Routing Tables

A routing table is an electronic document that stores the routes to the various nodes in a computer network. The nodes may be any kind of electronic device connected to the network. The Routing Table is usually stored in a router or networked computer in the form of a database or file. When data needs to be sent from one node to another on the network, the routing table is referred to in order to find the best possible route for the transfer of information.

Almost all computers and network devices connected to Internet use routing tables to compute the next hop for a packet. It is electronic table that is stored in a router or a networked computer. The routing table stores the routes (and in some cases, metrics associated with those routes) to particular network destinations. This information contains the topology of the network immediately around it. The construction of routing table is the primary goal of routing protocols and static routes.

Routing tables can generally be maintained manually when the network is small and static. The routing tables for all static network devices never change unless and until the administrator of the network changes them manually. In dynamic routing, the devices themselves automatically build and maintain their own routing tables. They do this by exchanging information regarding the network topology using routing protocols. This enables the devices in the network to automatically adapt to the changes in the network like device failures and network congestion as and when they occur.

Know more about USB

USB is a high-performance serial bus communication technology. Most new computers and associated peripheral devices like printers and scanners contain built-in support for this technology. USB hubs for file and printer sharing also exist. USB and FireWire are the most popular, competing standards for networking computer peripherals.

Multiple versions of USB have been developed by the computer industry:

* USB 1.0 and 1.1: the first commercial versions supported a maximum data rate of 12 Mbps
* USB 2.0: the current version supports a much faster theoretical maximum rate of 480 Mbps
* USB 3.0: the future standard is expected to support up to 4.8 Gbps

Using USB for Local Networking
To build a USB network, simply connect USB cables to the USB ports on those devices. USB is plug and play compatible, meaning the operating system USB driver software automatically detects and configures device connections. One USB network supports up to 127 devices.

USB interfaces are backward compatible; for example, a USB 2.0 and a USB 1.1 can be networked. When two ends of a connection support different versions of USB, the link automatically runs at the lower speed of the older version.

Understand Broadband Router

A broadband router combines the features of a traditional network switch, a firewall, and a DHCP server. Broadband routers are designed for convenience in setting up home networks, particularly for homes with high-speed cable modem or DSL Internet service. A broadband router supports file sharing, Internet connection sharing, and home LAN gaming.

A broadband router follow the Ethernet standard for home networking. Traditional broadband routers required Ethernet cables be run between the router, the broadband modem, and each computer on the home LAN. The newer wireless routers also support broadband Internet access and the Ethernet standard without the need for cabling.

Several manufacturers offer broadband router products to the consumer. Features that differentiate broadband router products include the number and type of ports available on the unit for cabling computers, external modems, or other network devices.

Note: Image reference is taken from the answers.com.

Physical Network Connection With Routers

The basic hardware component used to connect heterogeneous networks is a Router.Physically,routers resembles bridges that means each router is a special purpose hardware system dedicated to the task of interconnecting networks.Like a bridge,a contains a processor and memory as well as a separate I/O interface for each network to which it connects.The network treats a connection to a router, the same as the connection to any other computer.

The most important that you have to kept in your mind about router is that it is not only used to connect two similar technology,it can also be used to connect two different types of network technology. Router can connect two LAN's,a LAN and a WAN,or two WAN's.Furthermore,when a router connects two network in the same general category,the networks do not need to use the same technology.For ex:- A router can connect an Ethernet LAN to a frame relay network.Thus,each cloud represents an arbitrary network technology.On summarizing this whole,we can say that a router is a special purpose system dedicated to the task of interconnecting networks.A router can interconnect networks that use different technologies,including different media,physical addressing schemes or frame formats.

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Enter into world of Technology

Goal of Internet

The main goal of internetworking is to provide a universal service across heterogeneous networks.To provide universal service among all computers on an internet,routers must agree to forward information from a source on one network to the specified destination on the other network.The task is complex because as all we know that different frame formats and different addressing schemes are used by different networks.Hence,to overcome this problem protocol software is needed on computers and routers to make universal service possible.The main task of these internet protocols is to overcome the differences in frame formats and physical addresses to make communication possible among networks that use different technologies.
For knowing more about protocols for internetworking you can visit:
http://networkingconcepts4u.blogspot.com/2009/02/protocol-for-internetworking.html

Internet Architecture

With the help of routers it is possible for an organization to choose network technologies appropriate for each need,and to use routers to connect all networks into a single network.As all we know that router is used exactly two connections but commercial routers can connect more than two networks.Thus,a single router could connect any number of networks.However,an organization seldom uses single router to connect all of its networks.There are two main reasons behind it:

1.As all we know that router must forwarded each packet,the processor in given router is insufficient to handle the traffic passing among an arbitrary number of networks.

