Open Forum 2016 04112016 10 th November 2016

Open Forum 2016 04/11/2016 10 th November 2016 NICC Standards Limited

SIP Overload Control (SOC) Task Group Philip Williams – BT Chair of Group 04/11/2016 NICC Standards Limited

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 04/11/2016 NICC Standards Limited

Choice of standards SIP Overload Control IETF Body RFC 7339 Id Nodal Purpose SIP Transport PL / MR Restriction type/parameter Control Piggy-Backed Distribution on Responses target → source (Via Header) Hop-by-hop Parameter value derivation Not defined SIP Rate Control IETF RFC 7415 Nodal SIP MR IETF RFC 7200 Destination SIP PL / MR / W see left Target node notifies subscribing source nodes (Subscribe-Notify Requests) Not defined PL = Proportional Loss; MR = Max Rate; W = Window 04/11/2016 SIP Load Control Event Package NOCA-GOCAP ETSI ES 283 Nodal+ * MR Master (target) notifies Slaves (sources) Defined precisely, with SLAs note NICC Standards Limited

RFC 7415 - 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 04/11/2016 NICC Standards Limited

SRC (SOC) signalling architecture traffic load direction Source Node Target Node SIP Requests responses Client -side SOC SIP Client Via SIP Server requests oc; oc-algo=rate; Via oc=…; oc-algo=rate; oc-validity=…; oc-seq=…; Server -side SOC local application(s) requests responses SIP Responses 04/11/2016 NICC Standards Limited

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 • • • 04/11/2016 NICC Standards Limited

Restriction Policy ● Message priority – criteria: – – restriction exempt? Request Method? emergency call? within dialog? ● Restriction exempt Request Methods ACK BYE CANCEL PRACK 04/11/2016 NICC Standards Limited

Key performance objectives Objective 1 Total rate received by target ● Bound by goal rate – capacity of target node ● Maximise rate received – utilisation of target node ● Value of control variable – unique – convergence fast – adaptation stable 04/11/2016 Objective 2 Distribution of control rates over sources ● 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 NICC Standards Limited

Rates at target of overload 04/11/2016 NICC Standards Limited

Next stages • Complete & issue ND 1653 • Additional guidance required 04/11/2016 NICC Standards Limited