Published on January 24, 2009
Essential Networking Concepts : Essential Networking Concepts This part introduces concepts that are essential to understanding the specific subfield of computer networking that includes bridges, switches and routers. It also covers the intro to OSI reference model layers, because this model is a useful basis for networking. It also discusses various dimensions along which network designs can differ, such as scope, scalability, robustness, and auto configurability. What is a Layers? : What is a Layers? Understanding, designing, and building a computer network would be too difficult a task unless the problem were partitioned into smaller subtasks, traditionally by dividing the problem into parts, called layer. Each layer communicates with its peer layer in another node through the use of a protocol by the devices like route, switch and bridge. Layers defined by ISO : Layers defined by ISO 1) Physical layer 2) Data link layer 3) Network layer 4) Transport layer 5) Session layer 6) Presentation layer 7) Application layer Computer networking device : Computer networking device Computer networking devices are units that mediate data in a computer network. Computer networking devices are also called network equipment, Intermediate Systems (IS) or InterWorking Unit (IWU). Examples: Router, Switch and for hybrid networks i.e. Bridge. Modems, Network cards etc. such and such. Router : Router A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding information. Routers generally contain a specialized operating system (e.g. Cisco's IOS or Juniper Networks JUNOS or Extreme Networks XOS), RAM,NVRAM, flash memory, and one or more processors. TYPES OF ROUTERS : TYPES OF ROUTERS There are basically 2 types of routers: Static Routers Dynamic Routers Static Routers : Static Routers Static router: In this type the system administrator is defining the shortest path in the network. In static routers, system administrator is giving the shortest path by giving some commands. Static router is not so efficient than dynamic routing. static routing have some limitations and used in the relatively Smaller range of the network. Dynamic Routers : Dynamic Routers In the dynamic routing the router can define the shortest path by itself between the nodes. Dynamic routing is the clever type of routing and normally used in lot of places in the world while routing. In this type the router is programmed in such a way that router itself is taking the shortest path and system administrator does not have to do any thing. It saves time and cost. Switch : Switch A network switch is a computer networking device that connects network segments. In the past, it was faster to use Layer 2 techniques to switch, when only MAC addresses could be looked up in content addressable memory (CAM). With the advent of ternary CAM (TCAM), it was equally fast to look up an IP address or a MAC address. Types of switches : Types of switches There are basically 2 types of switches: Unmanaged switches Managed switches Unmanaged switch : Unmanaged switch These switches have no configuration interface or options. They are typically found in SOHO or home environments Managed Switch : Managed Switch These are ones which allow access to one or more interfaces for the purpose of configuration or management of features such as Spanning Tree Protocol, port speed, VLANs, etc. High-end or "enterprise" switches may provide a serial console and command-line access via telnet and Secure Shell, as well as management via SNMP. Network Bridge : Network Bridge A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model, and the term layer 2 switch is often used interchangeably with bridge. Bridges are similar to repeaters or network hubs, devices that connect network segments at the physical layer, however a bridge works by using bridging where traffic from one network is managed rather than simply rebroadcast to adjacent network segments. Types of Bridging : Types of Bridging There are basically 2 types of bridging: Transparent bridging Source route bridging Transparent bridging : Transparent bridging This method uses a forwarding database to send frames across network segments. The forwarding database is initially empty and entries in the database are built as the bridge receives frames. If an address entry is not found in the forwarding database, the frame is rebroadcast to all ports of the bridge, forwarding the frame to all segments except the source address. Source route bridging : Source route bridging With source route bridging two frame types are used in order to find the route to the destination network segment. Single-Route (SR) frames comprise most of the network traffic and have set destinations, while All-Route (AR) frames are used to find routes. Bridges send AR frames by broadcasting on all network branches; each step of the followed route is registered by the bridge performing it. Each frame has a maximum hop count, which is determined to be greater than the diameter of the network graph, and is decremented by each bridge. Frames are dropped when this hop count reaches zero, to avoid indefinite looping of AR frames Internetworking protocol : Internetworking protocol In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication. Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together are known as a protocol suite; when implemented in software they are a protocol stack. The terms are often intermingled; people may use the term "protocol" to refer to a software implementation, or use "protocol stack" to refer to the specification.