Businesses are always increasing their requirements for interactive multimedia, and high bandwidth network applications, IPv6 is crucial to the long term viability of enterprise internetworks and the public Internet at large. although it is important for the future growth of the Internet, the development of IPv6 have been portrayed as a not easy task to migrate which could easily confuse IT professionals like network administrators who are in the process of devising a forward looking network strategy. The ramifications of migrating our internetwork infrastructure to an updated protocol would be bound to cause some confusion. But if the IPv6 are not explained explicity enough, there's a possibility that the Internet will continue with a outdated set of protocol components, while end user and business requirements for sophisticated network services expand exponentially. It's time to discuss the business case of IPv6 in details.
Many of the discussions about a new Internet protocol points on the prediction that the Network Layer addresses will eventually run out, due to IPv4's outdated 32-bit address space. The Internet Network Information Center (InterNIC) is the authority that assigns blocks of IP addresses to large network service providers and network operators. Since 1991, InterNIC has been increasingly frugal about the way these addresses are handed out, though most predictions for IPv4 address exhaustion target a time frame that starts well into the next decade.
With the long term in mind, IPv6 has been developed with an enormous 128-bit address space that should guarantee globally unique addresses for every conceivable variety of network device for the foreseeable future (i.e., decades). IPv6 has 16 bytes of addressing, or . . .
340,282,366,920,938,463,463,374,607,431,768,211,456
The addressing gets priority since its one of many important issues that IPv6 designers needs to take into account. Other IPv6 capabilities have been developed in direct response to currently critical business requirements for more scalable network architectures, improved security and data integrity, integrated quality of service (QoS), autoconfiguration, mobile computing, data multicasting, and more efficient network route aggregation at the global backbone level. IPv6 is a big package, and addressing is only the most visible component of the work.
IPv6 will reap benefits with a smooth transition occuring to extend the life of IPv4 indefinitely with changes to the protocol standards and various proprietary techniques. One IPv4 example is the extension found in network address translators (NAT) that preserve IPv4 address space by intercepting traffic and converting private intranet enterprise addresses into globally unique Internet addresses. Other examples include the various quality o service and security enhancements to IPv4.
Although these extensions may be valuable in some short term cases, eventually there will be a limit connectivity, interoperability, and performance in enterprises that are considerably network dependent. Usually, IPv4 extensions are no substitute for a protocol suite was developed from the ground up with scalable addressing, advanced routing, security, quality of service. Network proprietors need to be very cautious of vendor claims that all the shortcomings of IPv4 can be solved by extension products such as NAT and proprietary security gateways. The economics of IPv4 extensions can be measured only when the resulting reduction in connectivity is taken into consideration. There is eventually no replacement for IPv6 in businesses that need the high levels of internal and external connectivity that will be required by emerging multimedia, interactive, and transaction oriented network applications. The future of such crucial business tools as intranets and the World Wide Web is closely tied to the availability of robust, advanced internetwork protocols.
By conservative estimates, IPv6 will support thousands of addresses for each square meter of the Earth's surface.
Over the next few years, conventional computers on the Internet will be connected by a variety of new devices, including palmtop personal digital assistants (PDA), hybrid mobile phone technology with data processing capabilities, smart set-top boxes with integrated Web browsers, and embedded network components in equipment ranging from office copy machines to kitchen appliances. As new devices make debut their way onto the Internet, they will strain the existing network fabric in ways the early IP protocol designers could have predicted. Some of the new devices requiring IP addresses and connectivity will be consumer oriented, but the majority will also become integral to the information management functions of corporations and institutions of all sizes.
IPv6's 128-bit address space will permit businesses to install a huge array of new desktop, mobile, and embedded network devices in a cost effective, managed manner. Furthermore, IPv6's advanced autoconfiguration features increases the feasibility for a myriad of devices to connect vibrantally to the network, without incurring unsupportable costs for the administration for an ever-rising number of add ons, moves, and changes. The business requirement for IPv6 will be driven by end user applications. To remain competitive in the coming era of high density networking, businesses should exploit IPv6 to build a highly scalable address space and reliable autoconfiguration services that will remain viable in the face of an explosion of end user networking requirements.
