IETF 78 - SOC - SCE
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IETF 78 - SOC - SCE

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IETF 78 - SOC - SCE IETF 78 - SOC - SCE Presentation Transcript

  • Session Capacity Estimate (SCE)draft-jones-sip-overload-sce-00
    IETF 78
    SIP Overload Control WG
    Paul E. Jones
    Gonzalo Salgueiro
    Victor Pascual
  • Session Capacity Estimate (SCE)
    • SCE is a measure of how much capacity exists on a SIP entity
    • Capacity means number of additional communication sessions the device can accept
    • It is comparable to a gateway reporting how many DS0s it has available
    • But more suitable for other devices that do not necessarily have a single limiting resource
    • It summarily represents the available capacity of a device at a given point in time
    • Taking into consideration available memory, CPU utilization, media processing capacity, licenses, etc.
    • Can work in combination with rate control mechanisms
    • Overloading the ability to handle communication sessions is different than overloading the ability to handle messages
  • Example SCE Calculation
    • Let’s assume that a SIP device measures capacity for memory, CPU, media processing, licenses, etc.
    • For each resource, the device will calculate remaining capacity in terms of how many sessions the device might be able to handle given resources consumed by existing sessions (implementation specific)
    • The SCE value is the minimum of all of the computed capacity values, since the session capacity is constrained by the component with the least available capacity
  • Conveyance of the SCE
    The SCE value is conveyed through normal SIP signaling exchanges between devices
    Via: SIP/2.0/UDP 192.168.1.10:5060; branch=z9hG4bK776asdhds;sce=275
    During periods when no other SIP exchanges take place, OPTIONS “ping” message might be used
    SCE could be transmitted either uni or bidirectionally
  • Utilizing the SCE
    A peer receiving session capacity information can use the SCE value as a part of its decision-making process in selecting the next-hop or even rejecting new communication sessions, such as when an intermediary device has received an SCE value of '0' from its next-hop peer(s)