SIPPING Working Group D. Malas Internet Draft Level 3 Communications Expires: February 2007 August 16, 2006 SIP End-to-End Performance Metrics draft-malas-performance-metrics-04.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on February 16, 2007. Abstract This document defines a set of metrics and their usage to evaluate the performance of end-to-end SIP-based services in both production and testing environments. The purpose of this document is to combine a set of common metrics, allowing interoperable performance measurements, easing the comparison of industry implementations. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [1]. Malas Expires February 16, 2007 [Page 1] Internet-Draft SIP End-to-End Performance Metrics August 2006 Table of Contents 1. Introduction...................................................2 2. Terminology....................................................3 3. SIP Performance Metrics........................................4 3.1. Registration Request Delay (RRD)..........................4 3.1.1. Successful REGISTER Completion RRD...................4 3.1.2. Failed REGISTER Attempt RRD..........................5 3.2. Session Request Delay (SRD)...............................6 3.2.1. Successful Session Setup SRD.........................6 3.2.2. Failed Session Setup SRD.............................7 3.3. Session Completion Delay (SCD)............................8 3.3.1. Successful session completion SCD....................9 3.3.2. Failed session completion SCD........................9 3.4. Average Hops per INVITE (AHI)............................10 3.5. Session Duration Time (SDT)..............................12 3.5.1. Successful session completion SDT...................12 3.5.2. Failed session completion SDT.......................13 3.6. Session Establishment Rate (SER).........................14 3.7. Session Defects (SD).....................................14 3.8. Ineffective Session Attempts (ISA).......................15 3.9. Session Disconnect Failures (SDF)........................15 3.10. Session Completion Rate (SCR)...........................16 3.11. Session Success Rate (SSR)..............................18 4. Metric Correlations...........................................18 5. Additional Considerations.....................................19 5.1. Back-to-back User Agent (B2BUA) Considerations...........19 5.2. Data Collection Considerations...........................19 5.3. Testing Documentation....................................19 6. Security Considerations.......................................19 7. IANA Considerations...........................................19 8. Conclusions...................................................20 9. Acknowledgments...............................................20 10. References...................................................20 10.1. Normative References....................................20 10.2. Informative References..................................21 Author's Addresses...............................................21 Intellectual Property Statement..................................21 Disclaimer of Validity...........................................21 Copyright Statement..............................................21 Acknowledgment...................................................22 1. Introduction SIP has become a standard among many service providers, vendors, and end users. Although there are many different standards for measuring the performance of signaling protocols, none of these have been adapted for use with SIP. This document is intended for providing a Malas Expires February 16, 2007 [Page 2] Internet-Draft SIP End-to-End Performance Metrics August 2006 guideline for the above listed entities in providing a standard approach for measuring and reporting SIP performance metrics with an end-to-end perspective. This will allow a common approach and understanding of performance expectations between service providers, vendors, and the users of those services based on SIP. The metrics defined in this document DO NOT take into consideration durations, impairments, or failures associated with the actual application processing of a request or response. Metrics associated with single device application processing are out of scope of this document. Some metric inputs in this document are affected by external variables to SIP. The following list provides examples, but should NOT be considered exhaustive: . Network connectivity . Switch and router performance . Server processes and hardware performance Note that some metrics in this document may not apply to all applications of SIP. This document provides an overview of pertinent metrics, which may be used individually or as a set based on the usage of SIP within the context of a given service. This document provides a common subset of metrics with a common industry agreed upon definition. This document does not provide any standard or benchmark value regarding IETF recommended performance criteria to compare any output value derived from the following described metrics. 