Tunneling

• This process involves wrapping a packet written according to one protocol in a packet with a header written according to another protocol. The entire packet, including it's header, goes inside the body of the carrying packet.
  
  

Firewall Solution

• Firewalls are the biggest reason an organization would implement tunneling. VoIP traffic may be trusted, but the administration of firewalls to allow incoming calls is difficult to organize. One method of allowing through traffic of a certain type is to dedicate a port on the receiving device and leave it open. VoIP session management is dealt with following the session initiation protocol. SIP programs cannot be made to use the same port: The protocol specifies random ports. Wrapping VoIP packets in another protocol enables them to be channeled to a specific port.
  
  

Protocol Definition

• The IP-in-IP Protocol is managed by the Internet Engineering Task Force. The definition of the protocol can be downloaded for free by visiting the task force's website.