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© 1999, Cisco Systems, Inc.
Introduction to Voice over IP and other Integrated Services Voice Signaling Is the Key to Enhanced Services Session 408 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
1
Agenda • Analog/Digital Signaling • ISDN/SS7 Signaling • QSIG • H.323 • SIP • Media Gateway Controller 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
In the Beginning—Well Almost!
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
2
Line Signaling: On-Hook
R
Switch Switch
T
Called Station Telephone Network
R
Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 5
© 1999, Cisco Systems, Inc.
Line Signaling: Off-Hook 1. Signaling supervision R
Switch Switch
T
Called Station Telephone Network
R
Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 6
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Line Signaling: Dial-Tone 2. Call information (network to user) R
Switch Switch
T
Called Station Telephone Network
Dial-Tone R
Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 7
© 1999, Cisco Systems, Inc.
Line Signaling: Addressing 3. Dialing the destination R
Switch Switch
T
Called Station Telephone Network
Tones or Pulses R
Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 8
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
4
Line Signaling: Ringing 4. Call information (network to user) Ringing R
Switch Switch Switch Switch
Ring Gen
T
Called Station Telephone Network
Ring Back R
Switch Switch Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 9
© 1999, Cisco Systems, Inc.
Line Signaling: Off-Hook 5. Call Completion R
Switch Switch
T
Called Station 300–3400 Hz @ 4khz
Telephone Network
R Switch Switch
T
Calling Station 408 1038_05F9_c2
R - Ring T - Tip 10
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
5
Applications of Line Signaling
Loop Start
Loop Start
FXS
FXS
Loop Start
Loop Start
FXO
FXS
408 1038_05F9_c2
PBX
11
© 1999, Cisco Systems, Inc.
Trunk Signaling R T PBX PBX
R T Switch Switch
Switch Switch
R1
R1
T1
T1
R
PBX PBX
T
• Loop Start • Ground Start • E&M 408 1038_05F9_c2
R - Ring T - Tip R1 - Ring 1 T1 - Tip 1 12
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Application—Foreign Exchange (Loop Start)
Switch Switch
LATA 1
LATA 2
591-XXXX
555-XXXX Loop Start
Loop Start
PBX PBX
FXO
FXS
Caller Calls 591-4242 and the Call Appears as a Local Call
• Limitations: Simultaneous trunk seizure (glare) Lack of far-end disconnect notification 408 1038_05F9_c2
13
© 1999, Cisco Systems, Inc.
Ground Start Supervisory Signaling—From PBX Ground Sensor
1. PBX grounds the ring lead R
- 48 VDC
Off-Hook
2. CO switch senses the ground
4. PBX sensing the ground, closes the loop, removes ring ground
Telephone Switch
PBX
T - 48 VDC
Off-Hook
3. CO switch grounds the tip lead
408 1038_05F9_c2
Tip Ground Detector R - Ring T - Tip 14
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Application—Foreign Exchange (Ground Start)
Switch Switch
LATA 1
LATA 2
591-XXXX
555-XXXX
Ground Start
Ground Start PBX PBX
FXO
FXS
Caller Calls 591-4242 and the Call Appears as a Local Call
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© 1999, Cisco Systems, Inc.
Ground Start Benefits and Limitations • Benefits Reduces glare by quickly recognizing incoming seizure (tip ground) Provides remote disconnect supervision
• Limitations Mixed voice and signaling Tip and ring cannot be reversed CO switch and PBX must have same potential ground 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Ear and Mouth (E&M) Separate Signaling Path 2 Wire E&M
4 Wire E&M
T R
PBX
T and T1
CO Switch R and R1
E M
E Signaling Interface Exchange
Signaling Interface Exchange
M
• 2 wire and 4 wire refer to the voice wires • The switch listens on the ear (E-lead) • The switch signals on the mouth (M-lead) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
E&M Type 1 M
- 48 VDC Off-Hook PBX
M
M-Lead Detector
Ground On-Hook
- 48 VDC
E-Lead Detector
Line Equipment E
E
2-Wire, Nonsymmetrical
Open On-Hook Ground Off-Hook
• Common ground must exist between PBX and line equipment 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
9
E&M Signaling States E&M Type Type I
Type II
Type III
Type IV
Type V
408 1038_05F9_c2
Condition
M-Lead/SB
E-Lead/SG
On-Hook
Ground
Open
Off-Hook
Battery
Ground
On-Hook
Open
Open
Off-Hook
Battery
Ground
On-Hook
Ground
Open
Off-Hook
Loop Current
Ground
On-Hook
Open
Open
Off-Hook
Ground
Ground
On-Hook
Open
Open
Off-Hook
Ground
Ground 19
© 1999, Cisco Systems, Inc.
