Week 3

Question 1

Explain the Network ISP: Single Global Transit ISP

Answer 1

• one global router connected to the hundreds of thousands of access ISPs

Question 1

Explain the Network ISP: Multiple Global Transit ISP

Answer 1

• multiple global transit isps, and access isps choose among the global providers

Question 2

What is the ISP hierarchy in a regional ISP?

Answer 2

Access ISP < Regional < Tier-1 ISPs

Question 3

What level is Points of Presence not included at?

Answer 3

access ISP level

Question 4

Explain Points of Presence (PoP)

Answer 4

like a gaetway for users to access the internet.

Question 5

What is ISP peering?

Answer 5

directly connecting networks together so that all traffic between them passes over direct connection. cost-free and efficient

Question 6

Explain IXPs (internet exchange point)

Answer 6

Allow ISPs to connect directly instead of going through third parties. multiple networks can go to the same IXP.

Question 7

How do networks bypass upper level ISPs / charges?

Answer 7

1. peering with lower level ISPs
2. IXPs

Question 8

What are the 4 types of delay, in order?

Answer 8

Processing –> Queuing –> Transmission –> Propagation

Question 9

Difference between Processing and Queuing delay?

Answer 9

processing: examining packet header

queuing: packet is waiting to be transmitted onto link

Question 10

What does the queuing delay depend on?

Answer 10

1. Transmission rate of the input and output links
2. Number of packets that arrived earlier

Question 11

Transmission vs Propagation delay?

Answer 11

Transmission: pushing all bits ONTO the link

Propagation: moving from one router onto the next through a link

Question 12

Calculating transmission delay

Answer 12

L /R

L = # of bits in a packet
R = transmission rate

Question 13

Calculating propagation delay

Answer 13

distance / propagation speed

propagation speed = 2x10^8

Question 14

What is traffic intensity?

Answer 14

bits * Arrival rate / Service rate

Question 15

How does traffic intensity relate to queuing delays and what’s a good traffic intensity?

Answer 15

The queuing delay increases exponentially when traffic intensity increase. When traffic intensity > 1, average delay is infinite.

A good traffic intensity is less than 0.80

Question 16

How does the traceroute program work?

Answer 16

Can find internet delay/loss

1. sends packets to destination and routers along the way.
2. when routers get these packets it sends it backs to source
3. sender measures time interval between transmission and reply

Question 17

Why are some delays shorter on further away sites?

Answer 17

Traffic is not consistent, due to QUEUING delays

Question 18

Throughput vs Delay?

Answer 18

Throughput: how much data you can send in a time

Delay: how long it takes for data to get from A to B

Question 19

What is throughput?

Answer 19

bits/time unit.

The RATE at which are being sent, from sender to receiver.

Question 20

What is throughput affected by?

Answer 20

ONLY based off the transmission rates!

Question 21

What is bottleneck link?

Answer 21

The SLOWEST link between 2 routers / systems on a path. This sets the THROUGHPUT of the entire path.