Many Communications Providers in the UK will grow to a point where it makes sense from them to acquire their own number ranges from Ofcom and to build their own network from which to provide their products. One decision which they need to make is how to arrange for calls to their numbers to be delivered to their network. If the CP chooses to use BT to route calls to them, as many do, then they need to decide between two interconnect products which BT offer. This article discusses the benefits and drawbacks of each one.

Interconnect under the Standard Interconnect Agreement (the SIA)

The SIA was originally put in place as part of the initial deregulation of telecoms in the UK in the 1990s, and reflects the priorities of and the technology in common use at that time. The SIA, to a large extent, establishes a long-term, "peer-peer" relationship between BT and the CP entering into the agreement. As examples, the SIA may not be modified without the consent of both parties, and termination of the agreement requires 24 months' notice with an obligation to negotiate a new agreement if one party so desires. Disputes are to be resolved by the parties, and referred to Ofcom for resolution in the event that the parties cannot agree. There is an "SIA Working Group", at which every SIA-interconnected carrier may have a seat, which proposes alterations to the SIA.

Technologically, the SIA reflects that which was in common use at the time it came into being. This means that calls are carried across dedicated physical circuits between specialised telecom switches. There are a handful of manufacturers of suitable equipment, and it is expensive. The initial circuits take a long time to be put in - 85 working days is the shortest contractual time from order to delivery - and it takes a number of weeks for additional capacity to be provided in the event that the CP's business is successful.

As the SIA was designed to accommodate the needs of large telcos, the process and amount of paperwork required are appropriate for them - making them burdensome for a small business. As a result, many new entrants to the market hire consultants to navigate this process for them. It takes between nine months and a year to get an interconnect under the SIA up and running, which is a long time in today's time-to-market driven world.

Interconnect using IP Exchange

IP Exchange is approximately a decade old, and is BT Wholesale's offering aimed at the smaller CP. Rather than carrying calls over dedicated circuits, they're carried over the internet. Rather than requiring specialised equipment, the CP can use open-source software on commodity hardware to handle calls. It doesn't take the best part of a year to get up and running; it can be done in a couple of weeks. Capacity can be scaled up or down within a few days. It's much easier to find experienced IP telephony engineers than those who understand the technologies specified by the SIA.

However. IP Exchange provides the CP with no security. BT are able to impose changes to many parts of the contract on 28 days' notice. For the rest, BT may propose changes; the CP has 28 days to object and, if they do not, then the changes take place. If the CP objects, the contract specifically discourages the involvement of Ofcom or any other regulatory authority. There is no reciprocal mechanism for the CP to propose changes.

BT may terminate the contract on 30 working days' notice for any reason. If the CP has number ranges allocated to it by Ofcom, hosted by BT, this is insufficient time to move them to another provider, meaning that there will be an interruption to the CP's business. The CP may also terminate the contract on the same terms, except that BT may extend the period to 75 working days should BT need to do so.

Lastly, BT and Ofcom agree that IP Exchange is an "unregulated service." Quite what this means is unclear, as all telecoms services in the UK are subject to a degree of regulation, but, in practice, Ofcom are unwilling to intervene in disputes between BT and other CPs where they're interconnected using IP Exchange.


IP Exchange ought to be the natural choice, but the lack of regulatory oversight and security of tenure make it a risky foundation upon which to build a business. Nonetheless, it is increasingly the first choice for CPs wishing to interconnect with BT - there are more than 170 of them, according to BT's last annual report. They deserve better protection against an increasingly maverick BT than they receive.