2. Terminology The following terms will be used throughout this document: End-to-End - This is described as two or more elements utilized for initiating a request, receiving the request, and responding to the request. It encompasses elements as necessary to be involved in a session dialog between the originating UAC, destination UAS, and any interim proxies (may also include B2BUA's). This may be relative to a single operator's set of elements or extend to encompass all elements (if beyond a single operator's network) associated with a session. Time Begin (TB) - This is the time stamp to begin determination of the duration until the relative response is received. This begins Malas Expires February 16, 2007 [Page 3] Internet-Draft SIP End-to-End Performance Metrics August 2006 when the relative request has been processed by the application and is being sent from the proxy or UA. Time Stop (TS) - This is the time stamp to end determination of the duration relative to the necessary response received by the initiator of the request. This ends when the application recognizes the response. 3. SIP Performance Metrics The following metrics may be utilized for many different SIP applications. In regards to all of the following metrics, message re-transmissions must be excluded in order to provide accurate metric results. Some metrics are calculated based on the final response message. These metrics do not take into consideration route advances to additional signaling functions based on "final" failure responses. In these unique cases, the final response related to the initial setup attempt should be utilized for input to the metric. 3.1. Registration Request Delay (RRD) Registration Request Delay is utilized to detect failures or impairments causing delays in responding to a UAC REGISTER request. RRD is measured for both successful and failed REGISTER requests. This metric is measured from the originating UAC perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate seconds and/or milliseconds. The following represents the calculation for this metric: RRD = Time of Final Response - Time of REGISTER Request This metric is commonly calculated as an average. The following represents the calculation for this metric as an average: SUM (Time of Final Response - Time of REGISTER Request) ARRD = ------------------------------------------------------- SUM # of REGISTER Requests 3.1.1. Successful REGISTER Completion RRD In a successful registration attempt, RRD is defined as the time interval from the moment the initial REGISTER message containing the necessary information is passed by the originating UAC to the intended registrar until the 200OK is received indicating the registration attempt has completed successfully. This dialog Malas Expires February 16, 2007 [Page 4] Internet-Draft SIP End-to-End Performance Metrics August 2006 includes an expected authentication challenge prior to receiving the 200OK as describe in the following registration flow examples. The following flow provides an example of identifiable events necessary for inputs in calculating RRD during a successful registration completion: UA1 Registrar | | |REGISTER | TB---->|--------------------->| /\ | 401| || |<---------------------| RRD |REGISTER | || |--------------------->| \/ | 200| TS---->|<---------------------| | | 3.1.2. Failed REGISTER Attempt RRD In a failed registration attempt, the interval is defined from the initial REGISTER request and the final response indicating a failure received from the destination registrar or interim proxies. A failure response is described as a 4XX, 5XX, or possible 6XX message. RRD may be used to detect problems in downstream signaling functions, which may be impairing the REGISTER message from reaching the intended registrar. The following flow provides an example of identifiable events necessary for inputs in calculating RRD during a failed registration attempt: UA1 Registrar | | |REGISTER | TB---->|--------------------->| /\ | 401| || |<---------------------| RRD |REGISTER | || |--------------------->| \/ | 401| TS---->|<---------------------| | | Malas Expires February 16, 2007 [Page 5] Internet-Draft SIP End-to-End Performance Metrics August 2006 3.2. Session Request Delay (SRD) Session Request Delay is utilized to detect failures or impairments causing delays in responding to a UA session request. SRD is measured for both successful and failed session setup requests. This metric is also known as Post Dial Delay (PDD) in telephony applications of SIP. This metric is measured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate seconds and/or milliseconds. The following represents the calculation for this metric: SRD = Time of Status Indicative Response - Time of INVITE This metric is commonly calculated as an average. The following represents the calculation for this metric as an average: SUM (Time of Status Indicative Response - Time of INVITE) ASRD = --------------------------------------------------------- SUM # of INVITE Requests 3.2.1. Successful Session Setup SRD In a successful request attempt, SRD is defined as the time interval from the moment the INVITE message containing the necessary information is passed by the originating agent or user to the intended mediation or destination agent until the first provisional response is received indicating an audible or visual status of the initial session request. In SIP, the message indicating status would be a non-100 Trying provisional message received in response to an INVITE request. In some cases, a non-100 Trying provisional message is not