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

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Outline Overview Centralized Network Architectures Distributed Network Architectures Using H.323 Distributed Network Architectures Using SIP Comparing Network Architectures Interconnecting VoIP Protocols Understanding Gateways Guidelines for Selecting the Correct Gateway Enterprise Central and Remote Site Gateway Interconnection Requirements Service Provider Gateway Interconnection Requirements Summary Lesson Self-Check

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Centralized Network Architectures MGCP or Megaco/H.248 Cisco CallManager at central site for managing call control Centralized applications Up to 10,000 IP Phones per cluster CAC (to limit number of calls per site) SRST for remote branches

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Distributed Network Architectures Using H.323 No call control signaling for intrasite and off-net calls through the IP WAN Transparent use of the PSTN if the IP WAN is unavailable Logical hub-and- spoke topology for the directory gatekeeper Only one type of codec configured for the WAN

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Distributed Architecture: Span Engineering The Span Engineering overall deployment model is multisite-distributed.

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Distributed Network Architectures Using SIP SIP is an ASCII-based application layer control protocol SIP components: –SIP user agent –SIP proxy server –SIP redirect server –SIP registrar server

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Centralized Call Control vs. Distributed Call Control

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Interconnecting VoIP Protocols MethodDescription Translation through TDMVoIP1 -> TDM -> VoIP2 Widely available Adds latency Single-protocol architectureMigrates all devices and services to single VoIP protocol Limits flexibility Protocol translationVoIP -> translator -> VoIP2 Lack of standards for protocol translation

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Analog vs. Digital

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Gathering the Requirements Is an analog or digital gateway required? What is the required capacity of the gateway? What type of connection is the gateway going to use? Is Foreign Exchange Office (FXO), FXS, E&M, T1, E1, PRI, or BRI signaling required? What signaling protocol is used? H.323, MGCP, or SIP? Is voice compression a part of the design? If so, which type? Are direct inward dialing (DID), calling line ID (CLID), modem relay, or fax relay required? Is the device acting only as a gateway or as a gateway and a router/LAN switch? Is inline power for IP Phones required? Is remote site survivability required? To which country is the hardware shipped?

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Remote Site Enterprise Gateway Considerations QoS capabilities for voice quality Security to ensure privacy of communications over the WAN Appropriate number and type of voice interfaces and features Survivability of telephone service in the event of a WAN outage Analog and digital fax/modem capabilities

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Central Site Enterprise Gateway Considerations Dial plan integration Voic integration Gateway for PBX interconnect Inline power requirements for IP Phones

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Service Provider Gateway Considerations Signaling interconnection type –SS7 supports a high volume of call setup. Carrier-class performance –Gateways must have redundancy and QoS support. Scalability –Gateways must support rapid growth.

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Practice Item: Scenario 1 Cisco CallManager acts as the call agent. The voice gateway provides physical connectivity for end devices. The voice gateway does not contain full call-signaling protocol implementation. The call agent manages voice gateways. Call control signaling for all calls crosses the IP WAN. CAC limits the number of calls per site. SRST is used for remote branches.

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Practice Item: Scenario 2 The voice gateway provides physical connectivity for end devices. The voice gateway has the functionality to perform call setup and teardown. Gatekeepers are used to provide call control. Gatekeepers provide a scalable approach to dial plan resolution. There is no call control signaling for intrasite and off-net calls through the IP WAN.

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Summary Centralized network architectures use MGCP or Megaco/H.248 to provide enterprise-wide gateway control from a central controller. Distributed network architectures require gateways and endpoints to contain the intelligence necessary to perform call control functions using H.323 or SIP. SIP networks allow companies to build large-scale networks and provide flexibility to integrate to web-based applications. Selection of the appropriate network architecture requires a thorough understanding of the differences in call control between architectures.

© 2006 Cisco Systems, Inc. All rights reserved. CVOICE v Summary (Cont.) Choices for interconnecting differing VoIP networks include translation through TDM, migrating to a single-protocol environment, or using protocol translators. A voice gateway converts voice packets to analog or digital signals. When you are selecting a gateway, you must consider what protocols are supported, the density and types of interfaces on the gateway, and the features that are required. Enterprise interconnection design issues include distributed versus centralized call processing, SRST, QoS, and fax/modem relay requirements. Service provider interconnection requirements typically include use of SS7 to signal the PSTN, carrier-class performance, and scalability.

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