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NE40E V800R010C00 Feature Description - NAT and IPv6 Transition 01

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Centralized DS-Lite Deployment Solution

Centralized DS-Lite Deployment Solution

Networking Description

Figure 4-5 shows a centralized Dual-Stack Lite (DS-Lite) scenario. Each routed customer premises equipment (CPE) runs Point-to-Point Protocol over Ethernet IPv6 (PPPoEv6) or IPv6 over Ethernet (IPoEv6) to dial up to log in to a broadband remote access server (BRAS). The BRASs are not equipped with Carrier Grade NAT (CGN) boards. Each BRAS assigns an IPv6 address to the connected CPE's WAN interface and an IPv6 address prefix to the CPE's LAN interface. Each CPE assigns a private IPv4 address to a residential terminal and uses the IPv6 address prefix to assign an IPv6 address to the residential terminal. The CPE uses the IPv6 address of the WAN interface to establish a tunnel to a CGN device.

A CPE directly forwards user IPv6 packets over routes. The CPE encapsulates user IPv4 packets into IPv4 over IPv6 packets before forwarding them, in which the source IP address is set to the CPE's WAN interface address and the destination address is set to the CGN device's IPv6 address specified in a DS-Lite instance.

Upon receipt of the user packets along the IPv4 over IPv6 tunnel, the BRAS forwards them at Layer 3 to the CGN device. The CGN device decapsulates the packets, replaces the source IPv4 address and port number in each packet, and forwards the packets to the IPv4 network. Since DS-Lite functions are deployed on a CGN device attached to the BRAS, this solution is called centralized DS-Lite.

Figure 4-5  Centralized DS-Lite solution

Address Allocation Solution

A BRAS assigns an IPv6 address to the CPE, and the CPE assigns a private IPv4 address to a PC. A CGN device assigns a public IPv4 address and port range to the CPE.

DS-Lite Translation

The CPE functions as a Dynamic Host Configuration Protocolv4 (DHCPv4) server to assign an IPv4 address (for example, to each residential user, and the BRAS assigns IPv6 addresses only. Before a residential user accesses IPv4 services, the user sends a packet with a private IPv4 address along an IPv4-in-IPv6 tunnel to a CGN device. The CGN device translates the private IPv4 address to a public IPv4 address. The CGN device forwards the user packet along an IPv4 over IPv6 tunnel to the CPE. Upon receipt of the user packet, the CPE forwards it to the IPv4 network to access IPv4 services.

Updated: 2018-07-04

Document ID: EDOC1100027155

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