Network Modelling and PSTN-NGN Migration
ITU-BDT Regional Seminar on Fixed Mobile Convergence and new network architecture,
Tunis, November 2005
Dipl.-Ing. Soulaimane El Bouarfati
Dipl.-Ing. Frank Weber
Prof. Dr.-Ing. Ulrich Trick
University of Applied Sciences Frankfurt/Main
Research Group for Telecommunication Networks
This work was partially funded by the Bundesministerium für Bildung und Forschung of the
Federal Republic of Germany (Förderkennzeichen 1711403). The authors alone are responsible
for the content of the paper.
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
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Kleiststraße 3
D-60318 Frankfurt
Germany
Tel.: (+49) 6196/641127
E-Mail: trick@e-technik.org
Web: www.e-technik.org
Research group for telecommunication networks
Review
Introduction
2
New Network Model
3
Procedure for Designing a Network
4
Interworking between Networks
5
PSTN-NGN Migration
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1
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
1
1 Introduction
Changes in Telecommunication Networks
− NGN (Next Generation Networks), Voice/All over IP,
UMTS Release 5, Fixed/mobile Convergence
− Network integration: e.g. PSTN, ISDN, GSM
→ More complex networks
Reduction of complexity
− By using a structured network model
→ OSI Reference Model with 7 Layers, ISDN- and generic protocol reference model
−
−
But: Restricted to certain Layers or Strata
But: Important network functions such as „Services“, „Mobility“, „Security“,
„Quality of Service“ are spread over different Layers and Planes → not modelable
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→ New network model required!
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
2 New Network Model
Characteristics
− For modelling arbitrary Telecommunication Networks
−
−
1) Graphical Model
2) Calculation Model for variant calculation
−
−
−
−
−
Strata: Layer(s)
Planes
Functional columns
Network Management
Concrete network characteristics such as number of subscribers, traffic dimensions
→ Solving the problem of modelling overall network functions such as Security and
Mobility
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
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→ Overcoming the restrictions of OSI Reference Model
Research group for telecommunication networks
2
New Network Model with Strata and Functional Columns
Network Management
Basic Network Functions
Services
Security
Mobility
Quality of Service
Business
Stratum
Application
Stratum
Service
Stratum
Transport
Stratum
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Physical
Layer
Management Plane
Control Plane
User Plane
Network Characteristics
3 Procedure for Designing a Network –
Step 1: Definition of Requirements
−
Step-by-Step modelling
Step 1: Definition of requirements for
− Basic network functions
− Services
− Security
− Mobility
− Quality of Service
−
−
Network Management
Network Characteristics
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→ „Natural“ approach
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
3
Definition of Network Requirements
Basic Network Functions
Services
IP-based
Signalling
Transport
Simple Telecommunication
Services und
Service
Features
(e.g. Call
Hold, Call
Forwarding)
Three Party
Conference
IP-based
Network
Management
Enhanced
Services and
Service
Features
Confidentiality
Mobility
Quality of Service
Personal
Mobility
Integrity
Authentication
Session
Mobility
QoS
Negotiation
Access
Control
Liability
Availability
Service
Mobility
Resource
Reservation
Device
Mobility
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IP-based
Media
Transport
Security
Anonymity
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
Step 2: Deriving Functions
from Requirements
Basic Network Functions
Basic Network Functions
Business
Stratum
RTP (e.g.
