before our ALB to give us static ips to whitelist on our APN sim cards we on our devices. The APN send traffic from the same source IP through the global accelerator to our ALBs. We noticed that it seems new connections are capping around plus minus  60k; if we remove the global accelerator, new connections jump to 105k.

We also noticed that if we change the source IP, the new connections jump up but eventually get capped at plus minus 60k again.

I checked documentation but cant find any mention of a limit for single source IP to global accelerator or ALB.

Thank you in advance for any suggestions or help.

Brettski-AWS · Accepted Answer

In theory, given the 16 bit number that represents the source port number; and subtracting for "reserved" ports on any particular operating system, ~60k sessions from a single IP address is about right. Especially if it is a single port that the application is connecting to.

The reason you're seeing far more than that to ALB directly is probably because your connections are happening to each ALB node. If you look at the DNS response for the ALB you should see two or three IP addresses; connections to those will multiply the ~60k number.

So this isn't an AWS limit; it's a TCP (and UDP) limit.

Oneswitch · Answer

Thank you for the quick response. I found that limit, but because the Global Accelerator has two static IPs, I was expecting around 120k before starting to see the cap. The "reserved" ports may bring the count down a bit more, or one IP may be preferred above another one cause of the location of the source IP.

Does Global Accellerator before and ALB have a concurrent connection limit from single source IP

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