I’m Ready to Receive the Number Now—Wink Start Sending Switch
Receiving Switch Off-Hook
On-Hook
Sending Switch Goes Off-Hook Wink
On-Hook
Off-Hook Receiving Switch Goes Momentarily Off-Hook for 140 to 200 msec DTMF Digits Sending Switch Waits a Minimum of 210 msec Before Sending Addressing
Off-Hook Receiving Switch Goes Off-Hook After Connection Is Established 408 1038_05F9_c2
On-Hook 20
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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I’m Always Ready to Receive— Immediate Start Sending Switch
Receiving Switch Off-Hook
On-Hook
Sending Switch Goes Off-Hook
DTMF Digits Sending Switch Waits a Minimum of 150 msec Before Sending Addressing
Off-Hook Receiving Switch Goes Off-Hook After Connection Is Established 408 1038_05F9_c2
On-Hook 21
© 1999, Cisco Systems, Inc.
E&M Signaling and Wink Start or Immediate Start
PBX PBX
Switch Switch
E&M
E&M
• The only caveat—make sure your signaling type matches up with your PBX 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
11
Primary Trunk Signaling Method Switch Switch
CO Trunks
CO Trunks
EM PBX PBX
EM
PBX PBX
Tie Trunks
Tie Trunks
EM
EM
• PBX to local exchange office (telephone company) • CO trunks • Direct inward dial (DID) trunks • Direct outward dial (DOD) trunks • PBX to PBX connections • Tie trunks 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Voice Evolution: The Formative Years
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
12
Digital Signaling— Better and Cheaper
Distorted Analog Communications
Clear Digital Communications
2 x 4 KHz = 8 KHz 300–3400 Hz @ 4 KHz 408 1038_05F9_c2
8 KHz x 8 Bits = 64 kbps 25
© 1999, Cisco Systems, Inc.
T1 Signaling Format Time Slot #X
Time Slot #24 7
1
8
1
6
7
6
A
12
18
C
18
24 D Channel Associated Signaling (CAS) or Robbed Bit Signaling
fo rI SD N
B
Us ab le
12
or PB X
Extended Super Frame
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8
1
Si gn al in g
1
24 Common Channel Signaling
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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E1 CAS Signal Format Time Slot #16
Time Slot #16
1
1
A
B
C
D1
A
B
C
D17
2
A A
B B
C C
D2 D3
A A
B B
C C
D18 D19
A A
B B
C C
D4 D5
A A
B B
C C
D20 D21
A
B
C
D6
A
B
C
D22
5 6
A
B
C
D7
A
B
C
D23
7
A
B
C
D8
A
B
C
D24
8
9 A 10 A
B B
C C
D9 A D10 A
B B
C C
D25 D26
9 10
11 A 12 A 13 A
B B
C C
D11 A D12 A
B B
C C
D27 D28
B
C
D13 A
B
C
D29
13
14 A 15 A
B B
C C
D14 A D14 A
B B
C C
D30 D31
14 15
7 8
8
gn Si
4
Semi-Multiframe (SMF) 2
7
al
2 3
11 12
Channel Associated Signaling 408 1038_05F9_c2
6
X
5 6
5
PB
4
Semi-Multiframe (SMF) 1
4
or
3
3
in
0
2
g
1
8 X
N
7 X
SD
6 X
rI
5 X
fo
4 0
le
3 0
ab
2 0
Us
1 0 0
Common Channel Signaling 27
© 1999, Cisco Systems, Inc.
Sample Call
Telephone Network CO CO Switch Switch
CO CO Switch Switch
T1 Robbed Bit Signaling Using E&M, A and B Bits = 0, Off-Hook
2 Wire
Loop Start Signaling
T1 Leased Line PBX PBX
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Voice Evolution: Dawn of the Digital Age Touch Tone Phones Faxes Wow! This Is Better than Fire
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© 1999, Cisco Systems, Inc.
