Black Box MT722AE-X21T Manual De Usuario

When the Fradswitch links are configured for X.25, they operate synchronously at data rates up to 
2.15 Mbps. The links interface is DTE or DCE, and the data rate is determined by the external clock rate.

You can order the Fradswitch with interfaces for RS-232/V.24, X.21, or V.35.

The links packet size supported by the Fradswitch is configurable (up to 4096 bytes), and the frame window
range is selectable in the range of 1 through 7 (for modulo-8 operation), or 1 through 127 (for modulo-128
or extended operation).

Fradswitch links fully support switched virtual circuits (SVC) and permanent virtual circuits (PVC). The links
protocol is LAPB per ITU   X.25, and the Fradswitch can act as either DTE or DCE with respect to the layer 2
and layer 3 protocols.

When a link is configured for Frame Relay, packets are processed as follows. If the Fradswitch is located at
the user side (acting as an end device), the received Frame Relay packets are converted into async or X.25
format and are routed to the appropriate port. (See Figure 2-4.) If the Fradswitch is located at the network
side, the received Frame Relay packets are routed to another Frame Relay link. (See Figure 2-5.)

Acting as a FRAD (Frame Relay Assembler/Disassembler), the Fradswitch can either convert the
asynchronous data into X.25 packets and concentrate the packetized data stream over the Frame Relay 
link, or directly run asynchronous data over Frame Relay.