International Service Point Code (ISPC) is a key component within the Signaling System No. 7 (SS7) network, used for the identification and routing of signaling messages across different telecommunications networks. The International Service Point Code (ISPC) is a fundamental element in the SS7 signaling network, crucial for the identification and routing of signaling messages on an international scale. Managed by the ITU-T, ISPCs ensure that signaling points across different countries can communicate effectively, enabling the global connectivity that modern telecommunications rely on.

What is an ISPC?

• ISPC (International Service Point Code): A unique identifier assigned to a signaling point within an SS7 network. It is used for routing signaling messages internationally.
• Purpose: The ISPC is essential for ensuring that signaling messages are delivered to the correct destination across international boundaries.

Structure of ISPC

ITU Point Codes (Checkout ISPC list)

• Bit Length: 14 bits.
• Format: Represented as three-part codes (e.g., 3-232-1).
• Components:
  • Zone (Z): 3 bits, representing a geographical region.
  • Network (N): 8 bits, identifying a specific network within the zone.
  • Signaling Point Identification (SPI): 3 bits, specifying a particular signaling point within the network.

ANSI Point Codes

• Bit Length: 24 bits.
• Format: Represented as a single 24-bit code (e.g., 5360).
• Components:
  • The ANSI standard does not divide the point code into zones, networks, and signaling point identification, but rather treats it as a single continuous 24-bit identifier.

Example

An ITU (14 bit) ISPC might be represented as follows: 2-158-0

• 2: Zone (Z): 3 bits, representing a geographical region.
• 158: Network (N): 8 bits, identifying a specific network within the zone
• 0: Signaling Point Identification (SPI): 3 bits, specifying a particular signaling point within the network.

An ANSI (24 bit) ISPC might be represented as follows: 0-20-240

The ANSI standard does not divide the point code into zones, networks, and signaling point identification, but rather treats it as a single continuous 24-bit identifier (e.g., 5360)

Allocation and Management

• ITU-T (International Telecommunication Union – Telecommunication Standardization Sector): The international body responsible for the allocation and management of ISPCs.
• Process: Telecommunications operators request ISPCs from their national regulatory authority, which in turn coordinates with the ITU-T or with ANSI (American National Standards Institute) for allocation.

Role in SS7 Network

1. Routing: ISPCs are used by SS7 signaling points (such as Signal Transfer Points, or STPs) to route signaling messages correctly across international networks.
2. Identification: Each ISPC uniquely identifies a signaling point, enabling accurate delivery of messages between operators in different countries.

SS7 Network Components

• Signal Transfer Points (STPs): Network elements that use ISPCs to route signaling messages.
• Service Switching Points (SSPs): End points that originate, terminate, or switch calls.
• Service Control Points (SCPs): Databases that provide services such as number translation, prepaid billing, and more.

Example Scenario

Consider a scenario where a call is made from a user in Country A to a user in Country B:

1. Call Setup:
   • The SSP in Country A sends a signaling message to set up the call.
   • The message includes the ISPC of the destination signaling point in Country B.
2. Message Routing:
   • The STP in Country A uses the ISPC to determine the next hop for the message.
   • The message is routed through various STPs, possibly across multiple countries.
3. Delivery:
   • The message reaches the STP in Country B.
   • The STP routes the message to the SSP in Country B, where the call is terminated.

Importance of ISPC

• Global Connectivity: ISPCs enable seamless communication across international boundaries, essential for global telephony and mobile services.
• Efficient Routing: By using standardized codes, SS7 networks can efficiently route messages to their correct destinations.
• Interoperability: ISPCs ensure that different networks and operators can interoperate, providing consistent and reliable services to users worldwide.