7-3 MINI-LINK BAS
EN/LZB 111 0542 P2B Technical Description
7.2 Virtual Connections
ATM transport is accomplished by setting up virtual connections
along the system. The equipment supports point-to-point permanent
VCCs.
VCCs can be established between:
• A user port and a service port;
• A user port and a service-user port;
• Two user ports;
• A service-user port and a service port.
Service ports and service-user ports are ports toward a SN or a single
Service Node, such as a one-armed router. They are located on any
type of shelf, regardless of whether it is a
R-AAS or a C-AAS (CE Shelf), but they are never to be located on
ATs.
User ports are ports toward the customer premises network and are
always located on ATs.
The difference between service ports and service-user ports consists in
the fact that the latter can have connections towards a service port,
while connections between two service ports are not allowed. Thus,
for example, the port used to connect the system with a one-armed
router must be qualified as service-user port if connections must be
possible both between the router and the users and between the router
and a service network (connected via a service port). Otherwise, if
only connections between the router and the users are necessary, the
corresponding port can be indifferently qualified as a service port or
as a service-user port.
As another example, the E1/T1 ports of a C-AAS (CE Shelf) must be
qualified as service-user ports as to enable the possibility to establish
connections between them and the service port, ET, used to connect
the same C-AAS (CE Shelf) with the ATM network/switch.
The setting up of a VCC is a straightforward. The operator is merely
required to specify the two ports which are intended to be connected.
The system automatically establishes all the VC links necessary to
obtain the connection.
VCC between two user ports can be set up without consuming
resources in the ATM network or switch. This is enabled by the fact
that the R-AAS has full VC cross-connection capabilities. This same
characteristic is shared also by the C-AAS (CE Shelf).
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