It is true that IPv6 set the path for efficient multitiered routing hierarchies that strain the uncontrolled growth of backbone router tables. But many of the sophisticated features of IPv6 also bring direct benefits to end user applications at the workgroup and departmental levels. New IPv6 security features, for example, allows applications encryption and authentication services that are an critical part of the IP stack. For mobile business users and departmental staffs, the automatic configuration components of IPv6 will give the efficient assignment of IP addresses without the delays and cost associated with manual address administration, which are common in many current IP networks. IPv6's built in quality of service features lay the basis for more deterministic end to end service levels in time sensitive interactive and multimedia applications. IPv6 is very much both an end user issue and a business issue.
ATM and other switching methods are very valuable technologies for present and future internetworks, but ATM is, by itself, not a subsititue for today's packet routing, Internet architecture. Favourably, network owners do not have to make a decision between ATM or IPv6 since the two protocols will continue to provide very different and complementary roles in corporate networking. Large networks will obviously make use of both protocols. For forward thinking network designers, ATM is an ideal transmission medium for high speed IPv6 backbone networks. And indeed, a great deal of standards and development work is being devoted to integrating ATM and IPv6 environments. IPv6, like its predecessor, provides Network Layer services over all major link types, including ATM, Ethernet, Token Ring, ISDN, Frame Relay, and T1.
Some in the industry have described IPv6 as a issue that's outside the corporate network and the current time frame. In reality, IPv6 is an inside technology that is critical to the operations and continued efficiency of daily business activities. IPv6 will take hold and succeed is if all the businesses and institutions come to grips with the inadequacies of IPv4 and begin to route a blueprint for migration. In the past few years, Internet protocols have enabled a totally new style of distributed commerce that brings people together inside enterprises and allows enterprises access to the world. It is up to the networking community to ensure that this accomplishment continues. From a business performance perspective, networked enterprises that invest in IPv6 planning now will have a decided competitive advantage as the information age progresses.
IPv6, the Next Generation Internet Protocol, was approved by the Internet Engineering Steering Group on November 17, 1994 as a Proposed Standard. Since that time a many end user businesses, standards groups, and network suppliers have been working together on the specification and testing of basic IPv6 implementations. A number of IETF workgroups have defined IPv6 projects that are developing, including the basic IPv6 protocol specification, address architectures, Domain Name Servers (DNS), security, transition mechanisms, and Internet Control Message Protocol (ICMP).
Standards work on IPv6 have made network vendors devoted to a substantial number of development and testing projects. All of the major router vendors have committed to include IPv6 in their products.
Computer manufacturers such as Digital Equipment Corporation now Compaq Computer, Hewlett Packard and Sun Microsystems have started the task of delivering IPv6 on desktop machines and server. Network software vendors have pledged a wide range of support for IPv6 in network applications and communication software products. A test bed called the 6Bone has been established, which currently links a large number of IPv6 end and intermediate node devices in North America, Europe, and the Pacific Rim.
IPv6 has been developed to implement high performance, scalable internetworks to be viable well into the next century. A large proportion of this design process involved solving the inadequacies of IPv4. It is only by delving into the full range of IPv6 improvements that the full benefits to enterprise and provider networks can be evaluated. Some of the qualities of IPv6 are apparently beneficial enhanced features, such as the longer address space and common packet design. Other qualities are less tangible and relate to the fresh start that IPv6 would enable those who design and administer networks. With the clean slate that IPv6 provides, it will be possible to design a new, well structured, efficient routing hierarchy to replace today's chaotic patchwork of addressing anomalies and legacy routes. The following sections give an overview of the visible/apparent and the implicit/obscure improvements that IPv6 brings to enterprise networking and the global Internet.
IPv6 gives a framework for fixing some important problems that currently exist inside and between organisations. On the global surface, IPv6 will enable Internet backbone designers to dvelop a highly flexible and open ended routing hierarchy. At the level of the Internet backbone where major enterprises and Internet Service Provider (ISP) networks come together, it is essential to maintain a hierarchical addressing system, like that of the national and international telephone systems. Large central office phone switches, for example, only need a three digit national area code prefix to route a long-distance telephone call to the correct local exchange. Similarly, the current IPv4 system uses a casual form of address hierarchy to move traffic between networks linked to the Internet backbone.
