Wednesday, September 21, 2011
IPv6 Transitional Uncertainties and the role of R&E networks and universities
[Here is an excellent article on the uncertainties of IPv6 transition. R&E networks and universities probably have the single largest number of unallocated IPv4 address space.
Therefore I think they have a critical role in enabling and ensuring a smooth transition from IPv4 to some future network addressing scheme that enshrines the end-to-end principle and layer Internet architecture. Providing address blocks to open access community networks as part of the institution’s address space, retiring IP address blocks to insure elimination of energy hogging servers, partnering on deployment of R&E IPv6 3G/4G wireless networks, etc are some of the ideas I have blogged about in the past on how R&E networks can help in this transition.
Although I agree with Geoff that we need to prevent accidental transitional strategy, I remain skeptical that IPv6 is the future nirvana of networking. Maybe it is time to start thinking beyond IPv6 and DNS and look for solutions that are not only backwards compatible, but also provide significant new value to the end user. Alphanumeric addressing, XML routing, delay tolerant networking, etc are some of the ideas floating out there. –BSA]
Moving Beyond IPv6 and DNS
The Address plus Port (A+P) Approach to the IPv4 Address Shortage
IPv6 Transitional Uncertainties
By Geoff Huston
When we look back at previous technology transitions in our industry, they all look just so logical.
What about the transition from IPv4 to IPv6? Is this also an inevitable transition? There is no doubt that the designers of IPv6 certainly envisaged this as an inevitable transition. But there are some challenges here.
The first is that the transition does not provide for backwards compatibility. A host cannot switch from using IPv4 to IPv6 and still communicate with all the hosts still using IPv4. So the transition has an essential "dual stack" phase where, during the transition, hosts operate with both protocol stacks concurrently, using the IPv6 protocol stack to speak to other IPv6 hosts and the IPv4 protocol stack to speak to other IPv4 hosts. This lack of backwards compatibility in IPv6 makes the transition slightly more complex, but not prohibitively so. What it means is that applications and host operating systems need to be aware of IPv6 and explicitly have capabilities to use IPv6. It's not a seamless augmentation at the application interface level.
There an additional challenge here that is formidable, and one that was largely unforeseen when IPv6 was being designed. At the time there was the general impression that the telecommunications industry behaved prudently, and given the warnings of the prospect of exhaustion of the IPv4 address space, industry actors, being prudent and risk averse, would embark on the transition to IPv6 well in advance of IPv4 address exhaustion. And one or two did. But everyone else did not. And now we have the challenge of trying to undertake this dual stack transition while one stack is critically short of further address space. This factor radically alters the dynamics of the transition. In order to make the IPv4 part of the transition work for the requisite number of additional years it will be necessary to deploy additional "middleware" in the network, and head in a different direction architecturally.
The most obvious shift is probably going to be one of deployment of Carrier Grade NATs (CGNs) in access networks. This will allow a single public IPv4 address to be shared across multiple end clients. The longer the transition takes the more likely that this alone will not be sufficient, and we may expect to see a push to re-architect content into Content Distribution Networks that have points of presence in major access networks. It is also possible that network providers may resort to Application Level Gateways (ALGs) and managed services in an effort to further contain the level of IPv4 address and port consumption by user services.
The risk here is that after making this additional capital investment in network infrastructure, the network service provider is then highly motivated to protect the value of this investment. What lengths will network service providers be prepared to go to in order to protect this investment in transitional services? And if these transitional services generate higher revenues for the network service provider than basic commodity packet transit services, to what extent is the network service provider then motivated to lock itself into this "transitional" service model for an extended period? Would this imply that rather than being a transitory state we see these changes to the network lasting for an indefinite period.
If one sector of the industry finds that this transitional model of providing services sufficiently attractive, is it possible that it could have sufficient market influence such the entire service provider industry collectively locks into this "transitional" model as an enduring service model? If this was to eventuate the internet would be driven in an entirely different direction than IPv6!
The challenge we face is to sustain the IPv4 half of the dual stack environment in the face of continuing escalation of demand for addresses. For many years the conventional networking environment has included the use of a NAT device at the interface between the network and the user. Increased pressure on addresses is now forcing network service providers to place a second level of NAT inside their network as part of the network infrastructure.
