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rfc:rfc3133

Network Working Group J. Dunn Request for Comments: 3133 C. Martin Category: Informational ANC, Inc.

                                                             June 2001
              Terminology for Frame Relay Benchmarking

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 This memo discusses and defines terms associated with performance
 benchmarking tests and the results of these tests in the context of
 frame relay switching devices.

I. Background

1. Introduction

 This document provides terminology for Frame Relay switching devices.
 It extends terminology already defined for benchmarking network
 interconnect devices in RFCs 1242, 1944 and 2285.  Although some of
 the definitions in this memo may be applicable to a broader group of
 network interconnect devices, the primary focus of the terminology in
 this memo is on Frame Relay Signaling.
 This memo contains two major sections: Background and Definitions.
 The background section provides the reader with an overview of the
 technology and IETF formalisms.  The definitions section is split
 into two sub-sections.  The formal definitions sub-section is
 provided as a courtesy to the reader.  The measurement definitions
 sub-section contains performance metrics with inherent units.
 The BMWG produces two major classes of documents: Benchmarking
 Terminology documents and Benchmarking Methodology documents.  The
 Terminology documents present the benchmarks and other related terms.
 The Methodology documents define the procedures required to collect
 the benchmarks cited in the corresponding Terminology documents.

Dunn & Martin Informational [Page 1] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

 For the purposes of computing several of the metrics, certain textual
 conventions are required.  Specifically:
 1) The notation sum {i=1 to N} A_i denotes: the summation of N
 instances of the observable A.  For example, the set of observations
 {1,2,3,4,5} would yield the result 15.
 2) The notation max {I=1 to N} A_i and min {I=1 to N} A_i denotes:
 the maximum or minimum of the observable A over N instances.  For
 example, given the set of observations {1,2,3,4,5}, max {i=1 to 5} =
 5 and min {I=1 to 5} = 1.
 The terms defined in this memo will be used in addition to terms
 defined in RFCs 1242, 1944 and 2285.  This memo is a product of the
 Benchmarking Methodology Working Group (BMWG) of the Internet
 Engineering Task Force(IETF).

2. Existing Definitions

 RFC 1242, "Benchmarking Terminology for Network Interconnect
 Devices", should be consulted before attempting to make use of this
 document.  RFC 1944, "Benchmarking Methodology for Network
 Interconnect Devices", contains discussions of a number of terms
 relevant to the benchmarking of switching devices and should also be
 consulted.  RFC 2285, "Benchmarking Terminology for LAN Switching
 Devices", contains a number of terms pertaining to traffic
 distributions and datagram interarrival.  For the sake of clarity and
 continuity this RFC adopts the template for definitions set out in
 Section 2 of RFC 1242.

II. Definitions

 The definitions presented in this section have been divided into two
 groups.  The first group is formal definitions, which are required in
 the definitions of the performance metrics but are not themselves
 strictly metrics.  These definitions are subsumed from other work
 done in other working groups both inside and outside the IETF.  They
 are provided as a courtesy to the reader.

Dunn & Martin Informational [Page 2] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

1. Formal Definitions

1.1. Definition Format (from RFC1242)

 Term to be defined.
 Definition: The specific definition for the term.
 Discussion: A brief discussion of the term, its application and any
 restrictions on measurement procedures.
 Specification:  The working group and document in which the term is
 specified.  Listed in the references.

