special fields. If a packet is matched, the switch will add a corresponding VLAN tag to it automatically and thus the data of specific protocol can be automatically assigned to the corresponding VLAN for transmission. The network administrator can manage network clients based on their specific applications and services through protocol VLAN.

¾Encapsulation Format of Ethernet Data

This section simply introduces the common used encapsulation format of Ethernet data to understand the procedure for the switch to identify the protocol of packets. At present there are two encapsulation formats of Ethernet data, Ethernet II encapsulation and 802.2/802.3 encapsulation, shown as follows:

zEthernet II encapsulation

z802.2/802.3 encapsulation

DA and SA respectively refer to destination MAC address and source MAC address. The number indicates the length of the field in bytes, for example, the length of source MAC address is 12 bytes.

As the maximum length of Ethernet data is 1500 bytes, that is, 0x05DC in hexadecimal, the Length field in 802.2/802.3 encapsulation ranges from 0x0000 to 0x05DC, but the Type field in Ethernet II encapsulation ranges from 0x0600 to 0xFFF. The Type or Length field in the range of 0x05DD to 0x05FF is recognized as illegal and will be directly discarded. The switch identifies whether a packet is Ethernet II packet or 802.2/802.3 packet according to the ranges of the two fields.

802.2/802.3 encapsulation contains the following three extended formats:

z802.3 raw encapsulation

Only the Length field is encapsulated after source MAC address field and destination MAC address field, followed by DATA field without other fields. Currently only IPX protocol supports

802.3raw encapsulation format. The last two bytes of the Length field in 802.3 raw encapsulation is 0xFFFF.

z802.2LLC (Logic Link Control) encapsulation

The Length field, DSAP (Destination Service Access Point) field, SSAP (Source Service Access Point) field and Control field are encapsulated after source MAC address field and destination MAC address field. The value of Control field is always 3. DSAP field and SSAP field in 802.2 LLC encapsulation are used to identify the upper layer protocol, for example, when both the two fields are 0xE0, it indicates the upper layer protocol is IPX.

z802.2 SNAP (Sub-Network Access Protocol) is encapsulated based on 802.3 standard packets. In 802.2 SNAP encapsulation, the values of both DSAP field and SSAP field are always 0XAA, and the value of Control field is 3. The switch differentiates 802.2 LLC and 802.2 SNAP encapsulation formats according to the values of DSAP field and SSAP field.

The device determines the encapsulation format of its sending packets, and a device can send out packets of two encapsulation formats. Ethernet II encapsulation format is the most common used one currently.

802.3and Ethernet II encapsulation formats are supported in IP protocol, ARP protocol and RARP protocol, but not supported in all protocols. The switch identifies the protocol of the packets by

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TP-Link TL-SG3424P manual ¾ Encapsulation Format of Ethernet Data
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TL-SG3424P specifications

The TP-Link TL-SG3424P is a high-performance managed switch designed to meet the needs of small to medium-sized businesses. Offering 24 Gigabit Ethernet ports, this device is an ideal solution for improving network efficiency and ensuring seamless data transfer across multiple devices. The switch not only facilitates connectivity but also provides robust management features to enhance the performance and security of your network.

One of the standout features of the TL-SG3424P is its Power over Ethernet (PoE) capability, which allows it to deliver power and data over the same Ethernet cable. This feature is particularly beneficial for deploying devices such as IP cameras, VoIP phones, and wireless access points without the need for additional power sources. With a total power budget of 250W, the TL-SG3424P can support a diverse range of PoE devices, providing convenience and flexibility in deployment.

In terms of management, the TL-SG3424P offers a user-friendly web interface, allowing network administrators to configure and monitor the switch with ease. It supports advanced Layer 2 features, including VLANs, Quality of Service (QoS), and Link Aggregation. These features enhance network performance by optimizing traffic flow and prioritizing essential applications. The switch also includes comprehensive security features, such as Port Security and Access Control Lists (ACL), which help protect against unauthorized access and ensure data integrity.

The build quality of the TL-SG3424P is robust, designed to handle demanding network environments. It includes a fanless design, which ensures silent operation, making it suitable for office environments where noise can be a distraction. The metal chassis is durable and built for longevity, ensuring that the device will withstand rigorous usage over time.

Furthermore, the TL-SG3424P supports SNMP (Simple Network Management Protocol), allowing for centralized network monitoring and management. This makes it easier for IT teams to keep track of network health and performance, enabling timely interventions when necessary.

In conclusion, the TP-Link TL-SG3424P is a versatile and powerful managed switch that combines PoE capabilities with advanced network management features, making it a perfect choice for businesses looking to upgrade their network infrastructure. With its reliable performance and robust features, it provides an excellent solution for enhancing productivity and connectivity in any office setting.
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