IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet, but IPv6 uses 128-bit addresses and can connect up a virtually unlimited number of devices: 2 to the 128th power. IPv6 offers the promise of faster, less-costly Internet services than the alternative, which is to extend the life of IPv4 using network address translation (NAT) devices
IPv6 introduces several difficult issues related to managing email on large networks. For example, IPv4 has 4.3 billion IP addresses that can be tracked by tools such as Cloudmark Sender Intelligence to isolate spammers. Because the supply of IPv4 is scarce, each residential customer gets one IPv4 address. This means companies like Cloudmark can identify spammers by the IPv4 address they use.
With IPv6, however, residential customers will be given what's called a /64, which equals an enormous number of IPv6 addresses:18,446,744,073,709,551,616. Spammers will be able to switch from one IPv6 address to another in their residential block of IPv6 addresses, making it harder for carriers to isolate them. With a /64, a spammer can send one message per second for the entire year without using the same IPv6 address.
"With IPv6, you can no longer track negative reputation by IP address," San Diego says. "You lose the ability to block and throttle based on previous seen activity. Spammers will be able to continually change their sending IP address and easily shed any negative reputation."
Cloudmark is working with standards bodies to develop a common way to track spammers through IPv6 network prefixes. The company is also looking at positive reputation services using authentication techniques such as DomainKeys Identified Mail (DKIM).
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