Intel SIU520 SS7 manual Circuit-switched API Operation, Overview of SIU Operation

Application Note Building Fault-tolerant SS7 Systems Using the Intel® NetStructure™ SIU520 SS7 Signaling Gateway

Application	Application	Application
#0	#1	#N

Ethernet

API Layer/Ethernet Driver

	MAP or INAP or IS41
		ISUP	TUP
Configuration	TCAP
and
Management
	SCCP

MTP Levels 1-3

SIU 520

Figure 1. Structure of the Intel® NetStructure™ SIU520 SS7 Signaling Gateway

Overview of SIU Operation

The Intel NetStructure SIU520 SS7 signaling gateway is an SS7 network access product that provides a resilient interface to SS7 networks via a TCP/IP local area net- work (LAN). As shown in Figure 1, SIU520 software includes SS7 protocol layers, as well as a configuration and management module. The SIU520 supports multiple SS7 signaling links within the same pulse code modula- tion (PCM) trunk interface or over multiple PCM trunks. The SIU examines the timeslots carrying the SS7 informa- tion and processes them accordingly, outputting this data to the LAN using TCP/IP. Similarly, it takes commands from the TCP/IP LAN and converts those to SS7 signals for transmission to the SS7 network. In the receive direc- tion, information is conveyed to the user application in structured messages placed in a sequential queue.

For both circuit- and transaction-related operations, the SIU520 provides the ability to automatically distribute signaling information between a number of physically independent application platforms, thus providing a degree of fault tolerance within the application space.

The SS7 signaling may be presented from the network multiplexed in a timeslot on an E-1 (2.048 MB/s) or T-1 (1.544 MB/s, also known as DS1) bearer or by a V.35 (56/64 kb/s) synchronous serial interface.

For telephony operation (using a telephony layer 4 protocol such as ISUP or TUP), if the SS7 signaling is multiplexed onto a PCM bearer, the voice circuits may be passed transparently through the SIU to the application platform that terminates the physical circuits (see Figure 2).

Circuit-switched API Operation

The message-based application programming interface (API) operates transparently over TCP/IP Ethernet, using software modules provided by Intel. For circuit-switched (telephony) applications, each application platform termi- nates and hence controls a fixed range of physical cir- cuits, or circuit identification codes (CICs). CICs are con- figured in groups of up to 32, each group normally equating to all the circuits in a single E-1 or T-1 trunk. Each group is terminated on a fixed application platform or host processor, enabling the SIU to automatically direct API messages to the correct platform.

2