VoIP and IP Telephony
Reach Out and Ping Someone
ISAC Spring School 2006
21 March 2006
Anthony Kava, Sr. Network Admin
Pottawattamie County IT
Definition
VoIP – Voice over Internet ProtocolVoice Transport (i.e., trunking)Replacement for Traditional Circuits
IP TelephonyInternet Protocol for Telephone Applications
PC <-> PCPC <-> PhonePhone <-> Phone
Sometimes Interchangeable
Applications
Remote OfficesRoad WarriorsMessaging IntegrationNetwork ConvergenceToll BypassPBX ReplacementAdd-on to PBX
Benefits
Open ArchitectureInteroperabilitySingle NetworkUniformityReduced MaintenanceEnd-user MobilityResilient IP Network
Caveats
Infrastructure CostsElectrical PowerNew TechnologyComplexityReliabilityEmergency ServicesSecurity
Switching Comparison
Circuit-switchedEnd-to-end ChannelOpen for Call Duration Dedicated Bandwidth
Packet-switchedVoice Split into Data PacketsAsynchronous DeliveryShared Bandwidth
Network Considerations
BandwidthCODECs
G.711 μLaw / αLaw (64 Kbps)G.729 (8 Kbps)GSM (13 Kbps)
LatencyAcceptable Delay
PSTN (45 ms)Link + Encoding Delay
JitterBufferingDelaysDrops
CODEC Comparison
303.655.3G.723.1 ACELP
303.96.3G.723.1 MP-MLQ
103.78G.729a CS-ACELP
102.688G.729 x 3 Encodings
103.278G.729 x 2 Encodings
103.928G.729 CS-ACELP
3 to 53.6116G.728 LD-CELP
13.8532G.726 ADPCM
0.754.164G.711 PCM
Compression Delay (ms)MOS ScoreBit Rate (kbps)Compression Method
Source: http://www.cisco.com/warp/public/788/voip/codec_complexity.html
A Very, Very Brief History
1876 – “Mr. Watson, come here, I want you!”1973 – Network Voice Protocol (NVP)
ARPA Network Secure Communications (NSC) ProgramSecure, High-Quality, Low-Bandwidth, Real-time, Full-Duplex
1981 – Voice FunnelStreaming Audio/Video over Packet-switchingUsed for Video Conferencing over ARPANET during the 1980s
1999 – Cisco Introduces Their First IP Phone
IP Telephony ProtocolsH.323 – ITU Multimedia Standard
Video ConferencingGateway DevicesGatekeeperMost Widely DeployedBased on ISDN Q.931
Session Initiated Protocol (SIP)Leading VoIP Signaling ProtocolReal-time Transport Protocol (RTP)Superset of PSTN FeaturesText-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 PBXTrunking Over Single UDP Data Stream
Media Gateway Control Protocol (MGCP)Call AgentMedia GatewaySignaling Gateway
Example SIP MessageSIP/2.0 100 TryingVia: SIP/2.0/UDP 10.x.x.x:5060;branch=z9kG4bS690421ddFrom: "Tony Kava" <sip:[email protected]>;tag=am213z2vf3To: <sip:[email protected]>;tag=44E9C180-556Date: Mon, 20 Mar 2006 03:23:12 GMTCall-ID: [email protected]: Cisco-SIPGateway/IOS-12.xCSeq: 102 INVITEAllow-Events: telephone-eventContent-Length: 0
Text-based ProtocolThree-digit Codes like HTTPHeaders like SMTPEasy to Troubleshoot with Protocol Analyzer
SIP IP Phone Manufacturers
CiscoD-LinkGrandstreamLinksysPolycomSnomUnidenZultys
SIP Infrastructure / Demo
SIP ProxyAsterisk PBX
Soft PhoneX-Lite
Hard PhonePolycom IP 501
IP Telephony at PottCounty
IP Telephone TestBegan January 200517 x Cisco 7960 PhonesIT, EMA and PlanningAsterisk PBXDell PowerEdge 1750Rolm 9751Cisco 3825 RouterCisco 6509 CoresCisco 3550 Switches
Cisco 7960GIP Phone
Cisco 3550-24PWR
Cisco 6509 Core
Cisco 7960GIP Phone
Cisco 3550-24PWR
Cisco 3825
PSTN
Rolm 9751
Asterisk
IP Telephony at PottCounty
IP Telephone TestThe Good
Positive User FeedbackMinimal DowntimeSurvived EMA Exercise
The BadRouter Memory Leak BugShared Line AppearancesOccassional Echo
Cisco 7960GIP Phone
Cisco 3550-24PWR
Cisco 6509 Core
Cisco 7960GIP Phone
Cisco 3550-24PWR
Cisco 3825
PSTN
Rolm 9751
Asterisk
IP Telephony at PottCountyAsterisk PBX
Remote IP PhoneSoft Phone via VPNEasy to Create MenusCall Queue CapabilityAsterisk Gateway Interface (AGI)Helpful Apps
Ten Digit DialingAnyWho Reverse LookupBusiness Hours LogicIdentification ExtensionText-to-Speech (Festival)
[jailmenu]exten => s,1,Answerexten => s,2,DigitTimeout,5exten => s,3,ResponseTimeout,15exten => s,4,Background,jailmenu
exten => t,1,Playback,vm-goodbyeexten => t,2,Wait,1exten => t,3,Hangup
exten => i,1,Playback,pbx-invalidexten => i,2,Goto,s|3
; 1 - Information submenuexten => 1,1,Goto(jailsub1,s,1)
; 2 - Jail Administration Office (submenu)exten => 2,1,Goto(jailsub3,s,1)
; 3 - Sheriff's Office 2200exten => 3,1,Dial(SIP/[email protected],60)
VoIP / Convergence at PottCounty
PCSO: BeforeRolm 9751 SwitchT1 Split for Data / Voice
12 Channels Voice768K Data (12 Chan.)
Single Data ApplicationVideo Over ISDN Lines$285 (T1) + $500 (ISDN) = $785 / month
3 x ISDN3 x ISDN
T1
Cisco 2501
PCSO LAN
Multiplexer
Rolm 9751
MultiplexerCisco 2501
Rolm 9751
AS/400 LAN
PSTN
Polycom Video Polycom Video
VoIP / Convergence at PottCounty
PCSO: AfterRolm 9751 Switch12 VoIP Channels2 x T1 as IP Link (3 Mbps)LANs InterconnectedVideo Over IP with H323$285 (T1) + $285 (T1)= $570 / month ($215 less)
T1
T1
Cisco 2811
PCSO LAN
Rolm 9751
Cisco 3825
Rolm 9751
County LAN
Polycom Video Polycom Video
Any leftover questions?
ISAC Spring School 2006
21 March 2006
Anthony Kava, Sr. Network Admin
Pottawattamie County IT