based on
G.723)
Application
Stratum
UDP (TCP)
IP-based
Signalling
Transport
SIP
IP
DL
Phy
IP-based
Network
Management
SNMP
SIP
RTP (e.g. based on G.723)
Service
Stratum
SNMP
DL, IP, UDP
DL, IP, UDP (TCP)
DL, IP, UDP
Management Plane
Control Plane
User Plane
Phy
Phy
Phy
Transport
Stratum
Physical
Layer
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IP-based
Media
Transport
4
Step 3: Allocating Network Functions to Network Nodes
−
One individual column-based network model for each type of network element
−
Each network element model = Subset of total network model
−
Overlap of all network element models = total network model
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
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Type of Network, e.g. SIP/IP-based:
→ SIP User Agent
→ SIP Registrar Server
→ SIP Proxy Server
→ SIP Application Server
→ Conference Server
→ IP Router
→ Firewall
→ Bandwidth Broker
Research group for telecommunication networks
Step 4: Complete Functions in one or more Nodes if necessary
−
Aditional functions are automatically adopted from nodes into total network model
Step 5: Export Network Characteristics from Graphical Model into
Calculation Model
−
Automated readout of numeric network characteristics (e.g. number of subscribers,
traffic dimensions, costs) from up to four graphical network models
Step 6: Use Calculation Model
− Add further numeric characteristics to imported characteristics if necessary
→ Network calculations, cetwork optimisations, migration scenarios
− Arbitrary number of single scenarios for time sequence simulation
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Step 7: Export Results from Calculation Model into Graphical Model
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
5
Procedure for Designing a Network - Overview
Network to be modelled
Network Requirements
Deriving Functions for
the Network
Allocating Functions to
Network Nodes
Graphical Model
Export Network
Characteristics
Network Calculations
Migration Scenarios
Network Optimisation
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Calculation Model
Results from Calculation
Model
4 Network Interworking
−
In future: pure IP networks such as SIP/IP fixed networks, UMTS Release 7
−
While still converging: heterogeneous networks, both circuit and packet switched,
different protocol stacks
→ Interworking, gateways for connecting (2) networks
−
−
−
Full Model Realisation with EXCEL and VBA (Visual Basic for Applications)
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−
Steps 1 and 2: Graphical Model for each of the 2 networks
Step 8: Merging both Graphical Models → Relationship of network functions,
Interworking Function (e.g. ISUP-SIP)
Step 9: Allocating Interworking Functions to network nodes (e.g. Media Gateway
Controller)
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
6
Interworking of two different Networks
X-Y Interworking Function
Network Y, e.g. SIP/IP Network
Network X, e.g. PSTN Network
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IWF
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
5 PSTN-NGN Migration
Network 1
PSTN
Network 2
TGW
SIP/IP
AGW
RGW
PSTN Phone
PSTN Phone
SIP: Session Initiation Protocol
PSTN: Public Switched Telephone Network
PSTN Phone
TGW: Trunking Gateway
AGW: Access Gateway
RGW: Residential Gateway
IP Phone
IP Phone
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….
7
PSTN-/SIP/IP Migration
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
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User Traffic
− 0,119 Erl per PSTN subscriber
− 0,4 Erl per SIP/IP subscriber
Trunking Gateway (TGW)
− Traffic: 7.200 Erl (240 E1 à 30 Erl)
− Cost: 720 CU (Cost Unit)
Access Gateway (AGW)
− Traffic: 2.380 Erl (20.000 PSTN subscriber à 0,119 Erl)
− Cost: 12.500 CU
Residential Gateway (RGW)
− Traffic: 0,119 Erl
− Cost: 1,2 CU
IP-Phone
− Traffic: 0,4 Erl
− Cost: 1 CU
Research group for telecommunication networks
Subscriber Development in case of linear Migration
Subscriber Development
60.000.000
53 Mio
53 Mio
40.000.000
30.000.000
20.000.000
10.000.000
0
0
5
10
15
20
25
Point of Time
PSTN Subscriber
30
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Subscriber
50.000.000
SIP/IP Subscriber
8
Number of Gateways required
Number of Gateways required
Millions
3.000
2.650
2.500
53 Mio
50
40
Piece
2.000
1.500
30
20
1.000
max. 367
500
10
0
0
5
10
15
