VoIP Tutorials

Introduction

Modern telco carriers interconnect over SIP protocol for voice and SMPP protocol for SMS using the public internet, it is common that each carrier has their session border controllers (SBCs) or Short Message Service Center (SMSC) at different geographical locations. Let’s start with voice, For example, if you send a call to Bharti Airtel to India, likely you’re pointing your traffic to their SBC in the UK, so all traffic is being proxied through the United Kingdom then sent back to their gateways in India for final termination. For topology hiding it is also common that your RTP/Media will be proxied as well and the. sent over the public internet to India

What is subspace

Subspace is a dedicated, secure network for delivering tomorrow’s internet today. From mission-critical real-time applications to in-network applications, Subspace helps companies create the best possible real-time experiences. Subspace offers the world’s best connectivity for real-time applications.

The Public Network Challenges

As we know the public internet was designed for reliability and did not promise certain quality for real-time applications like voice, video, say you’re interconnecting to a Mobile Network Operator (MNO) Session border controller (SBC) over IP located in the UK for transit to route calls to India for example. if anything happens in the public internet between the UK and India the call quality will be degraded, or dropped. If internet routing is managed by the MNO manually, all calls to India will suffer from degraded quality until this route is fixed. Handling the global network connectivity problems in realtime is not an easy task and dropping for a few minutes or even seconds can result in users to immediately switch from your service.

Subspace as a Solution

To be proactive and solve this challenge, with a few clicks, UK MNO can send the media traffic to Airtel India via Subspace’s network by adding an entry in Subspace portal or API that will automatically provide them with a unique IP:Port that redirects to their SIP network in india.

After pointing via Subspace the traffic will be accelerated using best routes, solving any internet backbone, middle mile or last mile issues.

Subspace SIP Teleport’s proprietary algorithms ensure that your real-time application has the ability to deliver consistent voice, free of stutters, jitters, or lag, under even the most challenging network conditions, with up to 80% reduction in packet loss.

“Every millisecond counts for real-time applications. What if your users could interact with your application without network-induced lag, jitter, disconnects, and screen freezes?” Subspace.com

Adding native support for Subspace in the TCXC Stack

For the telecom wholesale industry & peering Contact Centers to benefit from the value that Subspace provides, we had to do this ! Let me explain, there is a limitation by design that can lead to causing subspace use case become not applicable for wholesale carrier traffic scenario due to authentication and authorization reasons. For example when initiating a call via Subspace network using SIP Teleport, the src IP where the call will be coming from is the subspace IP (CIDR 129.203.31.1/24), this is usually fine if the customer is using SIP registration method, however in wholesale (carrier to carrier) this means that the originators using SIP peering for authentication won’t be able to authenticate successfully by default, TCXC Authentication, Authorization, Accounting (AAA) will rejects the SIP request and send SIP error 403 to the customer.

To solve this problem, TCXC parses from SIP Teleport by subspace the real-IP that the call is coming from, so we have to challenge the special SIP header `X-Subspace-Forwarded-For` during authenticating, authorizing and accounting for this work properly.

To achieve this, we had to add support for the subspace special SIP header that SIP teleport uses to communicate the real IP address that the call came from in five components:

B2bua

Authentication

Authorization

Accounting

Web UI

In TCXC web portal we added a new checkbox for carriers that use subspace SIP Teleport to send their traffic via TCXC Network, once checked if the call is coming from subspace IP network and SIP header is set, the IPv4 authentication will use the value of the header as remote ip. If the box is unchecked the incoming call will use the regular authentication logic.

Currently this new feature is in BETA, we welcome all existing and future TCXC CSP members to take it for a test drive.

For Call centers, CPaaS providers that want to re-route to TCXC via subspace simply set your subspace network IP in outbound SIP proxy settings.