Esprit Statistical Multiplexer
- Up to 16 Asynchronous Data Channels
- Composite Link Rates to 256kb/s
- Channel Link Rates to 155.2kb/s
- Satellite Link Compatible
The conventional time division multiplexer (TDM) wastes the bandwidth of the communications line because the time slots in the frames are often unused. Vacant slots occur when an idle terminal has nothing to transmit in its slot. The Esprit statistical multiplexer dynamically allocates the bandwidth among the active terminals, varying the length of the frames in accordance with the input data streams, so that an idle terminal does not waste the line's capacity.
The Esprit provides comprehensive error-checking and correcting techniques and buffer management, as well as flow control, ensuring that no data is lost no matter how busy the channels are.
The Esprit 16 has sixteen asynchronous data channels operating at speeds up to 115.2Kbps to offer performance to satisfy the most demanding user. The high-speed composite link will operate at speeds up to 256Kbps and is able to control an ISDN terminal adapter or a dial up modem, switching off the link when data flow ceases.
The Esprit 8 has eight asynchronous data channels operating at speeds up to 38.4Kbps and composite link rate up to 64Kbps for the lower volume user.
Set-up of the Esprit is easy using the supervisor port. Simply connect a VT100 compatible terminal (or a PC running Terminal or HyperTerminal) and use the on-screen cursor driven menus. The set-up is stored in non-volatile memory and will be restored automatically each time the multiplexer is powered up.
Enhancements included in this powerful multiplexer include flash programming, static tolerant interface components and optionally larger channel buffers to accommodate satellite link delays.
Satellite Link Option
Link delay is the time required to move a frame from the sending multiplexer to the destination. A typical delay using a land circuit would be around 20 - 30 milliseconds.
To maximise efficiency, the Esprit continuously sends and receives frames and will have a certain amount of data "in-flight" all the time. The size of the channel buffers determines how much data may be in-flight since the data must be stored until it has been acknowledged by the remote multiplexer.
Satellite transmission must traverse a greater distance, and will introduce greater delay (sometimes as much as several hundred milliseconds). No data errors will occur but, as link delay rises, the channel buffers may become full and the multiplexer will have to flow-control as it awaits acknowledgement from the remote multiplexer. To prevent this problem, optional larger channel buffers can be provided to accommodate satellite link delays without compromising throughput.
Synchronous Tunneling
Synchronous tunneling is a method of converting synchronous data into packets and routing them to their destination over a network instead of directly via a dedicated link.
The Esprit multiplexer uses the HDLC protocol to communicate. Many routers understand HDLC, and are capable of packetising HDLC frames. Esprit data may therefore be 'tunnelled' between routers across an existing LAN or WAN, eliminating the need for a dedicated connection.
Esprit Specifications
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