Open Forum 2016 10th November 2016

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…

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

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 24.229 V13.4.0 (2015-12) §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

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

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

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 •••

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

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

Rates at target of overload

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