To support Dedicated Bearers we first have to have a way of profiling the traffic, to classify the traffic as being the type we want to provide the Dedicated Bearer for. The first step involves a request from an Application Function (AF) to the PCRF via the Rx interface. The most common type of AF […]
Category: IMS / VoLTE
A look at how characters are encoded in an SMS.
Another deep dive into deceptively simple seeming functions to do with SMS.
Using DNS to resolve E.164 phone numbers to routable SIP URIs
Peer behind the magic curtain at how IMS networks route your VoLTE and VoNR calls, and how iFC (Initial Filter Criteria) achieve this.
Adding support for AMR Codec in FreeSWITCH
Short messaging can be anything but simple…
Unlocking Carrier Privileges through certificate on a UICC
These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Registration-Termination Request / Answer allow a Diameter Client (S-CSCF) to indicate to the HSS (Diameter Server) that it is no longer serving that user and the registration has […]
The Diameter User-Authorization-Request and User-Authorization-Answer commands are used as the first line of authorization of a user and to determine which Serving-CSCF to forward a request to.
These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Server-Assignment-Request/Answer commands are used so a SIP Server can indicate to a Diameter server that it is serving a subscriber and pull the profile information of the subscriber. […]
These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Location-Information-Request/Answer commands are used so a SIP Server query a Diameter to find which P-CSCF a Subscriber is being served by Basics: The RFC’s definition is actually pretty […]
These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Multimedia-Authentication-Request/Answer commands are used to Authenticate subscribers / UAs using a variety of mechanisms such as straight MD5 and AKAv1-MD5. Basics: When a SIP Server (S-CSCF) receives a […]
Sending SMS over LTE using OsmoMSC and OsmoHLR and the SGs interface for SMSoS
How call routing in GSM works and it’s application in the Osmocom suite
So now we’ve covered the basics of what’s involved let’s get some traffic on our network. For starters we’ll need to start each of our network elements and bring up whichever BTS hardware we’re using. In order for our calls to have audio, we’ll need to set a parameter on the Media Gateway. We’ll cover […]
My first Pull / Merge in the Kamailio project was to fix the IMS P-CSCF config
Lessons learned about setting up VoLTE / IMS Networks at small scale.
How the P-CSCF address is assigned to a UE in Protocol Configuration Options (PCO) during bearer establishment.
An update to PyHSS to support IMS Authentication for VoLTE