© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Identifying Voice Networking Considerations Reviewing Traditional Voice Architectures and Features

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Analog-to-Digital Conversion Steps for converting analog signal to digital format: Filtering Sampling Digitizing –Quantization and coding –Companding (a-law, mu-law)

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v PBXs and Switches PBX: Used in private sector Scales to n * 1000 phones Mostly digital Uses 64-kbps circuits Uses proprietary protocols to control phones Interconnects remote branch subsystems and telephones PSTN switch: Used in public sector Scales to n * 100,000 phones Mostly digital Uses 64-kbps circuits Uses open-standard protocols between switches and phones Interconnects with other PSTN switches, PBXs, and telephones

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: PBXs and PSTN Switches

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v PBX Features PBX features: –Call holding – Conferencing –Transferring – Music on hold –Forwarding – Call history –Parking – Voice mail PBX can connect to PSTN through T1 or E1

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v PSTN Switch

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Local Loops, Trunks, and Interoffice Communications

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Foreign Exchange Trunks Foreign Exchange Office (FXO): Emulates a phone Connects to a station port of a PBX or to the PSTN switch Foreign Exchange Station (FXS): Emulates a PBX Provides connections for standard phones and fax machines

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Basic Telephony Signaling Local-loop signaling: Telephone to switch Trunk signaling: Switch to switch PBX to switch PBX to PBX Basic categories: Supervision signaling Address signaling Informational signaling

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Analog Signaling on a PBX Local-loop signaling: Loop start: –The simplest –For subscriber loops –Occurrences of glare Ground start: –Modification of loop start –More intelligent –For PBX loops –Minimizes glare Trunk signaling: E&M (recEive and transMit): –Between PBXs –Five types of signaling –Separate paths for voice and signaling

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v CAS and CCS Signaling Channel associated signaling: Signal for call setup in the same channel as a voice call Examples: –T1 or E1 signaling –DTMF Common channel signaling: Messages for call setup Examples: –ISDN –DPNSS –QSIG –SS7

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v ISDN Digital Signaling ChannelCapacityMostly Used For B64 kbpsCircuit-switched data D16/64 kbpsSignaling information

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Q Signaling Standards-based protocol for inter-PBX communications Enables interconnection of multivendor equipment Enables basic services and feature transparency between PBXs Is interoperable with public and private ISDNs Does not impose any restrictions on private numbering plans

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v SS7 Signaling Used between PSTN switches Signaling implemented on a separate data network Trunk channels used solely for voice transmission Replaces per-trunk in-band signaling

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v PSTN Numbering Plans Set of rules for routing voice calls through the PSTN Based on the ITU-T recommendation E.164 Example: North American Numbering Plan (NANP)

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example Country Codes Country Code ZoneCountry 11Canada, United States 12421Bahamas 17871Puerto Rico 18761Jamaica 202Egypt 2122Morocco 2132Nigeria 303Greece 343Spain 3863Slovenia 444United Kingdom 454Denmark Country Code ZoneCountry 515Peru 525Mexico 616Australia 636Philippines 6796Fiji Islands 77Kazakhstan, Russia 818Japan 868China 8868Taiwan 919India 9669Saudia Arabia 9959Georgia

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Example: Routing Calls Based on a Numbering Plan

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Portion of UK National Numbering Plan Number RangeDescription (01xxx) xxx xxxTrunk prefix (national long-distance calling prefix) (01xxx) xxx xxx (01x1) xxx xxxxx (011x) xxx xxxxx (02x) xxxx xxxx (01xxx[x]) xxxx[x] Geographic numbering optionsarea code and subscriber number (05x) xxxx xxxxMobile phones, pagers, and personal numbering (07xxx) xxxxxxReserved for corporate numbering. (0800) xxx xxx (0800) xxx xxxx (0808) xxx xxxx Freephone (except for mobile phone) Free emergency number

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v Summary A telephone system transports analog speech over a digital network. PBXs and public telephone switches share many similarities, but they also have differences. The telephone infrastructure includes local loops and trunks. In a telephony system, a signaling mechanism is required to establish and disconnect telephone communications. Each telephone must have a unique address based on the E.164 standard.

© 2007 Cisco Systems, Inc. All rights reserved.DESGN v