Ali, why do you think so? It is normal condition (at least in Russia/Ukraine). The only disadvantage is in some cases upper ISP can make some interruption in routing of lower ISP block. Also in most cases lower ISP have to use upper ISP's cnannels (not to be multihomed itself). But generally it is normal condition for resellers (lower ISP is the service reseller of upper ISP). Ali Dinçkan wrote:

Hello,

I have a question. I am searhing now what happens if an ISP use IP address space that is assigned to another ISP. Is there any technical control eleminate this condition? And what is the legal sanction of this misuse?

This might be intentional or unintentional. But ISP that use another ISP's IP address space damage the Internet nature.

Thank you for your answer in advance

Best regards,

Ali Dinçkan

-- WBR, Max Tulyev (MT6561-RIPE, 2:463/253@FIDO)

On 21-okt-2007, at 21:45, Ali Dinçkan wrote:

I have a question. I am searhing now what happens if an ISP use IP address space that is assigned to another ISP. Is there any technical control eleminate this condition? And what is the legal sanction of this misuse?

This might be intentional or unintentional. But ISP that use another ISP's IP address space damage the Internet nature.

This is why it's a good idea to have filters, but if it's happening then obviously there is insufficient filtering to stop it. In the future, address certificates could help here. Don't know about legal issues but I'd assume you'd have a decent case in court. However, the best way to resolve this is to first contact the party announcing the address space, and if they don't cooperate, their upstream ISPs. When I used to work at a large IP carrier our policy was always that if customers wanted to use address space from other ISPs, we'd only do that as long as the other ISP would allow it.