How does a MAC work?

The MAC sub-layer has two primary jobs to do:

1.Receiving and transmitting data. When receiving data, it parses frame to detect error; when transmitting data, it performs frame assembly.

2.Performing Media access control. It prepares the initiation jobs for a frame transmission and makes recovery from transmission failure.

Frame transmission

As Ethernet adopted Carrier Sense Multiple Access with Collision Detect (CSMA/CD), it detects if there is any carrier signal from another network device running over the physical medium when a frame is ready for transmission. This is referred to as sensing carrier, also “Listen”. If there is signal on the medium, the MAC defers the traffic to avoid a transmission collision and waits for a random period of time, called backoff time, then sends the traffic again.

After the frame is assembled, when transmitting the frame, the preamble (PRE) bytes are inserted and sent first. Next sart of frame Delimiter (SFD), DA, SA and through the data field and FCS field in turn. The followings summarize what a MAC does before transmitting a frame.

1.MAC will assemble the frame. First, the preamble and Start-of- Frame delimiter will be put in the fields of PRE and SFD, followed by DA, SA, tag ID (if tagged VLAN is applied). Ethertype or the value of the data length, and payload data field Finally, assemble the FCS data in order and put it into the responded fields.

2.Listen if there is any traffic running over the medium. If yes, wait.

3.If the medium is quiet, and no longer senses any carrier, the MAC waits for a period of time, i.e. inter-frame gap time to have the MAC ready with enough time and then start transmitting the frame.

4.During the transmission, MAC keeps monitoring the status of the medium. If no collision happens till the end of the frame, it transmits successfully. If there has been a collision, the MAC will send the patterned jamming bit to guarantee the collision event propagated to all involved network devices, then wait for a random period of time, i.e. backoff time. When backoff time expires, the MAC goes back to the beginning state and attempts to transmit again. After a collision happens, MAC increases the transmission attempts. If the count of the transmission attempt reaches 16 times, the frame in MAC’s queue will be discarded.

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Edimax Technology ES-5240G+ user manual How does a MAC work?
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ES-5240G+ specifications

Edimax Technology ES-5240G+ is a highly versatile and efficient Ethernet switch designed to cater to the networking needs of small to medium-sized businesses and home offices. With its robust features and reliable performance, this switch is an essential component for a seamless network infrastructure.

One of the standout features of the ES-5240G+ is its 24 10/100/1000Mbps Gigabit Ethernet ports. This allows for high-speed connectivity, enabling users to transfer large files quickly and efficiently. The switch is equipped with a non-blocking architecture, ensuring that all ports can be utilized simultaneously without any reduction in bandwidth. This is particularly beneficial for businesses that rely on high-speed internet and internal networks for their daily operations.

The ES-5240G+ supports advanced Layer 2 switching features, including VLAN (Virtual Local Area Network) support, port mirroring, and link aggregation. These features enhance network management and optimization, making it easier to segment network traffic and improve security. With VLAN support, users can create separate networks within the same switch, leading to improved performance and reduced broadcast traffic.

Moreover, the ES-5240G+ incorporates IEEE 802.3x Flow Control, which helps to prevent data loss during heavy traffic periods. This technology allows for effective communication between devices and ensures smooth data transmission, even in congested network environments. Additionally, the switch is equipped with Automatic MDI/MDI-X detection, eliminating the need for crossover cables and simplifying installation.

From a security perspective, Edimax has included features such as address filtering and port security, which help to protect the network from unauthorized access. The switch can restrict access to specific MAC addresses, providing an added layer of security for sensitive data.

In terms of energy efficiency, the ES-5240G+ is designed to comply with IEEE 802.3az Energy Efficient Ethernet standards. This technology helps to reduce power consumption during low-traffic periods, making it an eco-friendly choice for businesses looking to minimize their carbon footprint.

Overall, Edimax Technology ES-5240G+ stands out as a reliable and efficient Ethernet switch, equipped with a range of features that enhance network performance and security. Its capabilities make it an ideal choice for businesses seeking to streamline their networking infrastructure and improve operational efficiency.
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