Prognosemetoder – en oversikt - Telenor

It should be added that this scenario is assumed to be valid for
business users. For residential users the situation is more
unclear. There is, however, an ongoing development for ATM
over PON. Whether such a solution will be allowed to carry TV
channels and whether it will prove to be cost effective compared
to coax cables remains to be seen.
5.2 Scenarios with MAN
Possible early users of MAN will be universities, high-technology
companies, petrochemical companies, etc. For these
branches there is often use of common resources like super
computers and distribution of new video based services from
the universities.
Step 1
There are islands of communications using MANs. As the number
of these centres in Europe increases they want to interconnect.
The first step would be to interconnect the connectionless
networks using routers. The use of SDH based cross connect
would belong to this phase. These leased line services can also
be connected by SDH based cross connects. The situation is
basically described in figure 4.
Step 2
The next step would be to interconnect the MANs with ATM.
At this stage the transport mechanism in ATM is based on permanent
connections, i.e. virtual path VP. The use of VP does
not necessitate add-on functions in ATM to interconnect the
MANs. All the MANs have a logical connection between themselves
in a meshed topology.
Step 3
At this stage a connectionless (CBDS) server is introduced in
the ATM network. The CBDS server in ATM has some of the
same functions as the switching system in MAN; i.e., on the
basis of an E.164 address it can route the connectionless packet
through the ATM network to the user.
MAN also supports a connection oriented service. This is only a
leased transmission line service within a limited distance. MAN
can also be used as an access network to ATM. The bus is then
used as a concentrator of traffic from different subscribers that
only have small traffic interest between them. This may be an
early cost effective way to connect subscribers to a network in
high density areas.
Step 4
The next stage would be a B-ISDN network based on ATM
enhanced with CBDS. Although DQDB and ATM have the
same cell structure the network structures and functions are
quite different. When the users move to ATM based network
with full switching capabilities, the MAN networks will be a
bottleneck. It is therefore hard to see how a MAN in a flexible
way can evolve into a general access network of B-ISDN. However,
if CBDS is the only service requested, the MAN can serve
as the access network.
6 Conclusions
There is in this report indicated two possible scenarios for introduction
of a public broadband network. The first scenario, starting
with routers and frame relay and evolving towards an ATM
network, is believed to be a cost effective strategy for small to
medium populated countries. The second scenario, use of MAN
technology, might be a cost effective and convenient choice for
countries with clusters of universities, large companies, institutions,
etc. that have the need for switched broadband services
between each other.
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Figure 11 Step 4: Broadband network for business users
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Figure 12 MAN interconnect via ATM based on virtual path
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Figure 13 Broadband networks evolving from MANs
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