Router wifi | Router price | Best router | Tp-link router | Best router price in bd | Wifi router price

Router wifi | Router price | Best router | Tp-link router | Best router price in bd | Wifi router price 

Router (computing)

A router is a networking device that sends data packets from one computer network to another. On the Internet, routers direct traffic. Data packets are used to represent data sent over the internet, such as a web page or email. A packet is typically forwarded from one router to another router across the networks that comprise an internetwork (for example, the Internet) until it reaches its destination node.

RA router is linked to two or more data lines from various IP networks. The router reads the network address information in the packet header to determine the ultimate destination when a data packet arrives on one of the lines. The packet is then routed to the next network on its journey using information from its routing table or routing policy.

Home and small office routers, which simply forward IP packets between home computers and the Internet, are the most common type of IP router. More sophisticated routers, such as enterprise routers, connect large business or ISP networks to the powerful core routers that send data at high speeds along the Internet backbone's optical fiber lines.

Router operation

When multiple routers are used in a network, they can use a routing protocol to exchange information about destination addresses. Each router creates a routing table, or a list of routes, between two computer systems on the network.

The router's software is made up of two functional processing units that run concurrently, known as planes:

Control plane: A router keeps a routing table that specifies which route and physical interface connection should be used to forward a data packet. It accomplishes this through the use of internal pre-configured directives known as static routes, or by learning routes dynamically through the use of a routing protocol. The routing table stores both static and dynamic routes. The control-plane logic then removes non-essential directives from the table and creates a forwarding information base (FIB) that the forwarding plane can use.

The forwarding plane transports data packets between incoming and outgoing interface connections. It reads the header of each packet as it arrives, compares the destination to entries in the FIB supplied by the control plane, and routes the packet to the FIB-specified outgoing network.

Router of applications

A router may have interfaces for various physical layer connections, such as copper cables, fiber optic transmission, or wireless transmission. It also supports various network layer transmission standards. Each network interface is used to forward data packets from one transmission system to another. Routers can also connect two or more logical groups of computer devices known as subnets, each with its own network prefix.

Routers can provide connectivity within enterprises, between enterprises and the Internet, or between the networks of internet service providers (ISPs). The largest routers (such as the Cisco CRS-1 or Juniper PTX) connect the various ISPs and can also be found in large enterprise networks. Smaller routers are typically used to connect typical home and office networks.

Routers of all sizes can be found in businesses. The most powerful routers are typically found in ISPs, academic institutions, and research laboratories. Large businesses may also require more powerful routers to meet the ever-increasing intranet data traffic demands. A hierarchical internetworking model is commonly used to connect routers in large networks.

Routers for access, core, and distribution

Access routers, including small office/home office (SOHO) models, are used at home and at customer sites such as branch offices that do not require their own hierarchical routing. They are typically optimized for low cost. Some SOHO routers can run alternative free Linux-based firmware such as Tomato, OpenWrt, or DD-WRT.

Traffic from multiple access routers is aggregated by distribution routers. Because distribution routers are frequently in charge of enforcing quality of service across a wide area network (WAN), they may have a large amount of memory installed, multiple WAN interface connections, and extensive onboard data processing routines. They may also connect to clusters of file servers or other external networks.

A core router in an enterprise may provide a collapsed backbone connecting distribution tier routers from multiple buildings on a campus or large enterprise location. They are typically designed for high bandwidth but lack some of the features found in edge routers.

Router security

External networks must be carefully considered as part of the overall security strategy of the local network. A router may include a firewall, VPN handling, and other security functions, or they may be handled by separate devices. Routers also commonly perform network address translation, which limits connections initiated from external connections but is not recognized as a security feature by all experts. Some experts argue that open source routers are more secure and reliable than closed source routers because open source routers allow mistakes to be quickly identified and corrected.

Routing various networks

Routers are frequently distinguished based on the network in which they operate. An interior router is a router in a single organization's local area network (LAN). An exterior router is one that is connected to the Internet backbone. A border router, or gateway router, connects a local area network (LAN) to the Internet or a wide area network (WAN).

Internet access and an internal router

Routers designed for ISP and large enterprise connectivity typically exchange routing information via the Border Gateway Protocol (BGP). RFC 4098 classifies BGP routers based on their functions:

Edge router (also known as a provider edge router): A router located at the very edge of an ISP network. The router communicates with routers at other ISPs or large enterprise autonomous systems via the Exterior Border Gateway Protocol (EBGP).

Customer edge router (also known as a subscriber edge router): It is located at the edge of the subscriber's network and connects to its provider's autonomous system via EBGP. It is commonly used in (business) organizations.

