1. Open Forum 2015
11th November 2015

2. SIP Overload Control (SOC) Task Group
Philip Williams – BT
Chair of Group

3. Drivers SIP increasing Wider application Protocol efficiency
connectivity
applications
traffic
Wider application
not just session control
Protocol efficiency
verbose?
Generic overload control principles still apply 

4. Overload control imperative
Excessive nodal load
 high response times
 timeouts + caller abandons + retries
 ineffective workload
 ‘goodput’ crash
Nodal
Excessive destination focused load  high busy rate  ineffective workload ‘goodput’ reduction
Destination

5. SOC TG Strategy Basis – 3 IETF SOC RFCs Requirements Options Guidance
need for external restriction of load demonstrated
prior experience
Requirements
clarify: purpose, scope of application
integration with other functions / signalling protocols
overcome any RFC design issues or gaps
traffic priorities
Options
identify what should be optional and what shouldn’t
Guidance
implementation - fill in the gaps
highlight re-use opportunities
Recommendations
the detail

6. Progress – RFCs Well understood choices highlighted
some issues identified
Title
RFC
Purpose
Method
SIP Overload Control
7339
Nodal overload control
Hop-by-hop
(Via Header)
SIP Rate Control
7415
"
SIP Load Control Event Package
7200
Destination overload control
Subscribe-Notify

7. Progress - Requirements
Source (Client) SIP message restriction algorithms
Max Rate – ‘rate-based’ or
Proportional rejection – ‘loss-based’
Interaction with load-balancing & failover
Load-share → Restrict (SOC)
Restrict (SOC) → Load-share ?
Differentiated workload - message/session priorities
Target Server, Source Client: Which messages should they count?
Mixed protocol architecture, e.g. ISUP, BICC
ISUP AACC  SOC hop-by-hop
Non-conforming traffic sources
Can they be detected?
What action should be taken?

8. To be continued …
Would you like to be involved?