CHAPTER-14 IP TAX PROJECT IN BSNL Page 1
IP TAX IN BSNL IP TAX is the first step towards the Evolution of Current Generation Network to Next generation Network. In other words IP TAX is the replacement of existing Level I TAX exchanges to IP based network (Packet switching network) and rest all the network still remaining circuit switched network. Presently IP TAX will be installed in parallel to the Lev-I /Lev-II TAX and then it will replace circuit switched TAX completely with IP TAX. And it comes under class4 NGN. Fig.1 Page 2
Trunk Exchanges (class 4) or IP TAX As a first step towards NGN migration, operators can focus on to offload long-distance traffic from their TDM network. The generic reference diagram for IPTAX is shown in figure 1. Fig.2 Page 3
Based on this the following architecture is installed in BSNL: IP TAX ARCHITECTURE AS Signaling Gateway PSTN SS7 ISDN Media Gateway Trunking Gateway SOFTSWITCH BSNL s Core Network Session Boarder Controller Other service provider Network Management, OSS, BSS, Billing Fig.3 Basic elements are: 1 Soft Switch 2 Signalling gate way 3 Trunk Media Gateway Functions of Soft Switch (or Call Agent or Telephony Server or Media Gateway Controller) 1) Based upon Open Architecture 2) Provide all existing services available in TDM network 3) Performs Media Gateway Control Function 4) Performs Call control, signaling and interworking, Traffic measurement and recording functions 5) Provides Addressing, Analysis, routing and charging facilities Page 4
6) Interacts with Application Server to supply services not hosted on Softswitch Functions of Signalling Gateway 1) Provides interworking function between SS7 network and IP network 2) This involves providing various types of User Adaptations so that the SS7 signaling can be terminated in SGW and can be translated and messages transported over IP Network 3) Performs Packetization of signaling and ensures its transport through IP network Functions of Trunk Media Gateway Performs the functions of 1) Voice encoding & Compression 2) Packetization of voice channels 3) CNF (Comfort Noise Generation) 4) VAD (Voice Activity Detection) 5) Echo Cancellation 6) May provide the edge functionality and act as CE Functions of Announcement Server: Announcement server performs the function of giving the announcements as per requirements in the network. The protocols used are: Between Softswitch and media gateway H.248/MGCP Between two Softswitches - SIP(T) or BICC Between Softswitch and Signaling gateway - Sigtran suite of protocols Between two media gateways for actual packet transfer- RTP/RTCP Page 5
There are various protocols used for transporting CC7 signalling over IP like M2PA, M2UA, M3UA, SUA, IUA and V5UA, however, the choice of protocol used depends upon the network implementation. For large network M3UA may be used for transporting MTP Level 3 user part signaling messages (ISUP and SCCP) over IP using the SCTP. In BSNL there was an initial plan of 200K IPTAX pilot project. Out of this 200K capacity only 40K at New Delhi and 16 K at Chennai was installed. The equipment was supplied by M/s ZTE through M/s SOTL. Both of these sites were validation sites. After this a big project of 6476 K IPTAX lines project was planned by BSNL. In this new project the L1 bidder is again M/s ZTE. Till date only 2212 K capacity of IPTAX equipment has been supplied and installed in BSNL at about 119 locations. In BSNL it has been decided that stand alone Signalling gateways will not be purchased, the available SSTP network will be used as Signalling gateways. NMS has been installed at Chennai with FCAPS (Fault, Configuration, Accounting, Performance, Security) capabilities. In this project no separate NTP server is being used in IP TAX, the existing NTP server of our data network will be used for synchronization. Sample Questions:- 1). IPTAX is which type of NGN? a) Class 4 b) Class 5 2) Protocols used between Softswitch and media gateway: a) SIP b) H.248/Megaco 3. What is the first step towards evolution of NGN? e) Class 4 f) Class 5 g) Both h) None of these. Page 6
4. What is the replacement of existing Level I TAX exchanges? a) IP tax b) Level-II tax 5. IP TAX Based upon the a) circuit switching b) packet switching 1 a 2 b 3 a 4 a 5 b ANSWER KEY(IP TAX in BSNL) Page 7