Viewpoint: detailed explanation of the main functions of the backbone switch

Backbone switches are also different from general switches in terms of security design. They also have higher security and reliability. In backbone switches, Ethernet technology can be used to conveniently implement VLANs, it also supports more VLANs than common Ethernet switches. Generally, it supports 4 K VLANs. some backbone switches can even support port VLANs.

In this way, the number of VLANs is no longer limited to a maximum of 4 K VLANs in the 802.1q protocol, and n × 4 K (n indicates the number of ports) VLANs can be supported. in some backbone switches, dual (multi-layer) vlantags are also supported, which makes VLAN-based forwarding hierarchical and breaks through the limit of 4 k vlan numbers.

Larger MAC Address Table

Ethernet Forwarding is mainly based on the MAC address table. In a backbone switch, the port density is relatively high, and multiple normal lanswitches can be mounted to the backend switch, so there are many connected users, for example, all users in the entire enterprise network or users in the whole community. Therefore, the number of MAC address tables is usually above 10 KB, generally between 32 KB and 32 KB ~ K. Therefore, when selecting a backbone switch, the number of MAC address forwarding tables is an important indicator.

Supports layer-3 Switching

As a backbone switch, it must also have a layer-3 Switch capability, which is a notable feature of the backbone switch. Normal LANSwitch switches support layer-2 MAC address forwarding, and some support layer-3 forwarding to implement limited layer-3 routing. However, as a backbone switch, it is necessary to support cross-VLAN forwarding. This is inseparable from the network location where the backbone switch is located in the enterprise network, campus network, and Metro interface. Therefore, a layer-3 switch must have a layer-3 interface. Generally, layer-3 interfaces are divided by VLAN as the basic unit of layer-3 logical interfaces. Each VLAN must have its own independent subnet address. Therefore, in backbone switches, the number of subnet Gateway Addresses supported by VLANs is also an important indicator.

Supports more protocols

"One-time routing and multiple-times switching" is the guiding ideology of vswitches for Route switching. However, this three-layer forwarding method is time-consuming for first packet forwarding, especially on backbone layer switches. This forwarding mechanism restricts the forwarding rate. Now, the backbone switch basically uses hardware to implement the maximum matching forwarding mechanism, so that it can process layer-3 forwarding at wire speed. At the same time, the support for the three-tier forwarding table is also an important indicator of the backbone switch. Generally, the number of Route tables supported by the backbone switch and the backbone router is the same. Backbone switches also support a wide range of routing protocols, including RIP, OSPF, IS-IS, and BGP. The support for these routing protocols can fully ensure that backbone switches can run on not only the enterprise network, but also the carrier's junction layer and backbone layer.

Stream classification and QoS

The support for stream classification and QoS protection are also an important feature of backbone switches. The number of users connected to backbone switches is large, and the network requirements of users are also complicated. Therefore, the backbone switch should be able to provide QoS and Filter Based on stream classification for different users and different network environments. The number of stream categories will greatly affect the business capabilities of backbone switches at the junction points and meet the increasing business needs of users and their security assurance capabilities. Therefore, the current backbone switches should support QoS and bandwidth Assurance Based on stream classification.

Higher security requirements

Backbone switches are also different from general switches in terms of security design, and often have higher security and reliability. In terms of design, the manufacturer also tries its best to follow the telecom-level design scheme. For example, the redundant backup design of the power supply, the Dual Backup design of the main control routing board, the hot swapping design of the circuit board without interrupting the business, and the dual backup design of the Network Board. VRRP technology is preferred in backbone switches for high reliability.

More centralized network management

In terms of network device management, backbone switches also have their own characteristics. Because backbone switches are often on the operator's network equipment side, the number of access layer devices is large, and the maintenance workload is huge, it is urgent to provide devices with unified management and maintenance measures. Currently, backbone switches generally support cluster management protocols.

In cluster management, a single management IP address can be used to maintain a large number of network devices, and provides various convenient network maintenance methods, such as device topology discovery, device failure and link failure alarms, and unified device configuration, therefore, it has gradually become the main means of network device management.