Error control in Transport Layer vs Data Link Layer?

Question

I understand that under the TCP/IP Protocol Suite, error control, flow control and other such services are provided by both, the Transport Layer and the Data Link Layer.\n\nMy doubt is specific to error control using the Sliding Window protocol (used by the Transport Layer, if I'm not mistaken) and the Stop-and-Wait ARQ (used by the DLL). Do both these processes occur (in the context of the respective layers) *simultaneously?* Or is it *one or the other*? \n\nI also understand that for the Transport Layer, we are concerned with *frames* at either end points, whereas for the DLL, we are concerned with *frames* at each *hop* that a frame makes. Thus, my confusion is this: when we refer to *frames* in both Sliding Window and Stop-and-Wait ARQ, which Layer's PDU's are we talking about? How do these two processes occur?

Answer 1

Hello, hopefully I can help answer your question. Ill break it down from the beginning.

Stop and Wait, & Sliding window protocol are both methods used for flow control.

Stop and wait- waits for an acknowledgement for each data unit before sending another.

Sliding Window- Transmits several data united before requiring an acknowledgement

Sliding Window is considered more efficient for a few reasons. Sliding window uses full duplex, meaning traffic can be transmitted both ways on the link. Stop and Wait is half duplex, traffic can only go one way at a time. Additionally, with sliding window you are able to send more data before requiring and an acknowledgment therefore allowing more throughput.

Both of these protocols work at the transport layer. Transport layer uses "Segments". Only one would be used at a time.

1. Physical - Bits/Bytes
2. Data Link- Frames
3. Network- Packets
4. Transport- Segments

I hope this answers your questions!