1. Open Forum 2016
10th November 2016

2. SIP Overload Control (SOC) Task Group
Philip Williams – BT
Chair of Group
1st formal meeting end March, but need discussed on and off for some time before this…

3. Scope agreed – limited to:
SIP NNI - Network to Network Interface
can be extended easily e.g.
Request Method types
message priorities
Nodal overload control
‘hop-by-hop’
next node identified by IP address
not Destination control
generalised traffic identification
e.g. RFC 7200 – uses Subscribe-Notify
Open Forum 2015:
Drivers
Imperative – Nodal, Destination
Strategy
Requirements

4. SIP Load Control Event Package
Choice of standards
SIP Overload Control
SIP Rate Control
SIP Load Control Event Package
NOCA-GOCAP
Body
IETF
ETSI Id
RFC 7339
RFC 7415
RFC 7200
ES 283
Purpose
Nodal
Destination
Nodal+
Transport
SIP *
Restriction type/parameter
PL / MR MR
PL / MR / W
Control Distribution target → source
Piggy-Backed on Responses (Via Header) Hop-by-hop
see left
Target node notifies subscribing source nodes (Subscribe-Notify Requests)
Master (target) notifies Slaves (sources)
Parameter value derivation
Not defined
Defined precisely, with SLAs
3GPP: In TS V ( ) §4.12 Overload Control 3GPP endorses RFC 7339 & 7415.
GOCAP Transport – only defined for Diameter & RFC 6665.
Legality: NICC recommends using ETSI first, but use others if not available.
Equipment manufacturers:
note
PL = Proportional Loss; MR = Max Rate; W = Window

5. RFC SIP Rate Control
Identical signalling infrastructure to RFC 7339
specialisation
Restriction method
max admit rate only - ‘rate-based’
oc=‘rate’
algorithm not mandated
very effective default
Target node (‘server’) functions not defined
derivation of source control rates

6. SRC (SOC) signalling architecture
traffic load direction
Source Node
Target Node
SIP Requests
local application(s)
SIP
Client
SIP Server
local application(s)
requests
Via
oc;
oc-algo=rate;
Client
-side SOC
requests
Server-side SOC
Via
oc=…;
oc-algo=rate;
oc-validity=…;
oc-seq=…;
responses
responses
SIP Responses

7. ND 1653: SIP Overload Control in UK Networks, so far
Architecture
Identification of standard
Restriction algorithm
Load-sharing & Re-routing
Resilience/failover
Response codes for rejection by control
Emergency traffic
•••

8. Restriction Policy Message priority – criteria:
restriction exempt?
Request Method?
emergency call?
within dialog?
Restriction exempt Request Methods
ACK
BYE
CANCEL
PRACK

9. Key performance objectives
Total rate received by target
Objective 2
Distribution of
control rates over sources
Bound by goal rate
capacity of target node
Maximise rate received
utilisation of target node
Value of control variable
unique
convergence fast
adaptation stable
Precise, predictable
‘fair’ in some sense
SLAs agreed between CPs
guaranteed minimum rate
use capacity when unused by others
 Structure source max rate
SLA parameters
control variable

10. Rates at target of overload

11. Complete & issue ND 1653 Additional guidance required
Next stages
Complete & issue ND 1653
Additional guidance required