What is cable Modem

" Simply Dish cable connection to homes "

A cable modem is used in homes for cable services provide by the service provider.Coaxial cable is used to connect our home to cable operator office a modem is attached with television, which convert analog signal to digital signal Vice-Versa.

Baseband

Mainly used in LAN in which entire capacity of the medium is dedicated to a particular device, Simple and small than broad band.

     Digital communication technology in which (in contrast to 'broadband') the entire bandwidth (data carrying capacity) of a medium such as a wire, cable, or channel, is used to transmit a single signal. Therefore, only one communication channel is available at any given time. Baseband is cheaper and simpler (though less versatile) technology than broadband, and is employed in most types of local area networks such as Ethernet and Token Ring.

Why was the OSI developed

• Educational purpose
• To make a standard which help to vender for developed network hardware
• Making a good understanding people of networking concept
• It’s just a model which help making networking concept more depict able 
• Making Layering concept more clear than TCP/IP

Directory Service

User friendly information about network resources

     A directory service or name service, maps the names of network resources to their respective network addresses. With the name service type of directory, a user does not have to remember the physical address of a network resource; providing a name locates the resource. Each resource on the network is considered an object on the directory server. Information about a particular resource is stored as attributes of that object. Information within objects can be made secure so that only users with the available permissions are able to access it. More sophisticated directories are designed with namespaces as Subscribers, Services, Devices, Entitlements, Preferences, Content and so on. This design process is highly related to Identity management.