1. 5 Network Layer Part II Computer Networks Tutun Juhana
Telecommunication Engineering
School of Electrical Engineering & Informatics
Institut Teknologi Bandung
Computer Networks

2. Delivery and Forwarding of IP Packets

3. Direct Delivery

4. Indirect Delivery

5. Forwarding
Forwarding means to place the packet in its route to its destination
to deliver the packet to the next hop (which can be the final destination or the intermediate connecting device)
Two kinds of forwarding
The destination address –based forwarding (when IP is used as a connectionless protocol)
Label-based forwarding (when the IP is used as a connection-oriented protocol)

6. Forwarding Based on Destination Address

7. Forwarding Techniques
Next-Hop Method
Network-Specific Method
Host-Specific Method
Default Method
To make the size of the routing table manageable

8. Next-Hop Method
The routing table holds only the address of the next hop instead of information about the complete route

9. Network-Specific Method

10. Host-Specific Method

11. Default Method

12. Forwarding with Classful Addressing

13. Forwarding without Subnetting

15. Example 6.2
Router R1 in Figure 6.8 receives a packet with destination address Show how the packet is forwarded
Solution
The destination address in binary is A copy of the address is shifted 28 bits to the right. The result is or
12. The destination network is class C. The network address is extracted by masking off the leftmost 24 bits of the destination address; the result is The table for Class C is searched. The network address is found in the first row. The next-hop address and the interface m0 are passed to ARP

17. Forwarding with Subnetting

19. Forwarding with Classless Addressing

23. Address Aggregation
In classful addressing, there is only one entry in the routing table for each site outside the organization
In classless addressing, it is likely that the number of routing table entries will increase  The increased size of the table results in an increase in the amount of time needed to search the table  to alleviate the problem, the idea of address aggregation was designed

25. The routing table is sorted from the longest mask to the shortest mask
Longest Mask Matching
Packet arrives with dest. add
By longest mask matching correctly routed to Organization 4
The routing table is sorted from the longest mask to the shortest mask

26. STRUCTURE OF A ROUTER

27. Components
performs the functions of the network layer

28. Switching Fabrics