ATIS-0300018
Next Generation Interconnection Interoperability (NGIIF) Reference Document
Part III, Installation, Testing and Maintenance Responsibilities for SS7 Links and Trunks
Attachment G
Link Diversity Validation Guidelines
Version 12.0
2
[Above is the page number. They are always in 10 point, regular, centered, Arial. Style Sheet: Page number.]
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This document was developed by the Alliance for Telecommunications Industry Solutions’ (ATIS) sponsored Next Generation Interconnection Interoperability Forum (NGIIF). The NGIIF addresses next-generation network interconnection and interoperability issues associated with emerging technologies. Specifically, it develops operational procedures which involve the network aspects of architecture, disaster preparedness, installation, maintenance, management, reliability, routing, security, and testing between network operators. In addition, the NGIIF addresses issues which impact the interconnection of existing and next generation networks and facilitate the transition to emerging technologies. All changes to this document shall be made through the NGIIF issue resolution process.
Note Regarding Previous Versions
The NIIF Reference Document was formerly known as the Network Operations Forum (NOF) Reference Document. The NOF Reference Document was published and maintained by Bellcore. The last version of the NOF Reference Document is Issue 13.
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ATIS-0300018, NGIIF Reference Document, Part III, Installation and Maintenance Responsibilities for SS7 Links and Trunks, Attachment G, Link Diversity Validation Guidelines, Formerly NIIF 5013
NGIIF Reference Document, Part III, Installation and Maintenance Responsibilities for SS7 Links and Trunks, Attachment G, Link Diversity Validation Guidelines, is an ATIS standard developed by the NGIIF.
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LINK DIVERSITY VALIDATION GUIDELINES SIGNALING SYSTEM 7
Table of Contents
1 General 3
1.1 Purpose of Document 3
1.2 Definitions 3
2 Basic Premises 3
3 Operating Principles 3
4 Service Provider Responsibility 4
4.1 Installation 4
4.2 Auditing Process 4
5 Records (Database and/or Paper) 5
6 Physical Validation 5
7 Link Diversity Guidelines and Auditing Process 5
7.1 Distribution Frames and Mounting Blocks 5
7.2 Office Repeater Bays, DSX Bays, Patch Bays. 6
7.3 Digital Cross-connect System (DCS) 6
7.4 D4/D5 Bays (and associated channel bank equipment) 6
7.5 Fiber Optic Terminals and Multiplexers. 6
7.6 Power and Fusing 7
7.7 Clock/Timing Supplies/Synchronization 7
7.8 Access Equipment (Test, Billing, Monitoring) 7
7.9 Cable (inside) 7
7.10 Cable (entrance) 8
7.11 Interoffice Route 8
7.12 Cable (aerial/buried/underground) 8
7.13 Radio 8
8 Leased and Sub-leased Facilities 9
1 General
1.1 Purpose of Document
The purpose of this document is to provide guidance for the validation of diversity to providers of Signaling System 7 links to ensure the integrity of the Signaling System 7 network.
CAUTION:
Physical Validation should be considered as being able to cause link failures. Existing NGIIF Maintenance procedures (SS7 III) should be followed. When and if a company intends to perform physical validation of diversification by intrusive methods, the interconnected companies shall agree on the methodology, date, and time for the intrusive validation.
This document does not replace or supersede any existing contracts, tariffs or any other legally binding document.
1.2 Definitions
For the purpose of this document, the following definitions shall apply:
· Service Provider is any company providing telecommunications access services.
· Vendor/Manufacturers are any companies providing hardware/software to the telecommunications industry.
· Physical Validation shall be accomplished by an actual non-intrusive (i.e., not service affecting) check of the physical assignment compared to the documented assignment.
· Physical Diversification is the separation of all cables, cable runs, equipment bays, facilities and structures.
· Electrical Diversity is the separation of common power supplies, electronic equipment and fusing.
· Logical Diversification is defined as the condition where link facilities are physically diverse but not logically protected.
· Quad Links are CCS links that form the STP - to - STP interconnection.
· Link Pairs are combined link sets consisting of a link in each link set.
2 Basic Premises
Full SS7 Link diversity is essential to ensure the robustness of the entire telecommunications network. The lack of diversity on SS7 routes places the entire telecommunications network at risk.
Information included in this document is a result of Network Interconnection Interoperability Forum agreements and pertains to the validation of SS7 link diversification.
3 Operating Principles
Link diversification validation should be performed at a minimum of twice a year. At least one of those validations shall include a physical validation of equipment compared to the recorded documentation of diversity.
The validation of diversification is the responsibility of every network service provider that provides or utilizes SS7 links.
Diversification shall be in accordance with the Network Interconnection Interoperability Forum minimum recommended criteria for two-way and three-way diversity, as identified in the NGIIF Reference Document in Section III, SS7 Link and Trunk Document.
Limitations on diversification should be considered at the time of deployment; such limitations may consist of, geography, facilities, circuit design and tariffs.
4 Service Provider Responsibility
This section covers the responsibilities of the service provider in ensuring and maintaining link diversification.
4.1 Installation
When new links are being ordered it is the responsibility of the service provider to ensure that the assignment of links maintains all aspects of diversification for the purchasing customer.
Where it has been identified at the time of assignment that diversification cannot be maintained, the service provider shall ensure the maximum level of diversification possible at that point in time. The service provider shall inform the customer immediately and develop a path forward to reconcile the situation.
Documentation shall be generated to record the lack of diversification for future reference.
