Final answer:
The receiver's SCTP queue contains chunks 1 to 8, 11 to 14, and 16 to 20. Variables confirm the presence of 1800 bytes of available space, lastAck as 4, and cumTSN as 5 with no duplicates. The SACK message will acknowledge up to cumTSN 5 and report gaps for missing chunks 9, 10, and 15.
Step-by-step explanation:
Stream Control Transmission Protocol (SCTP) is a transport-layer protocol used for transmitting multiple streams of data. In the scenario described, the state of the receiver includes chunks received, available space in the queue, and specific tracking variables like lastAck and cumTSN. The contents of the receiver's queue contain chunks 1 to 8, 11 to 14, and 16 to 20. Since some chunks are missing, notably 9, 10, and 15, and the receiver acknowledges only up to chunk 4, chunks 5 to 8 are received but not yet acknowledged. The accumulated TSN (cumTSN) is at 5, which suggests that chunk 5 has been received but possibly not yet processed.
The receiver's queue would include:
- Chunks 1 to 8
- Chunks 11 to 14
- Chunks 16 to 20
Given variables:
- Available space in queue: 1800 bytes
- lastAck: 4
- cumTSN: 5
- No duplicate chunks received
The SACK message sent by the receiver will include the cumTSN as 5, indicating all chunks up to 5 have been received, and it will also include gap reports for missing chunks 9, 10, and 15. It does not report chunks 5 to 8 as missing because they are already in the queue.