The Advanced Intelligent Network • More efficient • Support real-time operations of telephone network’s capabilities • Supports transport transparency • Customer can create new applications and is provided greater control 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Public N-ISDN Intelligent Access to the Network BRI
PBX PBX11
BRI
Telephone Network
Switch Switch
PRI
Switch Switch
Supplementary Services
PRI
PBX PBX22
Supplementary Services
Scope of Bearer Services Scope of Teleservices Basic Rate Interface (BRI) (2B + D) Primary Rate Interface (PRI) (23B + D or 30 B + D) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Functional Devices and Reference Points Network Boundary per ITU-T
S
ISDN Terminal Equipment (TE1)
R Non-ISDN Terminal Equipment (TE2)
Customer Premises Switching Equipment (NT2)
Network Boundary in U.S. (No ITU-T Standard) T
U Local Loop Terminator (NT1)
ISDN Local Exchange (LE)
S/T Terminal Adapter (TA)
Standard per TA Manufacturer 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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ISDN Protocol Stack Application Application Presentation Presentation Session Session
I.451 = Q.931 Basic Call Control I.452 = Q.932 Supplementary Services
End-to-End End-to-End User User Signaling Signaling
Transport Transport Network Network
I.45X Call Control
Data Data Link Link
Further Further Study Study
X.25 X.25
X.25 X.25
LAPD LAPD
I.465/V.120 I.465/V.120
I.430 I.430 Basic Basic Interface Interface ++ I.431 I.431 Primary Primary Interface Interface
Physical Physical Control Control Signaling Signaling
Packet Packet
Telemetry Telemetry
Circuit Circuit Switch Switch
SemiSemiPermanent Permanent
D Channel 408 1038_05F9_c2
LAPB LAPB
Packet Packet Switched Switched
B Channel
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© 1999, Cisco Systems, Inc.
Q.931/932 Message Format Bits 8
• Call reference— establishes a unique value between user and the network
7
6
5
Octet 4
3
2
00
Protocol Protocol Discriminator Discriminator (Q.931) (Q.931) 00 00 00 11 00 00
00
00
00
00
1 00
Length Length of of CRV CRV
• Information elements—are self contained entities that further define the message
2 3 or 4
CR Flag
• Message type—can be grouped into call establishment, call info phase, call clearing and misc.
1
Call Call Reference Reference Value Value (1 (1 or or 22 bytes) bytes) 0 0/1
Message Message Type Type
4 or 5
Information Information Element Element Identifier Identifier
1
Length Length Information Information Element Element Identifier Identifier
2
Contents Contents of of Information Information Element Element
3
Next Next Information Information Element, Element, etc etc 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
17
Supplementary Services • Types: Number identification, call offering, call completion, multiparty, community of interest, charging, additional information transfer
• Control and invocation, three generic protocols: Keypad—uses the keypad and display information elements Feature key—uses the feature activation and feature indication information elements Functional protocol—facility message and facility Information element or specific messages like HOLD 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Q.931/Q.932 Call Completion Calling Party
Network
Called Party
Setup
Setup Acknowledge Information Call Proceeding
Setup Call Proceeding Alerting
Alerting
Connect
Connect Connect Acknowledge Connect Acknowledge
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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The Intelligent Network
Signaling Network
PBX PBX11
Switch Switch
Switch Switch
PBX PBX22
Telephone Network
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© 1999, Cisco Systems, Inc.
