Question

Consider sending a large file of F bits from Host A to Host B. There are three links (and two switches) between A and B, and the links are uncongested (that is, no queuing delays). Host A segments the file into segments of S bits each and adds 80 bits of header to each segment, forming packets of L=80+ S bits. Each link has a transmission rate of R bps. The link propagation delay, let's call it d, was not negligible. Find the value of S that minimizes the delay of moving the file from Host A to Host B.

Answer 1

From the given data,

Number of links =3

Number of switches=2

File size=F bitsze of each Segment= S bits

Number of segments=F/S

Header size= 80 bits

Packet size(L)=80+S bits

Transmission rate(R)=R bps

Transmission delay(T_delay)=L/R =(80+S)/R seconds

Time (T) required for the first packet to be transmitted to destination:

T=T_{delay *} Number of links

   =(80+S)/R *3