This process of transition is expected to take many years, I have heard commentary to suggest that five years is unrealistically short, and we should expect a transition that may take a decade or longer. But will CGNs last for a further decade of network growth during this extended transition? The next step after CGNs is to break apart the end-to-end network model and start to erect connectivity "barriers" or "walled gardens". The tools to do this include re-homing a copy of certain content "inside" the network as a next step, then, as a further step in address 'compression', using application level gateways rather than address level IP header translators.
The current approach to IPv4 exhaustion will see different regions experiencing different IPv4 scarcity pressures at any point in time. In the Asia Pacific Region the momentum to deploy CGNs as the first response to IPv4 address scarcity is already visible. However, other regions are not experiencing the same pressure at this time. If one were to project this further forward by 18 months to 2013 the European region would also have exhausted its pool of IPv4 addresses, but the other three regions may well be operating in a mode that is still able to meet regional demands for IPv4 addresses. It is highly likely that at that time the different regions will be experiencing very different market pressures for the provision of Internet services, due to differing transitional pressures from IPv4 exhaustion.
The consequent question is: What's the level of risk that the differing environments of transition lead to significantly different outcomes in each region as the process of transition takes of a different momentum in different regions? And if this eventuates will we still have a single coherent Internet as a common asset, or will we find that market forces interact in unpredictable ways that create different outcomes in each region?
What of the plan to ultimately converge to an IPv6 network? It may be useful to remember the myth of the long term plan. Are we still as firmly committed to the long term plans we formulated 5 or 10 years ago? Or have we found that our plans are continually modified and refined over time, and there is actually little left of the original plan. So will we be as firmly committed to the transition to IPv6 in five years time? Or will we manage to lose the plot and head into different directions because of the different spread of pressures on service providers in each of the regions. We will forget about the intention to preserve the concept of a single global network in amidst the difficulties of this disparate transition?
On Maintaining the Momentum for IPv6
Can we help the Internet during this transition, and try to ensure that the Internet remains a single coherent network with some essential architectural attributes of end-to-end clarity? Or, if we want to aim a little lower, can we at least minimize the potential for disastrous long term damage to this phenomenally productive and valuable networking environment that the Internet has enabled?
I don't know the answer to those questions, but I would like to offer a small number of thoughts that I have had when thinking about this topic.
If we want a single working Internet at the end of all of this, then we need to keep an eye on the larger picture of network evolution during transition. We need to find ways for self interest and local interest to converge with what is in our common interest. Without that convergence we will see a form of market failure where the common interest of a single global network, and the value that such a service can generate, being lost to network divergence through the exercise of differing local market pressures. I'm not sure that I understand how to ensure that self interest aligns with common interest in every circumstance, but what would be good to avoid is building a network that imposes major barriers and inefficiencies all in the name of address conservation in IPv4, and then citing the investment in this additional infrastructure as grounds for not progressing with the transition to IPv6.
Secondly, IPv4 addresses should be used in working networks and not hoarded. Its probably a natural reaction to impending scarcity to hoard a resource, but its not necessarily a good reaction. Hoarding behaviour exacerbates the scarcity of the resource in both its intensity and duration. This generalization is also true in the specific context of IPv4 exhaustion and transition. The scarcity of IPv4 addresses creates market uncertainty and market pain in the form of a reduced revenue outlook across the transition period. Extending this scarcity through hoarding and other forms of witholding addresses from use in the network acts to prolong the market pain and increase the unpredictability of the entire transition process.
And finally, we need to keep the transition as quick as possible. A rapid transition represents the best chance of achieving an IPv6 network as an outcome of this process. The more time we spend investing time, money and effort in deploying IPv4 address extension mechanisms, the higher the risk that we will lose track of the temporary nature of transition and the higher the possibility that we'll get stuck with the wrong Internet at the end! If we are truly committed to achieving a single and coherent IPv6 Internet then perhaps its necessary to act now to compress the timelines for transition, not extend them!
By Geoff Huston, Author & Chief Scientist at APNIC. (The above views do not necessarily represent the views of the Asia Pacific Network Information Centre.)
Related topics: IP Addressing, IPv6, Regional Registries, Top-Level Domains
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at 6:44 AM