Free DNS service Anycast DNS technology prepared for the international domain name system Free – to ensure the security of domain names as well as quick updates of domain name records . The system is connected throughout the world should not have died DNS story long and fast DNS updating

Tell on Anycast you can refer to the following introduction

Anycast DNS technology

I. Anycast concept

I.1. Anycast concept

1. The concept of Unicast
This information is a concept-oriented communication, only the exchange of information in which the information is sent from one point to another point, means that there is only one sender and a receiver. In Unicast model, a host will receive all of the data transmitted from a host that.

DNS Unicast


2. The concept of Broadcast

This is the concept of information exchange mode in which information is sent from one point to all other points, means from a source to all the destinations directly connected with it. In this model all hosts will receive the data transmitted from a host of.

3. The concept of Multicast

This is a concept of multi-direction information transmitted, only the information exchange mode in which information is sent from one point to another set of remaining, that is a source and destination (Many does not mean all ! ). In the multicast model, multiple hosts simultaneously receive data sent to the multicast group.

4. For Anycast
This is a concept of information transmission in any direction, namely a packet is sent to a single address, any user will be forwarded to a node (or interface) nearest (the closest is the closest distance determined by the routing protocol used) in the node set bearing anycast address. The difference between anycast and multicast packet data transfer process, rather than go to all team members, packets are sent only to a point is the latest member of the anycast group.
Described as follows: in the model node is configured the same Anycast address.

I.2. Analysis of Anycast

1. Mechanism of action

On the internet, Anycast is done by the use of global BGP routing protocol for synchronous and promote a range of destination IP addresses from various points on the Internet. So in the packet's destination network this anycast address range will be routed to the nearest point on the path selection algorithm in network routing protocols. Hosts on the network are configured the same Anycast address.

Co Che Hoat Dong Anycast


2. Applications for the DNS system

Anycast communication method commonly used in specific applications on the network, including applications DNS anycast used with advantages such as:

  • ACC Client, server and router do not need special software.
  • Not adversely affect the existing network, just take advantage of the existing infrastructure gap.
  • Load Balancing
  • Increased mobility
  • Improvements in latency
  • Dispersion mechanism, reduce the risk of DoS

Simple connection diagram included 02 server instance A & B has an IP address is



Perform queries from the client to access the website:

Truy Van TM Tu Client De Truy Cap Website

Router1 routing table check, have 02 path to the server

Router 1 Kiem Tra Bang Dinh Tuyen

Router fact seen as 01 instance of the address, Router select the shortest path to the destination on the principle of conventional Unicast routing, in this case will go through the Router 2 đến instance A.

Dinh Tuyen Unicast Di Qua Router 2

In fact, multiple routers connected so as the client at any location on the network will choose different paths to instance "closest" to the client via router, either to A or B.
II. Deployment model for the national DNS system

Current national domain name system server including 5 cluster servers located in countries in which 2 clusters in Ho Chi Minh City; 2 clusters in Hanoi and 1 clusters located in Da Nang. There are also 2 cluster servers located in a foreign country is hosting on the domain name server system using anycast technology to the distribution points around the world to ensure the query domain “.VN” from users all over the world will be done very quickly through the nearest DNS server is found in the domain name server “.VN”.
With the aim of ensuring safety and security, high availability, backup data, reduce query latency for the domain name system. vn, to do which VNNIC aims to build the cluster DNS server located in the country today converted using anycast technology to model applications as follows:

Anycast DNS system-cluster model:

Mo Hinh Cum He Thong DNS Anycast


The system includes:

  • Router Anycast routing tasks for full-Anycast DNS network, dynamic routing protocol BGP routing from the anycast network and promote the outward.
  • Firewall: duty to protect the anycast server side in.
  • The DNS server: receive and respond to the query domain.

Principle of operation following of Anycast DNS-server: On the DNS server configuration functions as a conventional DNS server, however, this DNS server is configured 2 network interface, an anycast address to receive and respond to the query domain, another interface to address the real network management functions. DNS server address is used for the very important role, service management, synchronize data between the DNS server requires a connection-oriented and reliable, therefore outside the anycast IP address is a physical address management activities to address.

Anycast DNS cluster-this will be located in different places and are routed, promotion in the Internet routing table, anycast technology deployment model for the national DNS system through the following VNIX:

Mo Hinh Trien Khai Anycast Cho DNS Quoc Gia


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