Like IP addresses in TCP/IP networks, point codes in SS7 networks identify individual network elments. Every element needs adress (a point code). Every link is considered point-to-point, but could be estabilshed from diffrent 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 convinence 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

• USA SS7 Point Code page
• UK SS7 Point Code page Ofcom are the public body that allocate Point Codes to telcos in the UK
• Germany SS7 Point Code page Bundesnetzagentur are the Federal Agency that allocate NSPC's to telcos in Germany
• ISPC Format Identification of international SS7 SP's(Signalling Points) is done using a Network Indicator NI=00 in the MTP(Message Transfer Part