I. Features of Layer 3 Switches
In addition to their excellent performance, Layer 3 switches also have some features that traditional Layer 2 switches do not have. These features can bring many benefits to the construction of campus networks and metropolitan area education networks, as listed below.
1. High scalability
When connecting multiple subnets, a Layer 3 switch only establishes a logical connection between the subnets and the Layer 3 switching module, unlike traditional external routers which require additional ports. This protects the user's investment in the campus network and metropolitan area network, and meets the needs of the school's rapidly growing network applications over the next 3-5 years.
2. High cost performance
Layer 3 switches have the ability to connect large networks and can essentially replace some traditional routers, but their price is close to that of Layer 2 switches. Currently, a 100Mbps Layer 3 switch costs only tens of thousands of yuan, roughly the same as a high-end Layer 2 switch.
3. Suitable for multimedia transmission
Educational networks frequently need to transmit multimedia information, which is a characteristic of educational networks. Layer 3 switches have QoS (Quality of Service) control functions, which can allocate different bandwidths to different applications.
For example, when transmitting video streams in campus networks or metropolitan area networks, a certain amount of dedicated bandwidth can be reserved for video transmission. This is equivalent to opening a dedicated channel in the network, preventing other applications from occupying this reserved bandwidth and thus ensuring the stability of video stream transmission. Ordinary Layer 2 switches do not have this feature, which results in jittery video transmission that fluctuates in speed.
In addition, video-on-demand (VOD) is also a frequently used service on education networks. However, some VOD systems use broadcast for transmission, and broadcast packets cannot cross network segments, thus preventing VOD from achieving cross-segment transmission. If unicast is used for VOD, although cross-segment transmission is possible, the number of simultaneous connections supported is very limited, typically a few dozen connections consuming all bandwidth. Layer 3 switches, on the other hand, have multicast capabilities, allowing VOD data packets to be sent to various subnets in a multicast format, achieving cross-segment transmission while ensuring VOD performance.
Advantages of Layer 2 and Layer 3 Switches
1. The transmission bandwidth between subnets can be allocated arbitrarily.
In traditional routers, each serial port can connect to a subnet, and the subnet speed transmitted through the router is directly limited by the interface bandwidth. In contrast, a Layer 3 switch defines multiple ports as a virtual VLAN (VLAN), and uses this VLAN as a single virtual interface. Information within the VLAN is then sent to the Layer 3 switch through the ports that make up the VLAN. Because the number of ports can be arbitrarily specified, the transmission bandwidth between subnets is unlimited.
2. Information resources are allocated reasonably.
Because network systems connected by Layer 3 switches have no difference in resource utilization when accessing subnets compared to accessing the global network, setting up a separate server is pointless. By establishing a server cluster directly within the global network, while maintaining broadband intranet transmission speeds, costs can be saved, the hardware and software resources of the cluster servers can be fully utilized, and various information resources can be configured and managed more effectively. This problem is difficult to solve in router-based networking.
3. Reduce costs.
In enterprise network design, it's common practice to use only two-layer switches to form a single broadcast subnet, connecting these subnets via routers. This creates an intranet, but routers are expensive, hindering cost reduction for enterprise networks supporting intranets. Now, in inline network systems, layer 3 switches are used. These switches allow for arbitrary subnetting of virtual subnets and enable communication between subnets through their layer 3 routing capabilities. This means that both subnetting and intranetting can be accomplished through switches, significantly reducing the need for expensive routers.
