Network Devices-Hub, Switch, Router, etc

Network devices are physical devices that are required for communication and interaction between hardware on a computer network. The network devices work as a group and have a single purpose which securely transfers data as fast as possible. To meet this goal there are several networking devices like repeater, bridge, hub, switch, router etc.

Hub

Hub is one of the basic networking devices which works at the physical layer and hence connect networking devices physically together. It is not really used in modern networks. In networking, it is just studied because it is helpful to understand switch if somebody understands it then he can easily understand a switch

It is a device that simply copies a data which received on any port to all its ports.  So, if a packet of data arrives on interface 1 of a 5 port hub, It will blindly copy that data out the interfaces 2 through 5. It’s a common connection point for devices in a network. Different segment of LAN commonly connected to the hub. It was a cheap and quick way to link up multiple computers in the early days.

Hub utilizes Carrier Sense Multiple Access with Collision Detect (CSMA/CD) to control Media access. Ethernet hub communicates in a half-duplex mode where the chances of data collision are inevitable at most of the times. This is the main issue with hubs though is that only one computer can talk at a time.

So, If 2nd computers going to talk at the same time, their traffic would get joined as it was echoed out the other interfaces.  This is called a collision, and it would corrupt the data being transmitted by both computers. So, each computer would have to try again, after a random time period.  This becomes a real problem when the network gets busy or when more than a hand full of computers are on a network.  A switch solves the collision issue. Hub is a single broadcast and single collision domain. It has two types:-

Passive Hub

They Just point contact for the wires to built in the physical network. They have nothing to do with modifying the signals.

Active Hub

Active hubs are smarter than passive hubs. They regenerate the original signals, concentrate and strengthen the signals before sending them to their destinations. Active hubs are also termed as ‘repeaters’.

Repeater

A repeater is an electronic device operates at the physical layer. It has two Ethernet ports. Repeater amplifies the received signal and retransmits the signals in the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. When the signal becomes weak, repeater copy the signal bit by bit and regenerate it at the original strength.

Bridge

If a router connects two different types of networks, then a bridge connects two sub-networks as a part of the same network. The basic role of bridges in network architecture is storing and forwarding frames between the different segments that the bridge connects.

Bridge works at the Physical and Data Link layer of the OSI Model and connects the different networks together and develops communication between them. It connects two local-area networks two physical LANs into larger logical LAN or two segments of the same LAN that use the same protocol.  We can also use the bridge to divide larger networks into smaller sections by sitting between two physical network segments and managing the flow of data between the two reducing the broadcast between them.

Bridge uses MAC addresses for transferring frames. By looking at the MAC address of the devices connected to each segment, bridges can forward the data or block it from crossing. Bridges can also be used to connect two physical LANs into a larger logical LAN.  There are three main types of bridges:-

Transparent Bridge

Transparent bridge maintains a list of MAC addresses and appears transparently for other devices on the network. The other devices are ignorant of its existence. It only blocks or forwards the data as per the MAC address.  Transparent bridges also save and maintain the source-route addresses of incoming frames by listening to all the connected bridges and hosts. They use a transparent bridging algorithm to accomplish this.

Source Route Bridge

A form of routing used to allow connection to be established between pairs of nodes on different token rings. Source route bridge uses the path which the packet takes through the network is implanted within the packet.

Translational Bridge

Translational bridges reorder source and destination address bits when translating between Ethernet and Token Ring frame formats. It converts the data format of one networking to another.

Network Devices-Hub, Switch, Router, etc 2

Switch

An Ethernet Switch is a device which is used to connect multiple computers and devices within  LAN. It is work at Layer Two (Data Link Layer) of the OSI model. Some switches also work at layer 3( Network Layer). These switches referred to as Layer 3 switches or multilayered switches.

Basic Function of a Network Ethernet Switch and a Network Ethernet Hub are same. That is to forward Layer 2 packets (Ethernet frames) from source device to the destination device. But, a Network switch is more intelligence than a hub. Because an Ethernet switch uses MAC addresses to make forwarding decisions. It does not know about the protocol carried in the data portion such as an IPv4 packet. The switch makes its forwarding decisions based only on the Layer 2 Ethernet MAC addresses.

Unlike an Ethernet hub that repeats bits out all ports except the incoming port; an Ethernet switch consults a MAC address table to make a forwarding decision for each frame. The MAC address table is sometimes referred to as a content addressable memory (CAM) table. Network Switches of different input and output bandwidths are available. Today’s Ethernet Network Switches can have bandwidths of 10, 100, 1000 or 10,000 Megabits per second.

Switch Features and Advantages

  • Connect network devices together in a Local Area Network (LAN).
  • Its learn Layer 2 (MAC) addresses and forward Layer 2 packets (Ethernet frames); to exact destination with the help of device mac address
  • It’s control of who has access to various parts of the network.
  • Provision to monitor network usage.
  • High-end switches have pluggable modules.
  • Allow to connect multiple device and port can be managed  VLAN can create security also can apply
  • First broadcast; then unicast & multicast as needed.
  • Switches use content accessible memory CAM table which is typically accessed by ASIC (Application Specific integrated chips).
  • Half/Full duplex
  • Connecting two or more nodes in the same network or different network
  • The switch has one broadcast domain [unless VLAN implemented]

Router

The router is a network device. It selects the best path for a data packet. The router is located at any gateway (where one network meets another). Its forward data packets from one network to another based on the address of the destination network in the incoming packet and an internal routing table. It also determines which port (line) to send out the packet (ports typically connect to Ethernet cables).

Routers also require packets formatted in a routable protocol. The global standard being TCP/IP, or simply “IP.” Routers operate at Layer 3 (network layer) of the OSI model and it uses the destination IP address in a data packet to determine where to forward the packet. Router store the IP address in Routing table and maintain an address on its own.

Gateway

Gateways usually work at the Transport layer and Session layer of the OSI model. It connects two networks together that may work upon different networking models. Gateway takes data from one system, interpret it, and transfer it to another system. It also is known as protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router. Gateway deals with numerous protocols and standards from different vendors. It performs all of the functions of routers.  In fact, a router with added translation functionality is a gateway.

Network Devices