Session Border Controller

This guide details the architectural and step-by-step configuration required to enforce Transport Layer Security (TLS) for SIP signaling and Secure Real-time Transport Protocol (SRTP) for media on Session Border Controllers. Readers will learn how Public Key Infrastructure (PKI) integrates into SBC signaling interfaces, how Mutual TLS (mTLS) handshakes are established with ITSPs, and how SDP crypto attributes are negotiated for end-to-end media encryption.

This guide explores the underlying mechanics of transmitting faxes over IP networks using G.711 Pass-Through and T.38 Fax Relay. You will learn how legacy T.30 analog modem signals are handled by IP gateways, the impact of packet loss and jitter on each protocol, and how SIP SDP re-INVITEs manage fax session setup. Understanding these differences allows network engineers to design reliable FoIP solutions over modern SIP trunks.

This guide explains the fundamental differences between Early Offer (EO) and Late Offer (LO) media negotiation in Session Initiation Protocol (SIP). You will learn how the RFC 3264 Offer/Answer model functions under both approaches, how message flows differ during call setup, and how Session Border Controllers (SBCs) handle interworking between the two models.

This guide explores Dual-Tone Multi-Frequency (DTMF) signaling transport methods in Voice over IP (VoIP) networks, focusing on Inband Audio and comparing it to RFC 4733 (formerly RFC 2833) dynamic RTP payloads and SIP INFO. Readers will learn the underlying mechanics of digit transmission, the impact of lossy audio compression codecs on inband tones, and how media gateways and Session Border Controllers (SBCs) handle DTMF interworking.