Without an address hierarchy, backbone routers would be forced to store routing table information on the reachability of every network in the world. Presented with the current number of IP subnets in the world and the growth of the Internet, it won't survive. With a hierarchy, backbone routers can use IP address prefixes to determine how traffic should be routed through the backbone. IPv4 apply a technique called Classless InterDomain Routing (CIDR), which enable flexible use of variable length network prefixes. With this flexible use of prefixes, CIDR permits substantial "route aggregation" at numerous levels of the Internet hierarchy, which suggest backbone routers can store a single routing table entry that allows contact to many lower-level networks.
But the availability of CIDR routing does not ensure an efficient and scalable hierarchy. In many cases, legacy IPv4 address assignments that originated before CIDR do not facilitate summarization. In fact, much of the IPv4 address space was formed before the current access provider hierarchy was built. The lack of uniformity of the current hierarchical system, coupled with the rationing of IPv4 addresses, suggests that the Internet addressing and routing that are increasingly are overloaded with complications at all levels. These issues affect high-level service providers and individual end users in all kinds of businesses.
Many of the same problems that exist today in the Internet backbone are also being experience at the level of the enterprise and the individual business user. When an enterprise can't summarize its addresses, backbone routing tables can expand in a way that is ultimately unsupportable. If an enterprise can't provide unique addresses to the Internet, it may be forced to deploy private, isolated address space that isn't visible to the Internet.
Users in private address spaces with non unique addresses frequently are restricted by gateways and network address translators in their connectivity to the outside world. NAT services are meant to enable an enterprise to have whatever internal address structure it desires, without concern for integrating internal addresses with the global Internet. The NAT device sits on the border between the enterprise and the Internet, converting private internal addresses to a smaller pool of globally unique addresses that are passed to the backbone and vice versa (see Figure 1).
Figure 1 | Network Address Translator
NAT may be appropriate in some businesses, particularly if full connectivity with the outside world is not necessary. However businesses that require robust interaction with the Internet, NAT devices are not always desirable. The NAT technique of replacing address fields in each and every packet that leaves and enters the enterprise is very demanding, and can result to a bottleneck between the enterprise and the Internet. A NAT may keep up with address conversion in a small network, but as Internet access increases, the NAT's performance must increase in a parallel fashion. The bottleneck effect is exacerbated by the difficulty of integrating and synchronizing multiple NAT devices within a single enterprise. It is highly unlikely that an business will accomplish the robust high performance Internet connectivity with NAT that is common today with multiple routers attached to an ISP backbone in an arbitrary mesh fashion.
NAT translators also run into problems when applications embed their IP addresses in the packet payload, above the Network Layer. This is the scenario for a with various applications, including certain File Transfer Protocol (FTP) programs, and the Windows Internet Name Service (WINS) registration process of Windows 95 and Windows NT. Unless a NAT avoids every packet all the way to the application level, it has no way of translating embedded addresses, which can result in application failures. NAT can also wreak havoc with Domain Name Servers that function above the Network Layer. NAT services are a valuable tool for certain limited cases, but in general it may be dangerous to the long-term health of the Internet to promote NAT as a replacement for the comprehensive solution that IPv6 brings.
IPv6 Renumbering Protocol
Another impact of IPv4's redunance relates to the ongoing requirement in many enterprises to renumber stations. When an business changes ISPs, it may have to either renumber all addresses to correspond with the new ISP-assigned prefix, or implement address translation devices. Renumbering is also a problem for many companies that undergo a merger or an acquisition that require network consolidation.
Address shortages and routing hierarchy problems increasingly are a threat to the network operations of larger companiess, but they also affect small sites even the isolated home worker who dials in to the office via the Internet. Smaller networks can be completely dropped from Internet backbone routing tables if they do not adhere to the address hierarchy. In the current system, ISPs with individual dial in clients cannot allocate IP numbers as freely as they wish. Consequently, many dial-in users must use an address allocated from a pool on a temporary basis. In other cases, small dial providers are forced to share a single IP address among multiple end systems.
