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By Jim Duffy
Network World, 6/23/97

Users should start planning their migration to IP Version 6 (IPv6) before the current IP Version 4-based (IPv4) technology runs out of gas.

Despite its reliability, IPv4 has address limitations, performance problems, security holes and a raft of other deficiencies. All need to be addressed for the Internet and related IP technologies to move forward - especially in light of the Internet's exploding popularity and growing use as a multimedia delivery system.

IPv6, the next iteration of the Internet Protocol, is the answer. In addition to providing extended addressing, IPv6 is designed to overcome other limitations of the current version, such as quality of service and configuring hosts and routers.

But adoption of IPv6 requires change - changes to applications, routing protocols and addressing servers, such as Dynamic Host Configuration Protocol, BOOTP and Domain Name System - say developers and vendors currently involved with the 6bone IPv6 test network. Some observers even question whether IPv6 is necessary if IPv4 can be enhanced to overcome its limitations.

''If you want to talk about a 'gotcha' or something that will make the transition slower, it's going to be applications,'' says Helen Sylvester, director of engineering for FTP Software, Inc. in Andover, Mass. ''They have to be IPv6-enabled.''

Despite all of the bells and whistles that come with the new protocol, addressing comes up as the No. 1 reason there needs to be an IPv6. IPv4's 32-bit address field will not accommodate the growth in Internet usage, expanding bandwidth requirements and steady increases in processing power, developers say.

IPv6 features a 128-bit address field that exponentially increases the number of devices the protocol can support compared to IPv4.

Some industry pundits even predict that IPv4 addresses will be exhausted within the next five to eight years. That is one of the reasons why the Internet Engineering Task Force (IETF) has issued a request for comment document, RFC 1933, on suggested methods for IPv4-to-IPv6 migration.

The migration methods the IETF recommends are dual stacks and tunneling. The dual stacks method refers to IP nodes that support IPv4 and IPv6 protocols. The tunneling approach advocates running IPv6 packets over existing IPv4 infrastructures. Vendors say dual stacks and tunneling should minimize any migration snags for users.

''They're the tools that essentially allow you to build a phased migration,'' says Mike Paratore, router marketing manager for Bay Networks, Inc. ''You don't have to migrate all of your routers to IPv6 immediately. You can have islands of IPv6 connectivity which you connect via either of these tunneling mechanisms.''

Bay will ship IPv6 on its routers in the second half of this year. Users are less than comforted by Paratore's assurances, however.

''I wonder what's going to break?'' says James Wiedel, director of networking in the computer services department at the University of Southern California at Los Angeles. ''I'm sure it's going to break things left and right, undoubtedly.''

Other users are just beginning to dip their toes into the IPv6 waters.

''We've just started a project to try and determine which one of the IPv6 stacks is the most stable for the PC and workstation environments,'' says Brian Power, network administrator at Memorial University in Newfoundland, Canada. ''At the moment, I don't have any results, so I don't know what my direction is going to be.''

Despite the built-in migration tools, the transition to IPv6 will present users with some pitfalls along the way, vendors say. Most will crop up when users retool applications to run in the new network environment, according to FTP's Sylvester.

For example, the user interface field in an application written for IPv4 needs to be expanded to handle the larger IPv6 addresses, Sylvester says. Also, users or developers will have to change how applications pass addresses down to the WinSock interface at the network layer, she says.

WinSock is an application program interface in Windows 95 and NT operating systems that binds applications to the TCP/IP protocol stack. FTP is currently shipping IPv6 software for Windows clients.

Avoiding hiccups

''You have to make a list of what applications you have that put packets on the wire,'' says Jim Bound, IPv6 architect at Digital. ''That is critical. That will be the biggest 'gotcha.' Users should be worrying about that right now, not tomorrow.''

Users who want to save themselves from worry should stick with IPv4 and use Network Address Translation (NAT) for expanding addressing, according to Toby Jessup, principal engineer for US WEST, Inc.'s !nterprise Networking Services arm. NAT servers at the boundary between private intranets and the Internet will allow users to expand addressing by keeping private network addresses distinct from Internet addresses, Jessup claims.

NATs save Internet addresses by allocating them to active Internet users only. When they disconnect from the Internet, the address goes back into a shared pool, reducing the number of Internet addresses organizations require, Jessup says.

''The incremental improvement that IPv6 [services] would represent over IPv4 may not be worth the leap,'' Jessup says.

Jessup's position might be a stretch, according to Sun Microsystems, Inc. Although NATs could provide some incremental improvement to IPv4 addressing, they may also give users the impression that they will not need IPv6.

''[NATs are] not a very scalable solution once the network starts to get very large, once it gets hierarchical,'' said Praveen Bhatia, product line manager for Sun's Solaris operating system. ''If you have a translator at every gateway [between domains] it starts to break down pretty quickly.

But consultants say users will not migrate en masse to IPv6 for years.