Router

2008-03-05T06:12:00.000-08:00

The very first device that had fundamentally the same functionality as a router does today, i.e a packet switch, was the Interface Message Processor (IMP); IMPs were the devices that made up the ARPANET, the first packet switching network. The idea for a router (although they were called "gateways" at the time) initially came about through an international group of computer networking researchers called the International Network Working Group (INWG). Set up in 1972 as an informal group to consider the technical issues involved in connecting different networks, later that year it became a subcommittee of the International Federation for Information Processing. ^[6]

These devices were different from most previous packet switches in two ways. First, they connected dissimilar kinds of networks, such as serial lines and local area networks. Second, they were connectionless devices, which had no role in assuring that traffic was delivered reliably, leaving that entirely to the hosts (although this particular idea had been previously pioneered in the CYCLADES network).

The idea was explored in more detail, with the intention to produce real prototype system, as part of two contemporaneous programs. One was the initial DARPA-initiated program, which created the TCP/IP architecture of today. ^[7] The other was a program at Xerox PARC to explore new networking technologies, which produced the PARC Universal Packet system, although due to corporate intellectual property concerns it received little attention outside Xerox until years later. ^[8]

The earliest Xerox routers came into operation sometime after early 1974. The first true IP router was developed by Virginia Strazisar at BBN, as part of that DARPA-initiated effort, during 1975-1976. By the end of 1976, three PDP-11-based routers were in service in the experimental prototype Internet. ^[9]

The first multiprotocol routers were independently created by staff researchers at MIT and Stanford in 1981; the Stanford router was done by William Yeager, and the MIT one by Noel Chiappa; both were also based on PDP-11s. ^[10] ^[11] ^[12] ^[13]

As virtually all networking now uses IP at the network layer, multiprotocol routers are largely obsolete, although they were important in the early stages of the growth of computer networking, when several protocols other than TCP/IP were in widespread use. Routers that handle both IPv4 and IPv6 arguably are multiprotocol, but in a far less variable sense than a router that processed AppleTalk, DECnet, IP, and Xerox protocols.

In the original era of routing (from the mid-1970s through the 1980s), general-purpose mini-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 specialised functions such as IPsec encryption.

Still, there is substantial use of Linux and UNIX machines, running open source routing code, for routing research and selected other applications. While Cisco's operating system was independently designed, other major router operating systems, such as those from Juniper Networks and Extreme Networks, are extensively modified but still have Unix ancestry.

Other changes also improve reliability, such as redundant control processors with stateful failover, and using storage having no moving parts for program loading. As much reliability comes from operational techniques for running critical routers as it does to the router design itself. It is the best common practice, for example, to use redundant uninterruptible power supplies for all critical network elements, with generator backup for the batteries or flywheels of those power supplies.

A router is something that you hook up multiple computers to the same internet connection. A lot of people buy routers that offer wireless connections so they can (with a wireless card installed) use their laptop or even desktop in a different room than where the internet is connected. For example, I have a desktop in my living room, but I use my laptop in my bedroom, and my roommate uses her laptop in her bedroom. Anyone with a wireless card installed can connect to your wireless network (what they call a group of computers connected through one connection) unless you set a password. Then, only people who have the password can access your wireless connection. Another use for a router is, for example, you have multiple computers set up in the same room, but only one internet connection. A router provides the link you need to hook them all up together and use the same internet (most routers allow you to connect up to four computers). Just remember, the more computers hooked up to a router and using the internet connection at once, the slower the internet connection will be.

The main function of a router is to distribute private IP addresses to computers in a network. Since every computer needs a unique IP address to receive data from the Internet properly, but all computers in the same network have the same IP, so router distribute a unique internal IP to each computer in the network.
For example, my external IP is 71.174.*.*, but my internal IP is 192.168.0.100.
And I don't think you need a router if you have a router modem. Having your own Router enables you to configure your own settings and protect yourself with a hardware firewall, enable encryption, and keep undesired people off your network if you use wireless. A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding, generally containing a specialized operating system (e.g. Cisco's IOS or Juniper Networks JUNOS and JUNOSe or Extreme Networks XOS), RAM, NVRAM, flash memory, and one or more processors. High-end routers contain many processors and specialized Application-specific integrated circuits (ASIC) and do a great deal of parallel processing. Chassis based systems like the Nortel MERS-8600 or ERS-8600 routing switch, (pictured right) have multiple ASICs on every module and allow for a wide variety of LAN, MAN, METRO, and WAN port technologies or other connections that are customizable. However, with the proper software (such as XORP or Quagga), even commodity PCs can act as routers. Routers connect two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.^[1] The term layer 3

switch often is used interchangeably with router, but switch is really a marketing term without a rigorous technical definition. In marketing usage, it is generally optimized for Ethernet LAN interfaces and may not have other physical interface types.

Routers operate in two different planes ^[2]:

Control Plane, in which the router learns the outgoing interface that is most appropriate for forwarding specific packets to specific destinations,
Forwarding Plane, which is responsible for the actual process of sending a packet received on a logical interface to an outbound logical interface.

Routers for Internet connectivity and internal use

Routers intended for ISP and major enterprise connectivity will almost invariably exchange routing information with the Border Gateway Protocol. RFC 4098^[3] defines several types of BGP-speaking routers:

Provider Edge Router: Placed at the edge of an ISP network, it speaks external BGP (eBGP) to a BGP speaker in another provider or large enterprise Autonomous System (AS).
Subscriber Edge Router: Located at the edge of the subscriber's network, it speaks eBGP to its provider's AS(s). It belongs to an end user (enterprise) organization.
Inter-provider Border Router: Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers' ASes.
Core router: A router that resides within the middle or backbone of the network rather than at its periphery.

Within an ISP: Internal to the provider's AS, such a router speaks internal BGP (iBGP) to that provider's edge routers, other intra-provider core routers, or the provider's inter-provider border routers.

"Internet backbone:" The Internet does not have a clearly identifiable backbone, as did its predecessors. See default-free zone (DFZ). Nevertheless, it is the major ISPs' routers that make up what many would consider the core. These ISPs operate all four types of the BGP-speaking routers described here. In ISP usage, a "core" router is internal to an ISP, and used to interconnect its edge and border routers. Core routers may also have specialized functions in

ABOUT ROUTER

Router

Routers for Internet connectivity and internal use