IPv6: Built for speed

Early testing of IPv6 indicates that the next-generation Internet Protocol can handle the demands of future high-performance computing. But among government agencies, only officials at the Defense Department and research agencies seem to be aware of its advantages.

The current version, IPv4, which has been around since the late 1970s, is showing its age. Most people agree that future high-performance networks, which will carry a wide range of data, voice and video traffic, will need something more.

Although IPv6 is the next-generation version of the protocol, it's not a newcomer. The Internet Engineering Task Force first defined IPv6 in 1998, but the protocol has only recently started to appear in tests of high-performance networks. Those early tests have shown promise.

The university-led Internet2 project, for example, which is developing next-generation Internet applications and technologies, demonstrated last year that IPv6 could support large-scale performance when terabytes of data were passed between Switzerland and Chicago.

Energy Department officials have tied the agency's future computational needs to Internet2 and other IPv6-based networks. Officials at other agencies such as NASA also have made extensive networking plans based on IPv6 environments.

But, as it seems to be the case with many cutting-edge technologies, the Defense Department is carving the path to wide-scale deployment. DOD officials decided last year that military networks must move to IPv6 by 2008.

DOD officials said they need more IP addresses to carry out their network-centric warfighting plans. Every soldier and piece of equipment will have a unique IP address a capability that IPv4 cannot provide.

Many technicians with expertise in IPv4 can sum up its shortcomings in a few words, such as comments from Charles Lynch, chief of the IPv6 Transition Office in the Defense Information Systems Agency.

"IPv4 has many features that are problematic, such as [packet] fragmentation, and has header options and padding that make its header variable length," he said. "The currently allocated address space within IPv4 is also a problem, since it has been scattered without much concern for address aggregation."

That means IPv4 has to first divide data packets into fragments. Each router reassembles the fragments before passing them on to the next router. IPv6 also fragments packets, but the fragments don't need to be put back together until they reach their destination.

The variable header size means that routers and host computers don't know ahead of time what they have to handle in terms of processing. And address aggregation is a way of collecting addresses in various groupings to limit the size of the routing tables, which IPv6 handles much better than IPv4, Lynch said.

Internet developers could probably retool IPv4 to solve these problems, Lynch said, "but the fundamental question has to be which is the better solution: trying to retool IPv4 or moving gracefully to a new and improved, yet similar protocol?"

Although IPv6 will not guarantee faster networking, it will eliminate many problems that could affect network performance in the future. For example, IPv6's converged infrastructure can handle data, voice and video transmissions.

Most of IPv4's problems stem from the protocol's limited address space of 32 bits. That quantity allows for more than 4 billion unique IP addresses, which was plenty for the nascent network of the 1970s and 1980s, but was inadequate by the 1990s.

To bypass this shortfall, the industry developed Network Address Translation (NAT) technology, which gives network hosts a way to share IPv4 addresses. But it also requires a NAT device at the exit router between each subdomain on the network and the backbone network to translate the local source address into a globally unique address, or vice versa.

"NATs have a tendency to break [converged] applications," said Dave Siegel, vice president of network administration and planning for telecommunications service provider Global Crossing. "So as more and more of these applications are required, then NATs will get in the way of their

delivery."

IPv6, whose 128-bit address space effectively provides for unlimited IP addresses, will enable every node on the network to have an IP address, which will largely eliminate the need for NATs and allow traffic to flow directly from one address to another.

Most of the advantages of IPv6 could come through removing or modifying NAT and other devices such as firewalls that affect direct peer-to-peer communications, according to a draft report from the Commerce Department's National Telecommunications and Information Administration, which was published earlier this year.

Another advancement promoted in IPv6 is a simpler packet header structure. Packet headers contain instructions that routers use to send packets to a targeted Internet address. IPv4 headers have a relatively complicated structure, causing routers to do a lot of intermediate processing before sending data packets.

"In IPv6, the header has been streamlined and cleaned up, and from a performance standpoint, that helps the routers to process things better and faster," said Cody Christman, director of product engineering for Verio Inc., a service provider that's part of the NTT Communications group of companies.

IPv6 headers, which are of a fixed length, are twice the size of IPv4 headers and have room to include flexible protocol extensions that also will help speed up router processing.

Even though these and other factors built into IPv6 mean the protocol is better prepared for high-performance networking, it's unclear how quickly government agencies will adopt it. Other than DOD and research agencies, most government organizations have not announced IPv6 initiatives.

They could be missing the boat, said Ray Williams, manager of IPv6 programs at Northrop Grumman IT.

"I think there will be a need for IPv6 sooner rather than later," he said. "Just the fact that everything on the network can get its own IP address simplifies things enormously and really increases end-to-end visibility [of the network]. It will help us get away from a lot of the problems we experience today."

Northrop Grumman might even take an initial hit "as we do a nice little business mapping end-to-end network topologies," Williams said. "But we are in the business of building applications, and IPv6 will help with that."

DOD officials expect IPv6 to provide the department with major networking improvements.

"We are at the forefront of a new beginning," Lynch said. "IPv6 will permit us to rethink the networking and communication paradigm." n

Robinson is a freelance journalist based in Portland, Ore. He can be reached at hullite@mindspring.com

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IPv6 benefits

If IPv6's ability to improve network performance is not enough to persuade agency officials to establish a plan to migrate to the next-generation IP, here are some other benefits that might convince them to consider a shift:

Security: IP Security (IPSec), which is optional with IPv4, is mandated for IPv6. Setting up a virtual private network through IPv4, for example, requires confirmation that the user with whom you're communicating also supports IPSec. IPv6 will eliminate this requirement.

Multicast: This function allows one node on the network to broadcast the same data to a number of different nodes. It has to be added to IPv4 environments but comes standard with IPv6.

Autoconfiguration: With IPv6, devices can attach to a network in a plug-and-play manner, establishing their own configuration from information provided by the network. This function provides mobile device users with easier access to the network and lets administrators establish ad hoc networks.

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