AWS ELB: How can I see how many bytes of outbound network traffic an SSL-enabled ELB generates

Question

I'm curious to know how much total outbound bytes an ELB generates. As far as I can tell, this will be something like

(size of http responses) + (size of SSL handshake transactions)

I can calculate the former by looking at my web server logs. However, I'm having a hard time getting to the number of bytes sent out while handling TLS handshakes. Does AWS provide this metric anywhere?

Details: I'm using a 'classic' ELB and all the request I handle are SSL requests.

Answer 1

The handshake of a TLS connection is pretty much constant and do not depend on your application. So your function is really : number of connections * ( size of http responses + constant)

Here is a good article that estimates the payload to average ~6.5k (depending on your certificate size) : http://netsekure.org/2010/03/tls-overhead/

The list of ELB metrics is available here : https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-cloudwatch-metrics.html This web page has also some good details about how to migrate from ELB to ALB and estimate your cost.

ALB has that metric exposed EstimatedProcessedBytes

Depending on your application, the TLS handshake overhead will be negligible compared to the amount of byte going out of your app. Unless you have an app with many short lived connections to exchange just a few bytes. IN that case, a refactoring of the app might help to save on outgoing bandwidth costs.