Subject: [RAI] [PMOL] SIP Perf Telephony Metrics: SER and SEER Updates

From: Daryl Malas <[email-masked]>
Date: Thu, 29 Jul 2010 03:21:09 -0600

All,

During the IESG review process, there were some comments about the response codes used in the SER and SEER metrics.  I have updated the text in these metrics and included the updates below.  Please review these and provide any feedback.  Specifically, are the response codes and their purpose clear, and are the right set of response codes for the purposes of these metrics.  If it is unclear the purpose of these metrics, please let me know.

Regards,

Daryl

----------------------

4.6.  Session Establishment Ratio (SER)

   This metric is used to detect the ability of a terminating UA or
   downstream proxy to successfully establish sessions per new session
   INVITE requests.  SER is defined as the number of new session INVITE
   requests resulting in a 200 OK response, to the total number of
   attempted INVITE requests less the total number of attempted INVITE
   requests less INVITE requests resulting in a 3XX, 401, 402, and 407
   response.  The 3XX, 401, 402 and 407 response codes were chosen,
   because they indicate an acceptable recoverable UA effect without the
   interaction of an individual user of the UA.  This metric is similar
   to Answer Seizure Ratio (ASR) defined in [E.411].  It is measured at
   the originating UA only.  The output value of this metric is
   numerical and SHOULD be adjusted to indicate a percentage of
   successfully established sessions.  The SER is calculated using the
   following formula metric.

   In order to simplify the formula, the following variable is used to
   summarize multiple SIP responses:

   a = 3XX, 401, 402, and 407

                 # of INVITE Requests w/ associated 200 OK
   SER = --------------------------------------------------------- x 100
     (Total # of INVITE Requests)-(# of INVITE Requests w/ 'a' Response)

   The following message exchange provides an example of identifiable
   events necessary for inputs in determining session establishment as
   described above:

                           UA1                 UA2
                            |                   |
                            |INVITE             |
               +----------->|------------------>|
               |            |                180|
               |            |<------------------|
      Session Established   |                   |
               |            |                   |
               |            |                200|
               +----------->|<------------------|
                            |                   |

   The following is an example call flow including a SIP 302 Redirect
   response.

                            UA1                 UA2                 UA3
                             |                   |                   |
                +----------->|INVITE             |                   |
                |            |------------------>|                   |
      INVITE w/ 'a' Response |                   |                   |
                |            |                302|                   |
                +----------->|<------------------|                   |
                             |                   |                   |
                             |INVITE                                 |
                +----------->|-------------------------------------->|
                |            |                                       |
                |            |                                    180|
       Session Established   |<--------------------------------------|
                |            |                                       |
                |            |                                    200|
                +----------->|<--------------------------------------|
                             |                                       |

4.7.  Session Establishment Effectiveness Ratio (SEER)

   This metric is complimentary to SER, but is intended to exclude the
   potential effects of the target UA from the metric.  SER is defined
   as the number of INVITE requests resulting in a 200 OK response and
   INVITE requests resulting in a 480, 486, or 600; less the total
   number of attempted INVITE requests less INVITE requests resulting in
   a 3XX, 401, 402, and 407 response.  The response codes 480, 486 and
   600 were chosen, because they clearly indicate the effect of an
   individual user of the UA.  It is possible an individual user could
   cause a negative effect on the UA.  For example, they may have
   misconfigured the UA causing a response code not directly related to
   a SSP, but this cannot be easily determined from an intermediary
   B2BUA somewhere inbetween the originating and terminating UA.  With
   this in consideration, response codes such as 415 and 420 were not
   included in the numerator of the metric.  If future response codes
   provide similar effects, they should be considered in addition with
   this metric.  This metric is similar to Network Effectiveness Ratio
   (NER) defined in [E.411].  It is measured at the originating UA only.
   The output value of this metric is numerical and SHOULD be adjusted
   to indicate a percentage of successfully established sessions less
   common UAS failures.

   In order to simplify the formula, the following variable is used to
   summarize multiple SIP responses:

   a = 3XX, 401, 402, and 407

   The SEER is calculated using the following formula:

        # of INVITE Requests w/ associated 200 OK, 480, 486, or 600
   SEER = -------------------------------------------------------- x 100
     (Total # of INVITE Requests)-(# of INVITE Requests w/ 'a' Response)

   Reference the example flow is Section 4.6.

---

From: Daryl Malas <[email-masked]>
Date: Mon, 9 Aug 2010 10:59:30 -0600

All,

This email is a duplicate, old message, so please ignore.

Regards,

Daryl

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Daryl Malas
Sent: Thursday, July 29, 2010 3:21 AM
To: [email-masked]
Cc: [email-masked]
Subject: [RAI] [PMOL] SIP Perf Telephony Metrics: SER and SEER Updates

All,

Regards,

Daryl

----------------------

                           UA1                 UA2
                            |                   |
                            |INVITE             |

                            UA1                 UA2                 UA3
                             |                   |                   |
                +----------->|INVITE             |                   |

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