SS7 Link Errors

The sections below describe the common cause that prevent an SS7 Signaling Link from coming into service or alignment.

Signaling Link Code Mismatch

The Signaling Link Code (SLC) is a number (0-15) which is assigned by both SS7 endpoints to identify a specific link within a link set. The value given to the SLC on the local end must match the SLC value assigned to the link on the remote or distant end. The SLC is configured in the SS7 - Link Set - Link object.

Network Indicator Mismatch

The Network Indicator (NI) value is defined by two bits (therefore values 0-3 are possible). The default value of the Network Indicator is set to National (0x02) for both ANSI and ITU. Some networks may require the Network Indicator to be set to International (0x00) or one of the spare values (0x01 or 0x03). To change the Network Indicator value, refer to the SS7 - Stack topic.

Example

Below is an SS7 trace displaying a Network Indicator mismatch (Network Indicator value is highlighted in yellow). The local stack is configured to a value of 2. The remote stack is set to 3.

Network Indicator codes

Link Status Signaling Unit (LSSU) Size Mismatch

The IMG 2020 transmits a Link Status Signaling Unit (LSSU) with a 1-octet status field for both ITU and ANSI. Some signaling points may require a different LSSU size. If a different LSSU size is required, this can be accomplished by one of two ways displayed below.

• Send a raw API message to change the setting. In order to accomplish this, a file needs to be created with the correct API hex digits. Contact Dialogic Technical Support Personnel and they can assist in creating the file. For information on sending an API message to the IMG 2020, refer to the RAW API Message and Sending RAW API topics.

• Modifying the LSSU size can be accomplished by creating a new custom SS7 variant. For information on how to create a new SS7 Variant or importing/exporting variants refer to the Signaling Variants or Importing / Exporting Variants topics.

Path and Rate Issues

The DS-1 carrying the signaling link must be configured for SS7 clear channel operation, be in service, and not experiencing any slips. Both parties must agree upon the timeslots utilized to carry the signaling link. Additionally, the data rate of the signaling link must be the same on both the local and remote endpoints.  Refer to the SS7 - Link Set - Link topic for more information. 

No Route Defined

A valid SS7 route must be defined to the destination to enable the IMG 2020 to send messaging. This is typically indicated by receiving the Signaling Link Testing Message (SLTM) with no SLTM message being sent by the IMG 2020.