Why network models are divided into layers?

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1. #seven
2. #layers
3. #systems
4. #organization
5. #moving
6. #mostly
7. #divides
8. #network
9. #model
10. #lower
11. #concern
12. #standards
13. #interconnection
14. #themselves
15. #international
16. #around
17. #developed
18. #communication
19. #considered