Network Devices
Network devices
Networking hardware, also known as network equipment or computer networking devices, are electronic devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data transmission in a computer network.
Repeater
A repeater operates at the physical layer. Its job is to regenerate the signal over 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.
A digital repeater amplifies the signal, and it also may retime, resynchronize, and reshape the pulses.
Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.
Hub
A hub is basically a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices. In other words, collision domain of all hosts connected through Hub remains one. Also, they do not have intelligence to find out best path for data packets which leads to inefficiencies and wastage.
Bridge
A bridge operates at data link layer. A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device.
Types of Bridges
Transparent Bridges:- These are the bridge in which the stations are completely unaware of the bridge’s existence i.e. whether or not a bridge is added or deleted from the network, reconfiguration of the stations is unnecessary. These bridges make use of two processes i.e. bridge forwarding and bridge learning.
Source Routing Bridges:- In these bridges, routing operation is performed by source station and the frame specifies which route to follow. The hot can discover frame by sending a special frame called discovery frame, which spreads through the entire network using all possible paths to destination.
Translating bridge - A type of bridge that interconnects two different types of LAN protocols, such as Ethernet and Token Ring. Translating bridges are generally very complicated devices.
Switch
A switch is a multiport bridge with a buffer and a design that can boost its efficiency a large number of ports imply less traffic) and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. In other words, switch divides collision domain of hosts, but broadcast domain remains same.
Methods of Switching
Local Area Network (LAN) Switches support different Switching Methods. Important Switching Methods are store and forward, cut-through and fragment-free. Switching Methods determine how a switch receives, processes, and forwards a Layer 2 Ethernet frame.
Store and Forward Switching
In Store and Forward switching, Switch copies each complete Ethernet frame into the switch memory and computes a Cyclic Redundancy Check (CRC) for errors. If a Cyclic Redundancy Check (CRC) error is found, the Ethernet frame is dropped and if there is no Cyclic Redundancy Check (CRC) error, the switch forwards the Ethernet frame to the destination device. Store and Forward switching can cause delay in switching since Cyclic Redundancy Check (CRC) is calculated for each Ethernet frame.
Cut-through Switching
In cut-through switching, the switch copies into its memory only the destination MAC address (first 6 bytes of the frame) of the frame before making a switching decision. A switch operating in cut-through switching mode reduces delay because the switch starts to forward the Ethernet frame as soon as it reads the destination MAC address and determines the outgoing switch port. Problem related with cut-through switching is that the switch may forward bad frames.
Fragment-Free Switching
Fragment-free (runtless switching) switching is an advanced form of cut-through switching. The switches operating in cut-through switching read only up to the destination MAC address field in the Ethernet frame before making a switching decision. The switches operating in fragment-free switching read at least 64 bytes of the Ethernet frame before switching it to avoid forwarding Ethernet runt frames (Ethernet frames smaller than 64 bytes).
Router
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. Data sent through the internet, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork (e.g. the Internet) until it reaches its destination node
A router is connected to two or more data lines from different IP networks.[b] When a data packet comes in on one of the lines, the router reads the network address information in the packet header to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.
Characteristics of Routers
1. Routers are multiport devices with high - speed backbones
2. Routers also support filtering and encapsulation like bridges
3. Like bridges routers are also self-learning, as they can communicate their existence. to other devices and can learn of the existence of new routers, nodes and LAN segments
4. As explained earlier, they route traffic by considering the network as a whole. It shows that they use a high level of intelligence to accomplish this task. This characteristic makes them superior than hubs and bridges because they simply view the network on a link-by-link basis
5. The packet handled by router may include destination address, packet priority level, least-cost route, minimum route delay, minimum route distance, and route congestion level
6. Routers constantly monitor the condition of the network, as a whole to dynamically adapt to changes in the condition of the network
7. They typically provide some level of redundancy so that they are less susceptible to catastrophic failure.
1. Static routing – Static routing is a process in which we have to manually add routes in routing table. Advantages –
1. No routing overhead for router CPU which means a cheaper router can be used to do routing.
2. It adds security because only administrator can allow routing to particular networks only.
3. No bandwidth usage between routers.
Disadvantages –
1. For a large network, it is a hectic task for administrator to manually add each route for the network in the routing table on each router.
2. The administrator should have good knowledge of the topology. If a new administrator comes, then he has to manually add each route so he should have very good knowledge of the routes of the topology.