Inter-provider border router: A BGP router used to connect ISPs that keeps BGP sessions open with other BGP routers in ISP Autonomous Systems.

Core router: A backbone router that resides within an autonomous system to carry traffic between edge routers.

Within an ISP: A router uses internal BGP to communicate with other ISP edge routers, other intranet core routers, or the ISP's intranet provider border routers in the ISP's autonomous system.

Internet backbone: Unlike its predecessor networks, the Internet no longer has a clearly identifiable backbone. See also default-free zone (DFZ).

The system routers of the major ISPs comprise what could be considered the current Internet backbone core. All four types of BGP routers described here are used by ISPs. A core router is used by an ISP to connect its edge and border routers. In virtual private networks based on a combination of BGP and Multi-Protocol Label Switching protocols, core routers may also have specialized functions.

Routers can also be used for port forwarding between private Internet-connected servers.

Routers for voice, data, fax, and video processing: Also known as access servers or gateways, these devices route and process voice, data, video, and fax traffic over the Internet. Most long-distance phone calls have been processed as IP traffic (VOIP) via a voice gateway since 2005. With the advent of the Internet, the use of access server-type routers grew, first with dial-up access and then again with voice phone service.

Multilayer switches are commonly used in larger networks, with layer-3 devices used to simply interconnect multiple subnets within the same security zone, and higher-layer switches used when filtering, translation, load balancing, or other higher-level functions are required, particularly between zones.

Router of History

Donald Davies proposed the concept of an interface computer for the NPL network in 1966. Wesley Clark developed the same concept the following year for use in the ARPANET. These computers, known as Interface Message Processors (IMPs), performed the same functions as routers today. The International Networking Working Group, an international group of computer networking researchers, came up with the idea for a router (called a gateway at the time) (INWG). 

Set up in 1972 as an informal group to discuss the technical issues involved in connecting different networks, it later became a subcommittee of the International Federation for Information Processing. These gateway devices differed from most previous packet switching schemes in two ways.First, they linked disparate networks, such as serial lines and local area networks. Second, they were connectionless devices with no role in ensuring reliable traffic delivery, leaving that function entirely to the hosts. This concept, known as the end-to-end principle, was previously pioneered in the CYCLADES network.

General-purpose minicomputers served as routers between the mid-1970s and the 1980s. Modern high-speed routers are network processors or highly specialized computers that have additional hardware acceleration to speed up both common routing functions like packet forwarding and specialized functions like IPsec encryption. For research and other purposes, Linux and Unix software-based machines running open source routing code are widely used. The Cisco IOS operating system was created independently. Junos and NX-OS are major router operating systems that are heavily modified versions of Unix software.

Router forwarding

A router's primary function is to connect multiple networks and forward packets destined for either directly attached networks or more remote networks. A router is classified as a layer-3 device because its primary forwarding decision is based on the information in the layer-3 IP packet, specifically the destination IP address. 

When a router receives a packet, it searches its routing table for the best match between the packet's destination IP address and one of the addresses in the routing table. When a match is found, the packet is encapsulated in the layer-2 data link frame for the outgoing interface specified in the table entry. To make decisions, a router typically does not examine the packet payload but only the layer-3 addresses.

The routing table itself can contain information derived from a variety of sources, such as manually configured default or static routes, or dynamic entries from routing protocols in which the router learns routes from other routers. A default route is one that is used to route all traffic to a destination that does not appear in the routing table; it is common – even necessary – in small networks, such as a home or small business, where the default route simply sends all non-local traffic to the Internet service provider. The default route can be configured manually (as a static route), learned by dynamic routing protocols, or obtained via DHCP.

A router must manage congestion when packets arrive at a rate faster than the router can process, in addition to deciding which interface a packet should be forwarded to, which is handled primarily through the routing table. Tail drop, random early detection (RED), and weighted random early detection are three commonly used policies (WRED). Tail drop is the simplest and easiest to implement: the router simply drops new incoming packets once the router's buffer space is depleted. 

When the queue exceeds a pre-configured portion of the buffer, RED probabilistically drops datagrams until it reaches a pre-determined maximum, at which point it drops all incoming packets, reverting to tail drop. Depending on the type of traffic, WRED can be configured to drop packets more easily.

A router also performs traffic classification and determines which packets should be processed first. This is managed through QoS, which is critical when deploying Voice over IP to avoid excessive latency.

A router also classifies traffic and determines which packets should be processed first. This is controlled by QoS, which is essential when deploying Voice over IP to avoid excessive latency.