Transcript ISDN REFERENCE MODEL

ISDN
REFERENCE
MODEL
BASIC RATE ACCESS (BRI)
• 2B + D
• S0 interface
B-CHANNEL
B-CHANNEL
D-CHANNEL
BRI
TELEPHONE CALL
408-526-1234
D-CHANNEL
CONVERSATION
B-CHANNEL
END
D-CHANNEL
E1 PRIMARY RATE INTERFACE (PRI)
• E1 PRI or S2 interface
• Used in Europe
• 30 B + D
B-CHANNEL
B-CHANNEL
D-CHANNEL
E1-PRI
REFERENCE POINTS
• Reference points characterize the different interfaces
TE1
TE 2
R
R
NT 2
T
NT1
U
LT
V
ET
T
NT1
U
LT
V
ET
TA
TE1
TE 2
S
TA
S
POINT TO POINT CONFIGURATION
•
•
•
•
Supported on BRI and PRI
Maximum 1 TE
Maximum 1 km (BRI)
Most straightforward wiring configuaration
TE
Max 1km
NT1
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
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 50 m
Max 7 - 10 m
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
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 !)
TE
Q.921 - LAPD
NT1
[
LT
ET
Q.931
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
CALL REFUSED
• Call can be refused for various reasons
TE
SETUP
RELEASE
COMPLETE
ET
ET
SETUP
RELEASE
COMPLETE
TE
CALL CLEARING
• Any side can clear the call
TE
DISCONNECT
ET
ET
DISCONNECT
RELEASE
RELEASE
RELEASE
COMPLETE
RELEASE
COMPLETE
TE