As peer to peer computing matures, a unique IP address gives the end users achieve direct connectivity to other users on the Internet to share a wide range of highly productive interactive applications, including real time collaborative authoring, desktop to desktop video and audio, network bulletin boards, and remote teaching. In general, today's environment of limited and poorly allocated addresses is already suboptimal, and it will degrade rapidly in the next few years as countless extra devices are linked to ISP rosters.
The Commerical or Business Advantages of IPv6
The large, flexible address space of IPv6 enables the definition of a flexible, hierarchical global routing architecture with many levels. An IPv6 address hierarchy can be aligned to geographic areas (like the Telstra telephone area code system), with allowances for the large backbone network topologies of provider networks that span geographic areas. (These will need network prefixes that aren't essentially geographic.) Using CIDR-style flexible prefixes, the IPv6 address space can be allocated in a way that facilitates route summarization and controls expansion of route tables in backbone routers. IPv6 addressing indicates that large business can avoid private address spaces indefinitely. It also implies that ISPs will have enough addresses to allocate to smaller businesses and dial in users that need globally unique addresses to fully exploit the Internet. In terms of the telephony metaphor: IPv6 addressing lets the network industry go beyond the current "party line" era, which, for many of today's internetwork users, is similar to the early period of the phone industry, when consumers had to share phone lines with neighbours.
Reducing Address Administration Workloads
IPv4 networks often apply the vibrant Host Configuration Protocol (DHCP) to cut the effort associated with manually assigning addresses to computers. DHCP is termed a "stateful" address configuration tool since it maintains static tables that determine which addresses are assigned to new or moved stations. A new version of DHCP is being developed for IPv6 to provide similar stateful address assignment.
IPv6 also include a new dimension to autoconfiguration with a "stateless" address autoconfiguration service that does not need a manually configured server. Stateless autoconfiguration makes it possible for stations to configure their own addresses with the assistance of a local IPv6 router. Generally, the station combines its 48-bit MAC address with a network prefix it learns from a neighboring router.
The robust autoconfiguration capabilities of IPv6 will be a positive to internetwork users at many levels. When a business is forced to renumber because of an ISP change, IPv6 autoconfiguration will permit hosts to be given new prefixes without manual reconfiguration of workstation or DHCP addressing. This function is also very useful on a smaller scale in businesses that have diffculties keeping updated with the moves and changes of vibrant end user populations. Autoconfiguration is even an crucial enabler of mobile computing because it gives mobile computers to receive valid IP addresses automatically, no matter where they connect to the network.
IPv6's Streamlined Format
IPv6 streamlines and enhances the basic header layout of the IP packet, improving greatly on IPv4 (see Figure 2). In IPv6, some of the IPv4 headers were dropped and others were made optional. The redesigned, simplified packet structure will, to some extent, offset the bandwidth cost of the bigger IPv6 address fields. The 16-byte IPv6 addresses are four times bigger than the 4-byte IPv4 addresses, but as a result of the retooling, the total IPv6 header size is only twice as large.
Besides the streamlined packet format, IPv6 features improve support for header extensions and options, changing the way IP header options are encoded to enable more efficient forwarding. Optional IPv6 header information is depicted in independent "extension headers" located after the IPv6 header and before the transport-layer header in each packet. Most IPv6 extension headers are not scrutinized or processed by intermediate nodes (which was the case with IPv4). IPv6 header extensions are now variable in length and have less stringent length limits. IPv6 gives network software designers a very straightforward technique for introducing new header options in the future.
Option fields already have been defined for trasmitting explicit routing information created by the source node, in addition facilitating authentication, encryption, and fragmentation control. At the application level, header extensions are available for specialized end-to-end network applications that require their own header fields within the IP packet.
