© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v5.01-1 Introduction to VoIP Introducing VoIP Network Technologies. - презентация

1 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Introduction to VoIP Introducing VoIP Network Technologies

2 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Outline Overview Business Case for VoIP VoIP Functions Components of a VoIP Network VoIP Signaling Protocols VoIP Protocols and the OSI Model VoIP Service Considerations RTP and RTCP Summary Lesson Self-Check

3 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Business Case for VoIP Cost savings Flexibility Advanced features: –Advanced call routing –Unified messaging –Integrated information systems –Long-distance toll bypass –Encryption –Customer relationship

4 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v VoIP Functions Signaling –SS7, H.323, SIP, MGCP, H.248 Database services – Billing, caller ID, toll-free numbers Bearer control –Call connect –Call disconnect Codecs –G.711, G.729

5 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Components of a VoIP Network

6 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Major VoIP Protocols

7 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v VoIP Protocols and the OSI Model Constant: Voice media packets use RTP/UDP Variable: Several signaling methods and link-layer protocols

8 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v VoIP Service Considerations Latency Jitter Bandwidth Packet loss Reliability Security

9 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Real-Time Transport Protocol Provides end-to-end network functions and delivery services for delay-sensitive, real-time data, such as voice and video Works well with queuing to prioritize voice traffic over other traffic Services include: –Payload-type identification –Sequence numbering –Time stamping –Delivery monitoring

10 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Real-Time Transport Control Protocol Monitors the quality of the data distribution and provides control information Provides feedback on current network conditions Allows hosts involved in an RTP session to exchange information about monitoring and controlling the session Provides a separate flow from RTP for UDP transport use

11 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Summary The business advantages of a VoIP network include more efficient use of bandwidth, lower costs, access to advanced features, and increased revenue opportunities. Replacing the PSTN with VoIP requires the user to understand and implement appropriate use of signaling, database services, bearer control, and codec functionality. The basic components of a VoIP network include IP Phones, gateways, gatekeepers, call agents, conferencing servers, and application servers. VoIP peer-to-peer signaling protocols, such as H.323 and SIP, are most commonly used in distributed VoIP architectures. VoIP client/server signaling protocols, such as MGCP and Megaco/H.248, are most commonly used in centralized VoIP architectures.

12 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Summary (Cont.) VoIP signaling protocols reside at the session layer of the OSI model and can operate over TCP or UDP based on their design. Issues such as latency, jitter, and packet loss are inherent in IP networks. Solutions are available to minimize the impact of these issues on voice quality. IP networks are less reliable and secure than the PSTN. Design approaches must address these issues to provide for secure transport of voice traffic with near PSTN reliability. RTP carries the voice payload and provides sequencing and time stamping to allow proper re-assembly and timing when the voice stream is played out at the receiving end. RTCP monitors the quality of voice sessions and provides feedback on current network conditions.

13 © 2006 Cisco Systems, Inc. All rights reserved. CVOICE v