1.2. Frame Relay Related Definitions

1.2.1. Access Channel

 Definition: Access channel refers to the user access channel across
 which frame relay data travels.  Within a given DS-3, T1 or E1
 physical line, a channel can be one of the following, depending of
 how the line is configured.  Possible line configurations are:
 A. Unchannelized: The entire DS-3/T1/E1 line is considered a channel,
 where:
 The DS-3 line operates at speeds of 45 Mbps and is a single channel.
 The T1 line operates at speeds of 1.536 Mbps and is a single channel
 consisting of 24 T1 time slots.  The E1 line operates at speeds of
 1.984 Mbps and is a single channel consisting of 30 DS0 time slots.
 B. Channelized: The channel is any one of N time slots within a given
 line, where:
 The T1 line consists of any one or more channels.  Each channel is
 any one of 24 time slots.  The T1 line operates at speeds in
 multiples of 56/64 Kbps to 1.536 Mbps, with aggregate speed not
 exceeding 1.536 Mbps.  The E1 line consists of one or more channels.
 Each channel is any one of 31 time slots.  The E1 line operates at
 speeds in multiples of 64 Kbps to 1.984 Mbps, with aggregate speed
 not exceeding 1.984 Mbps.
 C. Fractional: The T1/E1 channel is one of the following groupings of
 consecutively or non-consecutively assigned time slots:
 N DS0 time slots (NX56/64Kbps where N = 1 to 24 DS0 time slots per
 FT1 channel).

Dunn & Martin Informational [Page 3] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

 N E1 time slots (NX64Kbps, where N = 1 to 30 DS0 time slots per E1
 channel).
 Discussion: Access channels specify the physical layer interface
 speed of a DTE or DCE.  In the case of a DTE, this may not correspond
 to either the CIR or EIR.  Specifically, based on the service level
 agreement in place, the user may not be able to access the entire
 bandwidth of the access channel.
 Specification: FRF

1.2.2. Access Rate (AR)

 Definition: The data rate of the user access channel.  The speed of
 the access channel determines how rapidly (maximum rate) the end user
 can inject data into a frame relay network.
 Discussion: See Access Channel.
 Specification: FRF

1.2.3. Backward Explicit Congestion Notification (BECN)

 Definition: BECN is a bit in the frame relay header.  The bit is set
 by a congested network node in any frame that is traveling in the
 reverse direction of the congestion.
 Discussion: When a DTE receives frames with the BECN bit asserted, it
 should begin congestion avoidance procedures.  Since the BECN frames
 are traveling in the opposite direction as the congested traffic, the
 DTE will be the sender.  The frame relay layer may communicate the
 possibility of congestion to higher layers, which have inherent
 congestion avoidance procedures, such as TCP.  See Frame Relay Frame.
 Specification: FRF

1.2.4. Burst Excess(Be)

 Definition: The maximum amount of uncommitted data (in bits) in
 excess of Committed Burst Size (Bc) that a frame relay network can
 attempt to deliver during a Committed Rate Measurement Interval (Tc).
 This data (Be) generally is delivered with a lower probability than
 Bc.  The network treats Be data as discard eligible.
 Discussion: See also Committed burst Size (Bc), Committed Rate
 Measurement Interval (Tc) and Discard Eligible (De).
 Specification: FRF

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1.2.5. Committed Burst Size (Bc)

 Definition: The maximum amount of data (in bits) that the network
 agrees to transfer, under normal conditions, during a time interval
 Tc.
 Discussion: See also Excess Burst Size (Be) and Committed Rate
 Measurement Interval (Tc).
 Specification: FRF

1.2.6. Committed Information Rate (CIR)

 Definition: CIR is the transport speed the frame relay network will
 maintain between service locations when data is presented.
 Discussion: CIR specifies the guaranteed data rate between two frame
 relay terminal connected by a frame relay network.  Data presented to
 the network in excess of this data rate and below the Excess
 Information Rate (EIR) will be marked as Discard Eligible and may be
 dropped.
 Specification: FRF

1.2.7. Committed Rate Measurement Interval (Tc)

 Definition: The time interval during which the user can send only
 Bc-committed amount of data and Be excess amount of data.  In
 general, the duration of Tc is proportional to the "burstiness" of
 the traffic.  Tc is computed (from the subscription parameters of CIR
 and Bc) as Tc = Bc/CIR.  Tc is not a periodic time interval.
 Instead, it is used only to measure incoming data, during which it
 acts like a sliding window.  Incoming data triggers the Tc interval,
 which continues until it completes its computed duration.
 Discussion: See also Committed Information Rate (CIR) and committed
 Burst Size (Bc).
 Specification: FRF

