1. Delivery, Forwarding, and Routing of IP Packets
Chapter 6
Delivery, Forwarding, and Routing of IP Packets
Objectives
Upon completion you will be able to:
Understand the different types of delivery and the connection
Understand forwarding techniques in classful addressing
Understand forwarding techniques in classless addressing
Understand how a routing table works
Understand the structure of a router
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2. Delivery, Forwarding, Routing
Delivery refers to the way a packet is handled by the underlying networks under the control of the network layer
Forwarding refers to the way a packet is delivered to the next station(s)
Routing refers to the way routing tables are created to help with forwarding
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3. Connectionless vs. Connection-oriented
A network can be connectionless or connection-oriented
X.25 is an example of conn.oriented
IP is an example of conn.less
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4. Figure 6.1 Direct delivery
If netid of source is same as netid of destination, then you know
it is direct delivery. ARP is usually used to map IP address to
local (NIC) address.
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5. Indirect Delivery
Sender uses destination IP address and a routing table to find the IP address of the next router
Sender then uses that IP address and ARP to find the physical address of the next router
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6. Figure 6.2 Indirect delivery
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7. 6.2 FORWARDING
Forwarding means to place the packet in its route to its destination. Forwarding requires a host or a router to have a routing table.
The topics discussed in this section include:
Forwarding Techniques
Forwarding with Classful Addressing
Forwarding with Classless Addressing
Combination
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8. Forwarding Techniques
You look in a table for the final destination and it tells you which route to take to get there. This is not realistic on the Internet.
Several techniques can make the size of the routing table manageable
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9. This is not feasible on the Internet.
Figure Next-hop method - Table contains next hop only (bottom figure)
This is not feasible on the Internet. -
Routing table shows just the next hop.
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10. Figure 6.4 Network-specific method
This is host-specific.
This is network-specific.
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11. Figure 6.5 Host-specific routing
Host-specific routing can be used to direct to a specific router.
Host B
traffic is
sent thru
R3, not R1
and R2.
TCP/IP Protocol Suite