Hello!
This time I would like to share with you an overview of one of the most important techniques that will ease the transition from IPv4 to IPv6. Hope you find it useful!
Introduction
Carriers had to face the IPv4 depletion after the Internet Assigned Numbers Authority (IANA) had assigned the last two IPv4 address groups with the mask length of 8 bits in February 2011. Existing address resources can only be used in the short-term running of telecom carrier networks, which cannot meet demands for long-term service development. Existing solutions, such as IPv4 re-addressing or reusing, can only relieve the address exhaustion. Therefore, introducing of IPv6 was considered as the ultimate and direct solution. IPv6, however, brought no commercial opportunities, and existing alternative solutions meet carrier deployment requirement. As a result, there is no sufficient motive to replace IPv4 networks with IPv6 networks.
A good way to implement IPv4-to-IPv6 transition is to deploy NAT and build IPv4 and IPv6 dual-stack networks with dual-stack hosts. Maintaining both IPv4 and IPv6 networks increases the operating expense (OPEX), and existing carriers get more benefits from dual-stack networks than new carriers. New carriers prefer IPv6-only networks because their networks are assigned less IPv4 addresses. In addition, in the later phase of IPv6 evolution, most new networks and services run over IPv6, which makes dual-stack networks less significant. Carriers also face another problem, that existing IPv4 or dual-stack users have to go across IPv6-only networks before accessing IPv4 applications. The DS-Lite technique is used to address such a problem.
Overview of DS-Lite
Basically, Dual-Stack Lite (DS-Lite) uses IPv4-in-IPv6 tunneling and IPv4 Network Address Translation (NAT) techniques to allow private IPv4 users to travel through IPv6 networks to access public IPv4 networks.
In IPv4 to IPv6 transition, IPv6 networks are scaled up, and plans to establish IPv4 networks are being phased out. All backbone networks support the IPv4 and IPv6 dual-logic planes, and new devices on Metropolitan Area Networks (MANs) primarily run either the IPv4/IPv6 dual stack or only IPv6 (by application service providers [ASPs]). IPv6 and IPv4 coexist dynamically and in an order. These network deployment methods help carriers achieve the following goals:
Provide the same user experience when users access IPv6 and IPv4 services.
Allow IPv6 users to properly access IPv4 networks.
Ensure that services are not compromised after IPv4 users are migrated to IPv6 networks.
Since the mainstream operating systems support the IPv4 and IPv6 dual stack and user preferences differ, network providers have to provide both IPv4 and IPv6 services during the transition. This, however, does not mean that networks must support the IPv4 and IPv6 dual stack. In smooth evolution from IPv4 network to IPv6 network, network carriers use different evolution solutions and network models in each evolution phase based on infrastructure.
The tunneling technique is used in the primary phase of network IPv4-to-IPv6 evolution. In this phase, legacy access IPv4 networks cannot be upgraded to IPv6. A few IPv6 users are scattered on the networks. This means the cost of a network upgrade to IPv6 is high, and the input-output ratio is low, reducing the possibility of an upgrade to IPv6. As a result, the churn rate of IPv6 users increases. To address this problem, the tunneling technique can be used to allow IPv6 users to travel through IPv4 networks.
In addition to the tunneling technique, IPv4 and IPv6 dual-stack networks can be deployed. Such networks apply when both IPv4 traffic and IPv6 traffic are in a large volume during transition and when devices on new carrier networks are capable of IPv6. DS-Lite is used on such networks.
DS-Lite Technical Characteristics
Networking for the DS-Lite solution
A DS-Lite network consists of IPv4 and IPv6 dual-stack hosts and IPv6 networks. On a DS-Lite network, customer premises equipment (CPE) functioning as a home gateway and Carrier Grade NAT (CGN) devices functioning as carrier-class gateways run the IPv4 and IPv6 dual stack, and the other network devices run only IPv6. DS-Lite devices must support both IPv4-in-IPv6 tunnels and NAT44. Home users obtain both IPv6 and private IPv4 addresses and send user packets to a CPE. The CPE forwards the packets as follows:
Forwards IPv6 user packets directly to an IPv6-only network.
Forwards IPv4 packets to a DS-Lite device through an IPv4-in-IPv6 tunnel established between the CPE and DS-Lite device. Upon receipt of the packets, the DS-Lite device forwards them to a CGN device. The CGN device decapsulates tunnel information, converts each private IPv4 address to a public IPv4 address, and sends each packet to an IPv4 network.
IPv6-only DS-Lite networks are used when the networks are incapable of maintaining a large number of tunnels on a network, for example, a wireless network that focuses on transport efficiency, whereas tunnels increase costs. IPv6-only DS-Lite networks are also used on new sites or in the later phase of IPv6 evolution.
Conclusion
Even though a full transition from IPv4 to IPv6 is still years away, technologies like DS-Lite are making this process as easy as possible both for carriers and customers.
That’s all folks, hope you found my post useful, and don’t forget to comment if you have further concerns or remarks.
Thank you very much!
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