Consider a multicomputer in which the network interface is in user mode, so only

Question

Consider a multicomputer in which the network interface is in user mode, so only three copies are needed from source RAM to destination RAM. Assume that moving a 32-bit word to or from the network interface board takes 20 nsec and that the network itself operates at 1 Gbps. What would the delay be for a 64-byte packet being sent from source to destination if we could ignore the copying time? What is it with the copying time? Now consider the case where two extra copies are needed, to the kernel on the sending side and from the kernel on the receiving side. What is the delay in this case?

Explanation / Answer

By taking network time 1nsec /bit or 512nsec delay in time per packet.

If network operates itself in 1gbps means the network delivers 125 MB/sec

To copy 64bytes 4 bytes at a time, 320 nsec are needed on each side, or 640 nsec total(source +destination)

Adding the 512-nsec wire time, we get 1132 nsec
total. If two additional copies are needed, we get 1792 nsec..

Moving 64 bytes in 1792 nsec
is 35.7 MB/sec.

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.