Stock EL7 (and SL7) has a target called network-online.target. This is used to delay services until the network interface is configured and online. Whilst this is suitable for a scenario where the network gateway is statically configured or obtained via DHCP, it is not suitable for systems which run router discovery (eg rdisc). On such systems, network-online.target is reached before any network gateway is configured, so services which require access to off-wire resources (eg updaterpms) can fail to start correctly.
To solve this, an extra target called internet-online.target has been added. This target is only reached once network-online.target and any services required to provide full internet access have been started. Services that require off-wire resources to start correctly should depend on this target (using ‘after‘) instead of the network-online.target.