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Now the data center migration is not an isolated computer room, but a building group. A data center can contain many branches of data center, can be said to be a data center group, located in different branches of these data center position, but can through the network, to complete the corresponding service deployment. Like Ali, Baidu and other large Tencent, the Internet Co, in order to enhance the customer experience, in different capital data center will establish their own branches, in order to meet the access needs of customers in different regions, the data center is no longer confined to one or several room. These data centers to collaborative operation, you need to exchange information with each other, which has produced a DCI network interconnection needs, namely, Data Center Inter-connect, here include the physical network level and network level logic technology. In order to realize the different areas of the Internet data center, there are a variety of ways: direct Internet interconnection, interconnection line can be used, also can use optical fiber directly connected, you can also add some encryption means to prevent transmission of data leakage, it spawned a lot of new technology, this paper is to describe the DCI related technology, so that everyone on the DCI understand.

There are usually three ways to connect DCI. One is the three layer network interconnection, also known as the Internet data center front network, the so-called "front-end network" refers to the data center for the enterprise network or enterprise wide area network interconnection technology export, through the realization of IP front-end network of different data centers, parks or branch of the client access the data center through the front-end network, when the master the data center disaster, front-end network will achieve rapid convergence, the client accesses the backup data center to ensure business continuity; one is the two layer network interconnection, also known as the data center server in network interconnection, data center server in different network access layer, build a data center between the two layer network. In order to meet the needs of cluster server or virtual machine dynamic migration scenarios such as demand for the two layer network access; the last one is the SAN Internet, also known as the back-end storage Storage network interconnection, with the aid of DWDH, SDH and other transmission technology to achieve data center between the disk array data replication. Before the popularity of server cluster technology, these three modes of interconnection have their own space, but after the popularity of cluster applications, the first two kinds of network can not be adapted. Server cluster is to connect multiple servers on the network with cluster software, providing consistent services, and external performance as a logical server. Cluster software requires two layers of network interconnection between servers to realize the perception free switching of virtual machines. If using three layers of interconnection, will not be able to achieve the virtual migration, if using two floors up, security has become the biggest hidden danger, a two layer network formed dozens of data center, a broadcast storm will all data center do so paralysis, two methods are unable to adapt to the application of cluster deployment, then began to appear a lot of special technology DCI.
MPLS Technology
Based on the implementation of MPLS technology, the data center between the network is the core network has been deployed as MPLS technology, so you can directly through the VLL and VPLS to complete the direct data center two layer interconnection. MPLS includes two layers of VPN technology and three layer VPN technology, VPLS protocol is the two layer VPN technology, the degree of standardization is very high, in many industries have deployed applications. However, VPLS technology is more complex, the deployment and operation and maintenance management is difficult, a variety of access methods and types are many, many times the VPLS network built after a lot of people are afraid to go to the dynamic network configuration, easy problems. VPLS in the common network, which is rare in the domestic VPLS deployment, more is three layers of the MPLS, but to support the application server cluster, can not rely on MPLS, only VPLS.VPLS of this technique, the utility model has the advantages of MPLS technology can more easily achieve the metro / wide area network deployment based on defect is the need for core network / metropolitan area network support MPLS technology, technology is complex and not easy to maintain.
IP tunneling
IP tunneling technology is based on IP technology, in any IP network to open the corresponding two layers of tunnel to achieve data center interconnection. This scheme is far from the type of interconnection between data centers, and is the current direction of development. IP tunneling technology core idea is through the "MAC in IP" way, through the tunnel technology through the three layer network, realize the interworking of the two layers of network. The learning of MAC address is realized by controlling the plane using IS-IS protocol. The tunnel encapsulation adopts the dynamic packaging method similar to GRE, and finally it can support the dual homing high availability deployment mode. For example, CISCO OTV, H3C EVI, is this kind of technology, the technology of IP core network based on L2VPN, can complete the site edge equipment maintenance of routing and forwarding information, without the need to change the site inside and core network. That is to establish a tunnel on the IP network, pass through the two layers of data packets encapsulated by tags, so as to realize the two layer intercommunication of the cross data center. Data center two layer interconnection scheme is largely limited to the existing network type of users, this situation limits the application of the data center to the two layer interconnection scheme. IP tunneling technology is a new networking scheme, which can unify the networking of different types of Internet, and realize the interconnection of heterogeneous networks between two data centers.