Transcript Lecture 5

ISDN
Lecture 5
Paul Flynn
1
Functional Architecture
OSI
Low-layer capabilities
B-ISDN
I.327
High-layer
Capabilities
Broadband
Capabilities
N-ISDN
Local
Functional
Capabilities
TE
User-toNetwork
Signaling
Local
Functional
Capabilities
64 kbps based
Capabilities
Inter-exchange
Signaling
Capabilities
TE or
Service
Provider
SS7
User-to-User Signaling
2
Component Functionality Model
Control
Control
Switching
Transport
Access
End
User
End
User
3
Integrated Digital Network
Analog
Switch
FDM MUX
4kHz Analog
4kHz Analog
4
Integrated Digital Network
Digital
Switch
TDM/PCM
IDN
TDM/PCM
5
Present Service Access
Subscriber
PSTN - Public
Switched
Telephone
Network
CSPDN - Public
Circuit Switched
Data Network
Multiple, Disjoint,
Access Lines (Digital
and Analog)
PSPDN - Public
Packet Switched
Data Network
Analog
Dedicated
Lines
Digital
Dedicated
Lines
6
ISDN Service Access
PSTN - Public
Switched
Telephone
Network
Subscriber
CSPDN - Public
Circuit Switched
Data Network
Integrated
Services
Digital
Network
PSPDN - Public
Packet Switched
Data Network
Analog
Dedicated
Lines
Digital
Dedicated
Lines
7
ISDN Standards
8
Line Encoding
2 Binary, 1 Quaternary (2B1Q)
•
•
•
•
Two bits select one of four voltage levels
Amplitude and polarity vary
Utilizes up to 392 kHz
NO room for concurrent POTS voice as separate
entity
10
+3
+1
0
11
11
01
+1
+3
00
00
9
ISDN Channel Structure
B-Channel
-Bearer Services
D-Channel
-Signaling
-LBR telemetry
-LBR data
H-Channel
-HBR Data / Fax
-Video
-Hi-quality Audio
10
User Interface Structures
BRI:
Basic Access
2B+D
160 kbps =
2 B @ 64k each
D: 16 k
+ 16 k overhead
PRI: (NA)
Primary Access
23B+D
1.544 kbps =
23 B @ 64k each
D: 64k
+ 8 k framing
11
PRI Channel Structures
• North America Primary Rate Interface (PRI)
–
–
1
F
B8ZS Line Coding
AMI Signals
193 bits (125 Microseconds)
8 bits
Time # 0
8 bits
Time # 1
8 bits
Time # 2
Time#23
B-Channels
D-Channel
• ITU-T PRI
256 bits (125 Microseconds)
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
8 bits
Time # 0
Time # 1
Time # 2
Time #16
Time #17
Time #18
Time #31
Timing
& Sync
B-Channels
D-Channel
12
ISDN Reference Points
& Functional Groups
• Architecture on subscriber premises is divided
functionally into groupings separated by reference points
• Functional Groupings: arrangements of physical
equipment or combinations of equipment
• Reference points: conceptual points used to
separate groups of functions
• Separation permits development of interface standards at
each reference point
13
Integrated Services Bus
Network (ISBN)
14
ISDN Reference Configurations
I.411
U
S
TE1
NT1+2
T
S
TE1
NT2
NT1
S
R
TE2
U
TA
U
NT1+2
I
S
D
N
N
E
T
W
O
R
K
15
ISDN Internetworking
K
ISDN
P
Specialized
network
resource
Telephony networks
or dedicated networks
M
Specialized
Service Provider
N
T
Customer
Equipment
ISDN
16
ISDN
Reference Points & Functional Groups
TE1 (Terminal equipment type 1) - Subscriber
equipment that uses ISDN with standard ISDN
I/F (e.g. digital phone, voice/data terminal, Fax)
Reference Point S (system) - Interface of individual
ISDN terminals. Separates user’s equipment from
network related communications functions.
S
TE1
T
NT2
NT2 (Network Termination 2) - Intelligent
device performing switching &
concentrating functions (e.g. digital
PBX, terminal controller or LAN). Up
to Layer 3. Supports Multi-drop.
Reference Point T (terminal) - Minimal ISDN termination
on customer premises.
U
NT1
Reference Point U - Interface
between carrier ISDN exchange
& NT1
NT1 (Network Termination 1) - Physical &
Electrical termination on user premises
(Layer 1). Isolates user from subscriber
loop technology.
