TBE 2710 Chapter 12 Signaling

Signaling Functions Switch to switch communication Switch to station communication Supervising Addressing Alerting Call Progress

Signaling Methods: In Band... Loop-Start Signaling Ground-Start Signaling Wink Start

General Call-State Model: In-Band

Signaling Methods: Out-of-Band or Clear Channel... ISDN – Primary Rate Interface (PRI) Used for PBX and Business customers Added features (CLID, RLT, etc.) Quicker call setup than in-band System Signaling No. 7 (SS7) Used for PSTN Carrier Networks Enables multiple network services

Signaling System 7 Standard Method for Linking Central Offices Supports CLASS Services Required for: Local Number Portability (LNP) E800 services Calling Name/Number Delivery (CNAM) Advanced Intelligent Networking (AIN)

Architecture of SS-7 SCP SP STP STP SP SP User SP STP STP User SP SP SP=Signal Point STP=Signal Transfer Point SCP=Service Control Point

Purposes of SS7 Improves Call Management Enhances Network Management Separates Network Control From Hardware Supports User Database Handles Addressing And Supervision Supports 800 Number Portability Supports Local Number Portability

SS7 Vs OSI

SS7 Messaging ISDN User Part – (ISUP) Call Setup Messages IAM, ACK, DIS, etc… Transaction Capability User Part (TCAP) Transports INAP messages SCP Database queries E800, LNP, CNAM, etc.

SS7 Signaling Examples Call Setup CNUM/CNAM E800 LNP Global Title Translation Point Code CNUM/CNAM E800 LNP

IP Signaling IP traffic and PSTN traffic merging Gateways required for conversion Protocols H.323 Media Gateway Control (Megaco) SIP

H.323 Large, open, flexible protocol with many options (good/bad), somewhat proprietary though H.225 – call control Session master/slave H.245 – multimedia control Negotiates capabilities of endpoints (intelligent or dumb). Gatekeeper RAS – registration, admission, status Uses Q.931 messages (PSTN) over TCP/IP Can be setup as peer to peer with intelligent endpoints

Media Gateway Control Megaco and H.248 Controls interaction between Media Gateway and Media Gateway Controller (softswitch, ie. Gatekeeper in H.323) Call Control in central controller

SIP Simple protocol for multimedia applications over IP Text messaging between endpoints Addresses are a URL Decentralized – intelligent endpoints Presence Servers keep track of users status and availability, and where to be reached (Instant Messaging uses SIP) Proxy server – routes information, locates users and stores their preferences Uses other protocols SAP, SDP, TRIP, RSVP, AAA

SIP Advantages Operates over Any Network Provides Expanded User Choices Enables Developers to Create New Applications Supports Multimedia Allows User to Specify Best Way to Communicate

SIP Architecture

SIP Call Setup