BGP Influencing outgoing traffic
At the enterprise network edge, when BGP is employed, it is typically an eBGP peering that takes place between the enterprise edge router(s) and the ISP router(s). In such a scenario, an enterprise will advertise specific IPv4 or IPv6 addresses for internal services that they want users on the Internet at large to be able to access.
In the event that the enterprise has two or more ISP connections, outgoing traffic from the local AS to the Internet can be manipulated as desired.
This can be done by adjusting the Local Preference attribute, which is used to select the outbound eBGP path. You always have ultimate control over what eBGP path your traffic will take, even if neighboring BGP ASes are attempting to influence it using various BGP attributes. This is because you have complete control over the BGP attributes used by your devices.