In the event that a database assigns and maintains diversification, the service provider shall have in place an alerting mechanism to inform them if an assignment violates diversification.
Where diversification cannot be implemented at the time of interconnection, the customer shall be informed and the service provider shall have a mechanism (automatic or manual) in place that will re-address the lack of diversification periodically.
The service provider shall provide diverse link assignments at the earliest time possible so that diversification can be achieved. Where a rearrangement is required, the company initiating the rearrangement shall follow existing NGIIF guidelines associated with the affected interconnecting companies.
Every effort must be made to avoid the use of a tandem or hub office link circuit design.
Leased facilities must be verified, as facilities of different carriers may have a common Point of Presence (POP).
Interconnected link records (including office assignment records) must include adequate detail for link diversity to be verified.
4.2 Auditing Process
Once a year, the service provider shall verify all supporting documentation of link assignments to ensure that diversification is maintained. In the event that diversification violations have been detected, which affect the provisioning of the circuit, the service provider shall:
· notify the customer of the violation and provide a commitment for reconciliation, and
· initiate corrective actions to eliminate the violation.
In order to validate that all supporting documentation is correct and consistent, the service provider shall compare all sources of documented link assignments to ensure diversification. Where a conflict between two or more sources is identified, such conflicts shall be reconciled.
It may be in the best interest of the service provider and the customer that when anomalies in records are identified, a physical check be performed to ascertain the correct assignment.
Six months after the documentation validation process has been completed, the service provider shall conduct an additional validation of diversification. At this point in time, a physical validation shall be performed.
A physical validation shall be performed by comparing the documented assignment with the physical assignment of one end of the link. The interconnected party shall be required to perform the same function at their end of the connection. (See caution note in Section 1)
5 Records (Database and/or Paper)
Link assignment records should include all aspects of diversification (Physical, Electrical, and Logical).
Where link assignment records are in a database, a back up of the database should be maintained.
Records must be verified for all aspects of diversity prior to physical verification. Where a compromise of diversification is identified in the supporting documentation, a physical check should be performed to ensure physical diversification is maintained and the associated documentation corrected.
Where rerouting has taken place for any reason, diversification should be verified and records should be updated within 24 hours internally as well as between interconnected companies.
6 Physical Validation
When a company intends to perform physical validation of diversification by intrusive methods, the interconnected companies shall agree on the methodology, date and time for the intrusive validation.
Physical validation can be performed by ensuring that the documentation for the links being audited is consistent with the physical assignment. The interconnected parties should confirm that the data is consistent.
Physical verification is a confirmation of records by an actual on-site physical check.
Physical validation includes the verification of identification of SS7 nodes and associated components as outlined in the NGIIF Reference Document, Section 11, SS7 Component Identification.
7 Link Diversity Guidelines and Auditing Process
This section covers network components that should be validated for diversification.
7.1 Distribution Frames and Mounting Blocks
7.1.1 Guideline
Termination of diverse CCS links should be on separate Main Distributing Frame (MDF) mounting blocks.
7.1.2 Process
· Verify that diverse CCS links are assigned to separate blocks on circuit records.
· Visually inspect MDF locations to ensure that CCS links are installed as indicated in the records.
7.2 Office Repeater Bays, DSX Bays, Patch Bays.
7.2.1 Guideline
Diverse CCS links should not traverse a single bay of these types. Each link should be routed through separate and distinct bays.
7.2.2 Process
· Verify in records that diverse CCS links are assigned to separate bays.
· Visually inspect bay locations to ensure that CCS links appear as indicated on the records.
7.3 Digital Cross-connect System (DCS)
7.3.1 Guideline
Diverse CCS links should not traverse a single DCS.
7.3.2 Process
· Verify that diverse CCS links are assigned to separate Digital Cross-connect Systems.
· Interrogate DCS databases to ensure that CCS links are assigned as indicated on records.
7.4 D4/D5 Bays (and associated channel bank equipment)
7.4.1 Guideline
The channel bank equipment associated with each diverse CCS link should be located in separate bays, separate line-ups if possible.
7.4.2 Process
· Verify in records that diverse CCS links are assigned to separate bays.
· Visually inspect bay locations to ensure that diverse CCS links appear as indicated on records
7.5 Fiber Optic Terminals and Multiplexers.
7.5.1 Guideline
Diverse CCS links should not transit the same fiber terminal or the same multiplex equipment.
7.5.2 Process
· Verify in records that CCS links are assigned to separate equipment.
· Visually inspect bay locations to ensure that CCS links appear as indicated on records.
7.6 Power and Fusing
7.6.1 Guideline
No components of diverse CCS transmission paths should share a common fuse within the same power distribution unit (PDU).
7.6.2 Process
· Verify in records that diverse CCS links are assigned to separate equipment bays. This will usually ensure service through separate fuses.
· Visually inspect bay locations to ensure that diverse CCS links appear on equipment that is served through separate fuses.
7.7 Clock/Timing Supplies/Synchronization
7.7.1 Guideline
Synchronization of diverse CCS Links should be in accordance with NGIIF established guidelines as outlined in Part III of the NGIIF Reference Document, Installation & Maintenance Responsibilities - SS7 Link and Trunk Installation and Maintenance Access Services, Section 3, Subsection E, Synchronization.
7.7.2 Process
· Visually inspect bay locations to ensure that diverse CCS links appear on equipment that is connected to a primary and secondary timing source.
7.8 Access Equipment (Test, Billing, Monitoring)
7.8.1 Guideline
Diverse CCS links from the same network element should not traverse a single access unit.