received, but rather a 200 message is received as the first status message instead. In these situations, the 200 message would be used to calculate the interval. The following flow provides an example of identifiable events necessary for inputs in calculating SRD during a successful session setup without a redirect (i.e. 3XX message): Malas Expires February 16, 2007 [Page 6] Internet-Draft SIP End-to-End Performance Metrics August 2006 UA1 UA2 | | |INVITE | TB---->|--------------------->| /\ | | || | | SRD | | || | | \/ | 180| TS---->|<---------------------| | | The following flow provides an example of identifiable events necessary for inputs in calculating SRD during a successful session setup with a redirect (e.g. 302 Moved Temporarily): UA1 Redirect Server UA2 | | | |INVITE | | TB---->|--------------------->| | /\ | 302| | || |<---------------------| | || |ACK | | SRD |--------------------->| | || |INVITE | || |------------------------------------------->| \/ | 180| TS---->|<-------------------------------------------| 3.2.2. Failed Session Setup SRD In a failed request attempt, the interval is defined from the initial session request and a non-100 Trying provisional message or a failure indication response. A failure response is described as a 4XX, 5XX, or possible 6XX message. SRD may be used to detect problems in downstream signaling functions, which may be impairing the INVITE message from reaching the intended UA. The following flow provides an example of identifiable events necessary for inputs in calculating SRD during a failed session setup attempt without a redirect (i.e. 3XX message): Malas Expires February 16, 2007 [Page 7] Internet-Draft SIP End-to-End Performance Metrics August 2006 UA1 UA2 | | |INVITE | TB---->|--------------------->| /\ | | || | | SRD | | || | | \/ | 480| TS---->|<---------------------| | | The following flow provides an example of identifiable events necessary for inputs in calculating SRD during a failed session setup attempt with a redirect (e.g. 302 Moved Temporarily): UA1 Redirect Server UA2 | | | |INVITE | | TB---->|--------------------->| | /\ | 302| | || |<---------------------| | || |ACK | | SRD |--------------------->| | || |INVITE | || |------------------------------------------->| \/ | 480| TS---->|<-------------------------------------------| 3.3. Session Completion Delay (SCD) This metric is utilized to detect failures or impairments delaying the time necessary to end a session. SCD is measured for both successful and failed session completions. This metric is measured from the originating UAC or proxy perspective as relative to the end- to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate seconds and/or milliseconds. The following represents the calculation for this metric: SCD = Time of 2XX or Timeout - Time of Completion Message (BYE) This metric is commonly calculated as an average. The following represents the calculation for this metric as an average: Malas Expires February 16, 2007 [Page 8] Internet-Draft SIP End-to-End Performance Metrics August 2006 SUM (Time of 2XX or Timeout - Time of Completion Message) ASCD = --------------------------------------------------------- SUM # of Completed Sessions 3.3.1. Successful session completion SCD In a successful session completion, SCD is defined as the interval between sending a session completion message, such as a BYE, and receiving the subsequent 2XX acknowledgement. The following flow provides an example of identifiable events necessary for inputs in calculating SCD during a successful session completion: UA1 UA2 | | |INVITE | |--------------------->| | 180| |<---------------------| | 200| |<---------------------| |ACK | |--------------------->| |BYE | TB---->|--------------------->| /\ | | || | | SCD | | || | | \/ | 200| TS---->|<---------------------| 3.3.2. Failed session completion SCD In some cases, no response is received after a session completion message is sent and potentially retried. In this case, SCD is defined as the interval between sending a session completion message, such as a BYE, and the resulting Timer F expiration. The following flow provides an example of identifiable events necessary for inputs in calculating SCD during a failed session completion attempt: Malas Expires February 16, 2007 [Page 9] Internet-Draft SIP End-to-End Performance Metrics August 2006 UA1 UA2 | | |INVITE | |--------------------->| | 180| |<---------------------| | 200| |<---------------------| |ACK | |--------------------->| |BYE | TB---->|--------------------->| /\ |BYE | || |--------------------->| SCD |BYE | || |--------------------->| \/ | | TS---->|***Timer F Expires | 3.4. Average Hops per INVITE (AHI) This metric is used to indicate potential inefficient routing and to detect failure occurrences related to the number of elements traversed by a single SIP INVITE. AHI is defined as the number of hops traversed by an INVITE. It is calculated as an average. This metric requires the Max-Forwards value to be captured at both the originating UAC or proxy and the terminating UAS or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is measured in a numerical value indicating a number of hops. Variables = a = Initial INVITE "Max-Forwards" value b = Initial INVITE received by terminating UAS "Max-Forwards" value c = # of Hops for INVITE requests d = SUM # of INVITE requests Malas Expires February 16, 2007 [Page 10] Internet-Draft SIP End-to-End Performance Metrics August 2006 c = a - b This metric is calculated as an average. The following represents the calculation for this metric: AHI = (SUM of aggregate c's / d) The following dialog provides an example describing the inputs necessary for this calculation (The dialog continuation was omitted for clarity): UA1 Proxy 1 Proxy 2 UA2 | | | | |INVITE | | | |--------------->| | | | 407| | | |<---------------| | | |ACK | | | |--------------->| | | |INVITE (F4) | | | |--------------->|INVITE (F5) | | | 100|--------------->|INVITE (F6) | |<---------------| 100|--------------->| | |<---------------| | Message Details (Only the message details of the INVITE messages have been included for clarity. Also, some headers after Max-Forwards have been omitted for additional clarity.): (F4) INVITE UA1 -> Proxy 1 INVITE sip:ua2@biloxi.example.com SIP/2.0 Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 Route: From: UA1 ;tag=9fxced76sl To: UA2 (F5) INVITE Proxy 1 -> Proxy 2 INVITE sip:ua2@biloxi.example.com SIP/2.0 Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1 Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Max-Forwards: 69 Record-Route: Malas Expires February 16, 2007 [Page 11] Internet-Draft SIP End-to-End Performance Metrics August 2006 From: UA1 ;tag=9fxced76sl To: UA2 (F6) INVITE Proxy 2 -> UA2 INVITE sip:ua2@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/TCP ss2.biloxi.example.com:5060;branch=z9hG4bK721e4.1 Via: SIP/2.0/TCP ss1.atlanta.example.com:5060;branch=z9hG4bK2d4790.1 ;received=192.0.2.111 Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Max-Forwards: 68 Record-Route: , From: UA1 ;tag=9fxced76sl To: UA2 3.5. Session Duration Time (SDT) This metric is used to detect problems (e.g. poor audio quality) causing short session durations. SDT is measured for both successful and failed session completions. This metric is also known as Call Hold Time, and is traditionally calculated as Average Call Hold Time (ACHT) in telephony applications of SIP. This metric is measured from the originating UAC or proxy perspective as relative to the end- to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate minutes and seconds. The following represents the calculation for this metric: SDT = Time of BYE or Timeout - Time of 200 OK response to INVITE This metric is commonly calculated as an average. The following represents the calculation for this metric as an average: SUM (Time of BYE or Timeout - Time of 200 OK response to INVITE) ASDT = -------------------------------------------------------------- SUM # of INVITE w/ 200OK & BYE or Timeout 3.5.1. Successful session completion SDT In a successful session completion, SDT is calculated as an average and is defined as the duration of a dialog from receipt of a 200 OK response to an INVITE and an associated BYE message indicating dialog completion. Malas Expires February 16, 2007 [Page 12] Internet-Draft SIP End-to-End Performance Metrics August 2006 The following flow provides an example of identifiable events necessary for inputs in calculating SDT during a successful session completion: UA1 UA2 | | |INVITE | |--------------------->| | 180| |<---------------------| | 200| TB---->|<---------------------| /\ |ACK | || |--------------------->| || | | SDT | | || | | || | | \/ |BYE | TS---->|--------------------->| | | 3.5.2. Failed session completion SDT In some cases, no response is received after a session completion message is sent and potentially retried. In this case, SDT is defined as the interval between sending a session completion message, such as a BYE, and the resulting Timer F expiration. The following flow provides an example of identifiable events necessary for inputs in calculating SDT during a failed session completion attempt: UA1 UA2 | | |INVITE | |--------------------->| | 180| |<---------------------| | 200| TB---->|<---------------------| /\ |BYE | || |--------------------->| || |BYE | SDT |--------------------->| || |BYE | || |--------------------->| \/ | | TS---->|***Timer F Expires | Malas Expires February 16, 2007 [Page 13] Internet-Draft SIP End-to-End Performance Metrics August 2006 3.6. Session Establishment Rate (SER) This metric is used to detect the ability of a terminating UA to successfully establish sessions per INVITE request. SER is defined as the number of INVITE requests resulting in a 200 OK response, to the total number of attempted INVITE requests. This metric is also known as Answer Seizure Rate (ASR) in telephony applications of SIP. The input variables for this metric are captured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate a percentage (likely a fractional percentage) of successfully established sessions. The following represents the calculation for this metric: # of INVITE Requests w/ associated 200OK SER = ---------------------------------------- Total # of INVITE Requests The following flow provides an example of identifiable events necessary for inputs in determining session establishment as described above: UA1 UA2 | | |INVITE | +----------->|------------------>| | | 180| | |<------------------| Session Established | | | | | | | 200| +----------->|<------------------| | | 3.7. Session Defects (SD) Session defects provide a subset of SIP failure responses, which consistently indicate a failure in dialog processing. Defects are necessary to provide input to calculations such as Defects per Million (DPM) or other similar metrics. These failure responses are in response to initial session setup requests, such as a new INVITE. The input variables for this metric are captured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate a percentage (likely a fractional percentage) of defective sessions. The following failure responses provide a guideline for defective criterion: Malas Expires February 16, 2007 [Page 14] Internet-Draft SIP End-to-End Performance Metrics August 2006 . 