What are the Differences between Layer 2, Layer 3, and Layer 4 Switches?
Neo Switch Specialist Sep 5, 2023 Layer 2 Switch
The second layer of the OSI reference model is called the data link layer, and a Layer 2 switch uses MAC addresses in this layer to facilitate data exchange between different ports.
The main functions of a Layer 2 switch include physical addressing, error checking, frame sequencing, and data flow control.
Since this is the most basic switching technology, desktop switches typically fall into this category. Therefore, the complexity of the work performed by desktop switches is not very high, as they are at the lowest level of the network, and they only need to provide basic data link functionality.
Layer 2 switches are widely used and are generally applied in the access layer of a local area network (LAN) to connect users' computers. They are inexpensive and provide the necessary functionality for medium and small enterprises.
With a Layer 2 switch, you can easily send data frames from the source to the destination within the same VLAN without the need for physical connections or being located in the same place.
Therefore, software company servers can be centrally located while clients scattered in other locations can access data easily without delays, thus saving server costs and time.
Organizations can configure hosts in the same VLAN using these types of switches without the need for any internet connections, enabling internal communication.
To summarize the characteristics of Layer 2 switches:
1. Layer 2 switches can act as bridges, connecting various terminal devices of a computer network system on one platform. They can quickly and efficiently transmit data from the source to the destination on a LAN network.
2. Layer 2 switches perform switching by learning the MAC addresses of destination nodes from the switch's address table and rearranging data frames from the source to the destination.
3. The MAC address table provides a unique address for Layer 2 devices to identify the terminal devices and nodes to which data is being sent.
4. Layer 2 switches divide large and complex LAN networks into smaller VLAN networks.
5. By configuring multiple VLANs in a large LAN network without physical connections, switching becomes faster.
Layer 3 Switch
The third layer of the OSI reference model is called the network layer, and a Layer 3 switch can be seen as a combination of a router and a Layer 2 switch. It is more advanced and has stronger functionality compared to a Layer 2 switch.
Layer 3 switches have faster switching speeds than Layer 2 switches, and they can even be faster than traditional routers because they don't use additional hops to route packets, which results in better performance. For more information, refer to: What are the differences between Layer 2 and Layer 3 switches?
They typically perform switching at the data link layer and only route at the network layer when necessary, such as for communication between VLANs.
Layer 3 switches leverage the packet header information at the network layer to enhance the functionality of Layer 2 switches. They use IP address information for network path selection and facilitate data exchange between different network segments.
Layer 3 switches can isolate broadcast domains, have high data forwarding capacity, and provide effective routing control. They can achieve high-speed routing between hosts in different VLANs.
When the network scale is large, you can divide it into smaller independent VLAN segments based on specific application requirements to reduce the impact of broadcasts.
Layer 3 switches usually adopt a modular structure to accommodate flexible configurations. In large and medium-sized networks, Layer 3 switches have become essential configuration devices.
To understand the functionality of Layer 3 switches, it's necessary to first understand the concept of routing.
In Layer 3, the source device first looks at its routing table, which contains all the information about source IP addresses, destination IP addresses, and subnet masks.
Then, based on the information gathered from the routing table, it sends the data packet to its destination and can further transmit data between different LANs, MANs, and WANs.
It follows the concept of routing by delivering data between terminal devices using the shortest and most secure path.
Different networks can be interconnected using STM links, which have high bandwidth, or DS3 links. The type of connection depends on various parameters of the network.
To summarize the characteristics of Layer 3 switches:
1. They perform static routing to transfer data between different VLANs, whereas Layer 2 devices can only transfer data within the same VLAN network.
2. They perform dynamic routing in a similar way to routers, allowing switches to execute optimal packet routing.
3. They provide a set of multiple paths for packet delivery based on real-time network scenarios. Switches can choose the most feasible path to route packets, and popular routing technologies include RIP and OSPF.
4. They have the capability to identify relevant IP address information about the flow of traffic.
5. They can deploy QoS classification based on subnet division or VLAN traffic marking, instead of manually configuring switch ports like Layer 2 switches.
