This section will provide you with the details of few of the networking devices that are widely used in the IT industry to form networks.
NETWORK SEGMENT :
A network segment can be defined as a network link connecting two interfaces or a physical connectivity between the network interfaces of two computer devices. The physical layer connectivity could be a piece of copper or fiber-optic cable, an infrared or wireless. A network is built by connecting together multiple network segments using a hub, bridge, switch or a router.
HUB :
A hub is a network device that is used for connecting computers on a Local Area Network (LAN). It forwards all the packets it receives to all of its ports. Hubs work at the physical layer of the OSI model. There are two main types of hubs, passive and active. A passive hub simply splits the signal and forwards it. An active hub takes the incoming frames, amplifies the signal, and forwards it.
BRIDGE :
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges are similar to repeaters or network hubs; however bridges are more intelligent than hubs. A bridge maintains a table with MAC addresses (Media Access Control address also called Ethernet Address is a unique hardware address that each network device has burned into it.) of all attached nodes, and on which segment they are located. It takes an incoming frame, reads the destination MAC address and consults the table to decide what should be done with the frame. If the location of the destination MAC address is listed in the table, the frame is forwarded to the corresponding port. The frame will be discarded if the destination port is the same as the port from which the frame arrived. If the location is not known yet, the frame will be flooded through all outgoing ports.
SWITCH :
A network switch is a networking device that performs transparent bridging which connects multiple network segments with forwarding based on MAC addresses. The switch connects devices together to form the LAN. Switches can connect at 10,100, or 1000 megabits per second, at half or full duplex. Half duplex means that the device can only send or receive at any given time, whereas full duplex can send and receive, at the same time.Switches were developed to improve network performance even more. Switches are very similar to bridges as they also maintain a table with MAC addresses per port to make forwarding decisions, operate at the Data Link layer (layer 2) of the OSI model. Some of the main differences between switches and bridges are:- Switches have more ports than bridges. Switches are meant to replace hubs and improve network performance by creating a separate collision domain per port.- Bridges switch in software whereas switches switch in hardware (integrated circuits).- Switches offer more variance in speed; an individual port can be assigned 10 Mb/s, 100 Mb/s, 1 Gb/s or even more.
SWITCH Vs HUB
A hub is a fairly unsophisticated broadcast device. Hubs do not manage any of the traffic that comes through them, and any packet entering any port is broadcast out on every other port (every port other than the port of entry). Since every packet is being sent out through every other port, packet collisions result--which greatly hinder the smooth flow of traffic.A switch isolates ports, meaning that every received packet is sent out only to the port on which the target may be found. If it is not, then the switch will broadcast the packet to all ports except the port from which the request originated. Since the switch intelligently sends packets where they need to go the performance of the network can be greatly increased.
ROUTER :
Routers are used to interconnect multiple networks and route information between these networks by choosing an optimal path to the destination. A router forwards data packets across a network towards their destinations, through a process known as routing. Routing occurs at Layer 3 of the OSI model.A router acts as a junction between two or more networks to transfer data packets among them. A router is different from a switch. A switch connects devices to form a local area network (LAN). In order to route packets, a router communicates with other routers using routing protocols and using this information creates and maintains a routing table. The routing table stores the best routes to certain network destinations, the "routing metrics" associated with those routes, and the path to the next hop router.A router that connects clients to the Internet is called an edge router. A router that serves solely to transmit data between other routers, e.g. inside the network of an ISP, is called a core router. Depending on their function, these routers will support any number of routing protocols including IS-IS OSPF IGRP EIGRP RIP BGP and EGP.
FIREWALL :
A firewall is a security device which provides a solution to enforce security policies. Firewalls can either be hardware or software based.A firewall's basic task is to control traffic between computer networks with different zones of trust. Normally, a Firewall is deployed between a trusted, protected private network and an untrusted public network. Typical example where the Firewalls are usually placed is between the users of a LAN and the Internet. A firewall has built-in filters that can disallow unauthorized or potentially dangerous sources from entering the network. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. It also logs attempted intrusions.
MODEM :
Modem is short for modulator/demodulator. It is a device that connects your computer to a phone line in order to communicate with other computers. Modem converts the digital signal from a computer to an analogue signal that can be transmitted along an ordinary phone line. The signal is then converted back to digital form by the modem at the receiving side so that it can be processed by a receiving computer. This allows computers to connect to the Internet through a telephone line. Basically, modems do for computers what a telephone does for humans.
