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I have researched the topic of Network Tunnel but the information on this is rather confusing and inconsistent. So could someone please explain:
In general, What is tunneling? Is it simply an act of encapsulating a packet with another header and destine it to another point?
What is the purpose of tunneling? A switching or routing network is capable of delivering traffics, why then would you need a tunnel? What is the advantage?
The non technical explanation of the reason we like to use them "or need them" is not only encryption but within that tunnel we can supply routes to your computer or remote site that are private networks through the tunnel. This allows Site A to not only connect to Site B but I can have routes to other internal networks at Site A from Site B over a public circuit like the internet.
Examples, with normal communication I can connect to a remote ip address but not access all the internal private ip addresses because the internet doesn't support those addresses of course.
If I put a tunnel between two sites I can access networks like 192.168.1.0 for example even though it's in a diffrent location. It's almost like combining Lans.
Source: http://www.differencebetween.com/difference-between-encapsulation-and-vs-tunneling/
Tunneling
Tunneling is a method used to transfer a payload of one protocol using an internetwork transportation medium of another protocol. The data that need to be transferred are typically frames/packets belonging to a certain protocol (different to the protocol used to send data). Because of this, the payload cannot be sent as it is produced by its origin. The frames need to be encapsulated in an additional header, which provides the routing information necessary to transmit the data correctly, before sending. A tunnel (a logical path, which interconnects the end points between that the frames must travel) is created and the frames are routed between the tunnel endpoints through the internetwork.
When the encapsulated packets reach the destination end point of the tunnel, they are de-encapsulated and the original packets contained inside are sent to the intended destination. This overall process including the encapsulation and de-encapsulation is called tunneling. Both Layer 2 and Layer 3 (of Open Systems Interconnection Reference Model) use tunneling. Typical Layer 2 tunneling protocols are PPTP (Point-to-Point Tunneling Protocol) and L2TP (Layer Two Tunneling Protocol). Layer 3 usually uses IPSec tunnel mode as a tunneling protocol.
Encapsulation
Encapsulation is the process of encapsulating the packets inside an additional header before tunneling. This additional header contains the routing information necessary to send the encapsulated payload through the intermediate internetwork. This information is essential because the payload is sent through a network (protocol) different to the network in which the data was created. In Layer 2 (which uses frames as the unit of exchange) tunneling, both PPTP and L2TP do encapsulation in a PPP (Point-to-Point Protocol) frame. In Layer 3 (which uses packets as the unit of exchange) tunneling, IPSec tunnel mode encapsulates IP (Internet Protocol) packets with an additional IP header.
Difference
Tunneling is a method used to transfer a payload of one protocol using an internetwork infrastructure of another protocol. Encapsulation is the process of encapsulating the frame with an additional header so that it can be sent (tunneled) through the intermediate network correctly. Tunneling is referred to the whole process of encapsulation, transmission and de-encapsulation, while encapsulation is only a step within this entire process. However, regardless of this whole-part relationship, tunneling is sometimes also known as encapsulation.
To put it simply, tunneling is the process of encapsulating data (think of it as putting inside a capsule) into another form of data so the network devices directly interact with the outside capsule...
The easiest concept of encapsulation to explain is a VPN encrypted tunnel(Virtual Private Network) where the original data is concealed in the header of another packet... You can also encapsulate data without encryption to get around firewall restrictions... consider this scenario: -At work, you have a proxy server that only allows access to certain websites. -The proxy server does not monitor DNS traffic over UDP port 53. -You can then create a VPN tunnel with an external host over port 53. -The VPN tunnel created above is NOT monitored by the proxy. -You can tunnel any kind of traffic you want and the proxy server will not bother to inspect it.
Hope I helped to create some understanding :-)