1.2.8. Cyclic Redundancy Check (CRC)

 Definition: A computational means to ensure the accuracy of frames
 transmitted between devices in a frame relay network.  The
 mathematical function is computed, before the frame is transmitted,

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 at the originating device.  Its numerical value is computed based on
 the content of the frame.  This value is compared with a recomputed
 value of the function at the destination device.  See also Frame
 Check Sequence (FCS).
 Discussion: CRC is not a measurement, but it is possible to measure
 the amount of time to perform a CRC on a string of bits.  This
 measurement will not be addressed in this document.
 Specification: FRF

1.2.9. Data Communications Equipment (DCE)

 Definition: Term defined by both frame relay and X.25 committees,
 that applies to switching equipment and is distinguished from the
 devices that attach to the network (DTE).
 Discussion: Also see DTE.
 Specification: FRF

1.2.10. Data Link Connection Identifier (DLCI)

 Definition: A unique number assigned to a PVC end point in a frame
 relay network.  Identifies a particular PVC endpoint within a user's
 access channel in a frame relay network and has local significance
 only to that channel.
 Discussion: None.
 Specification: FRF

1.2.11. Data Terminal Equipment (DTE)

 Definition: Any network equipment terminating a network connection
 and is attached to the network.  This is distinguished from Data
 Communications Equipment (DCE), which provides switching and
 connectivity within the network.
 Discussion: See also DCE.
 Specification: FRF

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1.2.12. Discard Eligible (DE)

 Definition: This is a bit in the frame relay header that provides a
 two level priority indicator, used to bias discard frames in the
 event of congestion toward lower priority frames.  Similar to the CLP
 bit in ATM.
 Discussion: See Frame Relay Frame.
 Specification: FRF

1.2.13. Discardable frames

 Definition: Frames identified as being eligible to be dropped in the
 event of congestion.
 Discussion: The discard eligible field in the frame relay header is
 the correct -- and by far the most common -- means of indicating
 which frames may be dropped in the event of congestion.  However, DE
 is not the only means of identifying which frames may be dropped.
 There are at least three other cases that apply.
 In the first case, network devices may prioritize frame relay traffic
 by non-DE means.  For example, many service providers prioritize
 traffic on a per-PVC basis.  In this instance, any traffic from a
 given DLCI (data link channel identifier) may be dropped during
 congestion, regardless of whether DE is set.
 In the second case, some implementations use upper-layer criteria,
 such as IP addresses or TCP or UDP port numbers, to prioritize
 traffic within a single PVC.  In this instance, the network device
 may evaluate discard eligibility based on upper-layer criteria rather
 than the presence or absence of a DE bit.
 In the third case, the frame is discarded because of an error in the
 frame.  Specifically, frames that are too long or too short, frames
 that are not a multiple of 8 bits in length, frames with an invalid
 or unrecognized DLCI, frames with an abort sequence, frames with
 improper flag delimitation, and frames that fail FCS.
 Specification: FRMIB

1.2.14. Discarded frames

 Definition: Those frames dropped by a network device.

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 Discussion: Discardable and discarded frames are not synonymous.
 Some implementations may ignore DE bits or other criteria, even
 though they supposedly use such criteria to determine which frames to
 drop in the event of congestion.
 In other cases, a frame with its DE bit set may not be dropped.  One
 example of this is in cases where congestion clears before the frame
 can be evaluated.
 Specification: DN

1.2.15. Forward Explicit Congestion Notification (FECN)

 Definition:  FECN is a bit in the frame relay header.  The bit is set
 by a congested network node in any frame that is traveling in the
 same direction of the congestion.
 Discussion: When a DTE receives frames with the FECN bit asserted, it
 should begin congestion avoidance procedures.  Since the FECN frames
 are traveling in the same direction as the congested traffic, the DTE
 will be the receiver.  The frame relay layer may communicate the
 possibility of congestion to higher layers, which have inherent
 congestion avoidance procedures, such as TCP.  See Frame Relay Frame.
 Specification: FRF

