hw3 assigned

p = prob of link corrupting a frame, between 1 and 0
what is the avg # of transmissions required for a frame to go through the link?
P(k) = p^(k-1)*(1-p)
E(k) = sum<k=1..inf>(k*P(k)) = (p-1)*sum<k=1..inf>(k*p^(k-1)) = diff<p>(sum<k=1..inf>(p^k)) = diff<p>(1/(1-p) - 1) = diff<p>(p/(1-p)) = (1-p+p)/(1-p) = 1/(1-p) (that was way too stupid of a process and took way to long to derive what I already knew)

link utilization = Ttran/Ttotal
LU avg = (1-p)/(1+2a)

stop and wait ARQ
case 1: damaged frame -> B sends NAK
case 2: lost frame -> both parties waiting (deadlock, avoid by timeout)
case 3: lost ack/duplicate frame

media access control
resource contention on bus topology -> crazy junk