INTERNETWORKING DEVICES

Internetworking devices are used to setup physical network connections for data transmission across a network. All devices have separately installed as per network requirements and scenarios.

Network Interface Card (NIC)

A Network Interface Card (NIC) or Network Adapter is a hardware device that connects devices to a network. It is a circuit board that is installed on network devices. The NIC having a transceiver which allows a network device to transmit and receive data via the transmission medium. It operates at the layer 1 and layer 2 (physical and data link layer) of the OSI model. It can support a transfer rate of 10 Mbps, 100 Mbps, 1000 Mbps. The user can select an NIC depending on the type of network and media. It allows both wired and wireless network communications.

In a network, each device should have its own address to uniquely identify it within a network. This address is known as physical or MAC (Media Access Control) address. MAC is a unique 12-digit hexadecimal (6 bytes/ 48 bits) hardware number of a computer, which is embedded into network card (known as Network Interface Card) during the time of manufacturing. MAC address is represented as 6 pairs of hexadecimal digits separated by colons. First 3 bytes of the MAC address are Manufacturer ID and last 3 bytes are Serial ID.

Format of MAC address:

MM-MM-MM-SS-SS-SS

MM:MM:MM:SS:SS:SS

Ethernet cards are of two types:

1. Wired
2. Wireless

 

Repeater

Repeaters are used to regenerate and amplify weak signals. It is a device which on receiving a signal  reshapes and amplify the data signal to its original level and retransmits it at a higher level so that the signal can cover longer distances. Repeaters operate at the layer 1 (physical layer) of the OSI model. It has 2 ports to connect two network segments only. Repeater cannot perform any action on the data.

According to the types of signals that they regenerate, repeaters can be classified into two categories

1. Analog Repeaters : which can only amplify the analog signal.
2. Digital Repeaters : which can reconstruct a distorted signal.

HUB

A hub is a multiport repeater. A hub can connect multiple network segments. Hubs cannot perform any action on data like repeaters, so it broadcasts data to all other connected devices on a network. A hub operates at the layer 1 (physical layer) of the OSI model.

Hub types:

1. Active hub – It requires power supply to amplify or regenerate signals
2. Passive hub –It does not require power supply to amplify or regenerate the signals. It simply connects signals of a network segments.

Bridges

A bridge can only connect two separate LAN segments. It operates at the layer 2 (data link layer) of the OSI model. Data in data link layer of the OSI model is known as frame and the frame contains MAC address of the source/sender and the destination/receiver. Bridge use a MAC address table to determining how to transmit traffic between LANs. Bridges break the network into two separate segments and directs transmission to the appropriate segment. It listens to all traffic on the LAN segment, determines the destination MAC address, looks up the destination MAC address in the MAC address table and then passes the frame to the correct segment.

Switch

A switch is a multiport bridge used to connect the multiple devices together in a LAN segment. It operates at the layer 2 (data link layer) of the OSI model. The switch uses a MAC address (Content Addressable Memory) table to stores the MAC addresses of devices on a network and transfers data packets only to that port which is connected to the destination device. It increases the speed of the network. Some switches can operate at different speeds (Ethernet switch supports 10Mbps/100Mbps/1000Mbps etc.).

Layer 3 Switch or multilayer switch has the characteristics of both switch and router. It operates at both layer 2 and layer 3 of the OSI model. It forwards traffic from one network to another based on MAC address as well as on IP address. Layer 3 switch does not support WAN port.

Managed and Unmanaged Switch

An Unmanaged Switch is a plug-and-play switch that allows connected devices to communicate with each other over the network without  any option of configuration . It does not give any control to users.

Managed switches are designed to work for large enterprise network. Managed switch gives the network administrator greater security and more features and flexibility. Managed switch ports can be configured.

Router

Router operates at the layer 3 (network layer) of the OSI model. It has LAN and WAN ports and can connect multiple different networks. Router routes or forwards the packet from one network to another based on the IP address. It uses a database table called routing table to select the best route for the packet to reach the destination.

When a data packet is received, the router inspects the IP address in data packet and determines the best path for the packet from the routing table. Routing can be two types:

1. Static Routing
2. Dynamic Routing

Static Routing: In static routing, the routing information in routing table is configured manually by network administrator. Static routing used in small network.

Dynamic Routing: In dynamic routing, routing protocols allows routers to share routing table information about the network with other routers to build the routing table dynamically. 

NIC, Repeater, HUB, Bridge, Switch and Router operate at different layers of OSI model

Device	OSI Layer
Repeater	Physical
HUB	Physical
NIC	Physical
	Data-link
Bridge	Data-link
Switch	Data-link
Router	Network

Gateway

Gateway is a device that connects different network types and protocols. It does the translation between different network technologies. Gateways acts as a gate between the networks. Gateway works at all levels of the OSI model. It may be a router, firewall, server, or other device that routes the traffic from an internal network to the outside network.

Modem

A modem (modulators-demodulators) is a network device that coverts digital signals to analog signals and analog signals to digital signals It enables computer to transmit data over telephone or cable line.

Access Point(AP)

Access Point is a device that provides connection between wired and wireless network. APs consist of a transceiver (transmitter and receiver) device used to setup a wireless LAN. It operates at the layer 3 (network layer) of the OSI model.