A new white paper issued by the Siemens Industry Automation Division features the launch of the IPv6 Internet standard. This new address standard will mean that IP (Internet Protocol) addresses will be 128 bits in length in future instead of the present 32. The increase in address space required as a result, will have a lasting effect on development of the ‘Internet of Things’ and consequently will also impact on automation.
IPv6 for automation technology
The introduction of IPv6 in automation technology is more than just a simple quadrupling of the existing 32 bit IPv4 address to a 128 bit address to increase the number of IP addresses. The massively expanded address space also allows us to do without the previously introduced address conversions due to limited IPv4 address space. In future, this will allow problem-free direct communication between end-systems without the complicated and error-prone address acrobatics resulting from network address translation (NAT). There will only be pure ‘end-to-end’ communication in the future. Limiting technologies such as NAT/PAT will no longer be required.
What are the user benefits that will be achieved with the introduction of the new IPv6 technology?
* Consistent diagnosis from the ERP level to the management level all the way down to the field level.
* Hierarchical setup of network structures.
* Optimised routing.
New IT technologies will be based exclusively on IPv6, while simultaneously coexistence between IPv4 and IPv6 must be considered for a long time. Today, there is no longer a question as to whether there will be a transition from IPv4 to IPv6, but when.
In future, IPv6 will be predominant on the ERP level, because new functions within the software will be based directly on IPv6 services. Because of the increasingly close mesh between automation and office IT communication, IPv6-based communication services are of growing importance for integrated diagnostics, including for programmable controllers.
Basics of IPv6
Turning point/initial situation
On February 1, 2011, The Internet Assigned Numbers Authority (IANA) issued the last free address block to the Asia-Pacific Network Information Center (APNIC). With this move, there were no more free IPv4 addresses to distribute to the five Regional Internet Registries (RIRs), who can now only pass on the remaining IPv4 addresses they hold to their customers.
For users of the Internet Protocol IPv4, this meant the switch to the IPv6, defined 15 years earlier, had begun. In the short term, users will still be given IPv4 addresses from the Regional Internet Registry pool, but in the mid-term, worldwide availability using these will not be ensured. The only way out of this is the use of globally unique IPv6 addresses so that end-to-end communication can once again be ensured.
Standardisation
The standardisation, which began in 1998 with RFC 2460 as the official successor to the IPv4 protocol, is today in a stable condition. Many extensions such as the coexistence of IPv4/IPv6, DHCPv6, neighbour discovery, and many more have since been described in the various RFCs. The following RFCs are recommended for more in-depth information:
* RFC 3315, Dynamic Host Configuration Protocol for IPv6.
* RFC 4291, IP Version 6 Addressing Architecture.
* RFC 4294, IPv6 Node Requirements.
* RFC 4862, IPv6 Stateless Address Autoconfiguration.
* RFC 4861, Neighbor Discovery for IP version 6.
IPv6 address structure
In contrast to IPv4, the IPv6 addresses are written in 8 x 16 bit fields of four hexadecimal numbers each. These are separated from each other with a colon. There is always a 64 bit subnet prefix and a 64 bit interface ID.
Mathematically, 340, 282, 366, 920, 938,463,463, 374, 607, 431, 768, 211, 456 addresses are possible. To more or less illustrate this unimaginably large number, every proton in the universe could have its own IP address. Or, in other words, every square metre of the earth’s surface could have 6,5 x 10²³ addresses.
Since sufficient addresses are available to allow unambiguous addressing, and thus a direct connection between nodes, network address translation (NAT) and port address translation (PAT) are no longer necessary.
Many addresses at one interface
With IPv6 addressing, every network interface is given at least one address; in most cases, however, several addresses. Alongside the link-local address (LLA, always formed automatically for each interface), which is important for issuing addresses, this can also include a unique local address (ULA) or even a global address (GA).
Note: The LLA, which is automatically generated by each device and is always unambiguous, allows all devices on the local subnet to be reached via IPv6. The devices are thus always available and diagnosable. Manual configuration or any other setting of the IPv6 address is not necessary.
IPv6 address assignment
One of the most important new features of IPv6 is automatic address assignment. Using the auto-configuration, any IP node can create a unique link-local address itself without requiring manual configuration or a DHCP server.
For additional use of router discovery: further IPv6 addresses; router addresses and configuration parameters are provided to the node. It is hoped that this will significantly reduce the effort required for administration of networks in particular.
Dual stack
The term dual stack generally refers to a complete duplication of the IPv4 and IPv6 stacks across all levels in the protocol stack, from the application layer to the network layer. The dual-stack approach ensures that the further-developed components can always interoperate via IPv4 using only IPv4 components. In automation technology, it ensures compatibility with existing system components.
Investment protection
The introduction of IPv6 is primarily driven by the fact that the address range of the global IP network (Internet) has been exhausted. An expanded address space was defined already many years ago with IPv6 to address this shortage.
Therefore, the implementation of the new addressing primarily affects the backbone area of a company and will later migrate gradually via the IT infrastructure to the automation level. This transition will take a long time and will also make it necessary for the two procedures to exist parallel to each other.
The simultaneous use of IPv4 and IPv6 communication requires above all, from the network perspective, support in the Layer 3 devices (routing). In principle, existing layer 2 devices (switches) allow both IPv4 and IPv6 communication; to support IPv6, however, adjustments on this level are also necessary.
This duality means there is stock protection for existing systems and retrofitting or upgrading is only required in exceptional cases.
Note: Due to space constraints, this White Paper had to be edited for print. The full document, including OPC and PLC examples can be viewed at http://instrumentation.co.za/+C17490
For more information contact Keshin Govender, Siemens Southern Africa, +27 (0)11 652 2412, [email protected], www.siemens.co.za
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