2. PennNet Phone
•
Started as part of the sip.edu initiative
•
Ran SER 0.9.x for several years
•
Gained traction due to cost savings, now nearing conclusion of
migration to entirely VoIP deployment
•
14K VoIP handsets now, targeting 18K
•
Roughly 100K calls per day, spikes considerably higher
•
Uncomplicated architecture for now
•
Replicated proxies and registrars, Asterisk, SEMS
4. Bridged Line Appearances
•
Event package using XML bodies to deliver line
state to subscribers
•
Fine for small groups
•
Local patches to the existing got us BLA in
deployment
•
But…
5. Bridged Line Appearances:
Limitations
•
XML bodies quickly increased NOTIFY packet size
•
Fragmentation, retransmission
•
Fragmentation of almost every packet,
considerably worse for large BLA groups
•
Underpowered handsets quickly overwhelmed by
fragmented packets
•
Stuck states
7. What is SCA?
•
Broadsoft spec for shared line events
•
•
Widely implemented by handset vendors
SCA group receives notifications when a member does
something interesting
•
line seize, ringing, answered, held
•
Held calls can be retrieved by any other member of the
group
•
Line state delivered in compact Call-Info headers!
8. SCA at Penn
•
Agreement that BLA was a dead end
•
In-house familiarity with SER/Kamailio code
•
3-4 months of development
•
•
RFC 3891 support (“Replaces” header) to
retrieve held calls
Rapid rollout following successful testing
9. SCA at Penn: Results?
•
Largest supported group size
•
BLA: 6
•
SCA: 24 (imposed by handset limitations)
•
8000+ handsets using SCA, many with multiple
SCA lines
•
Stuck states? Almost eliminated.
10. SCA at Penn: Results?
•
Opens possibility of using other vendor
handsets
•
•
•
Tested with Polycom, Aastra, Cisco, Yealink
Likely to work with Snom, Grandstream, others
BYOD?
