1. Network Layer

2. The Network layer, or OSI Layer 3, provides services to exchange the individual pieces of data over the network between identified end devices. To accomplish this end-to-end transport, Layer 3 uses four basic processes:  Addressing  Encapsulation  Routing  Decapsulation

3. Routing The source and destination hosts are not always connected to the same network. In fact, the packet might have to travel through many different networks. Along the way, each packet must be guided through the network to reach its final destination. Intermediary devices that connect the networks are called routers. The role of the router is to select paths for and direct packets toward their destination. This process is known as routing. Each route that a packet takes to reach the next device is called a hop.

4. Protocols in Network Layer The Internet Protocol (IPv4 and IPv6) is the most widely-used Layer 3 data carrying protocol

5. Why separate hosts into network ? Performance

6. Packet tracer broadcast domain

7. Security

8. Address Management

9. Network layer in an internetwork

10. Network layer at the source

11. Network layer at a router

12. Network layer at the destination

13. IP Addressing (IPv4) Internet Address Class full Addressing

14. An IP address is a 32-bit address. Note: The Internet Protocol was designed as a protocol with low overhead. It provides only the functions that are necessary to deliver a packet from a source to a destination over an interconnected system of networks. The protocol was not designed to track and manage the flow of packets. These functions are performed by other protocols in other layers. IPv4 basic characteristics: Connectionless - No connection is established before sending data packets. Best Effort (unreliable) - No overhead is used to guarantee packet delivery Here, Unreliable means simply that IP does not have the capability to manage, and recover from, undelivered or corrupt packets. Media Independent - Operates independently of the medium carrying the data.

15. The IP addresses are unique and universal. Note:

16. Dotted-decimal notation

17. Example 1 Change the following IP addresses from binary notation to dotted- decimal notation. a.10000001 00001011 00001011 11101111 b.11111001 10011011 11111011 00001111

18. Example 2 Change the following IP addresses from dotted-decimal notation to binary notation. a.111.56.45.78 b.75.45.34.78

19. In classful addressing, the address space is divided into five classes: A, B, C, D, and E. Note:

20. Finding the class in binary notation

21. Finding the address class

22. Example 3 Find the class of each address: 0 a.00000001 00001011 00001011 11101111 1111 b.11110011 10011011 11111011 00001111

23. Finding the class in decimal notation

24. Example 4 Find the class of each address: a.227.12.14.87 b.252.5.15.111 c.134.11.78.56

25. Netid and hostid

26. Blocks in class A

27. Millions of class A addresses are wasted. Note:

28. Blocks in class B

29. Many class B addresses are wasted. Note:

30. The number of addresses in class C is smaller than the needs of most organizations. Note:

31. Blocks in class C

32. Network address

33. In class full addressing, the network address is the one that is assigned to the organization. Note:

34. Example 5 Given the address 23.56.7.91, find the network address. Ans. 23.0.0.0 (kelas A)

35. Example 6 Given the address 132.6.17.85, find the network address. Ans. 132.6.0.0 (kelas B)

36. Example 7 Given the network address 17.0.0.0, find the class.

37. A network address is different from a netid. A network address has both netid and hostid, with 0s for the hostid. Note:

38. Sample internet (classful)

39. Gateway

40. IP Private Range Total 10.0.0.0 to 10.255.255.2552 24 172.16.0.0 to 172.31.255.2552 20 192.168.0.0 to 192.168.255.2552 16 Private addresses (others are called Public IP or Global address) :