Robust Native Security
Encryption, authentication, and data integrity safeguards are increasingly a standard aspect of enterprise internetworking. Traditionally, vendors in the IPv4 arena have been less than successful in adding robust security features to Network Layer components. This is largely due to the lack of interoperability caused by proprietary security extensions.
To solve this situation, IPv6 provides native data security capabilities that are based on its flexible header extensions. The authentication header extension to IPv6 ensures that a packet is actually originated from the host indicated in its source address. This authentication is particularly crucial to safeguard against intruders who configure a host to generate packets with forged source addresses. This type of source address masquerading can spoof a server so that access may be gained to valuable data, passwords, or network control utilities. According to recent studies, IP spoofing is statistically one of the most common forms of deliberate intrusion, and with IPv4 there is no native way for a server to determine whether packets are being received from the legitimate endstation. Some enterprises have responded by installing proprietary firewalls in place, but these devices can introduce a number of new problems, including performance bottlenecks, restrictive network policies, and limited connectivity to the Internet.
The native authentication of IPv6 enables the industry a standards-based method to determine the authenticity of packets received at the Network Layer. Since the authentication headers in IPv6 are defined in IETF standards, it is highly likely that network products from different vendors will achieve interoperable authentication services. IPv6 implementations are required to support the MD5 algorithm for authentication and integrity checking, but since the specification is algorithm independent, other techniques may be utiliszed. IPv6 authentication is particularly valuable where autoconfiguration is deployed. Without Network Layer authentication, network intruders may take advantage of DHCP and similar services to gain unassisted entry to a network. IPv6 authentication can warrant that illicit autoconfiguration does not occur.
Confidentiality and Higher Privacy for Business
Along with packet spoofing, another major hole in Internet security is the widespread deployment of traffic analyzers and network "sniffers," which can covertly eavesdrop on network traffic. These generally helpful diagnostic devices can be misused by those seeking access to credit card and bank account numbers, passwords, trade secrets, and other valuable data. IPv4 provides no native data encryption scheme, so this must be accomplished in a less-than-interoperable manner, often at a higher layer.
IPv6 authentication headers do not allow privacy or confidentiality of data, so this is achieved with another standard header extension that provides end to end encryption at the Network Layer. IPv6 encryption headers enables fields that transmit encryption keys and other handshaking information, enabling interoperable encryption of the payloads in IP packets. IPv6 security headers can be used directly between hosts or in conjunction with a specialized security gateway that provides an additional level of security with its own packet signing and encryption methods.
Better Multicast and Anycast for Business
One of the fastest growing business requirements for internetworks is the ability to carry a stream of video, audio, news, financial, or other timely data to a group of functionally related but dispersed endstations. This is best accomplished by Network Layer multicasting techniques. Generally, a server sends out a stream of multimedia or time-sensitive data that needs to be received by subscribers. A multicast-capable network can automatically replicate the server's packets and route them to each subscriber in the multicast group using an efficient path (see Figure 3). Routers use multicast protocols such as DVMRP (Distance Vector Multicast Routing Protocol) and MOSPF (Multicast Open Shortest Path First) to vibrantally converge a packet distribution "tree" that connects all members of a group with the multicast server.
A new member becomes a member of a multicast group by sending a "join" message to a nearby router. The distribution tree is then adjusted to add the new route. Multicast services implies that servers can deliver a single packet that will be replicated and forwarded through the internetwork to the multicast group on demand basis. This maintains both server and network resources and, as a result, is superior to unicast and broadcast solutions. Multicast applications are being designed for IPv4, but IPv6 extends IP multicasting capabilities by defining a very large multicast address space and a scope identifier that is used to restrict the extent to which multicast routing information is propagated throughout an businesses. Multicasting is an crucial feature of IPv6, and it actually replaces the IPv4 broadcast feature by supporting both functions.
Anycast Specifications in IPv6 for Business
Anycast services are another innovation of the IPv6 specification that is not found in IPv4. Conceptually, anycast is a cross between unicast and multicast: Two or more interfaces on an arbitrary number of nodes are designated as an anycast group. A packet addressed to the group's anycast address is delivered to only one of the interfaces in the group, typically the "nearest" interface in the group, according to current routing protocol metrics. This is in contrast with multicast services, which deliver packets to all members of the multicast group. Nodes in an anycast group are specially configured to recognize anycast addresses, which are drawn from the unicast address space.
