Like IP addresses in TCP/IP networks, point codes in SS7 networks identify individual network elements. Every element needs address (a point code). Every link is considered point-to-point, but could be established from different elements of SS7 Network, so it could be named from A-Link (B-Link…, C-Link) to F-Link. In most cases, you either use A-Link or F-Link.
Identification of international SS7 SP’s(Signalling Points) is done using a Network Indicator NI=00 in the MTP(Message Transfer Part). Instead of our 24bit point code system, ISPCs (International Signalling Point Codes) are only 14bit.
ISPC Format:
_| N M L | K J I H G F E D | C B A || 3bits | 8bits | ||<----------------------------------->|<--------->|| Signalling Area Network Code (SANC) | SP ID* ||<----------------------------------->|<--------->|| International Signalling Point Code (ISPC) ||<----------------------------------------------->|
- SP ID= Signalling Point Identification
The first three most significant bits (NML) have a range of 0 to 7
The following eight bits (K-D) have a range of 000 to 255
The fields(bits) NML and K-D represent the SANC.
The three least significant bits (CBA) with a range of 0 to 7 identifies
an SP when combined with the SANC. This is an ISPC. (ex, 3-133-7)
An IP address is a four byte (each has 8 bits) integer (so 32 bit in total), noted for convenience like that:
3-133-7
or in decimal
7 + 133*8 + 3 * 4096 = 12288 (dec)
or hex:
3000 (hex)
in * you could use either the ISPC format ( so A-B-C) or decimal ( N ).
Telcordia Technologies is responsible for the administration and assignment of SS7 point codes in the United States and other North American Numbering Plan NANP countries.
See Also
- UK SS7 Point Code page Ofcom is the public body that allocates Point Codes to telcos in the UK
April 7, 2023
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