Internetworking Concept

Network Components :

The main idea of network is to help all organization increase its productivity by connecting all the computer or networks. Connection between networks has helped organization in many ways in spite of variation in time, location and type of computer or devices.

By being a part of network, a company can access information, processes and ways of doing business changes. It is very important for every organization to manage a corporate inter-network that helps to optimize its resources.

Network is characterized based on group employees in the following ways

• Main Office : It is the location where all computers are connected to a LAN. It is a data center where all information related to company is centralized. Main office might contain thousands of employees who depend on networks to do their work.
•  The other areas of office where require access to the resources at main office and each other are

• Branch Office : These are smaller groups of employees and they are connected through LAN. Even through some of the data's are stored in the branch office, most of the time they access the data from the main office. How frequently they access the data from the main office determines the type of WAN connection. It can be permanent of dial up connection.
• Telecommuters : Employees who access the resources from the outside are telecommuters.
• Mobile users : Some of the employees work from different locations and they require connection to the network. When they work at main or branch office, they connect to LAN. When they work outside the office, they use dial-up service to connect to the network.

In order to understand what types of equipment and services to install in your network, it is very important to understand the user and the business needs, then you can subdevide the network into smaller components,

Corporate Networking Strategy :

Three Layer Hierarchial Network Model :

To properly build an inter-network, a three layered hierarchical model is used to organize traffic flow. Hierarchical model also simplifies the task required for two computers to communicate and divides it into three layers. Each layer is focused on a specific function, as mentioned below:

• Access layer provides work-group/user access to the network
• Distribution provides policy based connectivity
• Core or backbone layer provides optimal transport between sites.

Figure show various aspects of hierarchical model.

Access Layer :

This layer includes hubs and switches. Access layers is also called as Desktop Layer because it focus on connecting client nodes, such as workstations on the network. This layer ensures that packets are delivered to end user computers. Access Layers has ability to expand or contract collision domains using repeater, hub or switch. Switches in access layer are not high-powered device such as those found at the core layer. Rather it is advanced version of a hub.
Access layer controls work-group access to the locally available resources. Traffic that flows to and from the local resources is restricted between resources, switches and users. In most of the network, access to the services such as database, centralized storage is denied. In this case the request  or traffic will be sent to next layer distribution layer.
At the access layer, user can

• Enable MAC address filtering : it is possible to program a switch to allow only certain systems to access the connected LANs.
• Create separate collision domain: A switch can create separate collision domain for each connected node to improve performance.
• Share bandwidth : Allows the same network connection to handle all data. Allows moving data from one network to another to perform load balancing.

Note : A collision domain describes a portion of a network where any communication sent by a node is received by any other node on the network. In broadcast domain any part or any node of a network can broadcast to any node of the network

Distribution Layer:
Distribution layer is also referred as Work-group layer. Usually routing between access layer and core layer is handled by distribution layer. It also provides policy based connectivity; it can read the packet and prioritize the delivery based on the set by user.
Functions of distribution layer include

• Packet filtering : Distribution layer processes the packets and transmit data  packets based on the source and destination information to create network borders.
• Access layer aggregation point : distribution layer  serves the aggregation point for access layer switches.
• Distribution layer serves as the boundary for broadcast and multi-cast domains.
• performs queuing of packet and provides security service.

It determines the fastest way in which the request can be forwarded to the server. When the path is selected the request will be sent to core layer.

Core Layer :
Core layer is considered as backbone of the network and includes the high-end switches and high-speed cables such as fiber cables. This layer of the network does not route traffic at the LAN. In addition, no packet manipulation is done by the devices in the layer. Rather, this layer is concerned with speed and ensures reliable delivery of packet.
Usually, the traffic is being transmitted to and from services common to all users. These services are known as global or enterprise services. Example of these services includes email, Internet access and video conferencing. When the user access to enterprise service, then distribution chooses the best path and forwards the request to core layer. Core layer provides the rapid transmit of request to the enterprise service.