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 All rights reserved 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 All rights reserved 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 All rights reserved → 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 All rights reserved → 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 All rights reserved 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 All rights reserved → „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 All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved 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) All rights reserved − 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 All rights reserved 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 All rights reserved …. 7 PSTN-/SIP/IP Migration Prof. Dr.-Ing. U. Trick University of Applied Sciences Frankfurt All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved − − 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 All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved 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 All rights reserved 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