2. Default Routing – This is the method where the router is configured to send all packets towards a single router (next hop). It doesn’t matter to which network the packet belongs, it is forwarded out to router which is configured for default routing. It is generally used with stub routers. A stub router is a router which has only one route to reach all other networks.
3. Dynamic Routing – Dynamic routing makes automatic adjustment of the routes according to the current state of the route in the routing table. Dynamic routing uses protocols to discover network destinations and the routes to reach it. RIP and OSPF are the best examples of dynamic routing protocol. Automatic adjustment will be made to reach the network destination if one route goes down.
A dynamic protocol have following features:
The routers should have the same dynamic protocol running in order to exchange routes.
When a router finds a change in the topology then router advertises it to all other routers.
Advantages –
Easy to configure.
More effective at selecting the best route to a destination remote network and also for discovering remote network.
Disadvantage –
Consumes more bandwidth for communicating with other neighbors.
Less secure than static routing.
Access Point
An access point is a device that creates a wireless local area network, or WLAN, usually in an office or large building. An access point connects to a wired router, switch, or hub via an Ethernet cable, and projects a Wi-Fi signal to a designated area. For example, if you want to enable Wi-Fi access in your company's reception area but don’t have a router within range, you can install an access point near the front desk and run an Ethernet cable through the ceiling back to the server room.
Advantages of Using Wireless Access Points
When you have both employees and guests connecting with desktops, laptops, mobile phones, and tablets, 20 devices on a wireless network adds up quickly. At 60 simultaneous connections each, access points give you the freedom to scale the number of devices supported on your network. But that’s only one of the advantages of using these network enhancers—consider these points:
•Business-grade access points can be installed anywhere you can run an Ethernet cable. Newer models are also compatible with Power over Ethernet Plus, or PoE+ (a combination Ethernet and power cord), so there is no need to run a separate power line or install an outlet near the access point.
•Additional standard features include Captive Portal and Access Control List (ACL) support, so you can limit guest access without compromising network security, as well as easily manage users within your Wi-Fi network.
•Select access points include a Clustering feature—a single point from which the IT administrator can view, deploy, configure, and secure a Wi-Fi network as a single entity rather than a series of separate access point configurations.
What Does Gateway Mean?
A gateway is a data communication device that provides a remote network with connectivity to a host network.
A gateway device provides communication to a remote network or an autonomous system that is out of bounds for the host network nodes. Gateways serve as the entry and exit point of a network; all data routed inward or outward must first pass through and communicate with the gateway in order to use routing paths.
Brouter
A bridge router or brouter is a network device that works as a bridge and as a router. The brouter routes packets for known protocols and simply forwards all other packets as a bridge would. Brouters operate at both the network layer for routable protocols and at the data link layer for non-routable protocols.
Difference between Router and Brouter
A router is a networking device that forwards data packets between computer network.
Brouter is a networking device which is used both as a bridge and as a router,It is combination of network bridge and a router.
Router operates at Network layer.
Brouter operates either at Data link layer or a Network layer.
Router stores routing table.
Brouter stores routing table when it is configured as a router and stores MAC address when configured as a bridge.
Router takes forwarding decisions based on IP address.
Brouter Forwarding decision are taken based on IP address when it is configured as a router, or It takes forwarding decisions based on MAC address when configured as a bridge.
Router is full duplex.
Brouter is full duplex when it is configured as a router and it is half duplex when configured as a bridge.
What is a Firewall?
A Firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization’s previously established security policies. At its most basic, a firewall is essentially the barrier that sits between a private internal network and the public Internet. A firewall’s main purpose is to allow non-threatening traffic in and to keep dangerous traffic out.
Network Firewalls support a wide variety of functions and capabilities with built-in features, including:
•Application and Identity-Based Control
Types of Firewalls
Packet filtering
A small amount of data is analyzed and distributed according to the filter’s standards.
Proxy service
Network security system that protects while filtering messages at the application layer.
Stateful inspection
Dynamic packet filtering that monitors active connections to determine which network packets to allow through the Firewall.
Next Generation Firewall (NGFW)
Deep packet inspection Firewall with application-level inspection.
What Firewalls Do?
A Firewall is a necessary part of any security architecture and takes the guesswork out of host level protections and entrusts them to your network security device. Firewalls, and especially Next Generation Firewalls, focus on blocking malware and application-layer attacks, along with an integrated intrusion prevention system (IPS), these Next Generation Firewalls can react quickly and seamlessly to detect and react to outside attacks across the whole network. They can set policies to better defend your network and carry out quick assessments to detect invasive or suspicious activity, like malware, and shut it down.
