In datacenters, the tagged VLAN is generally used to isolate each user's network, but there are two problems with this approach. One is the limited capacity of the tagged VLAN. This technique attaches one of 4094 VLAN identifiers (VLAN-IDs) to packets, so the maximum number of isolatable networks is 4094. A VLAN-ID must be unique over the entire datacenter network, so it is impossible to accommodate more than 4094 users at the same time. The other problem is the use of proprietary specifications by the vendors of the products used in datacenters.
For the products currently used in datacenters, most vendors use proprietary specifications in both network design and setup. Network design, for example, may be premised on a virtual chassis* being used for switch products, in which multiple switches are seen as a single switch, and on the tagged VLAN being used for communication within server products. For setup methods, individual vendors have proprietary control protocol specifications etc. It is thus necessary to assign the VLAN-ID to match the vendor specifications, and the control protocol used must also match the vendor specifications. Furthermore, as the numbers of servers and switches in datacenters increase to more than hundreds of units, the use of products from multiple vendors to avoid vendor lock-in and reduce costs increases the difficulty of datacenter network design and management.
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Agile automatic changes in network configuration in cooperation with migration
For cloud services, virtual machine migration among multiple datacenters in times measured in hours is necessary in order to take advantage of night-time electricity rates and to respond to disasters. Specifically, services can be migrated without interruption on a virtual machine that uses TCP (transmission control protocol), UDP (user datagram protocol), or other protocols, and the network configuration can be changed in cooperation with the migration within a very short time.
As a step toward solving the above two problems, a new standard network virtualization technology that does not use VLANs and that eliminates vendor dependence is needed for cloud services.