VoIP and IP Telephony

Transcription

1 VoIP and IP Telephony Reach Out and Ping Someone ISAC Spring School March 2006 Anthony Kava, Sr. Network Admin Pottawattamie County IT

2 Definition VoIP Voice over Internet Protocol Voice Transport (i.e., trunking) Replacement for Traditional Circuits IP Telephony Internet Protocol for Telephone Applications PC <-> PC PC <-> Phone Phone <-> Phone Sometimes Interchangeable

3 Applications Remote Offices Road Warriors Messaging Integration Network Convergence Toll Bypass PBX Replacement Add-on to PBX

4 Benefits Open Architecture Interoperability Single Network Uniformity Reduced Maintenance End-user Mobility Resilient IP Network

5 Caveats Infrastructure Costs Electrical Power New Technology Complexity Reliability Emergency Services Security

6 Switching Comparison Circuit-switched End-to-end Channel Open for Call Duration Dedicated Bandwidth Packet-switched Voice Split into Data Packets Asynchronous Delivery Shared Bandwidth

7 Network Considerations Bandwidth CODECs G.711 μlaw / αlaw (64 Kbps) G.729 (8 Kbps) GSM (13 Kbps) Latency Acceptable Delay PSTN (45 ms) Link + Encoding Delay Jitter Buffering Delays Drops

8 CODEC Comparison Compression Method Bit Rate (kbps) MOS Score Compression Delay (ms) G.711 PCM G.726 ADPCM G.728 LD-CELP to 5 G.729 CS-ACELP G.729 x 2 Encodings G.729 x 3 Encodings G.729a CS-ACELP G MP-MLQ G ACELP Source:

9 A Very, Very Brief History 1876 Mr. Watson, come here, I want you! 1973 Network Voice Protocol (NVP) ARPA Network Secure Communications (NSC) Program Secure, High-Quality, Low-Bandwidth, Real-time, Full-Duplex 1981 Voice Funnel Streaming Audio/Video over Packet-switching Used for Video Conferencing over ARPANET during the 1980s 1999 Cisco Introduces Their First IP Phone

10 IP Telephony Protocols H.323 ITU Multimedia Standard Video Conferencing Gateway Devices Gatekeeper Most Widely Deployed Based on ISDN Q.931 Session Initiated Protocol (SIP) Leading VoIP Signaling Protocol Real-time Transport Protocol (RTP) Superset of PSTN Features Text-based Protocol (like HTTP) Cisco Skinny Client Control Protocol (SCCP) Proprietary Protocol Used by Cisco Call Manager Inter-Asterisk exchange (IAX) Used by Asterisk Open-source PBX Trunking Over Single UDP Data Stream Media Gateway Control Protocol (MGCP) Call Agent Media Gateway Signaling Gateway

11 Example SIP Message SIP/ Trying Via: SIP/2.0/UDP 10.x.x.x:5060;branch=z9kG4bS690421dd From: "Tony Kava" To: Date: Mon, 20 Mar :23:12 GMT Call-ID: Server: Cisco-SIPGateway/IOS-12.x CSeq: 102 INVITE Allow-Events: telephone-event Content-Length: 0 Text-based Protocol Three-digit Codes like HTTP Headers like SMTP Easy to Troubleshoot with Protocol Analyzer

12 SIP IP Phone Manufacturers Cisco D-Link Grandstream Linksys Polycom Snom Uniden Zultys

13 SIP Infrastructure / Demo SIP Proxy Asterisk PBX Soft Phone X-Lite Hard Phone Polycom IP 501

14 IP Telephony at PottCounty IP Telephone Test Began January x Cisco 7960 Phones IT, EMA and Planning Asterisk PBX Dell PowerEdge 1750 Rolm 9751 Cisco 3825 Router Cisco 6509 Cores Cisco 3550 Switches Cisco 7960G IP Phone Cisco 7960G IP Phone PSTN Cisco 3825 Rolm 9751 Cisco PWR Cisco 6509 Core Cisco PWR Asterisk

15 IP Telephony at PottCounty IP Telephone Test The Good Positive User Feedback Minimal Downtime Survived EMA Exercise The Bad Router Memory Leak Bug Shared Line Appearances Occassional Echo Cisco 7960G IP Phone Cisco 7960G IP Phone PSTN Cisco 3825 Rolm 9751 Cisco PWR Cisco 6509 Core Cisco PWR Asterisk

16 IP Telephony at PottCounty [jailmenu] exten => s,1,answer exten => s,2,digittimeout,5 exten => s,3,responsetimeout,15 exten => s,4,background,jailmenu exten => t,1,playback,vm-goodbye exten => t,2,wait,1 exten => t,3,hangup exten => i,1,playback,pbx-invalid exten => i,2,goto,s 3 ; 1 - Information submenu exten => 1,1,Goto(jailsub1,s,1) ; 2 - Jail Administration Office (submenu) exten => 2,1,Goto(jailsub3,s,1) ; 3 - Sheriff's Office 2200 exten => 3,1,Dial(SIP/2200@10.x.x.x,60) Asterisk PBX Remote IP Phone Soft Phone via VPN Easy to Create Menus Call Queue Capability Asterisk Gateway Interface (AGI) Helpful Apps Ten Digit Dialing AnyWho Reverse Lookup Business Hours Logic Identification Extension Text-to-Speech (Festival)

17 VoIP / Convergence at PottCounty PCSO: Before Rolm 9751 Switch T1 Split for Data / Voice AS/400 LAN PCSO LAN 12 Channels Voice 768K Data (12 Chan.) T1 Single Data Application Cisco 2501 Multiplexer Multiplexer Cisco 2501 Video Over ISDN Lines $285 (T1) + $500 (ISDN) = $785 / month Rolm x ISDN PSTN Rolm x ISDN Polycom Video Polycom Video

18 VoIP / Convergence at PottCounty PCSO: After Rolm 9751 Switch 12 VoIP Channels County LAN PCSO LAN 2 x T1 as IP Link (3 Mbps) LANs Interconnected T1 Video Over IP with H323 Polycom Video Cisco 3825 T1 Cisco 2811 Polycom Video $285 (T1) + $285 (T1) = $570 / month ($215 less) Rolm 9751 Rolm 9751

19 Any leftover questions? ISAC Spring School March 2006 Anthony Kava, Sr. Network Admin Pottawattamie County IT