Example Protocol Stack
| OSI model layer | Protocol |
|---|---|
| 5. Session | X.225 |
| 4. Transport | UDP |
| 3. Network | IPv6 |
| Encapsulation | GRE |
| 3. Network | IPv4 |
| 2. Data Link | Ethernet |
| 1. Physical | Ethernet physical layer |
From what can be seen in the diagram above, protocol encapsulation (not specifically GRE) breaks the layering order in the OSI model terms. It may be viewed as a separator between two different protocol stacks, one acting as a carrier for another.
Read more about this topic: Generic Routing Encapsulation
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