Week 3 Flashcards
Explain the Network ISP: Single Global Transit ISP
- one global router connected to the hundreds of thousands of access ISPs
Explain the Network ISP: Multiple Global Transit ISP
- multiple global transit isps, and access isps choose among the global providers
What is the ISP hierarchy in a regional ISP?
Access ISP < Regional < Tier-1 ISPs
What level is Points of Presence not included at?
access ISP level
Explain Points of Presence (PoP)
like a gaetway for users to access the internet.
What is ISP peering?
directly connecting networks together so that all traffic between them passes over direct connection. cost-free and efficient
Explain IXPs (internet exchange point)
Allow ISPs to connect directly instead of going through third parties. multiple networks can go to the same IXP.
How do networks bypass upper level ISPs / charges?
- peering with lower level ISPs
- IXPs
What are the 4 types of delay, in order?
Processing –> Queuing –> Transmission –> Propagation
Difference between Processing and Queuing delay?
processing: examining packet header
queuing: packet is waiting to be transmitted onto link
What does the queuing delay depend on?
- Transmission rate of the input and output links
- Number of packets that arrived earlier
Transmission vs Propagation delay?
Transmission: pushing all bits ONTO the link
Propagation: moving from one router onto the next through a link
Calculating transmission delay
L /R
L = # of bits in a packet
R = transmission rate
Calculating propagation delay
distance / propagation speed
propagation speed = 2x10^8
What is traffic intensity?
bits * Arrival rate / Service rate
How does traffic intensity relate to queuing delays and what’s a good traffic intensity?
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
How does the traceroute program work?
Can find internet delay/loss
- sends packets to destination and routers along the way.
- when routers get these packets it sends it backs to source
- sender measures time interval between transmission and reply
Why are some delays shorter on further away sites?
Traffic is not consistent, due to QUEUING delays
Throughput vs Delay?
Throughput: how much data you can send in a time
Delay: how long it takes for data to get from A to B
What is throughput?
bits/time unit.
The RATE at which are being sent, from sender to receiver.
What is throughput affected by?
ONLY based off the transmission rates!
What is bottleneck link?
The SLOWEST link between 2 routers / systems on a path. This sets the THROUGHPUT of the entire path.
