Network hardware.

Network hardware.

1. Hierarchy of protocols.

   • Most networks are organized as a stack of layers.
     • The number of layers, its name, the content of each and its function define a network of another.
       • Each layer is a type of virtual machine that offers certain services to the layer that is above it.
         • Between each pair of adjacent layers there is an interface.
           • It defines primitive operations and services that puts the lowest layer available to the immediate top layer.
             • A set of layers and protocols is known as network architecture.

2. Aspects and designs for layers.

   • The key aspects that occur in computer networks are present in the various layers.
     • A mechanism for detecting errors in the received information uses error detection codes.
       • Another aspect of reliability is to find a functional route through a network.

3. Comparison between connection-oriented service and offline service.

   • The connection-oriented service is modeled from telephone systems.
     • The offline service is modeled from the postal system
       • Each type of service can be characterized based on its reliability, (never lose data).

4. Relationships between services and protocols.

   • Are different concepts.
     • A service is a set of primitives (operations) that a layer provides to the layer above it.
       • A protocol is a set of rules governing the format and meaning of packets that exchange equal entities in a layer.

5. Service primitives.

   • a service can be specified formally as a set of primitives available to user processes to access the service.
     • The set of primitives available depend on the nature of the service to be offered.
       • The connection-oriented primitives are distinct from the non-connected service.

6. There are two types of transmission technology that are widely used today.

   • Point to point links connect individual pairs of machines.
     • In a broadcasting network all the machines in the network share the communication channel.
       • Diffusion systems also provide the possibility to send a package to the different data by using a special code in the address field.

7. Personal area networks.

   • Generally called PAN allows devices to communicate within a person's range.
     • If the wireless technology is necessary to make this connection using cables.
       • PAN networks can also be built with other technologies that communicate within short ranges.

8. Local area networks.

   • Usually called LANs are privately owned networks that operate within a single building, such as a home, office or factory.
     • They are widely used to connect personal computers and household appliances in order to share resources and exchange information.
       • It uses different transmission technologies.
         • Most use copper cables, but some use fiber optics.
           • They have restrictions as to their size.

9. Metropolitan area networks.

   • A metropolitan area network or MAN, covers an entire city.
     • Cable TV is not the only MAN.
       • Recent developers in wireless high-speed Internet access have originated another one commonly known as WIMAX.

10. Wide area networks.

    • A Wide Area WAN network, covers an extensive geographical area, usually a country or continent.
      • In most WAN networks, lan subnetwork has two distinct components.
        • The transmission lines are moved in bits between machines.
        • Communication elements or switches are specialized computers that connect two or more transmission lines.
        • They are known as a router.

11. Interredes.

    • There are many networks in the world, often with different hardware and software components.
      • A collection of interconnected networks is known as Interred or Internet.
        • Connecting a LAN and a WAN network, or connecting two LANs is the usual way to form an Interred.
          • The benefit of forming a network is to connect computers between different networks.