|
Abstracts:
This article discusses major research subjects about the next generation
network (NGN) and the evolution of the NGN as well people's expectation
of SoftSwitch, an important basis of the NGN and issues in developing
SoftSwitch-based networks.
Keywords: Next Generation Network; SoftSwitch
1. Research on the Next Generation Network (NGN)
The IETF's research on the next generation network focuses on the
convergence of the IP network and the optical network. The NGN is
characterized by high bandwidth, high capacity and sufficient address
resources. The current R&D on the optical and IP networks is
carried out in those directions. China's 863 High-tech Communications
Project will deal with optical transfer systems and routers of the
tera bit order. Research on addresses in the NGN will deal with
the implementation of IPv6, E-NUM and interworking of existing network
numberings.
Currently, the ITU-T defines the NGN as the extension of the GII
(Global Information Infrastructure) and proposes the following as
subjects for study in regard to GII/NGN:
1) Switching between the first and second layers. The first layer
refers to optical switching introduced by the optical network infra-structure
and the second layer refers to switching introducing MPLS;
2) IP routing;
3) Provision of the service platform at the network edge;
4) Core network technology and the associated protocol architecture;
5) Transformation of inter-layer control capability. Generally
speaking, the difference between control and management can be measured.
The difference between cross-connection and switching is measured
by circuit granularity. Likely, the difference between protection
conversion of the bottom layer and dynamic routing of the IP layer
can be measured. Therefore, it is necessary to study the change
of inter-layer capabilities;
6) End-to-end service of the network. This involves convergence
between QoS and bandwidth control, convergence between control and
management, dynamic routing, protection conversion, etc.;
7) Access networks. This involves the capability required for transferring
packet data and voice over the access networks in the case of new
services, technologies or structures, and the capability of the
access networks to support services with different QoSs.
In addition, intelligent location and interworking with the traditional
networks are also key subjects for study in regard to the NGN.
The NGN involves new technologies for different layers of a telecommunications
network. ITU-T experts consider it as the embodiment of the GII
and will define it comprehensively from year-end 2002. SoftSwitch
is a technology at the control layer of the NGN. With associated
SoftSwitch-based technologies being in its infancy, the equipment
used will be relatively expensive and its networking capability,
capability of managing and operate the network and profitability
are yet to be verified. Besides, the related standards are being
developed. Since SoftSwitch is characterized by multiple protocols,
it is important for operators to ensure compatibility between various
equipment
2. Evolution of the Networks
With the traditional switches based on circuit switching, voice
signals are transmitted at the rate 64 kbit/s over networks. At
the interface of the switch, streams of 64 kbit/s signals enter
high-speed digital devices after being time division multiplexed.
Call routing and intelligent control are closely linked with the
circuit switched network.
The most complex part of the circuit switch is the software that
performs call processing. It routes calls and performs hundreds
of processing functions. At present, the processor running the software
in the circuit switch is highly integrated with circuit-switching
based equipment.
Unlike circuit switching, the key concept of SoftSwitch is the
separation between service/control and transfer/access, and connection
and communication between different entities are enabled through
standard protocols so that services can be provided more flexibly
over the network. To be more specific, SoftSwitch is an SW-based
distributed switch/control platform, which separates call control
from the gateway and uses protocols between service, control, access
and switching so as to implement a multi-vendor network operation
environment and introduce easily multiple services in the network.
However, the use of new technology takes considerable time. Networks
built in the last century will not be replaced overnight and the
SoftSwitch-based NGN will be tested by practice and the market.
Besides, professionals anticipate the convergence of the wireline
network with the mobile network, and the switch platform with the
service platform.
The NGN is expected to bring operators new applications and additional
value-added revenue at a low cost, and make people's life more colorful.
This service-oriented technology has promoted the development of
the Internet and e-commerce, facilitated the convergence of voice
service with Internet technologies, thus enabling operators to deploy
new services. The NGN, which integrates voice, data, fax and video,
requires a new solution and SoftSwitch is one of such solutions.
Currently, Chinese operators take a more practical view of the
NGN, increasingly concerning themselves about the application of
SoftSwitch-based equipment abroad, its service support capability,
service quality and capability of maintenance and management. Now
China Telecom is testing SoftSwitch-based network equipment in four
cities with a view to verifying the usability of the technology
and the maturity of the equipment and developing a rational business
model on the basis of an analysis of economic feasibility. At present,
large traffic of long-distance calls is being replaced by IP telephony
in the wireline network and that of local calls by mobile phone
calls. Therefore, wireline operators are eagerly seeking a way to
increase service revenue, reduce cost and expand their market. That
is why this test of China Telecom's is so strategically significant.
SoftSwitch-based network technology is designed to provide comprehensive
support capability to operate voice, multimedia and mobile services.
To protect their investment in networks, telecom operators expect
technology will evolve. However, especially in China, the PSTN has
great potentialities and there is still room for the existing circuit-switched
technology to develop. Thus, the adoption of new technology will
depend on its maturity, the return of investment (ROI) and market
needs.
