First, the RJ45 jack connects to the microcontroller through its integrated MAC/PHY to receive Ethernet data. Second, the system needs an external OLED display that can be used for user inputs like volume and bass control. It can also display information about the song being played. Finally, the system uses an MP3 audio decoder to output the data as audio, in this case music from the Internet. One issue with internet data is the large amount of packet losses and delays that must be handled. Data packets can become lost for 300ms or even longer. So, the reference design requires a large amount of buffering to make up for these latencies. Notice that the microcontroller only has 4kB of RAM. This is not nearly enough to handle the large amount of buffering required. Without a large RAM buffer, the user would hear clips and pops due to the missing data packets.