By Stephen Tomko H.323 vs. SIP

Internal PBX Call Extension number is dialed PBX receives extension Routes extension Routes call to the phone Call begins

Internal VoIP Call Extension number is dialed Server picks up extension Tells phone how to reach the other phone via IP VoIP phone establishes a connection to the other phone Via TCP/IP protocol stack Uses network mediums Both confirm connection and call begins

Difference? Extension is still dialed Call is still placed Still routed Call quality is equal

Convergence Data, voice, and video are all combined under one medium Many reliable mechanisms to provide reliability, security, and manageability already exist TCP, RTP, QoS params SSL, SSH, S-HTTP

How we handle calls VoIP, Video, and data must have sessions Sessions need protocols Think SS7 for landline Two largest protocols SIP H.323

SIP Background Created by the Internet Engineering Task Force (IETF) as a method to control “sessions” between one or many points February 1996 Designed around the HTTP protocol Session Codes E.g. 400 – user error, 500 – server error, etc…

H.323 Background Created by ITU-T as a method to control voice, audio, and data November 1996 A Suite of protocols H.225 H.235 H.245 Derived from Q.931 standard Think PSTN and ISDN signaling

SIP Components User Agent Client Creates and sends requests A SIP compatible phone is a User Agent doing the work of a User Agent Client Registar/Location Server Registers User Agents Stores locations Address resolution User Agent Server Accepts, Forwards and routes calls Proxy Server Routes calls Redirect Server Multifunctioned Discussed Later

H.323 Components Terminal Standard VoIP phone or any device that starts or terminates H.323 sessions Gateway Translates data from one incompatible network to another Think PSTN to Ethernet Gatekeeper Controls calls and sessions Address resolution Zone control Bandwidth control Multipoint Control Unit Bridges many sessions into one

pulver.com Proxy server nortel.com 1. INVITE SIP/2.0 From: Location Server jeff.pulver 2. INVITE SIP/2.0 From: 3. SIP/ ok From: 4. SIP/ OK From: 5. ACK SIP/2.0 From: 6. ACK SIP/2.0 From:

1. INVITE From: 2. SIP/ Moved temporarily Contact: nortel.com pulver.com Redirect Server Location Server Jeff.pulver 4. INVITE From: 3. ACK From: 5. SIP/ OK To: 6. ACK From:

H.323 Process Extensive H.225 – Call signaling Provides call signaling, alerting, and connected statuses for the call in question RAS Signaling Communication between terminals and gatekeepers Communication between gatekeepers H.245 Capability negotiation Defines what codecs to be used for audio/video/data H.264, G.729, T.140 Master/Slave determinator Settles all disputes between two devices during negotiation H.235 Encryption using SSL

H.323 vs. SIP

Business Value Converging data/voice/video under one medium - network Control how your business communicates Multipoint conferencing Unified communication allows all types of communication under one protocol All in one package

Why technology is important One word: Convergence umbrella Geographic locations are reduced H.323 All-in-one suite, managers many facets SIP Simplicity, small, modularity

Major Commercial products Nortel’s Application Server 5300 for SIP &catId=null&parId=0&prod_id=66621&locale=en-US &catId=null&parId=0&prod_id=66621&locale=en-US Avaya Aura for SIP aura#%20Avaya%20Aura%E2%84%A2%20Communication% 20Manager aura#%20Avaya%20Aura%E2%84%A2%20Communication% 20Manager Cisco UT Communications Manager (CallManager) for H.323/SIP