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Towards a modernisation of CERN’s telephony infrastructure
26/03/2015
Francisco VALENTÍN VINAGRERO
Anthony HESNAUX
IT-CS-CS
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Index• Today’s network• Project goals• A glimpse of SIP• BRAINS
26/03/2015
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Today’s network
26/03/2015
Alcatel PABX OmniPCX Enterprise
• Hybrid circuit switched – IP technology
• Geographically distributed – 4 nodes in 17 sites
• Monolithic design
• Add-ons for value-added services
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Today’s network
26/03/2015
Manages 12K fixed lines + 6K mobile phones (Closed User Group)
*Source: comstat.cern.ch
Operator 3
CERN’s national mobile operator network
CERN’s CUG
CERN’s fixed network
Non CERN phone user
Operator 2
Operator 1
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Today’s network
26/03/2015
• Around 5M calls/year
• Least Cost Routing (LCR) for outgoing calls
• Worldwide numbering plan with 800 destinations
• Local extensions with different external access rights
Internal
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Today’s network
26/03/2015
• Critical and safety services
• Switchboard
• Call Centers: Fire Brigade, CCC, Service Desk, IT Helpdesk
• TETRA interconnection
• Special analog lines: Red Phones & Lift Phones
• Integration with Mobile Telephony – CUG
• Integration with Unified Communications – Lync
• Integration with conferencing systems - Vidyo
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Alcatel PABX
Value Added
Services
Call Routing
Access
Traditional phones
Worldwide PSTN
networks
GSM UMTS
GSM gateways
Dial Plan management
Least Cost Routing
AccessRights
Call Centers
Switchboard
Billing Alarm mgmt
SOAP API
SIPISDN
Red phones
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Project goals
26/03/2015
• Replace the PBX by a software-based solution• Hardware/license costs• Avoid vendor lock-in• TETRA for critical communications
• Decouple call routing function to a new entity
• Capability to support non-Lync softphones• Today Lync is the only option for office phones
• Use SIP trunking with the external operators
• SIP core Network• Using open-source solutions• Fosters the introduction of new VoIP services
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A glimpse of SIP
26/03/2015
SESSION INITIATION PROTOCOL
Defined in 1996. RFC2543 in 1999 replaced by SIP v2 in 2002 (RFC3261)
Uses the HTTP request/response model.• Headers• Status codes• Dialog vs. Transaction• SIP URIs
sip:username@host:port
Application
Presentation
Session
Layers 1-3
Transport
SIP
RTP
UDP TCP TLS
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A glimpse of SIP
26/03/2015
Voice packetization is the key enabler of VoIP.
TIME DIVISION MULTIPLEXING
• End-to-end physical channel reserved • Constant bandwidth• Fixed number of channels 1 E1 = 30 channels• High infrastructure costs
MANUAL SWITCHING MECHANICAL SWITCHING AUTOMATIC PBX
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IP packetization and independent routing
• Fewer infrastracture costs• Packet loss and/or variable delay or Jitter • Changing packetization time and codec may help• QoS mechanisms needed
• Softphones and Softswitches – but with specific hardware for media handling
A glimpse of SIP
26/03/2015
IP Network
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A glimpse of SIP
26/03/2015
SIP in actionSIP ENDPOINT 1
SIP ENDPOINT 2
INVITEFrom: sip:[email protected]: sip:[email protected]: 1 INVITESDP OFFER in the body
100 TRYING
Transaction183 SESSION PROGRESS
200 OKFrom: sip:[email protected]: sip:[email protected]: 1 INVITESDP ANSWER in the body MEDIA SESSION
(RTP)
ACK
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A glimpse of SIP
26/03/2015
SIP in actionSIP ENDPOINT 1
SIP ENDPOINT 2INVITE + SDP
100 TRYING
Transaction 1 183 SESSION PROGRESS
200 OK + SDP
MEDIA SESSION (RTP)
ACK
BYE
200 OKTransaction 2
DIALOG
State machine TimersBilling
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• Center of all routing decissions for all real-time media sessions.• SIP transaction-aware redirect server
BRAINS
26/03/2015
BRAINS FRONT-END PROXY
BRAINSROUTING ENGINE
SIP User and IP based DDoS protection
Calling user rights
Called user location
INVITE
302 REDIRECT / 401 UNATHORIZED
DB
Boîte pour Reduire l’Alcatel-PBX et Introduire des Nouveaux Services
Box for Reducing the Alcatel-PBX and Introducing New Services
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Open-source alternatives
• Call Routing Engine: Asterisk (PJSIP) vs FreeSwitch (Sofia SIP)• Front End (Proxy): Kamailio(OpenSER) vs OpenSIPs
System architecture:• Cluster of CentOS 7 machines (OpenStack + Puppet)• Front end cluster reachable by incoming SIP trunks• Routing engine with local cached database• Provisioning and monitoring servers• DNS load balancing + SIP Options
BRAINS
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BRAINS
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BRAINSROUTING ENGINE
DBRE-1
BRAINSFRONT-END
FE-1
FE-2
FE-3
FE-M
DBRE-2
DBRE-3
DBRE-N
……
DNS
PROVISIONING SERVER
Master DBAIS
LanDB
SIP phone
SIP Gateway 2
SIP Gateway 1
INVITE
REGISTER
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Summary
26/03/2015
Progress:
• Technology review + shortlist of open source solutions• Concept validation • Architecture and roadmap proposal
Next steps:
• SIP trunking with external operators• BRAINS Beta service: Q3 2015• Key issues to be addressed:
• Evolution of Value Added Services• Solution for special analog lines
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Thank you!
26/03/2015
Questions?
