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Problems of QoS support in VOIP network of Mongolia
Keywords: Mongolia, ICT, QoS, recommendation, norm, service, class.
In Mongolia, ICT sector is intensively developing, the process of network convergence is carried out and the demand for convergent services is constantly increases. At the same time, the operators of Mongolia need to follow the international norms on quality of service parameters for IP networks. In this paper, the current status of ICT sector in Mongolia, communication quality parameters, the internationa norms on QoS parameters for IP networks and practical recommendations for improvement of QoS in VOIP networks of Mongolia is considered.
Fig. 1 . Functional structure of VoIP network
Ariunaa Tsogbadrakh,
Moscow Technical University of Communications and Informatics,
Mongolian Technical University of Science and Technology, optic2009@yahoo.com
1. The current status of ICT sector in Mongolia
ICT sector of Mongolia is comprised of telecommunications, information technology, radio and TV broadcasting, and postal services. Mongolia has become fully digitalized as for as switching and transmission system is concerned.
For the past year, the large scale initiatives such as "The launching of national satellite of Mongolia" project, "Postal services to every household" and "Broadband" national programs were submitted to and approved by the Government of Mongolia.
In the near future, there are number of large scale programs and projects need to be, developed and implemented such as "State policy on development of ICT sector of Mongolia by year 2021", "Launch of National Communications Satellite", establishment of "Mongolian Silicon Valley", "Switchover of radio and television broadcasting into digital technology", "Establishment of broadband network" and "Development of electronic government".
The national fiber optic network of Mongolia is now extended to reach 21 aimag centers and over 200 soums. ICTPA is planning to implement a project to extend fiber optic network in the next 2 years, which will connect remained soums. Four mobile operators providing mobile services for 3,313,871 million subscribers (by June, 2012) throughout the territory of Mongolia and are currently expanding their services. Nowadays, Mongolian more than 3 million mobile subscribers are benefiting from services offered in 3G environments and in Ulaanbaatar, 4G services started to offer, enabling communications through not only by voice, but also through video and other multimedia services. The fiber optic cable network has been extended to
over 13,000 km. The Information Communication Network Company is the owner of the national backbone and access network of Mongolia including international, long distance, rural and local transmission networks and local loops. In addition, private operators such as Mobicom, Gemnet, Skytel and Mongolian Railway are installed fiber optic networks in some locations.
There are about 70 ISPs, which share 30 Gbps bandwidth and provide services to more than 641,000 internet subscribers (by 2012), who are using xDSL, fiber optic, 3G and GPRS connections.
At the present stage of Mongolian ICT market for telecommunication services, there is a convergence process of different types of communication
services which are based on the different technologies. This way of development is completely coincides with world tendencies. Demand for convergent services constantly increases, generally, due to the role of a corporate segment in the ICT market. Also, in last years, the role of a private sector is intensively grows.
ICT sector is one of most dynamically developing sector in Mongolia. In Mongolia, IP technology develops on the basis of national Internet network. Therefore, research work for QoS support in VoIP network and network development methodology for the improvement of QoS is the most important and actual problem. In order to establish normal condition for network operations, it is neces-
195000 190000 185000 180000 175000
2008 2009 2010 2011 30.06.2012
Fig. 2 . The number of fixed line subscribers in Mongolia
FÜg.3 . The number of mobile service subscribers
r A
Branch office
Fig. 4. IP/MPLS network structure
Bulgan
Erdenet
Sukhbaatar
sary to provide high-quality services via modern telecommunication network, using the latest technologies.
PSTN (Public Switched Telephone Network) is the voice oriented telephone network. The reliability of the network is 99.999%. PSTN network is able to provide sufficient bandwidth for voice services. There are 183,074 fixed telephone users in Mongolia (by June, 2012). Since 2010, in Mongolia, the number of fixed line subscribers has been decreased year by year (Fig. 2), due to the introduction of mobile and IP services.
At the same time, in Mongolia, the number of IP service subscribers and the number of mobile service subscribers are grows quickly (Fig. 3).
In Mongolia, it is planned to construct the transport network (All-IP) on the basis of IP/MPLS technology (Fig. 4).
The IP/MPLS network structure in Mongolia is presented in Fig. 4. Apparently from Fig. 4, the network has the core (IP/MPLS Core) to which boundary IP/MPLS routers (Edge) are connected, in provinces.
Description of the network topology: In Mongolia, it is planned to construct! ring from 40 GE, 2 rings with 10 GE. Also there are linear connection between Zuunmod-Ulan-Bator, Ulan-Bator-Baruun-Urt, Ulan-Bator-Sainshand, Ulan-Bator-Sukhbaatar, Darkhan-Sukhbaatar, Baruun-Urt-Kherlen with the corresponding capacities (Fig. 5). Some project works has been started.
The transport network (All-IP) on the basis of IP/MPLS technology, which is under construction, will be allow to increase the general capacity, to increase the network reliability. Also QoS service parameters will be improved.
Kherlcn
(jlaangom
and
zadgad
40 GE 10 GE STM 16 GE
Main router
Edge router
Fig. 5 The topology of IP/MPLS network
2. The QoS parameters
Now, the operators of Mongolia are using and observing the following norms on quality parameters for IP network (Tab. 1).
These parameters don't reflect the feature of IP networks.
Now, the operators of Mongolia starting to take much attention on QoS for IP networks and plans to develop the comprehensive programs. Thus, we are recommending to use QoS parameters for IP networks, which are developed on the basis of international standards (Tab.2).
The international norms on QoS parameters for IP networks are presented in the Recommendation of ITU-T Y1541 [4].
On the following table (Ta6.3) it is illustrated QoS parameters for different classes of services.
In Mongolia it is planned to enter the classification of IP networks according to QoS.