17
The U-Interface
G.961, Digital Transmission System for Metallic Local
Lines for ISDN Basic Rate Access, 1993
ANSI T1.601, Integrated Services Digital Network –
Basic Access Interface for Use on Metallic Loops for
Application on the Network Side of the NT, 1992
18
ISDN
Reference Points & Functional Groups
TE2 (Terminal equipment type 2) - Non-ISDN
equipment. Require terminal adapter (TA)
S
TE1
NT2
U
NT1
S
R
TE2
T
TA
Reference Point R (rate) - Defines interface to
non-ISDN equipment (e.g. RS232)
TA (Terminal adapter) - interfaces
non-ISDN equipment to NT2
19
ISDN
Reference Points & Functional Groups
Functional Groups can be combined into
single devices.
T
NT2+1
TE1
S
R
TE2
U
TA
Reference Point T – Same description as S,
occurs between NT1 and NT2 devices.
Reference Point S – Occurs between NT2
capable device and terminal devices.
20
ISDN
Reference Points & Functional Groups
User Owned
??????????
S
TE1
T
NT2
Telco Owned
U
NT1
V
LT
ET
R
TE2
TA
Transmission Line to
Switching Office
Analog
Terminal
21
ISDN User Interface
Layered Models
Reference Model
C.O.
S
T
TE1
NT2
U
NT1
V
ET
LT
Procedural Model
3
3
D-Channel
B-Channel
3
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
22
TE1 Device Physical Layer
(
Analog-to-Digital Conversion,
Data sources / sinks, etc.
Circuit Circuit
B1
B2
Control
Requests /
Indications
Circuit
Switched
Control
Data
Packet
Switched
Data
D-Channel Control
S-Bus Multiplexing
23
Multidrop on the S-Bus
ISDN—Term
Ckt Pkt
Cont Data
ISDN—Term
Ckt Pkt
Cont Data
ISDN—Network Term
Pkt
Data
Ckt
Cont
D
B1
B2
24
ISDN Packet Switched Service
Circuit-Switched Mode
X.25
Terminal
Terminal
Adapter
ISDN
Central
Office
X.25
Packet
Switched
PDN
Used for X.25 Data on
B-Channel
25
How does it work?
TE1
TE1
ISDN CO Switch
NT
D Interface
NT
Bonding
X.25
X.25
U Ref Point
PSPDN
26
ISDN Protocols and Services
Application
Presentation
Session
End-to-end
User
Signaling
Transport
Network
Data Link
Physical
Q.931
Call Control
X.25 PLP
LAPD (Q.921)
X.25 PLP
Future
Frame Relay
LAPB
I.430 Basic Interface, I.431 Primary Interface
D-Channel
B, H-Channels
27
ISDN Circuit-Switching
ISDN User #1
Concept
ISDN User #2
OSI layer
7
B channel
6
5
6
5
4
3
4
3
2
1
2
1
D channel
4
3
2
1
OSI Layer 1
Digital
Network
Control
3
2
1
Local
exchange
OSI Layer 1
Control
Local
exchange
CCSS No.7 network
3
2
1
4
3
2
D channel
7
OSI layer
B channel
User Plane
1
Control Plane
28
ISDN Protocol Architecture
at the User-Network
Interface
Network Call control
Q.931
Data Link
X.25
Packet level
LAPD (Q.921)
Physical
V.120 or frame relay
LAPB
I.430 basic interface + I.431 primary interface
Signal
Packet
D channel
CircuitSemiPacketswiteched permanent switched
B channel
29
ISDN Call-Control Protocol
87654321
• Protocol discriminator:
– used to distinguish messages for usernetwork call control
Protocol discriminator
0000
Flag
0
Length of
call-ref value
• Call reference:
– identifies the B-channel call to which this
message refers
Call ref value
Message type
Other info elements
as required
• Message type:
– identifies which 1.45 1/Q.931 message is
being sent e.g. SETUP, DISCONNECT.
•
The contents of the remainder of the
message depend on the message type.
30
Q.931 Messages
• Circuit-mode connection control:
– refers to the functions needed to set up,
maintain, and cleara circuit-switched
connection on a B channel. This function
corresponds to call control in existing
circuit-switching telecommunications
networks.
• Packet-mode access-connection
control:
– refers to the functions needed to set up a
circuit-switched connection (called an
31
Functions of Q.931
messages
• Call establishment:
– used to set up a call initially. This group
includes messages between the calling
terminal and the network and between the
network and the called terminal.
• Call information:
– sent between user and network once a call
has been set up but prior to the
disestablishment (termination) phase. One
of the messages in that group allows the
network to relay, without modification,
information between the two users of the
32