SS7 Local Architecture SCP
• Service control point— database information
SCP
A or access links—access to STPs STP
STP
• Signal transfer point— routing of SS7 packets B or bridge links—connect STPs at the same level
STP
C or cross links—connect mated pairs of STPs, B and C links together make up a quad
STP
A or access links—access to STPs SSP
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SSP
• Service switching point— access switches or their proxy 38
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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SS7 Connection to Remote Network Local SCP
Regional SCP
STP STP
STP STP
STP STP
STP STP
SSP
D or Diagonal Links for Connecting a Local STP Pair to a Regional STP Pair
SSP
SCP
SCP
STP STP
STP STP
STP STP
STP STP
SSP
SSP
E or Extended Links Used to Connect SSPs to a Secondary Pair of Mated STPs F or Fully Extended Links Directly Interconnect Two SS7 Switches 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
SS7 Protocol Stack OMAP
ASE
TCAP Non-Circuit Non-Circuit Applications Applications
ISDN User Part (ISUP) Circuit-Related Services
Application TUP (ITU)
DUP (ITU) Presentation, Presentation, Session, Session, Transport Transport
Null SCCP Specialized Routing
Network Level 3
MTP
Level 2 Level 1
Network Signal Link Signal Data Link
OMAP - Oper., Maint. and Admin. Part ASE - Application Service Element ISUP - ISDN User Part DUP - Data User Part 408 1038_05F9_c2
Message Handling, Network Management Bit Bit Oriented Oriented Protocol Protocol Speeds up to 64 kbps
Data Link Physical
OSI Reference Model MTP - Message Transfer Part TCAP - Transaction Capabilities Application Part TUP - Telephone User Part SCCP - Signaling Connection Control Part 40
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
20
Protocol Usage— Network Elements TCAP
ISUP
Null Null
SCCP
SCCP
MTP L3 MTPL2 MTP MTPL2 MTPL1
MTP L3 MTPL2 MTP MTPL2 MTPL1
STP
SCCP
MTP
MTP L3 MTPL2 MTPL2 MTPL1
TCAP
STP
SCCP
SSP
MTP L3 MTPL2 MTP MTPL2 MTPL1
SSP STP
SCCP
STP
MTP L3 MTPL2 MTP MTPL2 MTPL1
ISUP
Null Null
SCCP MTP L3 MTPL2 MTP MTPL2 MTPL1
TCAP
SCP
Null Null SCCP
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MTP L3 MTPL2 MTP MTPL2 MTPL1 41
© 1999, Cisco Systems, Inc.
MTP Messages (Level 2 and 3) FCS
0 0 Length FSN/FIB BSN/BIB 1-2 Bytes (Always 1)
FCS
FCS
FLAG Fill-In Signal Unit (FISU)
Status 0 0Length FSN/FIB BSN/BIB variable
1 byte
SIF
SIO
FLAG
Link Status Signal Unit (LSSU) 0 0 Length FSN/FIB BSN/BIB
FLAG
Message Signal Unit (MSU) Up to 272 bytes in Length
BSN/BIBB—Backward Sequence Number/Backward Indicator Bit FSN/FIB—Forward Sequence Number/Forward Indicator Bit Length—0=FISU, 1 or 2 = LSSU, 3 or greater = MSU SIO—Service Information Octet, Type of Protocol and Standard SIF—Service Information Field, Transfer Control Information FCS —Frame Check Sequence 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Message Signal Units (MSUs) SIF
FCS
SIO
0 0 Length FSN/FIB BSN/BIB FLAG
Varies by Protocol/Function
SLS 4 Bits
Origination Point Code
Destination Point Code
14 Bits
14 Bits
or
Routing Label
SLS 8 bits (5 Used)
ITU
Origination Point Code
Destination Point Code
24 Bits
24 Bits
ANSI SLS = Signaling Link Selection Code
• Message discrimination—looks at the point code in the routing label to determine if the message is local • Message distribution (message is local)—uses the SIO to determine the user (application) part • Message routing (message is not local)—attaches a new routing label and determines the proper link for next signal point 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
ISDN User Part (ISUP)
• ISUP is used to set up and tear down all circuits used in the PSTN, Telephone User Part (TUP) is used internationally as well • Support for non-voice calls and supplementary services with end-to-end significance 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
22
ISDN User Part (ISUP) FCS
SIF
SIO
0 0 Length
Signaling Info
FSN/FIB
BSN/BIB
FLAG
Routing Label
CIC
2 Spare bits 14 14 Bits Bits
Message Type ( 1 Octet )
Circuit Identification Code Mandatory Fixed Parts Sample Message Types Initial Address Message (IAM)
Mandatory Variable Parts
Address Complete (ACM) Answer (ANM)
Optional Parts
Continuity (COT) 52 message types (ANSI, Bellcore & ITU) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
ISUP Call Flow TE
Setup
SSP
STP
SSP
TE
IAM IAM
Call Proceeding
Setup
Call Proceeding Alerting
ACM ACM
Connect
ANM
Alerting
ANM Connect B Channel Disconnect Release
Trunk
Trunk
REL REL RLC RLC
Release Complete
Q.931 408 1038_05F9_c2
B Channel
Disconnect Release Release Complete
SS7
Q.931 46
© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Signaling Connection Control Part (SCCP) • Larger more complete address space supplements MTP addressing by adding called party and calling party numbers (subsystem numbers—SSNs) • Protocol used for accessing databases and other network entities (i.e. TCAP) • Global title translation 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Signaling Connection Control Part (SCCP) Message Format FCS
SIF
TCAP
SIO
0 0 Length
SCCP xxxx 0011
FSN/FIB
BSN/BIB
FLAG
Routing Label
Message Type Mandatory Fixed Parts
Mandatory Variable Parts
Optional Parts
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
24
Transaction Capabilities Application Part (TCAP)
• General purpose remote operation function for SS7 • Originally designed to support database queries, such as calling cards and 800 numbers
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© 1999, Cisco Systems, Inc.
