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Call Control with SIP
Brian Elliott, Director of Engineering, NMS
Slide 2www.nmscommunications.com
SIP = Session Initiation Protocol
SIP version 2.0, RFC 3261, June 2002 RFCs 2976, 3262, 3265, 3515
Protocol for IP networks Transported over UDP, TCP, SCTP, etc. Session (call) control — not a media transport (use RTP), but has a text messaging capability Text-based protocol SIP transports SDP — Session Description Protocol
Describes media session — RFCs 2327, 3264 Text based protocol
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SIP Among IP Protocols
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SIP Network Infrastructure
Outbound Proxy Server
User Agent B
Inbound Proxy Server
User Agent A
SIP
SIP (before connected)
SIP
Media (RTP)
DNS Server
DNS
Presence/Redirection/
Registration Servers
SIP (after connected)
SIP
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SIP Infrastructure Components
User Agent Consists of User Agent Client (to make requests) and
User Agent Server (to handle requests) SIP phone, PDA, PSTN gateway, media server
Proxy servers Aggregate and route — resolve addresses with DNS
Location servers Updated by User Agent registration; queried by proxies in
routing
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SIP Messages
Message types Requests Responses
Every request has one or more responses Transaction = request + responses Dialog (or “call leg”) analogous to PSTN call
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Messages — Requests
INVITE — initiate a session ACK — acknowledge a session PRACK — provisional acknowledge CANCEL — cancel INVITE request BYE — terminate a session REGISTER — register user OPTIONS — query capabilities SUBSCRIBE — subscribe to a service NOTIFY — service notification INFO — miscellaneous info REFER — refer one user to another (transfer)
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Messages — Responses
1xx — provisional 100 — Trying 200 — Ringing 300 — Session Progress
2xx — success 200 — OK
3xx — redirection 300 — moved permanently 301 — moved temporarily
4xx — client error 400 — Bad Request 401 — Unauthorized 403 — Forbidden 404 — Not Found 481 — Call Does not Exist 486 — Busy Here
5xx — server error 6xx — global failure
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SIP Addressing
Uniform Resource Indicators (URIs) Look like email addresses
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SIP Message Format
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Message Flow — SIP “Call”
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SIP for NCC 1.0
To allow implementation of SIP User Agent using Natural Access framework
Familiar Natural Access development environment Familiar Natural Call Control (NCC) API and model
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Benefits of SIP for NCC
Reduced time-to-market with SIP-based products SIP integrated into Natural Access NCC API well known NCC API abstracts many low-level details of SIP,
simplifying development Easy conversion of PSTN applications using
Natural Call Control
Pay for SIP stack as you deploy No large up-front license fee
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Application or ServiceApplication or Service
For Building SIP User Agents
VOIPNetwork
SIP RTP
NMS SIPNMS SIP MediaProcessor
MediaProcessor
SIP Devices
SIP
RTP
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Typical Uses for NMS SIP for NCC
Terminate VoIPBearer Traffic
VoIP-PSTNGateway
Interworking Functions
SIP TelephonyApplication
VoIP-PSTNGateway
MediaServer
VoIPNetwork
SIP RTP
VoIPNetwork
SIP RTP
PSTN/PBXNetwork
SS7,ISDN,CAS
TDM
ApplicationServer
VoIP Networkor PSTN/PBX
BearerTraffic
SIP
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SIP for NCC — Landscape
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SIP for NCC Model
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Basic Call Control Features
Placing outbound call; receiving incoming call INVITE, ACK, CANCEL, BYE 1xx, 2xx PRACK (Provisional Reliable Acknowledgement)
Rejecting call with different causes 3xx, 4xx, 5xx, 6xx
Transferring call REFER
Macros provided for building up fields for SIP and SDP
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Special Features
Finding users and services REGISTER (nccRegisterUser)
SIP event notification SUBSCRIBE, UNSUBSCRIBE, NOTIFY
Advanced Configuration Transport options — UDP or TCP Outbound proxy — specify SIP proxy for sending all messages Persistent TCP connection reused instead of setting up and
tearing down for each session Configure Ethernet port to be used for all SIP in/out, or designate
Ethernet connection per session For future release…
OPTIONS, INFO, COMET, UPDATE
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Flows — Optional Call Acknowledge
nccAcknowledgeCall (callhd, Ies) NCCEVN_ANSWERED_CALL Manual or automatic — server option
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Call Transfer
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Provisional Acknowledge
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Operating Systems
Windows Windows 2000 SP4, Windows 2003 Server
Linux Red Hat Linux ES 3.0 Update 4
Solaris SPARC 9, 32-bit and 64-bit Intel 8, 32-bit
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Obtaining SIP for NCC 1.0
Download from NMS web site Natural Access 2005-1 SIP for NCC 1.0
License Downloaded version licensed for 8 ports for 30 days, for
evaluation purposes Contact NMS for deployment licenses
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Package Contents
Software package Nmssip — server component Sipmgr — SIP manager with NCC service Nccxsip.h — SIP extensions to NCC API Ctasip — NCC + VCE + MSPP SIP demo
Documentation SIP for Natural Call Control Developer’s Reference Manual
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CTASIP Demo Program
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CTASIP Demo Program
CTATEST-like demo program for SIP Places and receives SIP calls Performs SIP user registration 3 modes of audio support
SIP only — no audio Audio from RTP using Fusion and CG board Audio from RTP using Fusion and HMP
