Networking allows one computer to send information to and receive information from another.

Local Area vs. Wide Area

We can classify network technologies as belonging to one of two basic groups. Local area network (LAN) technologies connect many devices that are relatively close to each other, usually in the same building. Wide area network (WAN) technologies connect a smaller number of devices that can be many kilometers apart. In comparison to WANs, LANs are faster and more reliable.

Ethernet Technology
Ethernet is a local area technology, with networks traditionally operating within a single building, connecting devices in close proximity.

Basic Ethernet terminology.

• Medium - Ethernet devices attach to a common medium that provides a path along which the electronic signals will travel. Historically, this medium has been coaxial copper cable, but today it is more commonly a twisted pair or fiber optic cabling.

• Segment - We refer to a single shared medium as an Ethernet segment.

• Node - Devices that attach to that segment are stations or nodes.

• Frame - The nodes communicate in short messages called frames, which are variably sized chunks of information.

Each frame must include, for example, both a destination address and a source address, which identify the recipient and the sender of the message. The address uniquely identifies the node, just as a name identifies a particular person. No two Ethernet devices should ever have the same address.

Ethernet Basics

1. Each signal on the Ethernet medium is sent to all the nodes, even the one who sent it. Each node inspects the destination address and if it is not for it then it is discarded without checking the content. Exception is broadcast signal, which is meant to be sent to all the nodes on the medium, is not discarded by any node.
2. Ethernet send either transmits or receive signal at any particular period of time. It cannot send and receive simultaneously. At any given instance only one node can transmit data. To prevent collusion of signal, it sense and then only starts transmission i.e. node transmits data when no other node is transmitting.

Ethernet Devices

Repeaters : As the distance between the node increases, electronic signal goes on weakening. Repeaters connect multiple Ethernet segments, listening to each segment and repeating the signal heard on one segment onto other segment connected to the repeater.

Bridges: Bridges acts as repeater as well as traffic regulator. It connects two network segments and transmits only across when the node is on other side of the bridge. This way it acts as a filter and doesn't allows unwanted signals across the bridge.

Switches: Switched networks replace the shared medium of legacy Ethernet with a dedicated segment for each station. These segments connect to a switch, which acts much like an Ethernet bridge, but can connect many of these single station segments. Since the only devices on the segments are the switch and the end station, the switch picks up every transmission before it reaches another node. The switch then forwards the frame over the appropriate segment, just like a bridge, but since any segment contains only a single node, the frame only reaches the intended recipient. This allows many conversations to occur simultaneously on a switched network. Switched networks also employ either twisted pair or fiber optic cabling, both of which use separate conductors for sending and receiving data.

Routers: are advanced networking components that can divide a single network into two logically separate networks. Also we can say Routers links to networks. While Ethernet broadcasts cross bridges in their search to find every node on the network, they do not cross routers, because the router forms a logical boundary for the network.

One of the tools a router uses to decide where a packet should go is a configuration table. A configuration table is a collection of information, including:

• Information on which connections lead to particular groups of addresses
• Priorities for connections to be used
• Rules for handling both routine and special cases of traffic

Main function of router is to direct packet in a best route. For example when you type yahoo.com, router connected to your system decides whether to send this packet to LAN or to the router outside the network. If yes then it is directed to outside router which again does same thing.

Routers can be programmed to direct the packets as required. For example if you have two different lines to connect to internet then router can be configured to use particular line for particular work.

We can trace the route of message using an utility in Windows, tracert. For example trace to www.yahoo.com

c:\tracert www.yahoo.com

Tracing route to a1842.w3.akamai.net [203.199.74.25]
over a maximum of 30 hops:

  1   257 ms   316 ms   319 ms  172.23.119.14
  2     *      384 ms     *     172.29.254.133
  3   357 ms   321 ms   337 ms  172.29.254.146
  4   315 ms   318 ms   319 ms  121.243.104.93
  5   440 ms   259 ms   484 ms  203.197.13.6.static.vsnl.net.in [203.197.13.6]
  6   755 ms   840 ms   698 ms  59.163.55.170.static.vsnl.net.in [59.163.55.170]

  7   756 ms   928 ms   530 ms  203.199.74.25.static.vsnl.net.in [203.199.74.25]


Trace complete.

In the above example, request is routed through seven routers.

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Home Networking

The two most popular home network types are wireless and Ethernet networks. In both of these types, the router does most of the work by directing the traffic between the connected devices.

Let us learn home networking with real example. Let us network two computers, one is laptop, and another is desktop.

We will use 16port Network Switch to network this systems. One system will be connected to Internet using Tata Photon+, a high speed wireless broadband connnection.

Steps:
1. Connect laptop & desktop to switch using twisted pair cables.
2. Connect to Internet using Tata's dialer application
3. Open the properties of Tata Network and in the sharing tab, select share this connection, select local area connection, this is our local ethernet network. (System will inform you the IP address of local network will be changed to 192.168.0.1, this is OK)
4. Move to other computer, open the local network properties, in the IPv4, select "automatically get IP address" & "automatic DNS server"

With this you two computers are networked, both sharing internet, and other resources connected to them.

Test the connection by exploring the shared folders of each other.
Similarly test the internet connection by browsing any website. If Internet explorer does not open the site, then check the connections properties. The LAN should be selected.

VPN Connection Issue

Problem: After the VPN connection, browser unable to show pages outside of network