500 Server Internal Error . 503 Service Unavailable . 504 Server Timeout This set of failure responses was derived through correlating more granular ISUP failure responses as described in RFC 3398. 3.8. Ineffective Session Attempts (ISA) Ineffective session attempts occur when a proxy or agent internally releases a setup request with a failed or congested condition. This metric is also known as Ineffective Machine Attempts (IMA) in telephony applications of SIP, and was adopted from Telcordia GR-512- CORE [7]. The input variables for this metric are captured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate a percentage (likely a fractional percentage) of ineffective session attempts. The following failure responses provide a guideline for this criterion: . 408 Request Timeout . 500 Server Internal Error . 503 Service Unavailable . 504 Server Timeout This set was derived in a similar manner as described in Section 3.6, in addition 408 failure responses is indicative a congested state with a downstream element. This metric is calculated as a percentage of total session setup requests. The following represents the calculation for this metric: # of ISA ISA % = ----------------------------- Total # of Session Requests 3.9. Session Disconnect Failures (SDF) Session disconnect failures occur when an active session is terminated due to a failure condition that can be identified by a REASON header [5] in a BYE message. This occurs, for example, when a user agent (UA) is controlling an IP or TDM (Time Division Multiplexing) media gateway, and the media gateway notifies the UA of a failure condition causing the loss of media related to an Malas Expires February 16, 2007 [Page 15] Internet-Draft SIP End-to-End Performance Metrics August 2006 established session. The UA will release the session with a BYE, but should include a REASON header indicating the session was disconnected abnormally. The REASON value is utilized to determine the disconnect was a failure. This metric is also known as Cutoff Calls (CC) in telephony applications of SIP, and was adopted from Telcordia GR-512-CORE [7]. The input variables for this metric are captured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate a percentage (likely a fractional percentage) of session disconnect failures. This metric is calculated as a percentage of total session completed successfully as defined in Section 3.5. The following represents the calculation for this metric: # of SDF's SDF % = ------------------------------- Total # of Session Requests 3.10. Session Completion Rate (SCR) A session completion is defined as a SIP dialog, which completes without failing due to a lack of response from an intended proxy or UA. A session completes successfully when it begins with a setup request and ends with a session completion message. This metric is only used when at least one proxy is involved in the dialog. This metric is also known as Call Completion Rate (CCR) in telephony applications of SIP. The input variables for this metric are captured from the originating UAC or proxy perspective as relative to the end-to-end network under measurement. The output value of this metric is numerical and should be adjusted to indicate a percentage (likely a fractional percentage) of successfully completed sessions. The following dialog [4] provides an example describing the necessary events of a successful session completion: UA1 Proxy 1 Proxy 2 UA2 | | | | |INVITE | | | |--------------->| | | | 407| | | |<---------------| | | |ACK | | | |--------------->| | | |INVITE | | | |--------------->|INVITE | | | 100|--------------->|INVITE | |<---------------| 100|--------------->| Malas Expires February 16, 2007 [Page 16] Internet-Draft SIP End-to-End Performance Metrics August 2006 | |<---------------| | | | | 180| | | 180 |<---------------| | 180|<---------------| | |<---------------| | 200| | | 200|<---------------| | 200|<---------------| | |<---------------| | | |ACK | | | |--------------->|ACK | | | |--------------->|ACK | | | |--------------->| | Both Way RTP Media | |<================================================>| | | | BYE| | | BYE|<---------------| | BYE|<---------------| | |<---------------| | | |200 | | | |--------------->|200 | | | |--------------->|200 | | | |--------------->| | | | | The following dialog provides an example describing the necessary events of an unsuccessful session completion: UA1 Proxy 1 Proxy 2 UA2 | | | | |INVITE | | | |--------------->| | | | 407| | | |<---------------| | | |ACK | | | |--------------->| | | |INVITE | | | |--------------->|INVITE | | | 100|--------------->|INVITE | |<---------------| 100|--------------->| | |<---------------| | | | |INVITE | | | |--------------->| | | | | | | |INVITE | | | |--------------->| | | | | | | 408| | | 408|<---------------| | Malas Expires February 16, 2007 [Page 17] Internet-Draft SIP End-to-End Performance Metrics August 2006 |<---------------|ACK | | | |--------------->| | |ACK | | | |--------------->| | | This metric is calculated as a percentage of total sessions completed successfully. The following represents the calculation for this metric: # of Successfully Completed Sessions SCR % = --------------------------------------- Total # of Session Requests 3.11. Session Success Rate (SSR) Session success rate is defined as the percentage of successfully completed sessions compared to sessions, which fail due to ISA or SDF. This metric is also known as Call Success Rate (CSR) in telephony applications of SIP. The output value of this metric is numerical and should be adjusted to indicate a percentage of successful sessions. The following represents the calculation for this metric: SSR = 100% - (ISA% + SDF%) 4. Metric Correlations These metrics may be used to determine the performance of a domain and/or user. This would be to provide a metric relative to one or more dimensions. The following is a subset of dimensions for providing further granularity per metric: . To "user" . From "user" . Bi-direction "user" . To "domain" . From "domain" . Bi-direction "domain" Example: The SCR of SIP domain A is 99.97%. Malas Expires February 16, 2007 [Page 18] Internet-Draft SIP End-to-End Performance Metrics August 2006 5. Additional Considerations 5.1. Back-to-back User Agent (B2BUA) Considerations A B2BUA may impact the ability to collect these metrics with an end- to-end perspective. It is necessary to realize a B2BUA may act as an originating UAC and terminating UAS or it may act as a proxy. In some cases, it may be necessary to consider information collected from both sides of the B2BUA in order to determine the end-to-end perspective. In other cases, the B2BUA may act simply as a proxy allowing data to be derived as necessary for the input into any of the listed calculations. 5.2. Data Collection Considerations The input necessary for these calculations may be collected in a number of different manners. It may be collected or retrieved from call detail records (CDR) or raw signaling information generated by a proxy or UA. When using records, time synchronization must be considered between applicable elements. The information may also be transmitted through use of SNMP traps as described in the work in progress SIP MIB draft [6], or through a potential undefined new performance metric event package [3] retrieved via SUBSCRIBE requests. Data may be collected for a sample of calls or all calls, and may also be derived from test call scenarios. These metrics are flexible based on the needs of the application. 5.3. Testing Documentation In some cases, these metrics will be used to provide output values to signify the performance level of a specific SIP-based element. When using these metrics in a test environment, the environment must be accurately documented for the purposes of replicating any output values in future testing and/or validation. 6. Security Considerations Security should be considered in the aspect of securing the relative data utilized in providing input to the above calculations. All other aspects of security should be considered as described in [2]. 7. IANA Considerations There are no IANA considerations at this time. Malas Expires February 16, 2007 [Page 19] Internet-Draft SIP End-to-End Performance Metrics August 2006 8. Conclusions The proposed guideline provides a description of common performance metrics, and their defined use with SIP. The use of these metrics will provide a common viewpoint across all vendors, service providers, and customers. These metrics will likely be utilized in production SIP environments for providing input regarding Key Performance Indicators (KPI) and Service Level Agreement (SLA) indications; however, they may also be used for testing end-to-end SIP-based service environments. 9. Acknowledgments I would like to thank John Hearty for his efforts in scrubbing through the draft and providing insight regarding clarification of certain aspects described throughout the document. 10. References 10.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [3] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [4] Johnston, A., Donovan, S., Sparks, R., Cunningham, C., and K. Summers, "Session Initiation Protocol (SIP) Basic Call Flow Examples", BCP 75, RFC 3665, December 2003. [5] Schulzrinne, H., Oran, D., Camarillo, G., "The Reason Header Field for the Sessions Initiation Protocol (SIP)", RFC 3326, December 2002. [6] Lingle, K., Mule, J., Maeng, J., Walker, D., "Management Information Base for the Session Initiation Protocol (SIP)", draft-ietf-sip-mib-10, Work in Progress. [7] Telcordia, "LSSGR: Reliability, Section 12", GR-512-CORE, Issue 2, January 1998. Malas Expires February 16, 2007 [Page 20] Internet-Draft SIP End-to-End Performance Metrics August 2006 10.2. Informative References Author's Addresses Daryl Malas Level 3 Communications LLC 1025 Eldorado Blvd. Broomfield, CO 80021 USA EMail: daryl.malas@level3.com Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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