1. Broadcasting with failures
CIS 720
Broadcasting with failures

2. Broadcasting with failures
Type of failures:
- link failures
- halting failures: processor may crash and
never recovers
- omission failures: a processor may fail to
send a message
- byzantine failures

3. Broadcasting with failures
P1 has a value v1 to be sent to all other processes. Each process must deliver a message with value vj
C1: If P1 is normal then each normal process
Pj must eventually deliver vj, where vj = v1
C2: If any normal process Pj delivers vj, then
every normal processs Pi must eventually
deliver vi,, where vj = vi

4. C3: If any process Pj delivers vj, then every normal process Pi must eventually deliver vi, where vi = vj

5. Reliable Broadcast 1 P1: send v1 to all processes; deliver v1
Pj: receive vj;
deliver vj

6. Reliable Broadcast 2 P1: send v1 to all processes; deliver v1
Pj: receive vj;
deliver vj;
send vj to all processes

7. Reliable Broadcast 3 P1: send v1 to all processes; deliver v1
Pj: receive vj;
send vj to all processes;
deliver vj;

8. Reliable Broadcast 4 At most t failures, where t < N/2
P1: send v1 to all processes
wait for at least N – t copies of the message
deliver v1
Pj: receive vj;
send vj to all processes
wait for at least N - t copies of the message
deliver vj

9. Byzantine failures Process may not follow the protocol
It may send different values to different processes.