20 - TCP/IP Stack: Network Layer

Question 1

What is the Network Layer?

Answer 1

Responsible for routing packets across the Internet from the source host to the destination host

• IP makes no guarantees about packet delivery

Question 2

What is an IP address?

Answer 2

IPv4 addresses are actually 32-bit numbers in a dotted quad notation

• Use ipconfig in the shell to find your IP address
• IPv6 (128-bit number) system is being developed

Question 3

What is a Server Log?

Answer 3

Tracks IP addresses of those visiting sites on their servers, etc.

Question 4

What is a Router?

Answer 4

• Special hosts connected to multiple networks
  
  • Operates at the Internet Layer
• Communicate with other routers using a routing protocol
• Routers only concerned with the “next hop”

Question 5

What is ICMP?

Answer 5

Internet Control Message Protocol

• Used by network devices (how routers talk to each other)

Question 6

What is a ping utility?

Answer 6

• Takes an IP address and sends an ICMP “echo request” packet to that address
• Waits for a response for a while, then tries again
• Useful for network reconnaissance
• Can be used nefariously, in a Denial of Service attack (DOS)