ISDN%20REFERENCE%20MODEL

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ISDNREFERENCEMODEL
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BASIC RATE ACCESS (BRI)

• 2B D
• S0 interface

B-CHANNEL
BRI
B-CHANNEL
D-CHANNEL
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TELEPHONE CALL

408-526-1234
D-CHANNEL
CONVERSATION
B-CHANNEL
END
D-CHANNEL
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E1 PRIMARY RATE INTERFACE (PRI)

• E1 PRI or S2 interface
• Used in Europe
• 30 B D

E1-PRI
D-CHANNEL
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REFERENCE POINTS

• Reference points characterize the different
  interfaces

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POINT TO POINT CONFIGURATION

• Supported on BRI and PRI
• Maximum 1 TE
• Maximum 1 km (BRI)
• Most straightforward wiring configuaration

TE
NT1
Max 1km
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SHORT PASSIVE BUS

• Only on BRI
• Maximum 8 TE
• Each TE can be located anyware along the passive
  bus
• Passive bus distance maximum 200 m
• Distance TE to passive bus maximum 7 - 10 m

Max 200 m
NT1
Max 7 - 10 m
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LONG PASSIVE BUS

• Only on BRI
• Maximum 8 TE
• All TE must be concentrated at the last 50 m of
  the bus
• Passive bus distance maximum 500 m
• Distance TE to passive bus maximum 7 - 10 m

Max 500 m
NT1
Max 7 - 10 m
Max 50 m
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STAR CONFIGURATIONS

• Only on BRI
• Maximum 8 TE
• Passive bus in a box
• NT1 with multiple S0 ports
• Distance TE to NT1 maximum 7 - 10 m

Max 7 - 10 m
NT1
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THE DATA LINK LAYER

• The ISDN network does not impose the use of any
  data link layer protocol for the B channels
• On the D channel the use of Q.921 or LAPD is
  defined
• LAPD Link Access Procedure on the D channel
• Specified in CCITT I.441 and Q.921
• Q.921 protocol is used between the TE and the
  local ISDN switch (not end to end !)

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Q.931
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PROGRESS AND ALERTING

• Optional progress and allerting messages are
  possible

SETUP
SETUP
TE
ET
ET
TE
CALL PROCEEDING
PROGRESS
PROGRESS
ALERTING
ALERTING
CONNECT
CONNECT
CONNECT ACK
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CALL REFUSED

• Call can be refused for various reasons

SETUP
SETUP
TE
ET
ET
TE
RELEASE COMPLETE
RELEASE COMPLETE
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CALL CLEARING

• Any side can clear the call

DISCONNECT
DISCONNECT
TE
ET
ET
TE
RELEASE
RELEASE
RELEASE COMPLETE
RELEASE COMPLETE