User Manual

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, then the next, Start 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.

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

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

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.

During the transmission, MAC keeps monitoring the status of the medium. If no collision happens until the end of the frame, it transmits succe ssfully. If there is a collision happened, 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.

Publication date: January, 2005

Revision A1

29

Page 32 Page 34
Page 33
Image 33
Edimax Technology ES-516G+ user manual How does a MAC work?
Page 32 Page 34

ES-516G+ specifications

Edimax Technology has carved a niche for itself in the realm of networking devices, and one of its standout products is the Edimax ES-516G+. This 16-port Ethernet switch is designed to meet the demanding needs of small to medium-sized businesses and network enthusiasts.

At the core of the ES-516G+ is its capacity to support 10/100/1000 Mbps speeds across its 16 ports, enabling efficient data transmission and minimal latency for connected devices. This switch is a Layer 2 unmanaged switch, which simplifies the user experience by eliminating the need for complex configurations. Users can plug in their devices and start functioning immediately, making it an ideal option for those who may not have extensive networking knowledge.

One of the key features of the Edimax ES-516G+ is its support for Auto-MDI/MDI-X, which automatically detects the type of connection required for each port, whether it’s connecting to another switch or end devices like computers and printers. This eliminates the hassle of crossover cables and ensures seamless connectivity.

Moreover, the ES-516G+ incorporates advanced energy-saving technologies that are designed to minimize power consumption without compromising performance. This feature is particularly appealing for environmentally-conscious businesses looking to reduce their carbon footprint. It includes capabilities such as energy-efficient Ethernet (EEE), which adjusts power usage based on the link status and length of connected cables.

The switch features a compact metal housing, providing durability and a professional look suitable for any office environment. It also supports a fanless design for quiet operation, making it an excellent addition to workplaces where noise levels need to be kept to a minimum.

In terms of performance, the Edimax ES-516G+ employs store-and-forward switching technology, which helps to minimize errors by ensuring that only error-free packets are forwarded. This significantly enhances network performance and reliability.

Overall, the Edimax Technology ES-516G+ stands out as a robust, efficient, and user-friendly solution for enhancing network performance in small to medium-sized businesses. Its combination of speed, plug-and-play convenience, energy-saving features, and reliability makes it a compelling choice for users seeking to expand their network capabilities. Whether for a bustling office or a home network, the ES-516G+ is engineered to deliver a seamless, high-performance networking experience.
Top Page Image Contents