NETWORK SEGMENT :
A network segment can be defined as a network link connecting two interfaces or a physical connectivity between the network interfaces of two computer devices. The physical layer connectivity could be a piece of copper or fiber-optic cable, an infrared or wireless. A network is built by connecting together multiple network segments using a hub, bridge, switch or a router.
HUB :
A hub is a network device that is used for connecting computers on a Local Area Network (LAN). It forwards all the packets it receives to all of its ports. Hubs work at the physical layer of the OSI model. There are two main types of hubs, passive and active. A passive hub simply splits the signal and forwards it. An active hub takes the incoming frames, amplifies the signal, and forwards it.
BRIDGE :
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges are similar to repeaters or network hubs; however bridges are more intelligent than hubs. A bridge maintains a table with MAC addresses (Media Access Control address also called Ethernet Address is a unique hardware address that each network device has burned into it.) of all attached nodes, and on which segment they are located. It takes an incoming frame, reads the destination MAC address and consults the table to decide what should be done with the frame. If the location of the destination MAC address is listed in the table, the frame is forwarded to the corresponding port. The frame will be discarded if the destination port is the same as the port from which the frame arrived. If the location is not known yet, the frame will be flooded through all outgoing ports.
SWITCH :
A network switch is a networking device that performs transparent bridging which connects multiple network segments with forwarding based on MAC addresses. The switch connects devices together to form the LAN. Switches can connect at 10,100, or 1000 megabits per second, at half or full duplex. Half duplex means that the device can only send or receive at any given time, whereas full duplex can send and receive, at the same time.Switches were developed to improve network performance even more. Switches are very similar to bridges as they also maintain a table with MAC addresses per port to make forwarding decisions, operate at the Data Link layer (layer 2) of the OSI model. Some of the main differences between switches and bridges are:- Switches have more ports than bridges. Switches are meant to replace hubs and improve network performance by creating a separate collision domain per port.- Bridges switch in software whereas switches switch in hardware (integrated circuits).- Switches offer more variance in speed; an individual port can be assigned 10 Mb/s, 100 Mb/s, 1 Gb/s or even more.
SWITCH Vs HUB
A hub is a fairly unsophisticated broadcast device. Hubs do not manage any of the traffic that comes through them, and any packet entering any port is broadcast out on every other port (every port other than the port of entry). Since every packet is being sent out through every other port, packet collisions result--which greatly hinder the smooth flow of traffic.A switch isolates ports, meaning that every received packet is sent out only to the port on which the target may be found. If it is not, then the switch will broadcast the packet to all ports except the port from which the request originated. Since the switch intelligently sends packets where they need to go the performance of the network can be greatly increased.
ROUTER :
Routers are used to interconnect multiple networks and route information between these networks by choosing an optimal path to the destination. A router forwards data packets across a network towards their destinations, through a process known as routing. Routing occurs at Layer 3 of the OSI model.A router acts as a junction between two or more networks to transfer data packets among them. A router is different from a switch. A switch connects devices to form a local area network (LAN). In order to route packets, a router communicates with other routers using routing protocols and using this information creates and maintains a routing table. The routing table stores the best routes to certain network destinations, the "routing metrics" associated with those routes, and the path to the next hop router.A router that connects clients to the Internet is called an edge router. A router that serves solely to transmit data between other routers, e.g. inside the network of an ISP, is called a core router. Depending on their function, these routers will support any number of routing protocols including IS-IS OSPF IGRP EIGRP RIP BGP and EGP.
FIREWALL :
A firewall is a security device which provides a solution to enforce security policies. Firewalls can either be hardware or software based.A firewall's basic task is to control traffic between computer networks with different zones of trust. Normally, a Firewall is deployed between a trusted, protected private network and an untrusted public network. Typical example where the Firewalls are usually placed is between the users of a LAN and the Internet. A firewall has built-in filters that can disallow unauthorized or potentially dangerous sources from entering the network. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. It also logs attempted intrusions.
MODEM :
Modem is short for modulator/demodulator. It is a device that connects your computer to a phone line in order to communicate with other computers. Modem converts the digital signal from a computer to an analogue signal that can be transmitted along an ordinary phone line. The signal is then converted back to digital form by the modem at the receiving side so that it can be processed by a receiving computer. This allows computers to connect to the Internet through a telephone line. Basically, modems do for computers what a telephone does for humans.
