2.1.2. Signal Interface Unit (SIU)

An Intel-based black-box SS7 signaling server. Two models are available, the DSC131 and DSC231. The capacity of each SIU type is shown in Table 2.

Table 2. Capacity of SIUs 

	DSC131	DSC231
Signalling cards	2	12
Links	6	32
Linksets	6	8
Call Rate	100/sec.*	100/sec.*
* Call rates can depend on issues in the network such as the way in which signaling is presented. The values should not be considered absolute.

SS7 signaling is extracted from the E-1 or T-1 trunks into the system and the voice circuits can be passed transparently to the outgoing E-1 or T-1 ports. Alternatively, signaling can be connected using V.35 serial links. Signaling information is automatically distributed by the SIU, via TCP/IP, to the host that controls the telephony circuits. Typically this is the system where the voice trunks are terminated on Intel® Dialogic interface boards.

Two SIUs can be configured to share the same point code, providing fully resilient operation within a single point code. In normal operation, signaling can be load-shared across the two SIUs. Then, if one unit fails, the remaining unit handles all signaling. Multiple hosts can be connected to a single SIU, or to a resilient SIU pair, allowing large systems to be built.

Figure 6, Figure 7 and Figure 8 show some configurations using the SIU in conjunction with Intel® Dialogic boards. Table 3 summarizes the features and benefits of each configuration.

Table 3. SIU Configurations - Features and Benefits 

Configuration	Features	Benefits
SIU Configuration 1	V.35 SS7 connection to SIU (DCS131 or DCS231) Additional T-1/E-1 B channels are connected to voice resources on media servers SS7 signaling terminated on an SIU SIU distributes SS7 information to media servers over TCP/IP	Manage greater number of channels than a single card Reduced maintenance cost due to smaller overhead relative to management of more circuits
SIU Configuration 2	SS7 E-1/T-1 connected to SIU (DSC131 or DSC231) SS7 signaling terminated on SIU Voice channels routed through SIU via "drop and insert" E-1/T-1 SIU distributes SS7 information to media servers over TCP/IP	Additional T-1/E-1 B channels available for voice resources on media servers
SIU Configuration 3	SS7 link interconnects SIUs to provide a reliable management channel Dual SS7 links to separate SIUs SS7 distributed through a single or separate TCP/IP connection	Provides dual point code management Redundant SS7 links for back-up of signaling connections

Figure 6. SIU Configuration 1

The key features in this configuration are:

• V.35 SS7 connection to SIU (DCS131 or DCS231)
• T-1/E-1 voice channels are connected to voice resources on media servers
• SS7 signaling terminated on an SIU
• SIU distributes SS7 information to media servers over TCP/IP

Figure 7. SIU Configuration 2

The key features in this configuration are:

• SS7 connected with E-1/T-1 bearer channels to SIU (DSC131 or DSC231)
• E-1/T-1 voice channels connected to voice resources on media servers
• SS7 signaling terminated on SIU
• B channels routed through SIU via "drop and insert" E-1/T-1
• SIU distributes SS7 information to media servers over TCP/IP

Figure 8. SIU Configuration 3

The key features in this configuration are:

• SS7 link interconnects SIUs to provide a reliability management channel (for single point code management)
• Dual SS7 links to separate SIUs (for dual point-code management)
• SS7 distributed through a single or separate TCP/IP connection

Note: To arrange for this set up, you are using two T-1 or E-1 lines out of the SIU boards. This means that you are using one of the available slots of the SIU to pass the voice channels and signaling back out from one SIU to the other. Therefore, depending on the amount of bandwidth being administrated, you might need additional daughter boards.

See the documentation accompanying the DSC131 or DSC231 product for more detailed information.

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