IPv6 – Just 96 More Bits?

by Jeff Loughridge

My favorite professor in college joked that the answer to most questions in computer science is, “It depends.” How true. I’ve found few absolutes in my years working on IP networks. If you compare IPv6 (128 bit address space) with IPv4 (32 bit address space), is IPv6 just 96 more bits?

IPv6–with its long hexadecimal addresses–can be intimidating for engineers who have built a career on IPv4 networking. I recall my hesitation to get involved in turning up customer tunnels to Sprint’s IPv6 overlay network in the early 2000s. I felt that I could fix any problem thrown my way on IPv4. Why invest time to learn IPv6 when its adoption was so limited? Clearly, my sentiment my short-sighted, and I corrected my thinking.

I take the reassuring approach in talking to engineers who are new to IPv6. Gaurab Upadhaya of Limelight Networks put it well: only 96 more bits, no magic. After engineers understand IPv6 basics such as addressing, SLAAC, and neighbor discovery, they’ll begin to understand that the simple, connectionless packet service provided by IP is the same for both versions. Routing is routing (albeit with OSPFv3 for IPv6). The best practices for building scalable IPv4 networks carry over to IPv6 largely intact.

I tend to emphasize the differences between IPv4 and IPv6 in talking about network strategy, design (including migration and transition mechanisms), security, and business continuity. In these areas, the protocol deviations drive the discussion. Let’s take security.  IPv6 implementation introduces new attack vectors. Neighbor Discovery and Router Advertisements, not present in IPv4, can be   subject to denial of service and spoofing. Also, there is new way for malcontents to communicate with your infrastructure. Does your security policy align for IPv4/IPv6 and does it account for IPv6-specific security issues?

IPv4 exhaustion is imminent; engineers and IT leaders will be forced to make critical decision about IPv6 in 2012. Their discussions will likely include aspects of both IPv4/IPv6 similarities and differences.  As long as organizations are having these talks with the intent to act in the near term, they are better off than they would be by ignoring IPv6.

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