Attributes of VOIP Protocols & Tradeoffs

1. Attributes of VOIP Protocols & Tradeoffs SIP versus CMSS Reference Model SIP CMSS Signaling Gateway • Several versions exist culminating in  Uses SIP version 2.0 with extensions & RFC3261 usage rules for local & CLASS services  Call Control & Signaling Protocol  (Same as SIP)  Establishes real-time connections across diverse network infrastructure  For Multimedia CMS CMS CMSS, SIP, H323 (Peer-to-Peer) Call Agent (CA) Call Agent (CA)  Application Level Protocol  (Same as SIP)  Independent of Bearer Protocol (e.g. IP, ATM, MPLS, ..)  Independent of Transmission Tech- nology (e.g. Cable, DSL, 3G, TDM, ..)  Network & Media Independent like HTTP or SMTP Media Gateway Controller (Master) Media Gateway Controller (Master) MGCP NCS MEGACO IP-Phone MGCP NCS MEGACO IP-Network  Extensible, Reliable, & Secure (SIPS)  Extensible, Reliable. & Secure (SIPS)  Additional Cable Security Spec.  MGW Slave  IM, Presence, Location, Session-setup,  (Same as SIP) Session-management, Negotiation of user preferences & invoking of services TGW Slave PSTN Fax  Gate Controller Feature (DQoS)  Event Messaging Feature  Operations & Provisioning Feature  Electronic Surveillance Feature (calea) Protocols Comparison Tradeoffs in Master/Slave & Peer-to-Peer Item MGCP MEGACO NCS SIP H323 Item Master/Slave Peer-to-Peer Architecture Master/Slave Master/Slave Master/Slave Peer-to-Peer Peer-to-Peer (Physical control) (Physical control) (Physical control) (Logical features) (Logical features) Operation  Simple/dumb gateway devices  Smart GW devices; yet simple to implement  Application intelligence in  Peer interaction;SIP processing network servers does not increase over time Signaling Master/Slave Master/Slave Master/Slave Peer-to-Peer Peer-to-Peer Media RTP RTP RTP RTP RTP Service  Server-based development  Device-specific development development only, generic tools  Shorter time to market for  Possible short time to market new services across diverse for new features on specific networks devices Conference Yes Yes Yes No Yes Control Transport UDP UDP UDP now mostly TCP; mostly TCP earlier UDP Service  Only update control servers  Must update all GW devices deployment to deploy new features across the network  Services can be managed dynamically across network Encoding Text only Text or ASN.1 ASN.1 HTTPish ASN.1, Q931 Application Telephony Multimedia, Multimedia, Multimedia, Telephony Emphasis Telephony Analog Phone Multicast, Instant Messaging, Presence Cost  Cost-optimized GW devices,  Higher cost Smart GWs, leads to lower overall system higher overall system cost cost - Especially in large systems  Time-frame for obsolescence  GW devices may need HW & of GW devices is slower SW upgrades over time Address Local-name + Local-name + Local-name + SIP, E164-URLs Flat Alias, E164 Domain Domain Domain Suitability & Very large Very large Cable telephony, IP-PBX, Standalone GWs, Used for Gateways Gateways Analog Phone IP-Phones, Conferencing- 3G-networks Systems Examples  NCS/J.162  SIP  MGCP  H.323  MEGACO/H.248