Consider the network shown below. ISP B provides national backbone service to regional ISP A$.$

ISP C provides national backbone service to regional ISP D$.$ Each ISP consists of one AS$.$ B and C

peer with each other in two places using BGP$.$ Consider traffic going from D to A$.$ C would prefer to

hand that traffic over to B on the East Coast $($so that B would have to absorb the cost of carrying the

traffic cross$-$country$),$ while B would prefer to get the traffic via its West Coast peering point with $C$

$($so that $C$ would have carried the traffic across the country$).$ What BGP mechanism might B use, so

that $C$ would hand over D$-$to$-$A traffic at its West Coast peering point?

$[5$ points$]$

Hint: Think in terms of where should ISP B advertise its route to $A.$