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The 1990s saw a hastened growth of the IP industry, resulting
in an all-round information war on the world scene. Interconnected
networks built on the router/SDH architecture along with booming
TCP/IP-based services began shaking the belief of classic telecom
carriers. Vendors got down to a new round of product upgrading.
It was also a honeymoon for investors: with flooding bucks, the
Internet bandwidth was shot up at an amazing rate.
Communications equipment manufacturers and PC vendors, in consideration
of their own development, chose to join hands in late 1990s to develop
router-based broadband transmission products and broadband interfaces
for message exchange equipment. Meanwhile, the application of WDM
inevitably steered manufacturers to the research and development
of high-end TDM products. In that scenario, NORTEL shut down its
legacy SPC production lines and turned itself into a next-generation
equipment provider. ALCATEL came up with its P3 STAR broadband exchange.
SIEMENS, LUCNET, CIENA, ZTE and HUAWEI also poured in handsome resources
to evolve the single-wave 2.5Gbit/s SDH equipment to a high-end,
large-capacity network exchange, with the processing capacity doubled
semi-annually.
On the front of long-distance transmission equipment, while the
20Gbit/s product is still unveiled on the market, 40Gbit/s and 320Gbit/s
products are already lab successes. At the same time, the equipment
tailored for LAN's broadband evolution is now in commercial operation.
In that respect, the technical team of Beijing Telecom has been
keeping a close eye on the latest development of the industry. Referred
to as "Multi-port Broadband Manager", the aforesaid equipment
constitutes the bedrock for Beijing Telecom's planned broadband
transmission network, which is designed to be comprehensive and
of large capacity, high flexibility, scalability, viability and
maintainability. The hierarchical structure of the network is shown
in Figure 1.
Figure 1 The Hierarchical Structure of Beijing Telecom's Broadband
Transmission Network
The dotted line in Figure 1 represents the "Multi-port Broadband
Manager", which serves to integrate the TM, ATM equipment and
4/4, 4/4/1 cross-connectors in SDH into one module. The above elements
are linked to each other via fibers (or optical wavelengths) to
form a high-end LAN product, with 155Mbit/s as its minimum unit
(here jointly called a granule). Each "Multi-port Broadband
Manager" can exhibit a processing capacity of 320Gbit/s, 3.2Tbit/s
or even 7.7Tbit/s and a rich cross-connect capacity of 155Mbit/s.
In the mean time, large-size routers and ATM switches may be put
at the core node to build up an IP/ATM MAN. For the low-end part,
10Gbit/s and 2.5Gbit/s rings may be employed to establish campus
networks, endowing the whole network with a double value to achieve
both self- and commercial use. Such a MAN will create the most crucial
condition for all services on local and long-distance networks to
go broadband. In that sense, incumbent telecom carriers should do
a series of planning and hands-on work to change their mindset of
the network per se and its evolution path. Specifically, the work
can be visualized as follows:
1. Mindset change of the network per se
For a long time, incumbent carriers tended to regard SPC exchange,
DDN, FR, ATM and IP equipment as leading network elements. Most
often than not, the transmission equipment is only seen as supportive
parts for those leading elements.
One inference from the above description is that the building
block of the basic local network is the "Multi-port Broadband
Manager". As a result of competition among carriers, such a
network not only provides connection between independent service
nodes, but also becomes a commodity in its own right, say, when
providing leased broadband to other companies. Therefore, as the
whole network evolves to broadband, the basic network will play
a dominant role, while telephone exchanges, DDN, FR, ATM and IP
equipment in this sense only function as service nodes. A network
as such serves to build relationship between nodes and also gives
rise to new services.
2. The evolution path features modernization and standardization
of current services.
As time passes, the legacy telephone exchange needs to be upgraded.
Newly added exchanges should adopt the 155Mbit/s trunking interface.
Given that the basic network granule is 155Mbit/s, the connection
between exchanges may pass through DXC 4/1 or 4/4/1 for circuit
allocation. In this way, the telephone exchange will leave a very
small footprint, and the 2Mbit/s DDF may be removed, thus substantially
bringing down the total investment. With less power supply, no manual
hopping is necessary, and network protection mechanism may be pre-configured.
This serves to guarantee a strong flexibility and integrity for
the network management work.
For the time being, The standard 155Mbit/s interface is widely
deployed in equipment like FR, DDN, router and ATM. With STM-1 being
adopted for accessing VIP customers, private networks have also
become a key access means. Therefore, a wise technological choice
is very crucial when new equipment is introduced to access the network.
In order to give play to the benefits of the backbone network, the
choice of STM-1 as its basic granule should be a prerequisite. In
the network build-up stage, the equipment for carrying services
and the access equipment must adapt to the need of broadband evolution.
Or else, it would be more than an investment nightmare, since when
you came to your senses at one point and tried to revamp the network,
the evolution path would be dragged even longer.
All in all, the reality is that the access and backbone layers
of the next-generation network are both going broadband. In Beijing,
a local IP network based on TCP/IP is already put into operation.
Although the TDM-based "Multi-port Broadband Manager"
is lacking in a unified standard, its field-proven unparalleled
QoS is unarguable, so it won't be far for all telecom carriers to
connect to this particular network product.
The IP network will never replace the TDM network. This is decided
by their respective physical characteristics. On the driveway to
broadband, the two networks should fly their own colors on an equal
footing to construct a splendid network landscape in the future.
Author Biography: Mr. Wang Fule is now Chief Technical Officer
of Beijing Telecom Corp. His past duties include Deputy Officer
of Beijing Local Telephone Office and Chief Director of the Network
Division of Beijing Telecom Corp.
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