Data Link Layer

1. Data Link Layer Part I: Encoding

2. Network Architecture message segment packet frame signal

3. What is a Data Link?

4. The Sine Wave f(t) = Asin(B*t + C) A – amplitude B – frequency C – phase shift

5. Non-Zero Return EncodingSender Sends:

6. Non-Zero Return EncodingReceiver Gets: How many ones here? How many zeros here? Receiver does not know period/wavelength... Receiver can’t decode consecutive 1s or 0s

7. Non-Zero Return EncodingReceiver Solution -> Clock Receiver Receiver has a clock. One clock cycle = square wave period. Boundaries allow us to decode 1s and 0s. ? How do we determine clock cycle ? How do we keep clock cycle synchronized with square wave signal

8. Non-Zero Return EncodingReceiver Solution -> Clock End/Start Cycle End/Start Cycle End/Start Cycle End/Start Cycle Receiver • Sender/receiver know the clock cycle period. • Receiver uses square wave TRANSISTIONS to keep clock cycles • synchronized with square wave. • PROBLEM: Clock drift can occur over long period of consecutive 1s or 0s.

9. Manchester Encoding

10. 4b/5b Encoding