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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 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 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 header1
5.1.7 IPv4 packet header
  • Typical IP Packet
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 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 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 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)
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