Routers are small electronic devices that join multiple computer networks together via either wired or wireless connections.
Before home networking became popular, routers could be found only the closets of businesses and schools. Each cost thousands of dollars and require special technical training to set up and manage.
The largest and most powerful network routers form the Internet backbone. These routers must manage many terabits of data flowing through and between Internet Service Provider (ISP) network.
Routers became mainstream consumer devices when households began to accumulate multiple computers and wanted to share the home Internet connection
Home networks use Internet Protocol (IP) routers to connect computers to each other and to the Internet. Early generations of home routers supported wired networking with Ethernet cables while newer wireless routers supported Wi-Fi together with Ethernet. The term broadband router applies to any home wired or wireless router being used for sharing a broadband Internet connection.
What is a Router?
A router is a networking device that forwards data packets between computer networks through a process called Routing. Routers perform the traffic directing functions on the Internet. A data packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.
In technical terms, a router is a Layer 3 network gateway device, meaning that it connects two or more networks and that the router operates at the network layer of the OSI model.
Routers contain a processor (CPU), several kinds of digital memory, and input-output (I/O) interfaces.
They function as special-purpose computers, one that does not require a keyboard or display.
The router’s memory stores an embedded operating system (O/S). Compared to general-purpose OS products like Microsoft Windows or Apple Mac OS, router operating systems limit what kind of applications can be run on them and also need much smaller amounts of storage space. Examples of popular router operating systems include Cisco Internetwork Operating System (IOS) and DD-WRT. These operating systems are manufactured into a binary firmware image and are commonly called router firmware.
table, routers also can filter both incoming or outgoing traffic based on the addresses of senders and receivers.
Routing is most commonly associated with the internet Protocol, although other less popular routed protocols remain in use.
Why a Router is used?
A router is an electronic device and/or software that connects at least two networks and forwards packets among them according to the information in the packet headers and routing tables. Routers are fundamental to the operation of the Internet and other complex networks (such as enterprise-wide networks).
In order for devices on the network to connect to the Internet, the router must be connected to a modem. Therefore, most routers have a specific Ethernet port that is designed to connect to the Ethernet port of a cable or DSL modem. A modem is a device that provides access to the Internet.
A routing protocol specifies how routers communicate with each other, distributing information that enables them to select routes between any two nodes on a computer network. Routing algorithms determine the specific choice of route. Each router has a priori knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbours, and then throughout the network. This way, routers gain knowledge of the topology of the network.
The specific characteristics of routing protocols include the manner in which they avoid routing loops, the manner in which they select preferred routes, using information about hop costs, the time they require to reach routing convergence, their scalability, and other factors.
Although there are many types of routing protocols, three major classes are in widespread use on IP networks:
- Interior gateway protocols type 1, link-state routing protocols, such as OSPF and IS-IS
- Interior gateway protocols type 2, distance-vector routing protocols, such as Routing Information Protocol, RIPv2, IGRP.
- Exterior gateway protocols are routing protocols used on the Internet for exchanging routing information between Autonomous Systems, such as Border Gateway Protocol(BGP), Path Vector Routing Protocol. Exterior gateway protocols should not be confused with Exterior Gateway Protocol (EGP), an obsolete routing protocol.
Types of Routing
Routing protocols were created for routers. These protocols have been designed to allow the exchange of routing tables (A routing table is a set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed. All IP-enabled devices, including routers and switches, use routing tables.), or known networks, between routers. There are a lot of different routing protocols, each one designed for specific network sizes.
Two main types of routing:
- Static routing
- Dynamic routing
The router learns about remote networks from neighbour routers or from an administrator. The router then builds a routing table. If the network is directly connected then the router already knows how to get to the network. If the networks are not attached, the router must learn how to get to the remote network with either static routing (administrator manually enters the routes in the router’s table) or dynamic routing (happens automatically using routing protocols like EIGRP, OSPF, etc.).
The routers then update each other about all the networks they know. If a change occurs e.g. a router goes down, the dynamic routing protocols automatically inform all routers about the change. If static routing is used, then the administrator has to update all changes into all routers and therefore no routing protocol is used.
