Why use the leaf-spine topology network? (1)

Why use the leaf-spine topology network? (1)

The structure of the three-layer network has developed very mature, but the leaf-spine (leaf node, spine ridge node) structure is becoming more and more popular. How should network designers choose?

Despite the wide application and mature technology of the layer-3 network architecture, with the development of technology, its bottlenecks also emerge, resulting in more and more network engineers to abandon the network of this structure. So what other networks can replace this three-layer structure? The answer is the leaf-spine leaf ridge topology network structure.

As enterprises seek to maximize utility and data center utilization, the mainstream three-layer network topology is increasingly unable to meet their needs ." Network Topology refers to the interconnection of network devices. Devices communicate and connect through established protocols and connections.

Let's take a look at the standard network data center topology, which is a three-layer network structure: access layer-Client Connection Network; aggregation layer-switch access; core layer-switches and routes converge and connect internal and external networks.

Figure 1. Structure of a traditional three-tier network

The design of this model provides a Feasible Basis for the Network Topology Design of the data center. The model design diagram can be expanded to the topology of the entire network. The most important thing is the layer-3 model, which includes the network port density and the number of switches to match. The requirements for structured cabling can also be clearly indicated that the connection between layers is the same as the network topology of the data center. Therefore, although more devices are added to the real layer-3 network, the principle is consistent with the Model diagram.

Why is the L3 network structure short?

Based on performance bottlenecks and network utilization, senior network designers are exploring the topology of new data centers.

The Network Transmission Mode of the data center is constantly changing. Most networks are in the vertical (north-south) transmission mode-the communication between the host and other hosts in the network that are not in the same network segment is the device-switch-route to the destination. At the same time, hosts in the same CIDR block are usually connected to the same vswitch and can communicate with each other directly.

Figure 2: n-s network, vertical Network Structure

 

Figure 3: Simplified n-s Network. Data Transmission Mode

However, for the computing and storage infrastructure of modern data centers, the main network traffic model is not just communication between different network segments. Communication and network segments of the Intranet and Internet are distributed across multiple access switches. hosts are required to communicate with each other through networks. These changes in the network environment have led to two technological trends: network convergence and virtualization.

Network convergence: In the network structure, the storage network and the communication network are in the same physical network. The data transmission between the host and the array is transmitted through the storage network, and the logical topology is like a direct connection. Such as ISCSI.

Virtualization: converts a physical client to a virtual client. Virtual servers are the mainstream and trend of future development. They will simplify the movement of network nodes.

A horizontal Network (east-west) transmits data in a vertically designed network topology with a transmission bottleneck because the data passes through many unnecessary nodes (such as routers and switches ). If hosts on the network need to access each other through high-speed bandwidth, but through uplink ports, it may lead to potential and obvious performance degradation. The original design of the L3 network will aggravate this performance degradation. Because the Spanning Tree Protocol prevents redundant links from having loops, the dual-uplink access switch can only use one specified network interface link.