There are many ways to solve the NAT puzzle with many different types of NAT. So, for a beginner, the problem becomes very confusing We will see a table with the following valid methods of solving SIP for the NAT issue:
STUN: Simple traversal of UDP over NAT
TURN: Traversal of UDP over Relay NAT
ALG: Application Layer Gateways
MANUAL: Manual configuration (port forwarding)
UPNP: Universal Plug and Play
Method |
STUN |
TURN |
ALG |
MANUAL |
UPNP |
---|---|---|---|---|---|
Symmetric NAT |
No |
Yes |
Yes |
Yes |
Yes |
It requires phone support? |
Yes |
No |
No |
No |
No |
Scalability |
Good |
Poor |
Good |
Good |
Good |
User effort |
Small |
Small |
Small |
High |
Small |
Reliability |
Good |
Good |
Poor |
Good |
? |
Industry support |
Good |
Good |
Average |
Good |
Poor |
Most customers use the NAT device (cable, DSL, or optical fiber) provided by its Internet Service Provider. Thus, for the residential market, we have to deal with whatever the customer has and support all kinds of NAT. For the commercial SIP trunk market...