20
0
25
5
Number of TGWs
10
15
20
25
Point of Time
Point of Time
All rights reserved
0
Number of RGWs
Number of AGWs
Migration Costs
63,6
Mio
63,6
Mio
60
70
60
53 Mio
50
Millions
70
50
33,1 Mio53 Mio
40
30
40
30
33,1 Mio
264 240
20
10
Cost in CU
20
10
264 240
0
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Point of Time
TGWs Cost
AGWs Cost
RGWs Cost
IP-Phones Cost
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Millions
Migration Cost
Cost in CU
Piece
60
9
Interconnection of four different Networks
Gateway
E
PSTN
Gateway
A
Network 2
GSM
Gateway
B
Gateway
D
Gateway
F
Network 3
SIP/IP
Gateway
C
Network 4
UMTS-IMS
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Network 1
PSTN-SIP/IP- and GSM-IMS-Migration → All-IP Network
0,119 Erl average traffic per bearer channel (fixed subscriber)
max. 50000 bearer channels per local exchange
−
−
0,4 Erl average traffic per SIP/IP subscriber
max. 1 Million subscriber per CS (Call Server = SIP/IP-Softswitch)
−
−
0,025 Erl average traffic per GSM subscriber
max. 150000 mobile subscriber per MSC (Mobile Switching Center)
−
−
0,4 Erl average traffic per IMS subscriber
max. 1 million subscriber per S-CSCF (Serving-Call Session Control Function)
−
−
max. 19354 Erl per IP/PSTN- or IMS/GSM-Media Gateway
GSM/IP- and PSTN/IP-Gateways exchangeable
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−
−
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
Research group for telecommunication networks
10
Subscriber Development in case of simultaneous linear
Migration of 4 Networks
80
70
60
50
40
30
20
10
0
67 Mio
53 Mio
0
5
10
15
Point of Time
20
25
PSTN Subscriber
GSM Subscriber
SIP/IP Subscriber
IMS Subscriber
30
All rights reserved
Millions
Subscriber
Subscriber Development
Number of LEs, CSs, MSCs and CSCFs required in case of 4
Networks Migration
Number of Switching Node required
1.200
1060
1.000
600
447
400
200
67
0
0
5
10
15
20
(-92%)
53
25
Point of Time
PSTN-LEs
GSM-MSCs
SIP-IP-CSs
IMS-S-CSCFs
30
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Piece
800
11
Number of Media Gateways in case of simultaneous linear
Migration of 4 Networks
Number of Gateways required
250
209
Piece
200
→ redundant
150
100
50
0
0
5
10
15
20
25
30
GSM/SIP-IP-GWs
PSTN/IMS-GWs
GSM/IMS-GWs
Sum C/P-GWs
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Point of Time
PSTN/SIP-IP-GWs
Subscriber Development in case of sequential linear
Migration of 4 Networks: 1. PSTN, 2. GSM
80
70
60
50
40
30
20
10
0
0
5
10
15
Point of Time
20
PSTN Subscriber
GSM Subscriber
SIP/IP Subscriber
IMS Subscriber
25
30
All rights reserved
Millions
Subscriber
Subscriber Development
12
Piece
Number of Media Gateways required in case of sequential
linear Migration of 4 Networks: 1. PSTN, 2. GSM
Number of Gateways required
200
180
160
140
120
100
80
60
40
20
0
173 (-17%)
− Rapid SIP/IP Migration
→ Redundant PSTN-SIP/IP-Gateways
can be reused for GSM-SIP/IP and
GSM-IMS
0
5
10
15
20
25
30
GSM/SIP-IP-GWs
PSTN/IMS-GWs
GSM/IMS-GWs
Sum C/P-GWs
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Point of Time
PSTN/SIP-IP-GWs
Subscriber Development
80
70
60
50
40
30
20
10
0
0
5
10
15
20
Point of Time
PSTN Subscriber
SIP-IP Subscriber
GSM Subscriber
IMS Subscriber
25
30
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Subscriber
Millions
Subscriber Development in case of sequential linear
Migration of 4 Networks: 1. GSM, 2. PSTN
13
Number of Media Gateways required in case of sequential
linear Migration of 4 Networks: 1. GSM, 2. PSTN
Number of Gateways required
350
300
264 (+26% bzw. +43%)
Piece
250
−
−
Many GSM subscribers
0,4 Erl per IMS user
200
150
100
50
0
0
5
10
15
20
25
30
GSM/SIP-IP-GWs
PSTN/IMS-GWs
GSM/IMS-GWs
Sum C/P-GWs
PSTN/SIP-IP-GWs
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Point of Time
−
Use of the new network model recommendable
−
Proceed according to the steps 1 to 9
−
Migration of circuit to packet switched network
→ very strong reduction of the number of switching systems
−
Minimization of redundant media gateways by clever migration
−
Possibility of minimization of PSTN-SIP/IP migration costs by clever model use
−
Choose the most suitable Gateway type in each case
−
Migration costs can be related to providers (TGW, AGW, RGW) or users (IP-Phone,
RGW)
Prof. Dr.-Ing. U. Trick
University of Applied Sciences Frankfurt
All rights reserved
Summary
Research group for telecommunication networks
14