Anycasting is a new service, and its applications have not been envisioned fully. Initially, it is recommended that anycast addresses be restricted to intermediate nodes. This would enable, for example, an businesses to use a single anycast address to forward packets to a number of different routers on its ISPs backbone (see Figure 4). If all of a provider's routers have the same anycast address, traffic from the enterprise will have several redundant access points to the Internet. And if one of the backbone routers goes down, the next nearest device automatically will receive the traffic.
As anycast matures, it may become an vital method for allowing endstations to efficiently access well-known services, mirrored databases, Web sites, and message servers. For instance, a corporation with several Lotus Notes servers could give interfaces on these devices the same anycast address. Packets from end-user Notes applications would be automatically forwarded to the nearest interface in the anycast group. Essentially, this is a highly flexible and cost effective method of application load balancing. Anycast services could even be used to provide redundancy in the routing process by assigning all the DNS servers in an enterprise the same anycast address.
Quality of Service in IPv6 for Business
The IPv6 packet format contains a new 24-bit traffic-flow identification field that will be of great value to vendors who implement quality-of-service network functions. Network-layer Quality of Service (QoS) products are still in the planning stage, but IPv6 lays the foundation so that a wide range of QoS functions may be made available in a highly open and interoperable manner.
In action, IPv6 flow labels can be used to identify to the network a stream of packets that needs special handling above and beyond the default, best-effort forwarding. Flow-based routing could give internetworks some of the deterministic characteristics associated with connection-oriented switching technology and telephony virtual circuits. For example, desktop video or audio streams could be given a flow label that tells routers they need a controlled amount of end-to-end latency. Flow labels can also be used to give traffic flows a specific level of security, propagation delay (e.g., satellite transmission), or cost. Experimental work with non-standard IPv4 QoS implementations has already shown that it is quite feasible to convey video and audio streams across the mesh internetwork topologies without excessive degradation. IPv6 paves the way for production application of this sort.
The Transition to IPv6 for Business
Few in the industry would argue with the principle that IPv6 represents a major leap forward for the Internet and the enterprises that rely on internetworking technology. IPv6 improves on IPv4 in many areas that are of great near-term and long-term value to network-dependent businesses. What is not agreed upon in the industry, however, is what shape and speed the transition from IPv4 to IPv6 will take. Some are lobbying for a wholesale, rapid adoption of IPv6 in the very near future. Others prefer to let the IPv6 project wait until address-space exhaustion and other issues force conversion. But given the magnitude of a migration that affects so many millions of network devices, it is clear that there will be an extended period when IPv4 and IPv6 will coexist at many levels of the Internet.
With the reality of extended IPv4/IPv6 coexistence looming, IETF protocol designers have expended a substantial amount of effort to ensure that hosts and routers can be upgraded to IPv6 in a graceful, incremental manner. Great pains have been taken to ensure that the transition will not entail large scale redudancies of IPv4 nodes or "fork-lift" upgrades for entire user populations in a short time frame. Transition mechanisms have been designed to enable network administrators a large amount of flexibility in how and when they upgrade hosts and intermediate nodes. Hence, IPv6 can be deployed in hosts first, in routers first, or, alternatively, in a restricted number of adjacent or remote hosts and routers. The nodes that are upgraded initially do not have to be colocated in the same local area network or campus.
Another assumption made by IPv6 transition designers is the likelihood that many upgraded hosts and routers will need to retain downward compatibility with IPv4 devices for an extended time period (possibly years or even indefinitely). It was also assumed that upgraded devices should have the option of retaining their IPv4 addressing. To accomplish these goals, IPv6 transition relies on several special functions that have been built into the IPv6 standards work, including dual-stack hosts and routers and tunnelling IPv6 via IPv4.
