Timer

Buffer

Address

Dedicated line

0 to 63

0 to 64

1 to 63

1 to 64

0

n -1

N

n +1

Go-back-N method requires more storage at the receiving site

Selective repeat involves complex login than GO-back-N

Go-back-N has better line utilization

Selective repeat has better line utilization

Minimum

Maximum

Virtual

Both (a) and (b)