Quick Tech Tip: Concatenated Virtual Circuits

Two styles of internetworking are common:

* a connection-oriented concatenation of virtual circuit subnets,
* a datagram internet style.

In the concatenated virtual circuit model, a connection to a host in a distant network is set up in a way similar to the way connections are normally established. The virtual circuit consists of concatenated virtual circuits between the routers or gateways along the way from the source node to the destination node. Each gateway maintains tables telling which virtual circuits pass through it, where they are to be routed, and what the new virtual circuit number is. This process continues until the destination host has been reached.



Once data packets begin flowing along the path, each gateway relays incoming packets, converting between packet formats and virtual circuit numbers as needed. Clearly, all data packets must traverse the same sequence of gateways , and thus arrive in order.
This scheme works best when all the networks have roughly the same properties.
Concatenated virtual circuits are also common in the transport layer. In particular, it is possible to build a bit pipe using OSI, which terminates in a gateway, and have a TCP connection go from the gateway to the next gateway. In this manner, an end-to-end virtual circuit can be built spanning different networks and protocols.

Quick Tech Tip: InterNetworking

What are we talking about ? The interconnection of two or more networks, usually local area networks so that data can pass between hosts on the different networks as though they were one network. This requires some kind of router or gateway to facilitate the process of interconnecting two or more individual networks to facilitate communications among their respective nodes. Note: The interconnected networks may be different types. Each network is distinct, with its own addresses, internal protocols, access methods, and administration.
For different networks to interact, devices such as repeaters, bridges, routers, gateways are required. Repeaters are low level devices that just amplify or regenerate weak signals. They are needed to provide current to drive long cables. They copy individual bits between cable segments.
Unlike repeaters, bridges are store and forward devices. A bridge accepts the whole frame and passes it to the data link layer where the checksum is verified. Then the frame is sent down to the physical layer for forwarding on a different network.
Multiprotocol routers are conceptually similar to bridges, except that they are found in the network layer. They take incoming packets from one line to another, just as all routers do, but the lines may belong to different networks and use different protocols.
Transport gateways connect byte streams in the transport layer. Application gateways connects two parts of an application in the application layer.
When a gateway is between two WANs run by different organizations in different countries, the gateway is ripped apart in the middle and the two parts are connected with a wire.

Quick Tech Tips: Wide Area Networks - WAN

Wide Area Networks, or WAN, span a large geographical area. A WAN contains a collection of machines intended for running user programs. Transmission rates are typically 2 Mbps, 34 Mbps, 45 Mbps, 155 Mbps, 625 Mbps, etc.
The machines are connected by a subnet whose job is to carry messages from machine to machine. The subnet consists of two distinct components : transmission lines and switching elements. Transmission lines move bits between machines. The switching elements are specialized computers used to connect two or more transmission lines. It is the job of the switching element to decide which outgoing line to choose to forward the data on incoming line.
In WANs, the network contains numerous cables or telephone lines, each one connecting a pair of routers. When a packet is sent from one router to another via one or more intermediate routers, the packet is received at each intermediate router in its entirety, stored there until the required output line is free, and then forwarded. A subnet using this principle is called a point-to-point, store and forward, or packet switched network.
Second option for a WAN is satellite or ground radio system. Each router has an antenna through which it can send and receive. All routers can hear the output from the satellite, and in some cases they can also hear the upward transmissions of their fellow routers to the satellite as well.

MIMO ROUTERS - A quick summary

MIMO routers build on the MIMO technology, a relatively new set of technology protocols that reinvent the way signals are transmitted and received. MIMO routers send out multiple data streams at the same time and then use multiple antennas to sift through the signals for the requisite pattern. All this is done while maintaining a fast connection and, hence, a fast data stream. One characteristic sign of a MIMO router is multiple antennae.

Benefits of MIMO Routers. These include:
• Faster speeds.
• Greater distances between your paired devices.
• More simultaneous users.
• Less signal fading and dead spots.
• Better resistance to interference.

Concerns of MIMO Routers:

1. MIMO routers have a premium associated with them. The prices can fall as the product gets matured.
2. Pending 802.11N standard.

Introduction to Routers

A computer networking device which forwards data packets across a network toward their destinations, through a process of routing is known as Router. In companies and large corporations, a central computer system acts as a router to connect all of the company's computers to one network. This allows group participation and collaboration on large projects or just to connect all of the company's resources at one central location. It also aids in reliable communication between employees working on different floors in the building or in different countries.

1. Router is required to connect multiple networks, like your LAN to the Internet.
2. Routers store large tables of networks and addresses, then using algorithms to determine the shortest routes to individual addresses within those networks.
3. Routers not only facilitate intra-network communications, but also play a role in overall network performance.
4. Routers help in delivering the information faster.
5. Routers also protect LAN from Internet.
6. Router blocks any packet that has a destination address outside of the LAN. If the destination address is valid, the router could check the Packet for an error. If there is an error, the router could discard the Packet and send a message to the originating address.
7. Routers have address translation and filtering capabilities.