Computer network technologies and services by Unknown

Author:Unknown
Language: eng
Format: azw3
Published: 2016-02-25T16:00:00+00:00

4.2.4 DS-Lite A+P

IPv6-only network 1 R1

IPv6-only network 2 R2 IPv6-only ISP NAT IPv4-only network

AFTR

IPv6-only network 3 R3 Dual-Stack Lite Address+Port (DS-Lite A+P) solution consists in still having a provider’s IPv6-only network, but the NAT is moved onto the CPE so that the user can configure it according his needs.

Like in DS-Lite, an IPv4 packet outcoming from the CPE is still tunnelized as the provider’s network is IPv6-only.

The fact that the NAT on every CPE requires a public IPv4 address is solved by allowing to duplicate public IPv4 addresses, and the CPEs are distinguished based on the port. In fact each CPE uses a specific port range, and the AFTR, knowing the port range used by every CPE, is able to distinguish flows from and to a specific CPE nevertheless there are several CPEs having the same public IPv4 address.

This solution is similar to the DS-Lite one, but the private IPv4 address space is more under the control of the end user, because as the NAT is on the user’s CPE the user can configure it, even if with some limitations: he can not open and use ports which are not within his range. This method allows to save IPv4 addresses (but still less with respect to DS-Lite).

This solution in Italy is basically illegal because, as the port number is not recorded, in case of attack it would not be possible to trace back to the attacker.

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