In IPv6 blog series, we covered the NAT64 transition technologies - that allows IPv6 hosts to communicate with IPv4 resources on the network and 6rd - allowing IPv6 traffic tunneled over the IPv4 network. When service providers want to migrate their core network to IPv6, they must ensure that the existing IPv4 users continue to have access to IPv4 Internet as before. This is where DS-Lite comes - it is a tunnel technology that encapsulates IPv4 packets in IPv6 transport for delivery to the final destination IPv4. DS Lite combines IPv4 tunnel IPv6 with NAT - NAT performs IPv4-IPv4 translation before sending packets to a public IPv4 network
DS-Lite allows to allocate natively service providers IPv6 addresses new clients while continuing to. support IPv4 clients. The main functional components involved in DS-Lite B4 (Basic Bridging BroadBand) and AFTR (Address Family Translation Router) as shown in the figure below:
In a DS Lite enabled network, the subscriber device provides B4 features. Client device allocates private IPv4 addresses to the hosts in the home / customer networks. B4 connects with the service provider's access network using the IPv6 address assigned by the service provider uses this IPv6 address to establish a tunnel with the AFTR device.
AFTR is usually deployed at the edge of IPv6 network service provider and ends the tunnel created with the customer element B4. AFTR also provides IPv4 IPv4 NAT to translate the customer's address IPv4 private to public IPv4 addresses before sending packets to the public network
After sequence describes the connection setup process using DS Lite :.
- host with private IPv4 address initiates a connection to a resource on the public Internet
- traffic is sent to B4, which is the default gateway
- B4, using its service provider network facing IPv6 addresses establishes the tunnel with AFTR. AFTR address can be pre-configured or can be ascertained using DHCPv6
- B4 encapsulates the IPv4 packet in IPv6 transport and sent through to AFTR
- AFTR Ends tunnel and de-encapsulated IPv4 packet
- AFTR IPv4 IPv4 NAT device performs before sending traffic to the destination IPv4 network
There are many benefits that DS Lite provides:
- A lightweight solution to allow IPv4 connectivity to the IPv6 network
- avoids the need for multiple levels of NAT as in the case of LSN
- enables service providers to move their core networks and access to IPv6 and enabling them to enjoy the benefits of IPv6
- Allows coexistence of IPv4 and IPv6
- help to solve IPv4 address scarcity issue
- Enables seamless migration of native IPv6 environment
But as is always the case, the benefits are not without their own set of challenges:
- DS Lite does not provide IPv6 and IPv4 hosts to talk to each other
- Increases the size of the traffic due to the tunnel headers - requires that the MTU leadership to avoid fragmentation
- need to manage and maintain the links between the addresses of the clients and public addresses used for translation in AFTR device
- brings additional challenges for IPR provider service network
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