2 - Architecture and Principles

Question 1

Problems with IPv4

Answer 1

1. Running out of addresses
2. Congestion Control
3. Routing
4. Security
5. Denial of Service

Question 2

Goal of internet (DARPA)

Answer 2

multiplexed utilization of existing interconnected networks

1. Sharing (Solution: statistical multiplexing/packet switching
2. Interconnection (Solution: “narrow waist”)

Question 3

Packet Switching

Answer 3

No state established ahead of time

Many senders can send over the same network

Shares resources

+ no “busy signal”
- delay

Question 4

Circuit Switching

Answer 4

Conventional phone network uses

A signaling protocol sets up dedicated path out-of-band

+ better reservation of resources

Question 5

Narrow Waist

Answer 5

Interconnects many existing networks and hides underlying technology from applications

Question 6

Other DARPA Goals

Answer 6

Survivability: network works even if some devices fail (replication, fate sharing)

Heterogeneity: TCP/IP, “Best Effort”

Distributed Management: Addressing (ARIN, RIPE, etc), Naming (DNS), Routing (BGP)

Cost

Ease of attachment

Accountability

Question 7

What’s missing from DARPA

Answer 7

Security
Availability
Mobility
Scaling

Question 8

End-to-End argument (Examples that satisfy this)

Answer 8

1. Error handling in file transfer
2. End-to-end encryption
3. TCP/IP split in error handling

Question 9

End-To-End violations

Answer 9

NAT
VPN tunnels
TCP splitting
Spam
P2P systems
Caches