Problem 1. Make the assumption transmission is over a single link, so frames can

Question

Problem 1. Make the assumption transmission is over a single link, so frames can’t “jump over” each other in time.

a) Consider a go-back protocol with 3-bit sequence numbers and a window range of 7
frames. After sending frames numbered 0,1,2,3,4,5, the sender gets back the cumulative acknowledgment, "expecting 3". What frames are in the sender's window of allowed transmissions just after this event?

b) Consider a selective repeat protocol with a 4-bit sequence number and a window range of 8 frames. Suppose the state of the sender's window is frames 0,1,2,3,4,5,6,7, none acknowledged, and the sender has sent frames 0,1,2,3,4,5,6. Then the sender learns of acknowledgment of 0,1,2,5. What frames are in the sender's window range just after this event?

Explanation / Answer

Solution. a) Frames 0,1,2 are acknowledged and can be

removed from the window. The window now allows 3, 4,

5, 6, 7, new 0,1, so frames in this window currently are

allowed to be sent.

b) The range is 8 frames starting with the oldest

unacknowledged. This would be frames 3,4,5,6,7, 8.9.10.

However, 5 would not have to be re-sent.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.