Researchers in Hong Kong are helping
to build the technology needed to take the Internet to the next
generation. Demands of the information highway are expected to increase
dramatically over the next few years, especially with users turning
more and more to multimedia communications.
networks may seem fast, says Prof Victor O K Li, Chair of Information
Engineering at The University of Hong Kong (HKU), but restrictions
are inherent in their optical-electronic infrastructure.
Li and other researchers in Hong Kong are backing the adoption of
all-optical networks to overcome todays Internet bottlenecks
caused when optical signals are converted to electrical signals
networks will require new devices and a new means of processing
where data is sent.
processing electronically is easy, its difficult in
the optical domain because optical processing technology is not
very mature, said Prof Li. To succeed, processing needs to
be as simple as possible.
takes place in routers where the header of an information
packet is read and the payload is directed
to its destination (see illustration
Li and his team devised a self-routing address scheme which dramatically
simplifies the packet processing. The
scheme, which is awaiting US patent approval, was motivated by an
established algorithm which allows self-routing in a network with
a regular structure. By regular structure, we mean something
like the road system in Manhattan US where streets are set out like
a grid, said Prof Li.
address for Tokyo encodes all paths from other cities to Tokyo.
Below: Prof Li and presentation of his scheme
a typical fibre optical network may not have a regular structure,
he added. The question is, how do you implement self-routing
when there is no fixed structure?
research team invented a novel algorithm that can be used with an
irregular or arbitrary topology. In the example of a Hong Kong-Tokyo
transmission (above), the address would read as 010-0010-010-000-001.
is simplified since routers in each city only need to read their
own portion of the address.
Hong Kong router would read 0010, directing the transmission on
Link 3 (the third bit is a 1) bound for Beijing. Upon
receipt, the Beijing router reads 010 and forwards the transmission
on Link 2 for Tokyo. When the Tokyo router reads 000 it realises
the transmission is at its destination.
conventional electronic switching, the header of information packets
carries only the end address, and not the specific path to the destination.
Todays electronic routers therefore need to use look-up tables
stored in memory to work out the best routes to take. A lot
of processing is needed at each intermediate node, said Prof
Prof Lis photonic switching scheme, paths are predetermined
so the packet header may specify any intermediate routers. Its
a much simpler process, said Prof Li.
important feature of the innovation, added Prof Li, is that the
same address can be used for packets originating anywhere around
the world and destined for the same place.
The length of the header (in bits) is equal to the number of links
in the whole network. In the example, there are 16 links in the network,
and the header has 16 bits. Since each packet typically has a payload
of tens of thousands of bits, the header is a very small percentage.
Victor O K Li