3. Practical recommendations
for improvement of QoS parameters in VOIP network
When will be ready your VoIP system for operation and maintenance, need to provide related work in order to support reliable operation with high quality of services.
Operators of Mongolia should follow the control for all process in order to introduce VoIP technology - since introduction and finishing with VoIP network expansions. For improvement of QoS in VoIP network, it is recommended to implement following measures:
• Planning and optimization of VoIP network with use of simulation programs such as OPNET, NS2, NS3, NetCracer etc;
• Right choice of audiocodecs, elimination of all undesirable and unwanted effects from input audiosignals, reduction of noise, suppression of pauses in speeches, application of a method for reduction of delays, packet loss and echo compensation;
• Traffic prioritation, marking and packet rerouting;
VoIP traffic has to be receive higher priority in comparison with data packets.
There are the list of factors to which it is necessary to pay attention:
— the calculation and monitoring of network oad, network productivity before VoIP introduction;
— generation of VoIP synthetic traffic (forecasting of call quality);
— definition of service level;
• Ensuring VoIP network security;
• Installation work and training of ICT staff;
• Network monitoring;
The norms on quality parameters
Tab.1
Tab.2
Recommended QoS parameters for IP networks in Mongolia
Indicator characteristics Indicators Norm
Assessment of the level for reliability of services Quantity of malfunctions counting on unit of the terminal equipment of in a year <0.1
Coefficient of network availability on the average in a quarter, % 99
Average time between network refusals, h 500-200
Average time of network restoration, min 300- 3600
Assessment of speed for access to the network Time for implementation of the request for connections to the network, working days. <3
Coefficient of the request for connections of the network, executed standard terms >0.95
Time of restoration for access to the network, h < 10
Assessment of quality for repair and maintenance Coefficient of requests for elimination of the malfunctions, executed standard terms >0,95
IP packet delay, msec 100-400
Assessment of quality for data transmission IP delay variation (jitter), msec 50
IP packet loss (coefficient) 10 3 to-*
Coefficient for IP packet errors 10‘4
Probability for premature disconnections of data transmission in a packet networks 2xio_s
Time for call establishment: sec
Assessment of VoIP connection quality IP addressing <1.5-7
IP-E.I64 <2-10
E. 164-IP <4-20
QoS parameters for different classes of services
Tab.3
The communication quality needs to be controlled by network monitoring. When local networks are used, the network administrator can control and manage the quality of transmitted audio signals by controlling the network load level and packet losses. Besides factors which directly belong to the VoIP applications, the network analyzer has to be capable to register and control the network load and other parameters. It is recommended to use the network analyzer for research work and network control.
Management
During voice transmission process via VoIP network, there can be appear such problems as physical level problems on access network, the overloaded port, incorrectly configured class of services, delay emergence. The network management strategy and diagnostics of faults is necessary. Network administrators have to carry out diagnostics of prob-ems in order to eliminate access network's faults, the overloaded ports's problem and ensure QoS parameters. QoS management between networks (IP-TDM-IP) is one of important tasks:
• ensuring the IP quality on the basis of RSVP protocol, IPv6, MPLS;
• approach to control of established standards for IP quality;
• methodology, for creation of quality control system;
• the negotiations of SLA between operators/operators and users;
• development of related recommendations and state standards for QoS improvement in IP networks of Mongolia;
• development and implementation of comprehensive programs on QoS control for all operators;
Conclusions: ICT sector is one of most dynamically developing sector in Mongolia. At the present stage of Mongolian ICT market for telecommunication services, there is a convergence process of different types of communication services which are based on the different technologies. This way of development is completely coincides with world tendencies. The transport network (All-IP) on the basis of IP/MPLS technology, which is under construction, will be allow to increase the general capacity, to increase the reliability of network. Also QoS service parameters will be improved.
Quality parameters which are used and observed all operators of Mongolia, at present,
don't reflect the feature of IP networks. There is a need to follow and use the international norms on QoS parameters for IP networks. In Mongolia it is necessary to enter the classification of IP networks according to QoS. VoIP traffic has to be receive higher priority in comparison with data packets. The implementation of practical recommendations for improvement of QoS parameters in VOIP network, will allow to coordinate operation work of various operators.
Due to use of scientific achievements, the careful research work on IP network for the improvement of QoS, the implementation of comprehensive programs on IP network quality in Mongolia will be able to reach the planned level and by 2021, Internet service users will be able to use Internet speed up to 100 Mbit/sec in Ulan-Bator and up to 70 Mbit/sec in a major cities and in province centers, as it was mentioned in the official documents. As the speed of Internet services will grow, in parallel will improve QoS in VoIP network.
References
1. Olifer V.G., Olifer N.A Computer networks. 3rd Edition, Peter, 2006, Moscow, Russia.
2. V.U. Deart. Multiservice network, 2007, 166 p., Moscow, Russia.
3. Jose Ignacio Moreno Novella, Francisco Javier Gonzales Castano. QoS requirements for multimedia services, 2010, 188 p., Madrid, Spain.
4. Network performance objectives for IP-based services. ITU-T Recommendation Y. 1541. http://www.itu.int/rec/T-REC-Y. 1541-200602-I/cn. February, 2006.
5. Olihr VG, Olifer NA. New technologies and equipment IP-based networks. St. Petersburg, 2000.
6. Gurgenidze A. Multiservice networks and broadband services. Moscow, 2003. 400 p.
7. Norenkov I.T. Telecommunication technologies and networks. Moscow, 2000. 248 p.
8. ICTPA White book-2013. Moscow, ICT technology White Book, 2013. 39 p.
9. ICTPA. ICT development tendency of Mongolia-2021, ICT Technology White Paper, 2011. 55 p.
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