Categories
IMS / VoLTE Kamailio Mobile Networks RFCs & Standards VoIP

Kamailio I-CSCF – SRV Lookup Behaviour

Recently I had a strange issue I thought I’d share. Using Kamailio as an Interrogating-CSCF, Kamailio was getting the S-CSCF details from the User-Authorization-Answer’s “Server-Name” (602) AVP. The value was set to: sip:scscf.mnc001.mcc001.3gppnetwork.org:5060 But the I-CSCF was only looking up A-Records for scscf.mnc001.mcc001.3gppnetwork.org, not using DNS-SRV. The problem? The Server-Name I had configured as a […]

Categories
GSM IMS / VoLTE Mobile Networks VoIP

Sending SMS with an alphanumeric String as the Source

If you’ve ever received an SMS from your operator, and the sender was the Operator name for example, you may be left wondering how it’s done. In IMS you’d think this could be quite simple – You’d set the From header to be the name rather than the MSISDN, but for most SMSoIP deployments, the […]

Categories
FreeSWITCH IMS / VoLTE Kamailio Mobile Networks VoIP

FreeSWITCH, Kamailio & IMS Extensions

Bad Extension is nothing to do with the Dialplan…

Categories
5G SA IMS / VoLTE Kamailio LTE Mobile Networks VoIP

The Surprisingly Complicated World of SMS: Apple iPhone MT SMS

Quirks and gotchas of working with SMS on IMS on iPhones.

Categories
FreeSWITCH IMS / VoLTE Kamailio Mobile Networks VoIP

FreeSWITCH as an IMS Application Server

Using FreeSWITCH as an IMS Application Server

Categories
EPC EUTRAN IMS / VoLTE LTE Mobile Networks

Lifecycle of a Dedicated Bearer – From Flow-Description AVP to Traffic Flow Templates

A look at how Dedicated Bearers get established for VoLTE.

Categories
EPC LTE Mobile Networks RFCs & Standards SDM VoIP

Basics of EPC/LTE Online Charging (OCS)

A glimpse into the complexities of prepaid billing (Online Charging) Diameter based networks.

Categories
EPC Mobile Networks RFCs & Standards VoIP

Docker & BIND as an ENUM Playground

A Bind environment in a Docker container for experimenting and learning ENUM for DNS based Call Routing.

Categories
5G SA EPC IMS / VoLTE LTE Mobile Networks SDM VoIP

IMS Routing with iFCs

Peer behind the magic curtain at how IMS networks route your VoLTE and VoNR calls, and how iFC (Initial Filter Criteria) achieve this.

Categories
FreeSWITCH IMS / VoLTE Mobile Networks VoIP

Adding support for AMR Codec in FreeSWITCH

Adding support for AMR Codec in FreeSWITCH

Categories
EPC GSM IMS / VoLTE LTE Mobile Networks RFCs & Standards

The Surprisingly Complicated world of MO SMS in IMS/VoLTE

Short messaging can be anything but simple…

Categories
EUTRAN IMS / VoLTE LTE Mobile Networks RFCs & Standards SDM VoIP

Diameter and SIP: Registration-Termination-Request / Answer

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 […]

Categories
EPC IMS / VoLTE LTE Mobile Networks RFCs & Standards SDM VoIP

Diameter and SIP: User-Authorization-Request/Answer

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.

Categories
EPC IMS / VoLTE LTE Mobile Networks RFCs & Standards SDM VoIP

Diameter and SIP: Server-Assignment-Request/Answer

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. […]

Categories
EPC IMS / VoLTE LTE Mobile Networks RFCs & Standards SDM VoIP

Diameter and SIP: Location-Info-Request / Answer

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 […]

Categories
EPC IMS / VoLTE LTE Mobile Networks RFCs & Standards SDM

Diameter and SIP: Multimedia-Authentication-Request/Answer

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 […]

Categories
EPC IMS / VoLTE Kamailio LTE Mobile Networks Software VoIP

Kamailio Proxy-CSCF Pull

My first Pull / Merge in the Kamailio project was to fix the IMS P-CSCF config

Categories
EPC EUTRAN IMS / VoLTE Kamailio LTE Mobile Networks RFCs & Standards SDM SIM Cards VoIP

Things I wish I knew about setting up private VoLTE Networks

Lessons learned about setting up VoLTE / IMS Networks at small scale.

Categories
EPC EUTRAN IMS / VoLTE LTE Mobile Networks SDM Security VoIP

VoLTE / IMS – P-CSCF Assignment

How the P-CSCF address is assigned to a UE in Protocol Configuration Options (PCO) during bearer establishment.

Categories
EPC EUTRAN IMS / VoLTE LTE Mobile Networks RFCs & Standards VoIP

IMS / VoLTE IPsec on the Gm Interface

The exchange between a UE and P-CSCF to put SIP traffic into IPsec encapsulated payloads.