East Coast Datacom Nx8- Dual Composite MUX High-Speed 16-Port TDM..., Operation Manual

Page: 23 / 77

166119
8/31/2006 19
The High/Low attribute determines whether a channel can be bumped or not, to make room
for another channel. High priority channels cannot be bumped, even by another high priority
channel. Low priority channels may only be bumped by high priority channels.
The Seek Backup/No Backup attribute defines whether a channel will be switched to the
backup link subject to available bandwidth and priority.
2.3.1.2 Failover Port Clock Rate
The failover rate is a channel port clock rate which may be different, typically lower, than the
channel rate on the primary, or home link. The purpose of this option is to allow a greater
number of backed-up channels to be accommodated on a single surviving link where
available bandwidth becomes more critical.
2.3.1.3 Channel Restoral Timer
Each channel may be configured with a timer that determines how and when the channel is
restored to it‟s home link when that link returns to service. This helps alleviate a channel
hopping back and forth under intermittent composite link conditions and creating circuit
disruptions to the terminal device.
In addition to time settings for this option ranging from immediate to one hour, a manual
choice is available. For this option, the channel will not be restored until either 1) the user
modifies the timer to a finite delay, or 2) the composite link on which the channel is currently
backed-up fails, AND the home link on which the channel was originally assigned is in
service.
2.3.2 Expanded Bandwidth Configuration
One of the simplest configurations using the dual link support in the Nx64 Dual Mux is that of
expanding the aggregate link capacity of the multiplexer up to 4.096 Mbps. With two links
between units, each channel may be assigned to either Link A or Link B, until the total
bandwidth available on both composites is consumed.
LINK A (e.g. 128Kbps)
EXPANDED BANDWIDTH CONFIGURATION
LINK B (e.g. 128Kbps)
Total Bandwidth = 256Kbps
(less 2 x 1600b/s link overhead)
Channel
Port #s
Channel
Port #s
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Timeslot
Map A
Timeslot
Map B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Timeslot
Map A
Timeslot
Map B
Figure 8
In the figure above, channels are assigned as needed to either of the composite links. It is not
required that the two links be of equal rate since the need may simply be for more aggregate
channel bandwidth than is available on a single link. In this example, channels 1, 3, 7, 8, 9,
10, 12, and 15 are assigned to Link A and channels 2, 4, 5, 6, 11, 13, 14 and 16 are assigned
to Link B.