1.2.16. Frame Check Sequence (FCS)

 Definition: The standard 16-bit cyclic redundancy check used for HDLC
 and frame relay frames.  The FCS detects bit errors occurring in the
 bits of the frame between the opening flag and the FCS, and is only
 effective in detecting errors in frames no larger than 4096 octets.
 See also Cyclic Redundancy Check (CRC).
 Discussion: FCS is not a measurement, but it is possible to measure
 the amount of time to perform a FCS on a string of bits.  This
 measurement will not be addressed in this document.
 Specification: FRF

1.2.17. Frame Entry Event

 Definition: Frame enters a network section or end system.  The event
 occurs when the last bit of the closing flag of the frame crosses the
 boundary.
 Discussion: None.

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 Specification: FRF.13

1.2.18. Frame Exit Event

 Definition: Frame exits a network section or end system.  The event
 occurs when the first bit of the address field of the frame crosses
 the boundary.
 Discussion: None.
 Specification: FRF.13

1.2.19. Frame Relay

 Definition:  A high-performance interface for packet-switching
 networks; considered more efficient that X.25.  Frame relay
 technology can handle "bursty" communications that have rapidly
 changing bandwidth requirements.
 Discussion: None.
 Specification: FRF

1.2.20. Frame Relay Frame

 Definition: A logical grouping of information sent as a link-layer
 unit over a transmission medium.  Frame relay frames consist of a
 pair of flags, a header, a user data payload and a Frame Check
 Sequence (FCS).  Bit stuffing differentiates user data bytes from
 flags.  By default, the header is two octets, of which 10 bits are
 the Data Link Connection Identifier (DLCI), 1 bit in each octet is
 used for address extension (AE), and 1 bit each for Forward Explicit
 Congestion Notification (FECN), Backward Explicit Congestion
 Notification (BECN) Command/Response (C/R) and Discard Eligible (DE).
 The EA bit is set to one in the final octet containing the DLCI.  A
 header may span 2, 3 or 4 octets.

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 Bit  7   6   5   4   3   2   1   0
    |---|---|---|---|---|---|---|---|
    |              FLAG             |
    |-------------------------------|
    | Upper 6 bits of DLCI  |C/R|AE |
    |-------------------------------|
    |   DLCI        |FE |BE |DE |AE |
    |               |CN |CN |   |   |
    |-------------------------------|
    |        User Data up to        |
    |          1600 Octets          |
    |-------------------------------|
    |      First Octet of FCS       |
    |-------------------------------|
    |      Second Octet of FCS      |
    |-------------------------------|
    |              FLAG             |
    |-------------------------------|
 Discussion: Frame Relay headers spanning 3 or 4 octets will not be
 discussed in this document.  Note, the measurements described later
 in this document are based on 2 octet headers.  If longer headers are
 used, the metric values must take into account the associated
 overhead.  See BECN, DE, DLCI and FECN.
 Specification: FRF

1.2.21. Excess Information Rate (EIR)

 Definition: See Burst Excess.
 Discussion: None.
 Specification: FRF

1.2.22. Network Interworking (FRF.5)

 Definition: FRF.5 defines a protocol mapping called Network
 Interworking between
 Frame Relay and Asynchronous Transfer Mode (ATM).  Protocol mapping
 occurs when the network performs conversions in such a way that
 within a common layer service, the protocol information of one
 protocol is extracted and mapped on protocol information of another
 protocol.  This means that each communication terminal supports
 different protocols.  The common layer service provided in this

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 interworking scenario is defined by the functions, which are common
 to the two protocols.  Specifically, the ATM terminal must be
 configured to interoperate with the Frame Relay network and vice
 versa.
 Discussion: None.
 Specification: FRF.5

