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SIP Overload

SIP Overload. Jonathan Rosenberg Volker Hilt Daryl Malas. Problem Definition. Proxy 1. Element Overloaded. INVITE. 503. Proxy A. Proxy 2. INVITE. Proxy 3.

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SIP Overload

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  1. SIP Overload Jonathan Rosenberg Volker Hilt Daryl Malas

  2. Problem Definition Proxy 1 Element Overloaded INVITE 503 Proxy A Proxy 2 INVITE Proxy 3 When all elements are overloaded, 503 creates MORE trafficAmplified further by retransmits ofINVITE since 503 is delayed or lost SIP Client

  3. R-P-H can be used to prioritize Added underutilization as a problem – 503 interpreted for cluster Added requirement that scope of load be clear Added requirement that solution give guidance on SIP message prioritization Clarify that prioritization is a matter of local policy Clarified REQ 1 that throughput has to be useful throughput (i.e., meet latency requirements) Added requirement that mechanism shouldn’t unduly award elements which don’t support Many other clarifications Requirements Document Changes

  4. Requirements document Open Issues • None • Next step: charter update, submission as WG item and last call

  5. Solution Design • Two drafts submitted: • draft-hilt-sipping-hopbyhop-overload-00 • draft-malas-sipping-congestion-header-01 • Drafts differ in • Type of information that is conveyed • Draft-malas: 0-5 for CPU, application, network, etc. • Draft-hilt: 0-100 single value • How information passed upstream • Draft-hilt: Load-Status header indicating server to which it applies • Draft-malas: has a server-id which matches sent-by • Scope of applicability • Draft-malas: Retry-After header field value • Draft-hilt: parameter in new header field • Diagnostics • Draft-malas: allows response to carry congestion from many downstream elements

  6. How does upstream element use load information to change behavior Do we standardize it? What behaviors are affected? Load balancing Throttling Routing (HBH vs. multi-hop) What information is reported (percentage? Q-value?) Depends on previous algorithm How is the load information computed? How is the load information passed upstream? Deal with backwards compatibility issue How does downstream element implement queueing discipline? Policing Do we use separate protocol or part of SIP itself? Temporal scope of load information Overall Design Space

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