Osi network layer
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OSI Network Layer. Network Fundamentals – Chapter 5. Objectives. Identify the role of the Network Layer, as it describes communication from one end device to another end device

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Osi network layer

OSI Network Layer

Network Fundamentals – Chapter 5


Objectives

Objectives

  • Identify the role of the Network Layer, as it describes communication from one end device to another end device

  • Examine the most common Network Layer protocol, Internet Protocol (IP), and its features for providing connectionless and best-effort service

  • Understand the principles used to guide the division or grouping of devices into networks

  • Understand the hierarchical addressing of devices and how this allows communication between networks

  • Understand the fundamentals of routes, next hop addresses and packet forwarding to a destination network


Course index

Course Index

  • 5.1 IPv4

  • 5.2 Networks – Dividing Hosts into Groups

  • 5.3 Routing – How Our Data Packets are Handled

  • 5.4 Routing Processes: How Routes are Learned

  • 5.5 Lab Activities


5 1 ipv4

5.1 IPv4


5 1 1 network layer communication from host to host

5.1.1 Network Layer – Communication from Host to Host

  • Network Layer

    • Provides services to exchange the individual pieces of data over the network between identified end devices

    • Basic process:

      • Addressing

      • Encapsulation

      • Routing

      • Decapsulation

    • Protocols

      • Internet Protocol version 4 (IPv4)

      • Internet Protocol version 6 (IPv6)

      • Novell Internetwork Packet Exchange (IPX)

      • AppleTalk

      • Connectionless Network Service (CLNS/DECNet)


5 1 2 the ipv4 protocol

5.1.2 The IPv4 Protocol

  • Role of IPv4

    It is used to carry user data over the Internet


5 1 3 the ipv4 protocol connectionless

5.1.3 The IPv4 Protocol – Connectionless

  • Connectionless Service


5 1 4 the ipv4 protocol best effort

5.1.4 The IPv4 Protocol – Best Effort

  • Best Effort Service (unreliable)


5 1 5 the ipv4 protocol media independent

5.1.5 The IPv4 Protocol – Media Independent

  • Media independent

  • Maximum Transmission Unit (MTU):the maximum size of PDU that each medium can transport.

  • fragmenting the packet or fragmentation: the process of an intermediary device - usually a router - will need to split up a packet when forwarding it from one media to a media with a smaller MTU


5 1 6 ipv4 packets packaging the transport layer pdu

5.1.6 IPv4 Packets – Packaging the Transport Layer PDU

  • IPv4 encapsulates, or packages, the Transport layer segment or datagram so that the network can deliver it to the destination host.

  • The encapsulated Transport layer PDU - remains unchanged during the Network layer processes.


5 1 7 ipv4 packet header

5.1.7 IPv4 packet header


5 1 7 ipv4 packet header1

5.1.7 IPv4 packet header

  • Typical IP Packet


5 2 networks dividing hosts into groups

5.2 Networks – Dividing Hosts into Groups


5 2 1 networks separating hosts into common groups

5.2.1 Networks –Separating Hosts into Common Groups

  • Subnet

    • Separating hosts into common groups

    • The factors of group

      • Geographic location

      • Purpose

      • Ownership


5 2 2 why separate hosts into networks

5.2.2 Why Separate Hosts Into Networks?

  • Performance

    • Dividing large networks so that hosts who need to communicate are grouped together reduces the traffic across the internetworks.

    • Broadcasts are contained within a network, so a network is also known as a broadcast domain.


5 2 3 why separate hosts into networks

5.2.3 Why Separate Hosts Into Networks?

  • Security

    • Dividing networks based on ownership means that access to and from resources outside each network can be prohibited, allowed, or monitored.


5 2 4 why separate hosts into networks

5.2.4 Why Separate Hosts Into Networks?

  • Address Management

    • Dividing large networks so that hosts who need to communicate are grouped together reduces the unnecessary overhead of all hosts needing to know all addresses


5 2 5 how to divide networks

5.2.5 How to divide networks?

  • Hierarchical addressing


5 2 6 dividing the networks networks from networks

5.2.6 Dividing the Networks – Networks from Networks

  • IPv4 is a Hierarchical addressing


5 3 routing how our data packets are handled

5.3 Routing – How Our Data Packets are Handled


5 3 1 device parameters supporting communication outside our network

5.3.1 Device Parameters - Supporting Communication Outside Our Network


5 3 2 ip packet carrying data end to end

5.3.2 IP packet—carrying data end to end


5 3 3 a gateway the way out of our network

5.3.3 A Gateway – The Way Out of Our Network

  • A router interface connected to the local network.

  • When a packet’s destination is a different network, the packet is sent to the gateway.


5 3 4 a route the path to network

5.3.4 A Route – The Path to Network

  • Three main features of route:

    • Destination network

    • Next-hop

    • Metric

  • Routing table

  • Routing protocols.


5 3 5 destination network

5.3.5 Destination network


5 3 6 the next hop where the packet goes next

5.3.6 The Next Hop – Where the Packet Goes Next


5 3 7 packet forwarding

5.3.7 Packet Forwarding

  • Forward it to the next-hop router

    • Have a exactly entry

    • No exactly entry but a default route exits

  • Forward it to the destination host

    • Direct connected network

  • Drop it

    • No entry and no default route


5 4 routing processes how routes are learned

5.4 Routing Processes: How Routes are Learned


5 4 1 routing protocols

5.4.1 Routing Protocols

  • Used for Sharing the Routes


5 4 2 static routing

5.4.2 Static Routing

  • Manually configured on the router


5 4 3 dynamic routing

5.4.3 Dynamic Routing

  • Dynamic Routing protocols are the set of rules by which routers dynamically share their routing information.

  • Common dynamic routing protocols:

    • Routing Information Protocol (RIP)

    • Enhanced Interior Gateway Protocol (EIGRP)

    • Open Shortest Path First (OSPF)


Summary

Summary


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