A doctor in Montreal wants to help a doctor in Vancouver for a delicate open-heart surgery. The surgery will be transmitted by video in real time. A digital color video is a series of images each consisting of a grid of pixels. To achieve smooth motion in digital video 25 images must be displayed per second. Since transmitting uncompressed video is totally out of the question, compression must be done.

The communication will have to go through 4 routers located respectively in Montreal, Toronto, Edmonton and Vancouver (Figure 7).

All links are 100 Mbps; Size of an image 100 Kbytes, after compression 20 Kbytes; For video transmission, it is necessary to transmit 25 compressed images per second; The packet length is 1000 bytes for the data and 100 bytes for the header; To simplify the problem, the ACK size is the same as the data size Queue delay of routers and PCs is 0 sec; The processing time at each intermediate router is 0.1 ms; Distance from Montreal to Vancouver is 5000 km; The propagation speed is 200 000 km / s; The propagation delay between PCs and routers is 0 sec.

Figure 7: Communication between Montreal and Vancouver

a. Calculate the average end-to-end delay (PC2 to PC1) for the transmission of a packet of 1100 bytes (1000 data and 100 header).

b. If the communication protocol between PC2 and PC1 is UDP and the packets are 1100 bytes (1000 data and 100 header), is it possible for this network to transmit in one second the 25 images? ? Justify your answer clearly.

c. If we use TCP with the technique send and wait (Stop and Wait), is it possible for this network to transmit in one second the 25 images? Justify your answer clearly.

d. If UDP is used, what is the smallest size of a packet to be able to transmit in 25 seconds the images on this network? Justify your answer clearly.

Edimonton Vancouver Montreal 100 Mbps 100 Mbps 1185 100 Mbps 100 Mbps 100 Mbps PC2(avec camra) PC 1 Edimonton Vancouver Montreal 100 Mbps 100 Mbps 1185 100 Mbps 100 Mbps 100 Mbps PC2(avec camra) PC 1