GC6 CLI Update



8th October 2018

With effect Wednesday 10th October we will be implementing the first phase of CLI changes for compliance with the revised General Condition 6 as previously discussed here

Outbound calls that do not have any valid Caller ID will not complete after this date.


We fully support supporting setting both the Presentation Number and Network Number independently,  by means of the P-Asserted-Identity and From header respectively. More detail on this can be found here.

Keeping it simple

To minimise impact of these changes we’ve implemented this in a manner that the vast majority of customers will be unaffected, and we will manipulate the CLI to meet the requirements behind the scenes even where only one CLI is present.

  • If the CLI you send is a number on your Simwood account, this will be used as both the Network Number and Presentation Number.
  • If the CLI you send is a valid number, but not on your Simwood account (e.g. a mobile number from call forwarding, or a number that is hosted with another operator where you use multiple outbound carriers) then we will use this as the Presentation Number and overwrite the Network Number
  • If there is no valid CLI, the call will be rejected (unless the trunk has a default CLI, which will be treated as above)

Withheld calls are unchanged, but it is essential that valid Caller ID is provided in the P-Asserted-Identity header if Privacy: id is set.

The bottom line is that if you are sending Caller ID at present, as is already required by our AUP, you should be unaffected by this change.

Controlling the Network Number

You can set a Default CLI (Presentation Number) and Network Number via the API on a per-trunk basis. If there isn’t a network number, we’ll allocate one.

Inbound Changes?

Another significant change in the new General Condition 6 is that CPs have an obligation to take steps to prevent calls that have invalid or non-dialable CLIs from reaching the called party.

So, not only must CLI be valid when calls are made, but calls with invalid CLI should not be allowed to reach your end users. As we announced last week, we offered similar functionality for years in the form of our Intelligent Call Rejection (ICR) service, and this will effectively become a standard feature helping you fulfil your obligation to your customers here.

However, we note that quite a lot of our calls arriving into our network do not have valid Network Numbers set. Indeed, many big players – including the incumbent – still haven’t got their 08979 number range for inserted network numbers from Ofcom, so we’ve not flicked the switch on this just yet.

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