the u201c closest u201d helper router this is performed by selecting the default route with the lowest routing metric which is part of the standard bgp path selection criteria used by bgp routers the routing metric can be determined through a routing protocol such as open shortest path first ospf intermediate system to intermediate system is is routing information protocol rip interior gateway routing protocol igrp and others or through manual configuration by a network operator in another embodiment helper router proximity is determined by each helper router 203 originating a unique prefix into the network via anycast using ospf is is rip igrp or others each constrained router 201 learns each helper router 39 s 203 anycast prefix step 415 each constrained router 201 may have a static default route pointing to the anycast prefix pre configured by a network operator based upon the anycast prefix es each constrained router 201 will select the u201c closest u201d helper router based upon which has the lowest routing metric which is typically the shortest latency path a datagram packet fig2 b traffic flow is shown as a broken line is received from outside the network 101 at a pe router 105 which may be a constrained router 201 step 417 the constrained router 201 receives the packet destined for a network outside of the network 101 the constrained router 201 performs a route look up on the destination address in the packet and does not find an exact match step 419 the constrained router uses the default route learned from the helper routers.