W9L2 - ALG and NAT

Question 1

RFC 1918 Private Address Space

Answer 1

On your own network you could have the same ip address as another person on their home network. However these couldn’t be routed on the internet. There is a translation layer on the access point to convert said address to a routable one when needed.

Question 2

ALG

Answer 2

Application Level Gateways

Question 3

How does ALG work?

Answer 3

Like a proxy, you create a connection with a server and that server creates a connection with an application on your behalf. It will have a private address you can connection to and a public address that the internet can connect to

Question 4

NAT

Answer 4

Network Address Translation

Question 5

How does NAT work?

Answer 5

Instead of establishing a connection on your behalf, it rewrites the packets that you send to have a public address. Will rewrite the port numbers if necessary. Will keep a mapping in order to convert back

Question 6

Advantages of NAT

Answer 6

Simple to implement
Usable with UDP, TCP, and ICMP packets
Does not require separate implementation for each protocol like ALG

Question 7

Disadvantages of NAT

Answer 7

Can’t connect private to private (peer to peer)
Does not allow inbound connections (port forwarding needed)
Single point of failure - if nat gateway breaks then all connections go with it

Question 8

Like a proxy, you create a connection with a server and that server creates a connection with an application on your behalf. It will have a private address you can connection to and a public address that the internet can connect to

Answer 8

How does ALG work?

Question 9

On your own network you could have the same ip address as another person on their home network. However these couldn’t be routed on the internet. There is a translation layer on the access point to convert said address to a routable one when needed.

Answer 9

RFC 1918 Private Address Space