Recitation

Active vs. Passive

• Active vs. Passive measurements. Explain what they are– Describe an active measurement experiment that

measures something that can not be measured by passive approaches

– Describe a passive measurement methodology that measures something that can not be measured by active approaches

Traceroute• Explain how traceroute works. Explain why we sometimes send UDP and not

ICMP packets.• One traceroute experiment gave us the following graph: Src->L->A->D->D-

>Dst. Do you notice the circle in D? Why is there?

• Descrribe how the graph Src->L->C->B->Dst can be acquired from the topology above

L

A B

C

Src DstD

DNS

• What is DNS? How is it used?• How can we use DNS to implement Content

Delivery Networks?• CNN website contains the following URLhttp://i

2.cdn.turner.com/cnn/dam/assets/140509111657-russia-victory-day-parade-t1-main.jpg. Describe the DNS translation steps

• Describe the issues raised to CDN, if we use 8.8.8.8 as DNS server

Packet switching

• Describe the differences between packet switching and circuit switching

• Why is packet switching better?• Why didn’t telephone use packet switching?

Packet loss

• You’d like to find the packet loss in each link of a network. How can you do it?

B C

A

Packet Dispersion

• Explain how to use packet dispersion to measure bottleneck link capacity