Only Dynamic routing uses routing protocols, which enable routers to:
- Dynamically discover and maintain routes
- Calculate routes
- Distribute routing updates to other routers
- Reach agreement with other routers about the network topology
Statically programmed routers are unable to find routes, or send routing information to other routers. They send data over routes defined by the network Admin.
A Stub network is so called because it is a dead end in the network. There is only one route in and one route out and, because of this, they can be reached using static routing, thus saving valuable bandwidth.
Dynamic Routing Protocols
There are 3 types of Dynamic routing protocols, these are differing by the way that discover and make calculations about routes;
1. Distance Vector
2. Link State
- Distance Vector routers find the best path from information send from neighbours
- Link State routers each have a copy of the entire network map
- Link State routers find best routes from this local map
In the original 1960s era of Routing, general purpose Computers served as Routers. Although general purpose Computers can perform routing, modern high-speed routers are highly specialized computers, generally with extra hardware added to accelerate both common routing functions such as packet forwarding and specialized functions such as IPsec encryption.
Other changes also improve reliability, such as using battery rather than mains power and using solid state rather than magnetic storage.
Modern routers have thus come to resemble telephone switches, whose technology they are currently converging with and may eventually replace. The first modern (dedicated, standalone) routers were the Fuzzball routers.
Evolution of Routers
From its gestation period 40 years ago until now, the Router has matured along with the Internet to become the linchpin of all Communications – data, voice and video. Its application seems limitless as the Internet is enhanced to support more and more features and Services.
- The First Router
BBN developed the Interface Message Processor for the ARPAnet, the Internets Predecessor, in late 1960s. The IMP could support 50Kbps links between nodes.
Bill Yeager develops the multiprotocol router at Stanford in 1980. Yeager’s project would pique the internet of Stanford researchers Len Bosack and Sandy Lerner and help launch Cisco.
Some of the first modern routers on the Internet in early 1980s were called Fuzzballs. They were Digital Equipment Corp. LSI -11 computers loaded with Software written by Davis Mills, inventor of the Network Time Protocol and the Exterior Gateway Protocol. Fuzzball refers to the router’s software, which includes a fast, compact operating system, support for the DARPA/NSF Internet architecture and a range of applications for Network Protocol development, testing and evaluation. A few Fuzzballs are still in Operation on the Internet today.
- Next was Birth of Cisco, the first Cisco Router
The AGS for Advanced Gateway Server shipped in 1986 as Cisco’s first commercial multiprotocol router. The Router supported TCP/IP and PUP among other Protocols. The highest line rate on the system was 100Mbps FDDI.
- The High-End workhorse
Ciscos first successful core enterprise multiprotocol router was the 7000 series which debuted in 1993. The 7000 series would be a mainstay in corporate networks for many years to come.
- Advancements in Integration
Routers were reduced to chip size, ushering in the development of Layer 3 switches – LAN switches that could also perform IP routing.
Layer 3 switches , like Cisco’s catalyst 6500, which debuted in the mid to late 1990s , have become a lower cost , higher speed alternative to routers in the core of enterprise IP networks. They are able to support Gigabit 1000Mbps – Ethernet Speeds.
- Colour me alternative
Some of the Ciscos competitors such as Extreme, unveiled Layer 3 switches in colours other than black , adding an Interesting twist to an otherwise staid Industry.
- For the carrier core
Cisco and its competitors designed megarouters for the core of carrier networks in anticipation of the explosion in growth of Internet traffic and the advent of managed services. These systems are designed to support Terabyte speeds.
- An Open Route
Other routing alternatives , like Vyatta’s appliance based on Open Source Linux on x86 hardware, have sought to become , low cost , feature rich options to Cisco’s dominance. An open Source operating system supports applications of hundreds of developers
- The next Generation
Cisco’s newest enterprise edge Router , the ASR 1000, is optimised for VoIP , firewall, QoS and other deep packet inspection applications. It is based on Cisco’s Quantum Flow Processor , which is designed to perform many functions in hardware instead of software , and is designed to support upto 10Gbps Ethernet line rates.
Institutions like the Department of Defence have found applications for routers in space. This advancement could result in much broader and lower cost access to satellite data and networks.