The Benefit of the Dual Stack Transition Method in IPv6
Once a few nodes have been converted to IPv6, there is the strong possibility that these nodes will require continued interaction with existing IPv4 nodes. This is accomplished with the dual-stack IPv4/IPv6 approach. A great many hosts and routers in today's multivendor, multiplatform networking environment already support multiple network stack components. For instance, the majority of routers in enterprise networks are of the multiprotocol variety. Likewise, many workstations run some combination of IPv4, IPX, AppleTalk, NetBIOS, SNA, DECnet, or other protocols. The inclusion of one additional protocol (IPv6) on an endstation or router is a fairly trivial undertaking at the current time. When running a dual IPv4/IPv6 stack, a host has access to both IPv4 and IPv6 resources. Routers running both protocols can forward traffic for both IPv4 and IPv6 end nodes.
Dual-stack machines can use totally independent IPv4 and IPv6 addresses, or they can be configured with an IPv6 address that is IPv4-compatible. Dual-stack nodes can use conventional IPv4 autoconfiguration services (DHCP) to obtain their IPv4 addresses. IPv6 addresses can be manually configured in the 128-bit local host tables, or obtained via IPv6 stateless or stateful autoconfiguration mechanisms, when available. It is expected that major servers will run in dual-stack mode indefinitely, or until all active nodes are converted to IPv6.
Improved IPv6 DNS
Domain Name Service is something that administrators must consider before deploying IPv6 or dual-stack hosts. The current 32-bit name servers cannot handle name-resolution requests for 128-bit addresses used by IPv6 devices. In response to this issue, IETF designers have defined an IPv6 DNS standard (RFC 1886, DNS Extensions to Support IP Version 6). This specification creates a new 128-bit DNS record type named "AAAA" (quad A) that will map domain names to an IPv6 address. Domain name lookups (reverse lookups) based on 128-bit addresses also are defined. Once an IPv6-capable DNS is in place, dual-stack hosts can interact interchangeably with IPv6 nodes. If a dual-stack host queries a DNS and receives back a 32-bit address, IPv4 is used; if a 128-bit address is received, then IPv6 is used. On sites where the DNS has not been upgraded to IPv6, hosts may resolve name-to-address mappings through the use of manually configured local name tables.
Applications that do not directly access the network stack will not need to be modified to run in the dual-stack environment. Network applications that directly interface with IP and related components will require updating if they are to use the IPv6 protocol. For example, applications that access the DNS must be enhanced with the capability to request the new 128-bit records -- a fairly trivial change. Applications that exploit IPv6 security, quality of service, and other features will need more extensive updating.
Routing in IPv6/IPv4 Networks
Routers running both IPv6 and IPv4 can be administered in much the same fashion that IPv4-only networks are currently administered. IPv6 versions of popular routing protocols, such as Open Shortest Path First (OSPF) and Routing Information Protocol (RIP), are already under development. In many cases, administrators will choose to keep the IPv6 topology logically separate from the IPv4 network, even though both run on the same physical infrastructure. This will allow the two to be administered separately. In other cases, it may be advantageous to align the two architectures by using the same domain boundaries, areas, and subnet enterprises. Both approaches have their advantages. A separate IPv6 architecture can be used to abolish the chaotic, inefficient IPv4 addressing systems with which many of today's enterprises suffer. An independent IPv6 architecture presents the opportunity to build a fresh, hierarchical network address plan that will obviously facilitate connection to one or more ISPs. This lays a foundation for efficient renumbering, route aggregation, and the other goals of an advanced internetwork routing hierarchy.
In most organizations where IPv6 is deployed incrementally, there is the strong chance that all IPv6 hosts will not have direct connectivity to each other through IPv6 routers. In many cases there will be islands of IPv6 topology surrounded by an ocean of IPv4. Favourably, IPv6 designers have fashioned transition mechanisms that allow IPv6 hosts to communicate over intervening IPv4 networks. The essential technique of these mechanisms is IPv6 over IPv4 tunnelling, which encapsulates IPv6 packets in IPv4 packets (see Figure 5).
