SS No. 7 Signaling

Telesis Systems Offering SS7 Signaling

• Telesis Business Phone Systems:
  • PX24X Hybrid IP PBX Business Phone System
• Telesis Switching Systems:
  • X1 Large Capacity TDM - IP Telephony Switch
• Combined VoIP Gateway and Signaling Converters:
  • Stillink 200
  • Stillink 800
  • Stillink 3200

Standards

Telesis systems support ISUP ETSI EN 300 356 version 3  and ITU-T recommendations.

Applications

Telesis systems are integrated systems that include both a voice switch and an SS7 switch. A Telesis system may serve as two types of signaling points in an SS7 network:

• SSP (Service Switching Point)
• STP (Signal Transfer Point)

Telesis systems have E1 interfaces with SS7 signaling. Both SSP and STP functions are available.

As an SSP, the Telesis system responds to all calls bound for known signaling points by looking at its routing table to determine how to route each call and then sending a message to the destination using the ISUP (ISDN User Part) protocol.

A unique feature of the Telesis system is that multiple SPs (Signaling Points) may be defined in a single system. So, several OPCs (Originating Point Codes) may exist in the same system. This results in the combining of both SSP and STP functions in a single Telesis system.

As an STP, the Telesis system acts as a router or gateway in an SS7 network. ISUP messages are routed based on Global Title (dialed digits) or DPC (Destination Point Code) or Calling Party Information Element parameters.

With Telesis`s OPC translation feature, ISUP traffic flowing in a private SS7 network may be routed to the public SS7 network.

Layers and Options

The physical layer (MTP1, Message Transfer Part-1) of SS7 signaling in Telesis systems is an E1 (ITU-T G.703) interface. 120 ohm balanced terminations are supported on any E1. The line code is HDB3 or AMI programmable. Options for the data link layer (MTP2) include programmable basic error correction methods or PCR (Preventive Cyclic Retransmission). For the network layer (MTP3), SLTM (Signaling Link Test Message) periods are set as desired, and acknowledgment of test messages (SLTA) is automatic. OPC and DPC as well as CIC (Circuit Identification Code) prefixes can also be set easily. Several parameters in ISUP messages are programmable. Some of these are:

• Calling-party number
• Calling-party category
• Calling-party nature of address
• Calling-party numbering plan
• Calling-party presentation indicator
• Calling-party screening indicator
• Called-party number
• Called-party numbering plan
• Called-party NOA-Nature of Address (fixed)
• Called-party NOA-Nature of Address (automatic by analyzing the called party number)
• Subservice
• Hop counter initial value
• Satellite indicator
• Echo control device indicator

Physical Links

Telesis systems support both terrestrial and satellite links. For terrestrial links, a basic error detection/correction function is utilized. Due to the delay arising in satellite links, the PCR (Preventive Cyclic Retransmission) error correction
function is used.

Link and Linkset Configuration

The link is an existing E1 interface on the Telesis system. Any 64 kbps channel on an E1 (except channel 0) is programmable as the signaling path. Several links may be grouped into a linkset sharing a common signaling path. Each linkset has its own OPC and DPC. In the same Telesis system, there may be several linksets, each having an individual OPC. Furthermore, selected channels of every E1 link can be programmed as unavailable for outgoing traffic, thereby yielding fractional E1 connections.

Route and Routeset Configuration

In a Telesis system, each link and/or linkset may have its own route number. It is possible to define numerous distinct routes. A given route to a particular destination and its accompanying alternate routes are grouped in a routeset. Each route in a routeset has a priority order. Routing to the next priority alternate route is possible in the event that a route becomes unavailable. Furthermore, it is possible to define which release causes stated in ISUP messages will lead to the alternate routes being used.

Message Routing

ISUP message routing is based on dialed digits (Global Title). As an SSP, the Telesis system converts dialed digits from a subscriber`s line to SS7 signaling messages. As an STP, the Telesis switch may realize routing according to:

• Dialed digits
• DPC
• Calling-party number
• Category of calling party
• NOA of calling party
• Numbering plan of calling party
• Presentation status of calling party
• Screening status of calling party

Related Readings

We recommend you to visit Telesis WiKi Pages for technical readings.