Specifications

Design Consideration for a VoFR Network 9
This table also assumes that the trunks in the primary office can be shared so
that new calls originating from or terminating at a remote office can be routed by
any available trunk at the headquarters. If the trunks at the main office cannot be
"pooled", then each small branch will need trunks dedicated to them at a 1:1 ratio.
2.2 Public vs. Private Networks
When designing a frame relay network, one important issue is whether to use a
public frame relay service or to build the network yourself using your own
equipment. One advantage of using a public frame relay network provider is that
they usually offer distance-independent charges. With this type of plan, there is a
fixed charge per DLCI and a variable charge depending on the information rate
that you require.
Since you are charged for each DLCI, you want to minimize the number of DLCIs
that are used. This was one reason why FRF.3.1 was developed. FRF 3.1
describes multiprotocol encapsulation in a single frame relay circuit (DLCI). This
is also the reason for the subchannel definitions in FRF.11.
When using a public frame relay network, careful planning is required to optimize
costs and performance. These factors are closely correlated. If you choose to use
a lower speed line or lower Committed Information Rate (CIR), then you save
money but on the other hand you will have sacrificed performance.
If a network is privately owned, then a separate DLCI can be used for each voice
connection, provided that enough DLCI numbers are available. So in private
networks there is no need for multiprotocol encapsulation in a single circuit. You
can use one (or more) DLCIs for each protocol.
With a private network, even though you own the switches, you still have to pay
for bandwidth from the carrier so you still have to deal with the cost and
performance trade-offs.
2.3 Tested PBXs Information with IBM 2212 and IBM 9783
Table 3 provides information about some PBXs tested with IBM 2212 and IBM
9783, such as make, model number, country, interface type T1 or E1, E&M
signalling type used, E&M type I to type V, and 2-wire or 4-wire E&M.
Table 3. Tested PBXs with IBM 2212 and IBM 9783
PBX Name Model No Country Interface Signalling Type 4 Wire /
2Wire
NEC APEX1000 Japan T!1,TTC2M Wink V 4
NEC SOLUTE3
00
Japan E&M,FXS Wink V 4
Pansonic EXA ACE Japan E&M Wink V 4
Panasonic EXA 2 Japan E&M Wink V 4
HITACHI CX-256 Japan E&M Wink V 4
HITACHI CX-300 Japan E&M Wink V 4
HITACHI CX-2530 Japan E&M Wink V 4