Tunnelling allows new IPv6 implementations to take advantage of existing IPv4 infrastructure without changes to IPv4 components. A dual stack router or host on the "edge" of the IPv6 topology simply attach to an IPv4 header to each IPv6 packet and carrys it as native IPv4 traffic through existing links. IPv4 routers forward this traffic without knowledge that IPv6 is involved. On the other side of the tunnel, another dual stack router or host de encapsulates the IPv6 packet and routes it to the target destination using standard IPv6 protocols.
To accommodate different administrative requirements, IPv6 transition mechanisms include two types of tunnelling: automatic and configured. To design configured tunnels, administrators manually define IPv6 to IPv4 address mappings at tunnel endpoints. On either side of the tunnel, traffic is transmitted with full 128-bit addresses. At the tunnel entry point, a router table entry is defined manually to tell which IPv4 address is allowed to traverse the tunnel. This requires a certain extent of manual administration at the tunnel endpoints, but traffic is routed through the IPv4 topology vibrantally, without the knowledge of IPv4 routers. The 128-bit addresses do not have to align with 32-bit addresses in any way.
Automatic Tunnelling
Automatic tunnels use "IPv4-compatible" addresses, which are hybrid IPv4/IPv6 addresses. Compatible addresses are made by adding leading zeros to the 32-bit IPv4 address to elongate them out to 128 bits. When traffic is forwarded with compatible addresses, the device at the tunnel entry point can automatically address encapsulated traffic by simply converting the IPv4-compatible 128-bit address to a 32-bit IPv4 address. On the other side of the tunnel, the IPv4 header is eliminated to unveil the original IPv6 address. Automatic tunnelling allows IPv6 hosts to vibrantally exploit IPv4 networks, but it does require the use of IPv4-compatible addresses, which do not bring the benefits of the128-bit address space.
IPv6 nodes using IPv4 compatible addresses cannot take advantage of the extended address space, but they can exploit the other IPv6 enhancements, including flow labels, authentication, encryption, multicast, and anycast. Once a node is migrated to IPv6 with IPv4 compatible addressing, the door is open for a very smooth transition to the full IPv6 address space with the assistance of an IPv6 based autoconfiguration service . IPv4 compatible addressing suggest that administrators can add IPv6 nodes while initially preserving their basic addressing and subnet architecture. Automatic tunnels are available when required, but they may not be used in cases where major backbone routers are upgraded all at once to include the IPv6 stack. This is something that can be achieved quickly and efficiently when backbone routers support full remote configuration and upgrade capabilities (e.g., Bay Networks Backbone Node and Access Node routers).
IETF members are putting as much effort into transition as they are the basic IPv6 protocol specification. It is assumed that the combination of tunnels, compatible addresses, and dual stack nodes ensures that network administrators will have an enormous range of flexibility and interoperability when they deploy IPv6. Transition services allow network dependent organizations to take advantage of the rich array of more technical IPv6 features.
ConclusionThe Business strategy for transforming today's networks into the IPv6 optimized networks of tomorrow, is pre empted on four main technologies: routing switches, management, access, and IP services. Business support for IPv6 is an vital element of its IP services strategy, and must consists of Enabling Services, Application Services, and Integration Services to deliver full IPv6 functionality.
IPv6 features such as encryption, tunneling, stateless autoconfiguration, are part of the Enabling Services group, enabling Internet Service Providers to provide new and value add services while improving the overall quality of network usage for business customers. And the implementation of IPv6 based migration strategies, such as dual stack and tunneling, are part of Integration Services group by allowing a smooth migration to the new protocol.
With diverse businessendorsement for transistion to IPv6, business can strengthens their leadership in the area of IP services and moves customers closer to their overall objective of optimising their networks for IP. IPv6 is a technology that enterprises must use as a highly complementary to the Internet industry or online world for conducting electroinc commerce, business to business transactions, electronic commerce for small business and Internet banking and financial transactions for financial institutions and consumers.
References:
Bay Networks, 1997, IPv6 White Paper [online]. Available
http://partnerweb.baynetworks.com/Products/Routers/Protocols/2789.html
Internet Architecture Board,19 Jan 1999, IPv6 The Business Case ftp://ftp.isi.edu/internet-drafts/draft-ietf-iab-case-for-ipv6-04.txt
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