2.The second reason behind this is redundancy,because redundancy improves reliability.To avoid a single point of failure,protocol software continuously monitors internet connection,and instructs the routers to send traffic long alternative paths when a network or router fails.

Thus,when planning an internet,an organization must choose a design that meet's the organization's need for reliability,capacity and cost.In particular,the exact details of internet topology often depends on the bandwidth of the physical networks,the expected traffic,the organization's reliability requirements,and the cost and performance of available router hardware.

Understanding Bridges

A bridge is an electronic device that is used to connects two LAN segments.Unlike a repeater,however a bridge is a digital device that uses the same network interface as a conventional computer and handles frames.The bridge listen to traffic on each segment in promiscuous mode.When it receives a frame from one segment,the bridge verifies that the frame arrived intact i.e there was no electrical interference on LAN during transmission and after that it forwards a copy of the frame to the other segment if necessary.Thus,two LAN segments behave connected by a bridge behave like a single LAN.A computer connected to either segment can send a frame to any of the other computers connected to the two segments.Because each segment supports standard network connections and uses the standard frame format that means computers do not know whether they are connected to a LAN or a bridged LAN.

When we compare bridges with LAN it is found that bridges are more useful and popular than repeaters because they help isolate problems.If two segments are connected by a repeater and lightning causes electrical interference on one of them,the repeater will propagate the interference to the other segment.In contrast if interference occurs on one of the two segments connected by a bridge,the bridge will receive an incorrectly formed frame,which the bridges simply discards the same way a conventional computer discards a frame that contains an error.Similarly,a bridge will not forward a collision from one segment to another.Thus,the bridge keeps problems on one segment from affecting the other.

Combining Switches and Hubs

From the last post it is clear that switching provides higher aggregate data rates in comparison to a hub,but the main drawback that occurred with the switched networks is the higher cost in comparison to hub.To overcome all these problems network administrator choose a compromise between the hub and the switched networks that means instead of connecting one computer to each port on a switch,the administrator connects the hub to each of the port of the switch and then connect each computer to one of the hubs.This result is very much closer to the conventional bridged LAN where each hub appears to be a single LAN segment, and the switch makes it appear that bridges connect all segments.The system also performs like a conventional bridged LAN where a computer must share a bandwidth with other computers connected to the same hub,communication can occur in parallel between a pair of computers attached to one hub and a pair of computers attached to another.

Repeater Vs Switch Vs Hub

Hello friends this is my post and i this post i am going to give you a brief description and difference between various networking devices.

As all we know various types of devices like repeaters,hub, routers, switch are used very frequently in the setup of any computer network.Here in this post we see all these devices one by one.

Repeater: A repeater is an electronic device that is used to receive a signal and after receiving, it transmit signal to the higher level so that it can move to long distance without any destruction in its value.In other words we can also say that repeater is a device that is designed to overcome signal attenuation means to recover signal degradation.All repeaters has two ports one for receiving the signal and other for its transmission. Repeaters can be used for carrying electrical signals in the form of copper wire or to carry light in the form of fiber optics.It is a layer 1 device that means Physical layer device.

Hub: In simple words we can say that a hub is a multi port repeater.It means it allows multiple machines to connect to the same network, by broadcasting traffic to all of its ports.The most practical implication of this is that only one device can send data at a time, otherwise a collision occurs. Hubs implement a collision detection multiple access method to detect when two machines attempt to send data at the same time. A hub supports broadcasting of any signal.It is also layer 1 device.

Switch:In general switch is very much different from the repeater and the hub , both of them works on IP address while the switch works on the MAC address. A switch works by keeping track of which MAC addresses are attached to each port. It inspects traffic and only sends it to the port that the destination device is on (based on the destination MAC address). A switch had a finite amount of memory in which it can store MAC addresses, smaller switches such as ones intended for desktop use have less memory then larger ones that may form part of an enterprise networks backbone. When a switches memory becomes full of active MAC addresses it will often revert to functioning like a hub and broadcast traffic to all ports.A switch is a layer 2 device(Data link Layer).