Network Devices B02

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 Repeater:

  • A repeater is a network hardware device that amplifies and regenerates signals as they pass through the network.
  • They do not amplify signal.
  • It's a 2-port device.
Hub:
  • A hub is a hardware device that relays communication data to all devices on a network.
  • It does not filter the data packets based on the mac address.

Types of Hubs
Active Hub:
  • A hub is a hardware device that relays communication data to all devices on a network.
  • These are used to extend the maximum distance between nodes.
Passive Hub:
  • These are used to extend the maximum distance between nodes.
  • These hubs relay signals onto the network without cleaning and boosting them and can’t be used to extend the distance between nodes.
Intelligent Hub:
  • These hubs relay signals onto the network without cleaning and boosting them and can’t be used to extend the distance between nodes.
  • It also enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub.

Switches

  • Switches are devices that connect other devices together in a computer network.
  • They are capable of creating temporary connections between two or more devices that are linked to them.
  • Switches manage the flow of data across a network by transmitting a received network packet only to the one or more devices for which the packet is intended.
Switching operation
  1. Data is sent onto the medium one frame at a  time
  2. Each frame has the destination and source MAC addresses
  3. Switch reads the addresses:
  4. Use the source MAC address of frame to keep a record of which computer is on which port (switching table)
  5. Forwards the frame to the port where the destination MAC can be found.
Network Switches and Bandwidth
  • Each port gets dedicated bandwidth.
  • Instead of having to share bandwidth with all ports.
  • Multiple conversations can occur simultaneously.
  • Can operate in full-duplex mode.
  • Can send and receive data simultaneously.
  • Hubs can only operate in half-duplex mode.
  • Can send or receive (but not both) at one time.
  • Switches are the preferred device because of these advantages.


Router

  • A router is a device like a switch that routes data packets based on their IP addresses. 
  • The router is mainly a Network Layer device. 
  • Most complex device.
  • Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. 
  • Router divide broadcast domains of hosts connected through it.

Multiport Repeater

  • A multiport repeater is just a repeater with several ports to which you can connect cabling.
  • Also referred to as hub.
  • Regenerates signal to full strength.
Routers Work with IP Addresses and Routing Tables
Default route -- where to send a packet when the router doesn’t have an entry in its routing table
Network unreachable --Message sent when the network can’t be found and no default route
Default gateway-- In a computer’s IP address configuration – the IP address of the computer’s router


Hubs and Network Bandwidth
  • Amount of data that can be transferred in an interval is network bandwidth.
  • Usually measured in bits per second (bps) and networks operate at speeds from 10 million bps up to 10 gigabit per second (Gbps).
  • Hubs share bandwidth with all other connected computers. Only can successfully transfer.
WAP: Wireless Access Point
A wireless access point (WAP) is a networking device that allows wireless-capable devices to connect to a wired network.
Wireless LANs are usually attached to wired networks.

NIC Basics.
provide a connection from computer to medium.
  1. receives messages in bits signals and assembles them into frames.
  2. then receives packets from network protocol.
  3. converts frames into bit signals suitable for the medium and transmits them.
Every NIC produced has a unique address. NIC won't work if duplicate MAC addresses exist.

MAC address

Two 24 bit hexadecimal numbers:
24 bit manufacturer ID 
24 bit serial numbers

48 bits address expressed in 12 hexadecimal.

NIC as Gatekeeper
When a frame arrives at a NIC, the NIC check’s the frame’s destination MAC address to see whether it matches it’s built-in MAC address.
It only permits inbound Communications if the destination MAC address matches the NIC burned-in address and is a broadcast address.

Indicator Light: Link light is usually green when the NIC has valid connection medium network.

NIC Driver: It provides the data link protocol (Ethernet, Token Ring, etc.) that controls the specific brand of network adapter installed in the computer.

Wireless NIC: NIC has a unique media access control (MAC) address burned into it at manufacture, to uniquely identify it; it also contains a small radio device and an antenna. However, the NIC must be compatible with the AP before communication can occur.





















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