TCAP Message Format FCS
SIF
TCAP
SIO
0 0 Length
SCCP xxxx 0011
FSN/FIB
BSN/BIB
FLAG
Routing Label
Transaction Portion (Nature of the Message) Invoke Component
Parameter Set Sequence
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
25
TCAP Call Flow TE
STP
SSP
Setup
SCP
Begin Begin Continue
Continue
Setup Acknowledge
Play Announcement and Collect Digits
Continue
Information
Continue
Pass Collected Digits End
End IAM
Actual Network Address
Call Proceeding
Q.931 408 1038_05F9_c2
SS7 51
© 1999, Cisco Systems, Inc.
AIN Limitations
• Sporadic deployment • Poor consistency Lack of interoperability between vendors and between service providers
• Master slave relationship • Intelligence resides in the network 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
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Voice Evolution: AIN Services These 900 Numbers, What Will They Think of Next
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© 1999, Cisco Systems, Inc.
Private N-ISDN (QSIG) PSTN PSTN
PINX22
PSTN PSTN
PSS1 PINX11
PSS1
PISN
PINX44
PSTN PSTN
PSS1
• Purpose: To extend facilities normally only available between extensions on a single PBX to all extensions on PBX’s that are connected together in a Private Network PINX—Private Integrated Services Network Exchange PISN —Private Integrated Services Network PSS1—Private Signaling System 1 (QSIG) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
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QSIG Benefits
• Multivendor ISDN PBX-based network • Networking of remote ISDN PBX’s • Interconnecting voice/fax and DP servers • Network wide applications • Support mobility 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
QSIG Reference Points TE
TE
S
TE
S
S/T T
PINX X
PINX Y
Q
Q C
S/T
TE
S/T
S
N Public ISDN A
TE
T Public ISDN B
PINX Z
Q
Network, e.g. Leased Line
C
C
• PINX—Private Integrated Services Network Exchange 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
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28
QSIG Protocol Layer 4–7
ROSE: ROSE: Remote Remote Operation Operation Service Service Elements Elements ACSE: ACSE: Association Association Control Control Service Service Elements Elements Network Network Specific Specific
End-to-End End-to-End Protocol Protocol Network Network Transparent Transparent
ECMA ECMA 148, 148, 157, 157, 163, 163, 164, 164, 173-178, 173-178, 185, 185, 186, 186, 191-194, 191-194, Supplementary Supplementary 202, Services 202, 203, 203, 211-214, 211-214, 220, 220, 221, 221, 224, 224, 225, 225, 241, 241, 242, 242, 250, 250, Services and and ANFs ANFs 251, 251, 263, 263, 264 264
Network
Link Layer
ISO ISO 11582, 11582, ETS300 ETS300 239 239 ECMA156, ECMA156, 161, 161, 165 165
QSIG QSIG Generic Generic Functional Functional Procedures Procedures
ISO ISO 11574, 11574, ETS300 ETS300 171/172/173, 171/172/173, ECMA ECMA 106, 106, 142, 142, 143 143
QSIG QSIG Basic Basic Call Call
LAPD, LAPD, ETS300 ETS300 402 402
Physical
Basic Basic Rate Rate I.430 I.430
Media
Copper Copper
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Interface Interface Dependent Dependent Protocols Protocols
Primary Primary Rate Rate I.431 I.431 Copper Copper
Optical Optical
57
© 1999, Cisco Systems, Inc.
Basic Call Completion PINX X
PINX Z
PINX Y Setup Setup Call Proceeding Call Proceeding Alerting Alerting Connect Connect Connect Acknowledge Connect Acknowledge
Terminal Node 408 1038_05F9_c2
Transit Node
Terminal Node
58
© 1999, Cisco Systems, Inc.
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QSIG Generic Functional Procedures End PBX
End PBX
Application
Application
...
