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DEFINITY Enterprise Communications Server Release 5
Maintenance and Test for R5vs/si
555-230-123
Issue 1
April 1997
Maintenance Commands and Trouble-Clearing Aids
Page 8-471status link
8
Level 2 The logical protocol that allows data communication between
these two endpoints. BX.25 specifies that this is the LAPB (Link
Access Protocol on the B-channel) protocol. Frames are sent at
level 2. Establishment of the protocol requires one end to send a
SABM (Set Asynchronous Balanced Mode) frame and the other to
respond with a UA (User Acknowledgment) frame. Both sides
send SABMs until they receive a UA at which time level 2 is up and
the Link Status field indicates "restarting". This should be a
temporary condition, because the link is unusable until level 3
comes up, and that occurs immediately.
Level 3 The logical protocol that allows multiplexing of many channels
onto one level 2 link. BX.25 specifies that this will be the X.25 data
phase protocol. Packets are sent at level 3 and are included in
level 2 frames. This protocol is established after level 2 is
established by one end sending a Restart packet, and the other
end sending a Restart Confirm packet.
Processor channel The connection of an application running inside the SPE to a
particular channel on a particular link. Processor channels are
identified by a number associated with an entry on the "change
communication-interface processor-channel" form. There the link
number and level channel number on that link are specified as
well as the application (for example, dcs) that uses that processor
channel are specified.