IPv6 – Optimal protocol to build the Internet

Box 1: IP (Internet Protocol) is one of the primary protocols making up the Internet today. Ipv6 (Internet Protocol version 6) is the next generation intended to replace IPv4. The main reason for this change is the limitation on the number of addresses that IPv4 can provide.

Box 2: Ipv6 has many advantages compared to Ipv4, such as: large address space, simplified configuration by SLAAC technology and more optimal routing.

The situation: Due to the shortage of Ipv4 addresses and the proliferation of loT devices, FPT Telecom has accelerated the deployment of Ipv6 to meet growing demand.

Figure 1 – IPv6 transition roadmap of FPT Telecom (source:
The development process: For the best result in the shortest time, surveys and consultation from world-leading ISPs is very important. Therefore FPT Telecom has consulted partners such as Microsoft, Juniper and large ISPs like AT&T... to find a solution for the deployment of IPv6  which suits its own circumstances.

6PE, 6VPE technologies are to be deployed for the core network to support rapid, low-risk development of infrastructure. These technologies enable the deployment of IPv6 to offer most of the services provided by FPT Telecom.

 Figure 2 - Logical model design of 6PE technology
To ensure the stability of its services once IPv6 is more widely deployed, FPT Telecom has chosen Dual Stack solution for broadband service customers without changing terminals.

Figure 3 – DualStack Model Design
The continuous challenges
The initial challenge in deploying IPv6 was that legacy modems did not support this technology. The temporary solution used the computer or third-party firmware to support IPv6 in lab environment. Currently almost all modems provided by FPT Telecom support IPv6 properly.
The next challenge was that there were many customer complaints about loss of Internet connection. The response team found out the modems did not function correctly with DNS protocol, while online customers could not resolve their DNS. The team promptly worked with the modem vendor to fix those firmware bugs.
Difficulties kept piling up as the access infrastructure ran into problems with inconsistent IPv6 support of the PON port on OLT devices. As a result, deploying one IPv6 profile for all customers would cause errors on devices which do not support IPv6 well. Thus the team had to change their design to provide a separate profile for each individual customer.

Improving product quality
By analysis of collected data, the technical team found out that during a long trial, customers suffered from unstable IPv6 connection. This was a relatively difficult problem because the number of IPv6 customers had reached 300 000. After nearly one month of research and close collaboration of technical units, it was found that the modem was programmed incorrectly in MAC address declaration in the DHCPv6 process. This caused some MAC addresses to overlap with each other. Currently every modem is being updated with corrected firmware.
When there were approximately 100,000 customers using IPv6, the RADIUS system was overloaded from storing IPv6 addresses for each customer. To increase system scalability, the technical team had to redesign BRAS equipment so that when customers are online, they would use IPv6 addresses provided by BRAS instead of RADIUS. This distributed provision of addresses is much more scalable than centralized provision.

Positive results
Currently FPT Telecom has started to see greater success, being the first ISP to have completed the IPv6 deployment plan for over 600 000 customers. In the global market, the company has proven its fast deployment capability with high quality, being ranked 12th among companies offering this service in the world. The amount of traffic in the IPv6 network is about 370Gbps. The main content pages of FPT such as Fshare and VnExpress have also had IPv6 support.