Data center networking topology has improved significantly for a few years. With the developments of high speed switching device and multilayer network architecture, we have more powerful data centers with low latency, scalability and higher bandwidth. But due to the exponential increase of internet traffic and emerging web application, still data centers performance is not up to the market to meet the requirement. In order to face the increasing bandwidth demand and power requirement in the data centers, new connection scheme must be developed that can provide high throughput, low latency and less power consumption. So the optimal solution would be using optical fiber link between server to access switch.
Figure 1 shows a block diagram of a typical data center with four layers hierarchical network architecture from the bottom to top. The first layer is the servers which are connected to upper access layer switch. The second layer is access switch where many servers are connected with ToR switch. The third layer is aggregation layer which is connected with bottom access layer switch. Forth or highest layer is core layer where core switches are connected with router at top and aggregation layer at bottom to form a data center block. When a request is generated by a user, the request is forwarded through the internet to the top layer of the data center. The core switch devices are used to route the ingress traffic to the appropriate server. The main advantage of this architecture is that it can be scaled easily and has a good fault tolerance and quick failover. But the main drawback is high power consumption due to the several layer architecture switches and latency introduce due to multiple store-and-forwarding processing.
Figure 1. Traditional data center architecture
As the amount and size of traffic increase exponentially, the architecture of traditional data center is not sufficient to handle traffic and to meet the future challenges. An electrical-optical hybrid network has been proposed. It connects servers with upper layer switch with high availability and low latency. Connecting servers directly with upper layer using both electrical and optical link would fulfill the requirement for the propose scheme. Figure 2 depicts the proposed architecture. The blue lines indicate electrical connectivity and black dashed lines indicate optical connectivity.
Figure 2. Proposed data center architecture
Due to the emerging demand, servers require high bandwidth and low latency communication. Optical connectivity consumes less power at the same bandwidth. Connecting server directly using optical and electrical links will meet the demand and at the same time better load balancing is achieved.
Data center interconnection could be provided by several schemes. Interconnection could be at layer 1, 2 or 3. Considering transportation option and layered architecture of data center, interconnection is recommended at layer 2 aggregation layer. Figure 3 shows a data center interconnectivity solution. Each data center is connected at its aggregation layer using high speed optical fiber.
Figure 3. Data center interconnects architecture
Each server has both optical and electrical connectivity. The electrical connectivity is usually useful for communication between servers and handling short data transfer, whereas optical connectivity is used for long bulked data transfer. This is necessary when transferring data between data centers that require large bandwidth and low latency. At the same time because of layered architecture server can communicate with each other via access layer and don’t need to go the upper layer. Load balancing is achieved due to both hybrid electrical and optical links. Due to the optical connectivity virtual Ethernet port aggregator switching situation enhanced, it becomes easier to move server virtually not only within the data center but also among the data centers. The hybrid links intra and inter data center networking scenarios have significantly improved.
As the number of optical switches is introduced in every layer, the load sharing capability of the network is increased and power consumption for data center is reduced. In each layer, the electrical switch is reduced and replaced with optical switch. So the overall cost and power consumption associated with electrical switches have reduced.
A electrical and optical architecture is presented. Use of optical connectivity has some advantages such as less power consumption, higher bandwidth and low latency. Introducing both types of switches in each layer helps in load balancing. This also helps us when we interconnect our data centers where we require large bandwidth between servers. Because of higher bandwidth, it is easier to move server virtually not only within the data center but also among the data centers. So a hybrid electrical and optical networking topology improves the overall scenarios for data center and also for big data network.