1. © 2003, Cisco Systems, Inc. All rights reserved.

2. Network Layer Protocol Overview
Module : TCP/IP
Network Layer Protocol Overview

3. Objectives Name two protocols that operate at the network layer
Identify three functions of the IP protocol
Identify three functions of the ICMP protocol
Identify a function of both ARP and RARP
Identify the function of DHCP
Identify three fields in an IP datagram
Describe the function of the protocol field in an IP datagram
Lesson Aim
<Enter lesson aim here.>

4. Network Layer Application Transport Network Data Link Physical
Internet Protocol (IP)
Internet Control Message Protocol (ICMP)
Address Resolution Protocol (ARP)
Reverse Address Resolution Protocol (RARP)
Dynamic Host Configuration Protocol (DHCP)
Transport
Lesson Aim
<Enter lesson aim here.>
Network
Data Link
Physical

5. IP Characteristics Packets are treated independently
Packet delivery is not guaranteed
Lesson Aim
<Enter lesson aim here.>
Lost or corrupted packets are not recovered

6. ICMP Application Transport Network Data Link Physical
Lesson Aim
<Enter lesson aim here.>
Destination unreachable
Echo (Ping)
Other
Network
Data Link
Physical

7. ARP IP: 172.16.3.2 = ??? IP: 172.16.3.2 = Ethernet: 0800.0200.1111
I need the MAC address of
I heard that broadcast. That is me. Here is my MAC address.
Lesson Aim
<Enter lesson aim here.>
IP: = ???
IP: = Ethernet:
Map IP
Ethernet
Local ARP

8. I heard that broadcast. Your IP address is 172.16.3.25
RARP
I heard that broadcast. Your IP address is
What is my IP address?
Lesson Aim
<Enter lesson aim here.>
Ethernet: IP: ????
Ethernet: IP:
Maps Ethernet IP

9. DHCP The DHCP server leases an address to the DHCP client. Client
DHCP client broadcasts discover message
Client
DHCP client broadcasts offer message
Server
DHCP client responds with request message
Client
Lesson Aim
<Enter lesson aim here.>
DHCP server seals the deal with acknowledgement message
Server
Client
The DHCP server leases an address to the DHCP client.

10. IP Datagram Byte 1 Byte 2 Byte 3 Byte 4 Word 1 Word 2 Word 3 Word 4
Ver.
IHL
Service Type
Packet Length
Identification
Flag
Frag. Offset
Time to Live
Protocol
Header Checksum
Source Address
Lesson Aim
<Enter lesson aim here.>
Destination Address
Options
Padding

11. Protocol Field Protocol Protocol Field
Transmission Control Protocol (TCP) 6
User Datagram Protocol (UDP) 17
Internet Control Message Protocol 1
Lesson Aim
<Enter lesson aim here.>
IPv6 41 58
ICMP for IPv6
EIGRP 88

12. Summary
The network layer provides a means for routing information from the source to a destination.
IP is a standard that defines the manner in which the network layers of two hosts interact.
ICMP is a protocol sent in response to errors in TCP/IP messages.
ARP maps IP network addresses to the physical addresses.

13. Summary (Cont.) RARP maps physical addresses into IP addresses.
DHCP automates the configuration of IP addresses on devices that use TCP/IP.
IP transfers information through the network in the form of a datagram.
IP uses a protocol number in the datagram header to identify which protocol to use for a particular datagram.