OSI Network Layer

1. OSI Network Layer
Network Fundamentals – Chapter 5
ITE I Chapter 6
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2. Objectives

Identify the role of the Network Layer, as it describes
communication from one end device to another end
device

Identify the most common Network Layer protocol,
Internet Protocol (IP), and its features for providing
connectionless and best-effort service

Identify the principles used to guide the division or
grouping of devices into networks

Identify the hierarchical addressing of devices and
how this allows communication between networks

Identify the fundamentals of routes, next hop
addresses and packet forwarding to a destination
network
ITE 1 Chapter 6
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3. Network Layer Protocols and Internet Protocol
(IP)
 Provides addressing via IP version 4 and increasingly
IPv6
 The routing of data
ITE 1 Chapter 6
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4. Network Layer Protocols and Internet Protocol
(IP)
 Internet Protocol version 4 (IPv4)
 Allows network devices to find each other
ITE 1 Chapter 6
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5. Network Layer Protocols and Internet Protocol
(IP)
 IP protocol is connectionless
 The receiver is not contacted before the data is sent
ITE 1 Chapter 6
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6. Network Layer Protocols and Internet Protocol
(IP)
 IP is an unreliable protocol i.e. does not guarantee data
delivery
ITE 1 Chapter 6
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7. Network Layer Protocols and Internet Protocol
(IP)
 IP uses the same protocol irrespective of the media
ITE 1 Chapter 6
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8. Network Layer Protocols and Internet Protocol
(IP)
 Transport Layer Segments or PDU are encapsulated in
Packets
ITE 1 Chapter 6
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9. Network Layer Protocols and Internet Protocol
(IP)
 IP Packets have fields just like TCP/UDP segments
 IP Encapsulate TCP/UDP segment with its header
Ver = IPv4
IHL = IP header length, Service Type =Priority (QOS),
Header Checksum = Error checking
Source Address =IP address of data source
Destination address = Data destination address
ITE 1 Chapter 6
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10. Hierarchical Addressing scheme (IP) and
grouping networks
 Enhances: Security, Manageability, Performance,
Troubleshooting, Scalability
Networks can be Divided
on:
Department
Purpose
Location
User – Permissions
User – Rights
ITE 1 Chapter 6
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11. Hierarchical Addressing aids performance
 Performance: Keeping traffic where it should be
increases network performance
Broadcast = The
ability to reach
all the devices
on your network
with the same
data
ITE 1 Chapter 6
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12. Hierarchical Addressing improves security
 Security: User permission and rights can be specified
ITE 1 Chapter 6
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13. Hierarchical Addressing aids data delivery
 Structure allows network devices to be quickly found
i.e. What network, then what host on that network
ITE 1 Chapter 6
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14. Networks and their address can be subdivided
with subnetting
 The host portion can be further subdivided into smaller
networks or subnets
Subnetting converts Host
bits into Network bits
ITE 1 Chapter 6
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15. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 Routers allow devices on different networks to pass
data between each other
ITE 1 Chapter 6
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16. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 To move packets to a different network a router is
required
ITE 1 Chapter 6
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17. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 Gateways are used to pass data to other networks
ITE 1 Chapter 6
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18. Gateways
 Gateways lead to other networks
ITE 1 Chapter 6
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19. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 A route consist of: Destination network, a Next hop
interface address and an Outgoing interface
ITE 1 Chapter 6
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20. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 A destination network is where the data is required to
be when its journey is complete
ITE 1 Chapter 6
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21. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 The next hop interface address tells the current router
what next interface to use for data to reach its
destination network
ITE 1 Chapter 6
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22. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 Routers move packet between subnets
ITE 1 Chapter 6
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23. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 Routing protocols allow routers to learn routing tables
that contain the location of networks
 Routing tables can be statically (manually) or
dynamically (automatically) configured
ITE 1 Chapter 6
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24. Fundamentals of Routes, Next Hop Addresses
and Packet Forwarding
 Routes or destination networks can be configured to
automatically build routing tables i.e.
(RIP,IGRP,EIGRP,OSPF etc)
ITE 1 Chapter 6
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25. Testing network addresses and connectivity
 Both ping and tracert are used by network engineers
to test network connectivity. For basic network
connectivity, the ping command works best. To test
latency (delay) and the network path, the tracert
command is preferred.
 The ability to accurately and quickly diagnose network
connectivity issues is a skill expected from network
engineer. Knowledge about the TCP/IP protocols and
practice with troubleshooting commands will build that
skill.
ITE 1 Chapter 6
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26. Ping example
ITE 1 Chapter 6
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27. Tracert example
ITE 1 Chapter 6
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28. Labs
 Lab 5.5.2 Examining a route (Destination networks,
Next hop interface, Gateway)
 Lab 6.7.1- Ping and Traceroute (Testing connectivity)
ITE 1 Chapter 6
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