Figure 8-1 Comparing PSTN and VoIP voice call setup

Circuit-switched Network Media Gateway

Media exchangeMedia control

IP Network

Call signalingCall signaling/Media

control

Media exchange

Figure 8-2 Relationship Between Signaling and Media Flow

IP Phone – Calling party

IP

Media Gateway

IP Phone – Called party

Call setup Signaling

Media Flow

8001 8002

Figure 8-3 Components of a Multimedia Communication Service

H.323 Terminal

H.323 MCU

H.323 Gatekeeper

H.323 Gateway

H.323 Gateway

H.323 Terminal

IP Network

PSTN ISDN

Figure 8-4 Gatekeeper

IP Phones

IP

Media Gateway

Router

IP

IP WAN

Gatekeeper

IP Phones

MCU

Router

Media Gateway

Figure 8-5 H.323 Zones

IP Phones

IP

Media Gateway

Router

IP

IP WAN

Gatekeeper

IP Phones

MCU

Router

Figure 8-6 Interdomain routing

AS 300

AS 200AS 100

BGP protocol running here connecting the three AS (Autonomous Systems) together

Figure 8-7 Signaling separate from VoIP conversation

Real time Transport Protocol VoIP Conversation

UDP

UDPUDP

Call setup signaling

1. Off hook

2. Send Dial tone

3. Dial number

6 Receive IP

4. is phone on hook? Yes

5 .Give caller ip address

7. set up UDP port

8. Ring signal

Called partyCalling party

Signaling uses TCP/IP

Conversation uses UDP

Media Gateway

Chapter 8 Figures

[FIG]Figure 8-1 Comparing PSTN and VoIP voice call setup[FIG]Figure 8-2 Relationship between signaling and media flow[FIG]Figure 8-3 Components of a multimedia communication service[FIG]Figure 8-4 Gatekeeper[FIG]Figure 8-5 H.323 Zones[FIG]Figure 8-6 Interdomain routing[FIG]Figure 8-7 Signaling separate from VoIP converstion