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C H A P T E R
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I N T R O D U C I N G
T H E
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1.2.11 Call routing
The V100 architecture supports point-to-multipoint topologies with programmable circuit routing.
Ultimately, system topologies may be designed ranging from simple point-to-point applications for mixed
voice/data services to full-mesh point-to-multipoint networks with dynamic call routing and redundant
trunk routes.
In order to assign the most efficient route for packets to reach the destination, hubs require knowledge of
the available aggregate routes to adjacent nodes in the network, together with the current bandwidth
loading on each trunk port. A Routing page tells the V100 which aggregate to use to reach the destination
port.
Each tributary channel in the network is assigned a numeric code according to its chassis, slot and channel
number, with destinations being specified for each tributary in terms of the code of the destination port. In
the case of telephony channels, either DTMF or E&M signalling digits are decoded and may be used to
directly call the destination or look up the route in a Directory to establish the destination channel. The
Directory translates real extension numbers into V100-style codes.
Calls are dynamically switched through the V100 network using the pre-programmed dialling codes.
Intelligent re-routing techniques are used to avoid congestion or link failure by selecting alternative paths.
If sufficient bandwidth cannot be found via any route, call progress tones keep the subscriber informed.
1.2.12 Dynamic Bandwidth Allocation (DBA)
The V100 may be programmed to allocate bandwidth dynamically between resources. Voice services are
granted dedicated bandwidth for the duration of the call or transmission, with remaining bandwidth
optionally transferred to the data ports. When the call ends, the bandwidth associated with it is returned
to a pool of dynamic bandwidth. All synchronous data channels configured with "DBA" clock source are
assigned to this pool, which is distributed between them in proportion to their bit rate. The V100 smoothly
adjusts the clock speeds on all DBA ports whenever a change occurs in the DBA pool.
Asynchronous data ports (including the remote management function) automatically use the DBA pool. In
the same way, channels are granted bandwidth from the pool in proportion to their bit rate but when they
become inactive and data stops flowing, the internal connection downspeeds to a nominal 2400bps and
the rest of the bandwidth is returned to the pool. The DBA pool has a lower priority than the voice or fixed
synchronous data channels and will only contain any bandwidth if these types of channel are limited by
careful configuration.
The DBA function may be invoked independently for transmit and receive, with the V100 routing engine
constantly assessing the optimum conditions even across complex networks. In this way, data networks
can make efficient use of bandwidth at all times, consistent with maximum Quality of Service (QoS) for
voice calls.
V100 Versatile Multiplexer Technical Manual Version 2.2
Page 13 of 231
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