Relationship between Propogation time and Transmission time

If efficiency (η)≥0.5 then relation ship between Tp and Tt are:

         

     T/Tt +2*Tp ≥ 1/2

 

⇒        2Tt ≥ T +2*Tp

⇒        Tt  ≥  2*Tp

 ⇒         L/B ≥2*Tp

⇒           L ≥2*Tp*B

 

 

Example:

bandwidth=4mbps

Tp  =1msec

L =?

η≥0.5

Sol:

L ≥2*Tp*B

    ≥2*1*10-3*4*106

≥8*103bits

 

Factor Affecting the efficiency:

η =1/1+2a

 

  =1/1+2*(Tp/Tt)

η=1/1+2*(d/v)*(B/L)

bandwidth and velocity are fixed ,now on increasing distance, efficiency  decrease i.e better for LAN not for WAN.

If Length of packet increase ,efficiency increase.i.e stop and wait is better for big packet(busty)

 

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