This is possible, at least at the edge of networks, but I think it would be simpler to do it on customer routers.
Cisco has a command "ip verify unicast reverse path" or something. This command breaks multicast under some conditions, but should work for smaller/simpler networks and edgerouters.
There is also the problem of complexity, if you are a transit and/or multihomed AS. Complexity can also be bad for your throughput in some routers eg. it may force the processor to make routing decisions, which is slow. And access-lists have to be maintained.
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Last time I checked, sometime around kernel 2.1.125, my 25MHz 386 with 2 3c509 could easily route 3mbps with 64 byte packets.
This is possible, at least at the edge of networks, but I think it would be simpler to do it on customer routers.
Cisco has a command "ip verify unicast reverse path" or something.
This command breaks multicast under some conditions, but should work for smaller/simpler networks and edgerouters.
There is also the problem of complexity, if you are a transit and/or multihomed AS.
Complexity can also be bad for your throughput in some routers eg. it may force the processor to make routing decisions, which is slow.
And access-lists have to be maintained.
/Anders