21' Networking and Internetworking Devices

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21?. Networking and Internetworking Devices

• 21.1 Repeaters
• 21.2 Bridges
• 21.3 Routers
• 21.4 Gateways
• 21.5 Routing Algorithms
• 21.6 ??

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Networking and Internetworking Devices(contd)

• An internet is an interconnection of individual
  networks. To creates an internet, we need
  internetworking devices called routers and
  gateways.
• An internet is different from the Internet.
• Internet is the name of a specific worldwide
  network.

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Networking and Internetworking Devices(contd)

• Connecting device

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Networking and Internetworking Devices(contd)

• Connecting devices and the OSI model

Gateway
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Router
Data link
Data link
Bridge
Physical
Physical
Repeater
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21.1 Repeaters

• is an electronic device that operates on only
  the physical layer of the OSI model.

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Repeaters(contd)

• Repeater allows us to extend only the physical
  length of a network.

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Repeaters(contd)

• Function of a repeater

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21.2 Bridges

• operate in both the physical and the data link
  layers of the OSI model.

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Bridges(contd)

• Bridges divide a large network into smaller
  segments

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Bridges(contd)

• Function of a bridge

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Bridges(contd)

• Types of Bridges
• Simple Bridges
• Learning Bridges
• Multiport Bridges

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21.3 Routers

• operate in the physical, data link, and
  network layers of the OSI model.

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Routers(contd)

• Routers relay packets among multiple
  interconnected networks.

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Routers(contd)

• Routing concepts
• Whenever there are multiple options, the router
  chooses the pathway.
• Least-Cost Routing
• Which path does it choose?
• Decision is based on efficiency(cheapest,
  fastest, shortest)
• Distributed Routing
• Packet Lifetime(number of hops)

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21.4 Gateways

• potentially operate in all seven layers of the
  OSI model(protocol converter).

Application Presentation Session Transport Network
Data link Physical
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Gateways(contd)

• Gateway

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21.5 Routing Algorithms

• - in routing the pathway with the lowest cost is
  considered the best.
• - as long as the cost of each links is known, a
  router can find the optional combination for any
  transmission.
• - Two common methods are used to calculate the
  shortest path between two routers distance
  vector routing and link state routing.

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Routing Algorithms(contd)

• Distance Vector Router
• each router periodically shares its knowledge
  about the entire network with its neighbors.
• 1. Knowledge about the whole network.
• 2. Routing only to neighbors.
• 3. Information sharing at regular intervals.

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Routing Algorithms(contd)

• Sharing Information
• Example of an internet

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Routing Algorithms(contd)

• Concept of distance vector routing

I periodically send my knowledge about the whole
internetwork to A, C.
I periodically send my knowledge about the whole
internetwork to B, D.
I periodically send my knowledge about the whole
internetwork to B, F, E.
I periodically send my knowledge about the whole
internetwork to A.
I periodically send my knowledge about the whole
internetwork to A, D.
I periodically send my knowledge about the whole
internetwork to C, E.
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Routing Algorithms(contd)

• Routing table(distance vector)

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Routing Algorithms(contd)

• Creating the table

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Routing Algorithms(contd)

• Updating the table
• Updating routing table for router A

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Routing Algorithms(contd)

• Updating routing table for router C

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Routing Algorithms(contd)

• Updated routing tables

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Routing Algorithms(contd)

• Updating routing table for router F

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Routing Algorithms(contd)

• New updated routing tables

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Routing Algorithms(contd)

• Final routing tables

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Routing Algorithms(contd)

• Link State Routing
• each router shares its knowledge of its
  neighborhood with all routers in the network.
• 1. Knowledge about the neighborhood.
• 2. To all routers.
• 3. Information sharing at regular intervals.

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Routing Algorithms(contd)

• Information Sharing

I send information about my neighbors to every
router.
I send information about my neighbors to every
router.
I send information about my neighbors to every
router.
I send information about my neighbors to every
router.
I send information about my neighbors to every
router.
I send information about my neighbors to every
router.
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Routing Algorithms(contd)

• Packet Cost
• is a weighted value based on a variety of
  factors such as security levels, traffic, or
  state of the link.
• Cost is applied only by routers and not by any
  other stations on a network
• Cost is applied as a packet leaves the router
  rather than as it enters

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Routing Algorithms(contd)

• Cost in link state routing

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Routing Algorithms(contd)

• LSP(Link State Packet)

Advertiser
Network
Cost
Neighbor




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Routing Algorithms(contd)

• Getting information about Neighbors(Initialization
  )
• Flooding of As LSP

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Routing Algorithms(contd)

• Flooding of Bs LSP

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Routing Algorithms(contd)

• Link State Database
• every router has exactly the same link state
  database

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Routing Algorithms(contd)

• Dijkstra Algorithm
• calculates the shortest path between two points
  on a network using a graph made up of nodes and
  arcs.
• Node networks and routers
• Arc connection between a router and a network
• Cost applied only to the arc from router to
  network

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Routing Algorithms(contd)

• Cost in the Dijkstra Algorithm

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Shortest Path calculation

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Routing Algorithms(contd)

• Routing Table
• In link state routing, the link state database
  is the same for all routers, but shortest path
  trees and the routing tables are different for
  each router.

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Routing Algorithms(contd)

• Link state routing table for router A

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21.6 ??