●Frame. Relay is simplified form. of （71) ，similar in principle to （72) ，in which synchron

●Frame. Relay is simplified form. of (71) ，similar in principle to (72) ，in which synchronous，frames of data are routed to different destinations depending on header information．

Packets are routed throught one or more Virtual Circuits known as (73) .Most Virtual Circuits are (74) ，which means that the network provider sets up all DLCI connections at subscription time． (75) are also part of the Frame. Relay specification．They privide a link that only lasts only as long as the session．

(71) A．Datagram Switching

B．Datagram Routing

C．Packet Switching

D．packet Routing

(72) A．X．21

B．X．25

C．X．28

D．X．29

(73) A．DLCIs

B．HDLCs

C．SDLCs

D．DLs

(74) A．Permanent Circuits

B．Permanent Virtual Circuits

C．Switched Virtual Circuits

D．Switching Circuits

(75) A．Permanent Circuits

B．Permanent Virtual Circuits

C．Switched Virtual Circuits

D．Switched Circuits