# Configure Protocols and Ports

For each service you will provide the protocol of the traffic to be balanced (either `TCP` or `UDP`) and a pair of ports:

Service port
: the port on which the NLB Service has to listen for the incoming traffic.

Target port
: the port on which the NLB Service has to forward the traffic. This is the
  port on which the members of the Instance Pool will actually receive the
  forwarded traffic.

> [!WARNING]
> Your Instance Pool [security groups]({{< ref "/product/networking/security-group/" >}}) 
> need to have an open ingress rule on the designated target port to work.