ROSE—Remote Operation Service Element ACSE—Association Control Service Element DSE—Dialog Service Element
SS SS Control Control 11 Service Service Element Element
SS SS Control Control nn
Coordination Function
Coordination Function
SS SS Control Control nn
... SS SS Control Control 11 Service Service Element Element
Transit PBX Generic Functional Transport
Generic Functional Transport
Generic Functional Transport
Protocol Control
Protocol Control
Protocol Control
DLC
DLC
DLC
PHY
PHY
PHY
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© 1999, Cisco Systems, Inc.
Voice Evolution: A Better Private Network
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
30
Why Packet-Based Telephony?
• Data networks are growing at a faster rate then voice networks • One network is cheaper and easier to manage then two • Leverage the flexibility inherent in data networks for voice 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
H.323 • International (ITU) standard for: Packet-based multimedia communications systems • Version 1 established in 1996, Version 2 in 1998 and Version 3 in the works • Refer to various annexes for more details • Leverages previous developments within ITU (i.e. Q.931) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
31
H.323 Terminal H.323
H.323
H.323
H.323
Router LAN B
LAN A
• Multimedia communications services over packet-based networks • Real-time audio, video and/or data communication • Point-to-point, multipoint, or broadcast 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
H.323 Gateways H.323
H.323 H.320 (Over ISDN)
Gateways LAN A
Telephone Network
H.324 (Over POTS) Speech Only (Telephone)
• Appropriate translation between transmission formats • Translation between communication procedures • Call setup and clearing on both sides 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
32
H.323 Gatekeeper Gatekeeper H.323
LAN A
H.320 (Over ISDN)
Gateways Telephone Network
Router
H.324 (Over POTS) Speech Only (Telephone)
Intranet H.323 LAN B ZONE
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© 1999, Cisco Systems, Inc.
H.323 Gatekeeper • Optional • Required features Address translation (alias to transport within zone) Admissions control (maybe null) Bandwidth control during the call (maybe null)
• Optional features Call control signaling/routing (under GK control) Call authorization Call management (call status, tracking, PBX-like services etc.) 408 1038_05F9_c2
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© 1999, Cisco Systems, Inc.
Cisco Systems Confidential
33
H.323 Multipoint Control Unit (MCU) Gatekeeper
MCU
H.320 (Over ISDN)
Gateways
Router
Telephone Network
LAN A
H.324 (Over POTS) Speech Only (Telephone)
Intranet
H.323
H.323 LAN B ZONE
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H.323 Terminal—Multipoint Control Unit (MCU) • An endpoint which provides support for multipoint conferences • A MCU consists of a multipoint controller (MC) and one or more multipoint processors (MP) • Endpoints establish a point to point connection with the MC • Actual video or audio distribution maybe centralized or distributed 408 1038_05F9_c2
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Scope of H.323 Recommendation Video Codec H.261, H.263
Video I/O equipment
Audio Codec G.711, G.722, G.723, G.728, G.729
Audio I/O equipment
Receive Path Delay (sync)
RTP
UDP
H.225 Layer
User Data Applications T.120, etc.
IP
System Control
TCP
H.245 Control Call Control H.225.0
System Control User Interface
RAS Control H.225.0
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RTCP
UDP
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Call Signaling Procedures— No Gatekeeper H.323 Calling Party Setup—H.225 Call Signaling Channel Call Proceeding
• Setup message to called party’s well known call signaling channel identifier
Alerting
H.225
Connect
H.245 Control Channel
H.245
H.323 Called Party
• Connect message contains H.245 control channel transport address for H.245 signaling • Capabilities exchange and master/slave determination over reliable channel
H.245 Logical Channel Setup (RTP) H.245 Logical Channel Setup (RTCP) H.245 Logical Channel Setup (RTP)
• Logical channels setup over unreliable channels for multimedia streams
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H.450 Supplementary Services
• H.450-1 Generic Functional Protocol • H.450-2 Call Transfer Supplementary Services • H.450-3 Call Diversion Supplementary Services
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H.323 Limitations
• Relatively slow—due to the extensive amount of message exchange • Designed with peer to peer multimedia communications in mind • Protocol format has some limitations 408 1038_05F9_c2
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Voice Evolution: End of the Intelligent Network? I Guess I Better Reboot My Phone
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Session Initiation Protocol (SIP)
