I apologize if this question has been asked already because I couldn't find anything related. I'm a beginner in networking and am reading through Computer Networking: A Top-Down Approach, as well as playing around with the Cisco Packet Tracer app.
My question relates to the following diagram from the book on queuing delays and packet loss:
The book says the following about output buffers/queues:
Each packet switch has multiple links attached to it. For each attached link, the packet switch has an output buffer (also called an output queue), which stores packets that the router is about to send into that link. The output buffers play a key role in packet switching. If an arriving packet needs to be transmitted onto a link but finds the link busy with the transmission of another packet, the arriving packet must wait in the output buffer. Thus, in addition to the store-and-forward delays, packets suffer output buffer queuing delays. These delays are variable and depend on the level of congestion in the network. Since the amount of buffer space is finite, an arriving packet may find that the buffer is completely full with other packets waiting for transmission. In this case, packet loss will occur—either the arriving packet or one of the already-queued packets will be dropped.
Here's what I'm wondering:
1) Are there output queues for information being transmitted from the internet to devices on a network? For example, if device C were a video game server transmitting data to video game console A, would the router for A's network have an "output" queue facing the direction of A?
2) On a related note, suppose device D is simultaneously sending data for a YouTube video that's playing on device B. If my understanding in #1 is correct, and each communication link has a corresponding output buffer, then it's my understanding that there would be two buffers: one for the link to A and one for the link to B. So why does streaming a YouTube video on a secondary device in my home network sometimes cause lag on a video game console if those queues are separate from each other? Is it because the router is unable to keep up with processing so much data at once?
I hope it's okay that I'm technically asking two questions here. I don't have a course or instructor and am self studying this material.