N1, N2, … Nn
LAN/WAN
fiber, cable, satellite
no physical shared memory between nodes
N1, N2
Even a cluster is a distributed system
Belief!
-processes sequential
-> events totally ordered
h->i, f->g, d->e..
-send before receive
->a-b, e->f,…
Lamport’s logical clock
each node
* its own events
* its communication events
Lamport’s logical clock
* monotonic increase of own event time
condition 1: Ci(a)
logical clocks plus PID to break ties
Latency
Elasped time
Throughput
Event per unit time
Bandwidth: throuput measure
RPC performance
Hardware overhead
Software overhead
Foucs of this lesson
How to reduce software overhead
Components of RPC Latency
1.client call
2.Controller latency
3.Time on wire
4.Interrupt handling
5.Server setup to execute call