• Internet telephony not telephony over Internet • Currently underdevelopment within the IETF (multiparty multimedia session control working group)
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SIP Architecture: Contacting the Proxy IP-Based IP Based Network
Invite Client
Invite
e
r
Client
Server
e
User Agents
Proxy 408 1038_05F9_c2
User Agents
S
Client
r
v
Server
Redirect 75
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SIP Architecture: Proxy Responding to Client IP-Based IP Based Network
Response OK Client
Response OK
e
r
Client
Server
e
Proxy 408 1038_05F9_c2
User Agents
S
User Agents
Client
r
v
Server
Redirect 76
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SIP Architecture: Client Acknowledgement IP-Based Network
Ack Client
Ack
e
r
Client
Server
e
User Agents
S
User Agents
Client
r
v
Server
Proxy 408 1038_05F9_c2
Redirect 77
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SIP Architecture: Contacting the Redirect Server Invite Contact Ack Client
Client
Server
Server
User Agents
User Agents
Proxy 408 1038_05F9_c2
Redirect
IP-Based Network 78
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SIP Architecture: Contacting the User Invite Response Ack Client
Client
Server
Server
User Agents
User Agents
Proxy 408 1038_05F9_c2
Redirect
IP-Based Network 79
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SIP Protocol • SIP addressing takes the form of a mail to URL (i.e. user@host, examples sip:
[email protected]) • Session Description Protocol (SDP) is used to form the message, analogous to Q.931 messages and information elements • Modeled around HTTP, but with UDP 408 1038_05F9_c2
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Internet Telephony Protocols SDP
H.323
RTSP
SIP
Media
RTCP
TCP
RTP
RSVP
UDP
IP 408 1038_05F9_c2
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SIP vs. H.323 • SIP uses text for encoding of messages. H.323 uses ASN.1 • SIP uses a single request to send all necessary information • UDP based. Recent changes by H.323 will allow utilization of UDP as well • H.323 has widespread usage 408 1038_05F9_c2
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Internet Telephony Evolution: Alien Life Form?
•picture of alien
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Gateway Control Protocols • Allows remote control of various devices • Create, modify, and delete connections. Generates and detect events (tones). Tracks resource states. • Fits in well with multimedia call signaling (i.e. H.323 and SIP) • Strong support for existing telephone networks 408 1038_05F9_c2
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Gateway Control Migration April ’99
October ’98
SGCP (IETF)
MEGACO (MGCP+) (IETF)
MGCP 1.0 (IETF)
July ‘98 Bellcore Cisco
IPDC
MDCP (IETF)
August ’98 Level 3
December ’98 Lucent
• SGCP—Simple Gateway Control Protocol
• MDCP—Media Device Control Protocol
• IPDC—IP Device Control
• MEGACO—Media Gateway Controller
• MGCP—Media Gateway Control Protocol 408 1038_05F9_c2
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GCP Protocol Relationship SS7 Network
Signaling Gateway
Signaling Gateway
Sigtran
SS7 Network
Sigtran
Media H.323+, SIP+, ISUP+ Media Gateway Gateway Controller Controller MGCP, H.GCP Megaco
MGCP, H.GCP Megaco PSTN Network
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Media Gateway
H.323 or SIP
Media Gateway
PSTN Network
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MGCP • Retains SGCP simplicity • Uses established standards (SDP) • Additional SDP functions for other network types IP, ATM
• Uses IPDC features Wildcards Event grouping Control extensions Endpoint audit Connection audit Restart 408 1038_05F9_c2
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MGCP Call Agent Signaling Between Gateway and Call Agent Notification
Call Agent
Signaling Between Call Agent and Gateway Notification Modification Creation
GW 1
IP Cloud
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Analog Call Using MGCP Call Agent 1
5
Q
3
2 e at St
4
Q
St ate
6
GW 1
GW 2
IP Cloud Monitor Calling Session
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Dialed Digits Called Session RTP Connection 89
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MGCP and SS7 Interoperability SSP Call Agent
STP STP
1
SSP
2
3 6
CO
TGW1
STP STP
Q
4
e at St
Q
St 5 ate
SSP
7
TGW2
CO
IP Cloud Monitor SS7/ISUP Calling Session Dialed Digits Called Session RTP Connection
Dialed Digits to CO Start the Call 408 1038_05F9_c2
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Summary
• Call signaling has taken an evolutionary path. The underlying core is to provide basic call control. The next step is understanding how new services are added (supplementary services)
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Please Complete Your Evaluation Form Session 408
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