Module5- OSI Network Layer

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1 Module 5 OSI Network Layer

description

OSI Network Layer

Transcript of Module5- OSI Network Layer

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Module 5

OSI Network Layer

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• IPv4• Networks – Dividing Hosts into Groups• Routing – How Our Data Packets are Handled• Routing Process: How Routes are Learned

Objectives

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IPv4

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Network Layer – Communication from Host to Host

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Network Layer ProtocolsLayer 3 uses four basic processes:

• Addressing• Encapsulation• Routing• Decapsulation

Addressing (routed protocol)

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The IPv4 Protocol – Example Network Layer Protocol

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The IPv4 Protocol –Connectionless

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The IPv4 Protocol – Best Effort

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The IPv4 Protocol – Media Independent

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IPv4 Packet – Packaging the Transport Layer PDU

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IPv4 Packet – Header

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Networks – Dividing Hosts into Groups

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Networks – Separating Hosts into Common Groups

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Grouping Hosts Geographically

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Grouping Hosts for Specific Purposes

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Grouping Hosts for Ownership

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Why Separate Hosts Into Networks ? –Performance

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Why Separate Hosts Into Networks ? –Performance

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Why Separate Hosts Into Networks ? –Security

• All users have access to the Internet• Each user can reach servers in its own department• Each user is blocking form reaching servers in other department

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Why Separate Hosts Into Networks ? –Address Management

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How Do We Separate Hosts Into Networks ? –Hierarchical Addressing

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Dividing the Network – Networks fromNetworks

• This is hierarchical addressing because the network portion indicates the network on which each unique host address is located.

• Routers only need to know how to reach each network, rather than needing to know the location of each individual host.

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Routing – How Our Data Packets are Handled

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IP Address – Carrying Data End to End

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A Gateway – The Way Out of Our Network

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Confirming the Gateway Settings

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Local Router Routing Table

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A Route – The Path to a Network

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A Route – The Path to a Network

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The Destination Network

• Packets with destination host addresses in one of the network ranges shown will be matched with the next hop that leads to that network

• The precedence of route selection for the packet going to 10.1.1.55 would be:1. 10.1.1.02. 10.1.0.03. 10.0.0.04. 0.0.0.0 (Default route if configured)5. Dropped

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The Destination Network

• The routing table shows the default route 0.0.0.0• The router may also use a default route (gateway of last resort) to forward the

packet. • The default route is used when the destination network is not represented by

any other route in the routing table.

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The Next Hop – Where the Packet Goes Next

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Packet Forwarding – Moving the Packet Towards its Destination

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Packet Forwarding – Moving the Packet Towards its Destination

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Packet Forwarding – Moving the Packet Towards its Destination

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Routing ProcessHow Routes are Learned

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Routing Protocols – Sharing the Routes

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Static Routing

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Dynamic Routing

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Good luck with this module!