6. They require more power to operate and provide higher bandwidth links between switches, which can exceed 10 Gbits.
7. They provide highly secure paths for data exchange.
Layer 4 Switch
The fourth layer of the OSI reference model is called the transport layer, and Layer 4 switches are switch products developed using Layer 4 switching technology, directly targeting specific applications.
Layer 4 switches support various protocols such as HTTP, FTP, Telnet, SSL, etc.
In Layer 4 switching, a virtual IP address (VIP) is assigned to each server group for lookup purposes, and each server group supports a particular application.
The addresses of each application server stored in the Domain Name Server (DNS) are VIPs, not the actual server addresses.
When a user requests an application, a VIP connection request (e.g., a TCP SYN packet) with the destination server group is sent to the server switch.
The server switch selects the best server within the group, replaces the VIP in the destination address with the actual server's IP, and forwards the connection request to the server.
In this way, all packets within the same range are mapped by the server switch and transmitted between the user and the same server.
Layer 4 switching technology has significant advantages over traditional Layer 2 and Layer 3 switching technologies.
From an operational perspective, Layer 4 switching is stable because it keeps packets within the interval between the source and destination.
On the other hand, routers or Layer 3 switches process individual packets and are unaware of where the previous packet came from or the next packet's destination.
They only inspect the TCP port number in the packet header, establish priority queues based on the application, and routers determine packet routing based on available links and network nodes. In contrast, Layer 4 switches determine the interval based on available servers and performance.
Summary
In summary, the differences between Layer 4 switches and Layer 2 switches and Layer 3 switches lie in their operational methods and application scenarios.
The solution provided by Layer 2 switches is a cost-effective "everywhere switching" solution. Although Layer 2 switches can partition subnets, limit broadcasts, and establish VLANs, their control capabilities are limited, lacking flexibility, and they cannot control the flow of information points. They also lack convenient and practical routing functions and are only suitable for small-scale LANs.
The solution provided by Layer 3 switches is a solution that supports multi-level dynamic integration. Although this multi-level dynamic integration can be achieved to some extent by traditional routers and Layer 2 switches, compared to using Layer 3 switches, this configuration requires more device configurations, occupies more space, requires more wiring, and has higher costs. Additionally, the data transmission performance is much poorer because routers in the configuration cannot overcome the routing transmission rate bottleneck in massive data transmission.
Layer 4 switches have versatile applications in networks. They can serve as the convergence point device in the network core, as well as be deployed at the edge access of the LAN distribution layer or even support desktop-level switching in workgroup environments.
Currently, the main technologies of Layer 4 switches, in addition to network load balancing, include packet filtering, quality of service, and primary-backup machine connections.
As information application levels continue to improve, the demands on networks become increasingly higher and more complex. Layer 4 switches and similar high-level network devices will play a more important role in future network environments.
NADDOD, as a leading provider of total optical network solutions, is able to provide the following Layer 2, Layer 3, and Layer 4 switch products:
|
Model |
Switch Layer |
Port Information |
|
Layer 2 |
8x 10/100/1000BASE-T RJ45 | 2x 1G SFP |
|
|
Layer 3 |
24x 10/100/1000BASE-T RJ45 | 4x 1G/10G SFP+ |
|
|
Layer 3 |
48x 10/100/1000BASE-T RJ45 | 4x 1G/10G SFP+ |
|
|
Layer 3 |
24x 10/100/1000BASE-T RJ45(4 Combo) | 4x 1/10GE SFP+ |
|
|
Layer 3 |
48x 10/100/1000BASE-T RJ45 | 4x 1G/10G SFP+ |
|
|
Layer 4 |
24x 10/100/1000BASE-T RJ45 | 24x 1G SFP | 4x 10G SFP+ |
|
|
Layer 4 |
48x 1G SFP | 4x 10G SFP+ |
|
|
Layer 4 |
24x 1G/10G SFP+|2x 40G/100G QSFP28 |
|
|
Layer 4 |
48x 1G/10G SFP+ | 8x 40G/100G QSFP28 |
|
|
Layer 4 |
48x 25G SFP28| 8x 40/100G QSFP28 |
|
|
Layer 4 |
32x 40/100G QSFP28 |
|
|
Layer 4 |
4 Slot(2 Types of Network Modules：N6400H-M32C/N6400H-M28X8C) |