SIP STX Lines to LSE

Introduction

London Stock Exchange Group (LSE.L) is a diversified international market infrastructure and capital markets business sitting at the heart of the world's financial community in London. STX is the 20 year old BT FeatureNet based fast and secure private telephone network used by member firms and other industry professionals across the UK, Republic of Ireland and the Channel Islands. White labelled and resold to the market by LSE.STX enables you to reach anybody on the network through five-digit dialling for a flat fee. This service was presented to LSE member firms as a 2Meg DPNSS bearer that is normally terminated directly on the turret trading system or PBX of the member institution.

BT FeatureNet is becoming end of life April 2020. LSE and BT have worked together to replace it with a Digital Transformation of STX to a cloud based application provided by BT. The new system supports connections from web based clients and smart phone clients however this document is only concerned with how you would connect the new service to a Turret Trading System or PBX which will be via an internet based SIP trunk.

Overview

LSE Dial Plan  

The new LSE service is based on a 5 digit dial plan and each member will be allocated a set of 5 digit extensions for the users they represent. This dial plan is likely to overlap with existing PBX dial plan and so should be created in a separate partition or will need number manipulation to make it work within existing member PBX dial plans.

LSE Certificates

The LSE will issue certificates to each member there will be a root CA certificate and a device certificate for each member device that will connect to LSE. The member will need to supply either the IP address of the device or the FQDN. The device certificate will be in PEM format and will contain both a signed certificate for the device and a private key to be used and will need to be loaded on the devices. The root CA should be put in the trusted root authority’s folder on the device.

LSE Resilience

The LSE will offer a resilient URL to act as the target for SIP trunks in testing we used commsdev.mvine.com to target the test environment in the real service LSE will issue the URL to use. This URL has a number of routes behind it and will use active DNS resolution to redirect the incoming traffic on failure. The LSE system will round robin behind this URL for both incoming and outgoing calls and will normally accept calls on any of their routes providing they come from an authenticated user. It does mean the SBC must be able to resolve the URL

On the member side when multiple trunks are used to connect to the LSE in a resilient fashion then the PBX needs to be configured to receive calls on any trunk at any time.  This is because the LSE will expect all connected routes to be active. For outbound calling PBX can round robin or use a priority list to suite themselves.

LSE SIP Trunk Details