Circuit ID - International Circuit Designations For Correspondent IPLCs

International Circuit Designations For Correspondent IPLCs

These were known as CCITT, now ITU-T, designations. In the interests of international recognition, a protocol with recognisable town names has been used.

The format is: –

Towns and cities have abbreviations accepted by the 2 corresponding PTOs and the CCITT/ITU-T.

Examples are:

• AMS = Amsterdam

• BS = Bristol

• DSSD = Düsseldorf

• FFTM = Frankfurt-am-Main

• KOB = Copenhagen

• L = London

• MDD = Madrid

• PS = Paris

Original CCITT Leased Circuit Types were:

Analogue

P = Audio circuit (however transmitted over distance) presented as Audio for voice

FP = Audio circuit (however transmitted over distance) presented as Audio for Fax modem

DP = Audio circuit (however transmitted over distance) presented as Audio for Data modem

XP = Audio circuit (however transmitted over distance) presented as Audio and switched by customer for alternate use by Voice or Data modem

L – PS P4 was the fourth analogue line between Paris and London normally used for voice transmission at that time. DSSD-L XP2 was the fourth analogue line between Düsseldorf and London alternately used for voice and data at that time.

Digital

NP became the Type designator for most correspondent International digital links.

BS – MDD NP12 and KOB – PS NP34 would have been typical uses of the scheme for links between Bristol & Madrid and Copenhagen & Paris.

Notes

The choice of letters in designating major town and cities could be seen to reflect a short form of the name in the language of the country and also to disambiguate with similarly named locations. København being the Danish home version of Copenhagen attracted KOB as the abbreviation. FFTO was the designation for Frankfurt-an-der-Oder, where there was the clear need to disambiguate references from FFTM.

The serial or the numbered occurrence of a link between two PTOs between 2 cities was usually the next free number in the system, but the CCITT allowed for the re-use of old serial numbers after a period of 6 months. A customer ordering 3 links could be allocated DP23, DP24 and then DP6 between 2 major cities. (DP6 had been ceased over 6 months earlier).

It can be considered that the serial or last number of the type of correspondent link between two places made the link unique but did lead to problems, for example when a major PTO in one country was setting up links in correspondent relations with more than one PTO in another country.

The development was away from correspondent IPC links to a situation where one facilities provider could provide the link over the international part and sometimes as afar as the distant end customer. This was the result of liberalisation and competition in home and overseas markets. In some cases the facilities provider would carry the link to their PoP in the distant country and then rent a national or local tail from the PTO in that country. That would attract a designation particular to that area and not reflect its international connection significance.