Communications Equipment •Communication Equipments: –Equipments that are, •Not a direct part of the network (like node, client, terminal, server etc.) but, •Indirectly they are a part of network and, –Are required for communication between the source and the destination.
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Communications Equipment Communication Equipments: –Equipments that are, Not a direct part of the network (like node, client, terminal, server etc.) but,
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Communications Equipment
•Communication Equipments:–Equipments that are,
•Not a direct part of the network (like node, client, terminal, server etc.) but,•Indirectly they are a part of network and,
–Are required for communication between the source and the destination.
–Receives the input signals from several devices, –Combines them into a single stream of data, and then –Transmits the data over a single communications line.
•Process of combining various signals into one is called:–Multiplexing
–De-multiplexer:•Device that,
–Recovers the input signal and divides them as,–Separate signals again.
•Process of separating the signals from a single signal is called:–De-multiplexing
–Most multiplexers today include,•Both multiplexing and de-multiplexing functionality.
Multiplexer / Demultiplexer•Advantages:
–Increases the efficiency of communications by reducing the,•Cost of communications by,
–Combining the data of various communication lines onto a single communication line.
•If each client had its own dedicated line, –The line would be idle most of the time.
–The process of combining the links onto 1 transmission line is,
•Transparent and hence,•The network behaves as if each connection was occurring over a separate physical line.
–Organizations need to lease (rent) only,•A single long-distance line to,•Transmit many voice and data signals between two offices in different cities.
Multiplexer / Demultiplexer•Multipoint line v/s Multiplexed line:
–Multipoint line:•Physically a single line and logically,
–Also a single communication channel.•Allows only,
–1 client to transmit over the line at a time.•Requires only,
–1 port / interface for connection.•Requires algorithm to avoid congestion.
–Multiplexed line:•Physically a single line is logically,
–Divided into multiple communication channels.•Allows,
–Many clients to transmit at the same time.•Requires,
–Many ports / intefaces for connection because,»The multiplexed line needs to be demultiplexed at some point of time into separate lines.
•Algorithm to avoid congestion is not required.
Communications Equipment•Multiplexing:
–Depending on how the signals are multiplexed (joined/combined) together, classification is:
–BOTTLENECK Problem:•Internet infrastructure uses WDM to give speeds of,
–MegaBytes per second (MBps) and,–GigaBytes per per second (GBps) yet,
•Internet users get the speeds only in,–KiloBits per second (Kbps).
–Reason:•Ultimately optical fibers are always connected to,
–Networks that use copper wire.•Copper networks can only carry,
–Electrical signals and not Light signals.•So some kind of conversion needs to be done at both the ends of transmission (Light to Electricity & vice-versa) and,
–These conversions take time and slow down end-to-end transmission.
•Moreover, customer’s home and the local telephone company end office are connected by,