Re: [sip-overload] soc-overload-control-05

["Vijay K. Gurbani" <[e-mail]>]

Eric: Closing this loop.  Please see inline.

On 01/03/2012 12:34 PM, NOEL, ERIC C (ERIC C) wrote:
> Vijay,
>
> Thanks for your reply and the suggested email threads.
>
> Another way to express my concern is that in reading your client
> default loss control algorithm, the client normalization of oc-loss
> seems to imply that the server estimates oc-loss assuming it could
> equally be rejecting all requests (initial-dialog or out-of-dialog or
> mid-dialog requests).

Correct.

> This is in contrast with my simulation implementation of rate and
> loss controls in support of the SIP overload control working group
> activities a few years ago.  There, both my simulated servers and
> clients used the implicit assumption that throttling was limited to
> the same requests in both the servers and clients (at the time just
> INVITE messages).
>
> Basically I am concerned that the throttling algorithms may not work
> properly if the clients normalize oc-loss/oc-rate/oc-other based on a
> "reduction/no reduction" mix of messages locally created, while the
> servers estimate optimal oc-loss/oc-rate based on a different mix.

True.  Following the discussion we have had, I will clarify that the
basis for calculating the "oc" parameter value must include all
the messages.  The suggested text is below.

OLD
5.3 Determining the 'oc' Parameter Value
    The value of the "oc" parameter is determined by the overloaded
    server using any pertinent information at its disposal.  The process
    by which an overloaded server determines the value of the "oc"
    parameter is considered out of scope for this document.

NEW
5.3 Determining the 'oc' Parameter Value
     The value of the "oc" parameter is determined by the overloaded
     server using any pertinent information at its disposal.  The only
     constraint imposed by this document is that the server control
     algorithm MUST produce a value for the "oc" parameter
     such that the receiving clients can apply it to all downstream
     messages (dialogue forming as well as in-dialogue).  Beyond this
     stipulation, the process by which an overloaded server determines
     the value of the "oc" parameter is considered out of scope for this
     document.

         Note that this stipulation is required so that both the
         and server have an common view of which messages to include
         in the calculation of the feedback.  With this stipulation
         in place, the client can prioritize messages as discussed
         in Section 5.10.1.

    As an example, a value of "oc=10" when the loss-based algorithm is
    uses implies that 10% of all messages (dialog forming as well as
    in-dialogue) are subject to reduction at the client.  Analogously,
    a value of "oc=10" when the rate-based algorithm is used indicates
    that the client should send SIP requests at a rate no greater than
    or equal to 10 SIP requests per second.

Is that okay?  Please let me know if you or anyone else has any further
issues with this.  If not, I will revise the draft.

Thanks,

- vijay
-- 
Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent
1960 Lucent Lane, Rm. 9C-533, Naperville, Illinois 60566 (USA)
Email: vkg@{bell-labs.com,acm.org} / [e-mail]
Web:   http://ect.bell-labs.com/who/vkg/