3. Advantages of SoftSwitch in Expectancy
1) Increased revenue
New services bring operators additional revenue and profits. Operators
expect SoftSwitch to provide many new services, so as to meet customers'
needs flexibly and quickly. New value-added services and various
functions enabled by SoftSwitch technology will provide the customers
with differentiated services.
2) Adaptation to Market Needs
The open network architecture and the independent service platform
can adapt to the changing market, speed up the establishment of
the service system and facilitate the deployment and upgrade of
services.
3) Retention of Customers
The new management and control mechanism can attract customers and
enhance the stability of the user base.
4) Reduction of Network Construction Cost
The investment in the telecommunications grade SoftSwitch system
is lower than that in the existing circuit-switched system. Besides,
the convergence of the wireline and mobile networks will lead to
the reduction of network construction cost.
5) More Effective Use of Network Resources
The existing telephone systems occupy a fixed channel during calls
while TDM technology allows several calls to be carried simultaneously
on a trunk line. Packet-based SoftSwitch can substantially improve
the utilization of bandwidth.
6) More Efficient Network Management
The SoftSwitch-based network allows operators to manage their networks
more efficiently. Its remote access function enables centralized
upgrade and configuration.
7) Lowered Operation and Maintenance Cost
The SoftSwitch-based network is advantageous over the traditional
network in terms of operation and maintenance cost.
8) High Reliability and Expandability
The SoftSwitch-based network has high reliability and can expand
and organize networks flexibly according to demands for services.
9) Quality Service
The SoftSwitch-based network can provide quality service for customers.
4. Challenges Faced by the SoftSwitch-based Network
Although at present quite a number of manufacturers are launching
SoftSwitch-based solutions and operators are actively carrying out
trials in this regard, it will take some time for new technologies
to improve themselves in the course of application. While emerging
operators are exploring the feasibility of providing voice service
over the packet bearer network, conventional operators are considering
the possibility of providing new services over the new architecture.
From the solutions provided by some manufacturers, we propose the
following as the major subjects for study.
1) Networking
In contrast with the traditional telecommunications networks, we
are inexperienced in the organization of the SoftSwitch-based network.
The answer to the following question is still under exploration:
whether to adopt the single-level network structure or the multi-level
structure. If the former structure is adopted, it only applies to
medium-sized networks even if several SoftSwitch solutions are used.
Being a plane network, its expandability can hardly meet the need
of large operators whose networks covers the whole country. Thus
some manufacturers propose that SoftSwitch should be divided into
two levels: the end exchange and the tandem exchange. Besides, people
have not cumulated enough experience concerning the operation and
maintenance of the SoftSwitch-based network. And issues related
to IP addresses, number resources, network safety and interconnection
and interworking between networks need to be solved.
2) Compatibility and Standardization
SoftSwitches of different manufacturers lack compatibility in terms
of technical standards and protocols, which are the key to the convergence
of networks. The BICC protocol, the SIP-T protocol and the H.248
protocol are under development. Now manufacturers and service providers
are actively participating in the development of standards with
the hope that advanced services and voice applications will be introduced
into data networks and smoothly converged with traditional networks.
Currently, standardization chiefly involves interoperability, media
control protocols (e.g., MGCP, H.248), communications between SoftSwitches
(e.g., SIP), protocols for expanding the service platform and API,
connection and safety standards of international telephony, and
the transfer of advanced services via SoftSwitch. The related standards
are, among others, H.323, MGCP, SIP, etc. However, the related SoftSwitch
standards remain to be perfected, unified and widely accepted. The
first and foremost challenge that SoftSwitch faces is multi-protocol,
since it supports quite a number of protocols, which are developed
by different standardization organizations. This causes some problems
for technical study, manufacturing and operation.
3) Application Program Interface (API)
An open service platform and standard APIs offer very promising
prospects for network operators to provide new services. However,
since standardization for open interfaces has not finished, third-party
service is for the time being limited to equipment by the same manufacturers.
Service provided by multi-vendor equipment is under exploration.
4) New Services
Although SoftSwitch theoretically facilitates the deployment and
provision of new services, yet we hardly see attractive business
prospects. At present, most SoftSwitch trials focus on the provision
of basic voice service, conferencing (including videoconferencing)
and on-line browse. The operation process of services is relatively
complex except for voice service. It will take time to put application
platforms into commercial use.
5) QoS and Safety of Networks
Feasible solutions need to be developed to use network resources
rationally and effectively and to address QoS and safety of networks
when the IP network is used to carry voice service.
6) Business Models
Currently, operators are very keen about the business opportunities
and profitability that SoftSwitch can offer. Therefore, it is of
great significance to strengthen the study of the business models
of SoftSwitch applications.
5. Conclusion
At the beginning of application, any new technology is not perfect
in every way; it needs to be improved through trials. We believe
that the trend is towards open network architectures and flexible
service platforms.
|
