THE VoIP TUNNEL
The internet in this example does not process the voice packets, nor the upper layer headers. They are sent through the internet without being examined. This idea is called a VoIP tunnel and Figure 7-3 depicts the concept. Two points should be noted here. First, the dotted lines in the figure represent the logical communications that occur between the peer layers through the exchange of the protocol headers (protocol control information). Physically, the traffic is moving down the layers when it is being sent, and up the layers when it is being received.
The VoIP tunnel is actually a tunnel for the voice packets, RTP and UDP. Strictly speaking, it is not an IP tunnel because IP is being invoked at each node, as suggested by the ...
Get Voice Over IP now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