1.2.23. Port speed

 Definition: See Access Rate
 Discussion: None.
 Specification: FRF

1.2.24. Service Interworking (FRF.8)

 Definition: FRF.8 defines a protocol encapsulation called Service
 Interworking.  Protocol encapsulation occurs when the conversions in
 the network or in the terminals are such that the protocols used to
 provide one service make use of the layer service provided by another
 protocol.  This means that at the interworking point, the two
 protocols are stacked.  When encapsulation is performed by the
 terminal, this scenario is also called interworking by port access.
 Specifically, the ATM service user performs no Frame Relaying
 specific functions, and Frame Relaying service user performs no ATM
 service specific functions.
 Discussion: None.
 Specification: FRF.8

1.2.25. Service Availability Parameters

 Definition: The service availability parameters report the
 operational readiness of individual frame relay virtual connections.
 Service availability is affected by service outages.
 Discussion: Service availability parameters provide metrics for
 assessment of frame relay network health and are used to monitor
 compliance with service level agreements.  See Services Outages.
 Specification: FRF.13

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1.2.26. Service Outages

 Definition: Any event that interrupts the transport of frame relay
 traffic.  Two types of outages are differentiated:
 1) Fault outages: Outages resulting from faults in the network and
 thus tracked by the service availability parameters, and
 2) Excluded outages: Outages resulting from faults beyond the control
 of the network as well as scheduled maintenance.
 Discussion: Service availability can be defined on a per-VC basis
 and/or on a per-port basis.  Frame relay port-based service
 availability parameters are not addressed in this document.  See
 Service Availability Parameters.
 Specification: FRF.13

2. Performance Metrics

2.1. Definition Format (from RFC1242)

 Metric to be defined.
 Definition: The specific definition for the metric.
 Discussion:  A brief discussion of the metric, its application and
 any restrictions on measurement procedures.
 Measurement units: Intrinsic units used to quantify this metric.
 This includes  subsidiary units, e.g., microseconds are acceptable if
 the intrinsic unit is seconds.

2.2. Definitions

2.2.1. Physical Layer-Plesiochronous Data Hierarchy (PDH)

2.2.1.1. Alarm Indication Signal (AIS)

 Definition: An all 1's frame transmitted after the DTE or DCE detects
 a defect for 2.5 s +/- 0.5 s.
 Discussion: An AIS will cause loss of information in the PDH frame,
 which contains a frame relay frame which may contain IP datagrams.
 Measurement units: Dimensionless.

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2.2.1.2. Loss of Frame (LOF)

 Definition: An NE transmits an LOF when an OOF condition persists.
 Discussion: A LOF will cause loss of information in the PDH frame,
 which contains a frame relay frame which may contain IP datagrams.
 Measurement units: Dimensionless.

2.2.1.3. Loss of Signal (LOS)

 Definition: Indicates that there are no transitions occurring in the
 received signal.
 Discussion: A LOS will cause loss of information in the PDH frame
 which contains a frame relay frame which may contain IP datagrams.
 Measurement units: Dimensionless.

2.2.1.4. Out of Frame (OOF)

 Definition: An NE transmits an OOF downstream when it receives
 framing errors in a specified number of consecutive frame bit
 positions.
 Discussion: An OOF will cause loss of information in the PDH frame
 which contains a frame relay frame which may contain IP datagrams.
 Measurement units: Dimensionless.

2.2.1.5. Remote Alarm Indication (RAI)

 Definition: Previously called Yellow Alarm.  Transmitted upstream by
 an NE to indicate that it detected an LOS, LOF, or AIS.
 Discussion: An RAI will cause loss of information in the transmitted
 PDH frame, which may contain a frame relay frame, which, in turn, may
 contain IP datagrams.
 Measurement units: Dimensionless.

2.2.2. Frame Relay Layer

2.2.2.1. Data Delivery Ratio (DDR)

 Definition: The DDR service level parameter  reports  the  networks
 effectiveness in transporting offered data (payload without address
 field or FCS) in one direction of a single virtual connection.  The

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 DDR is a ratio of  successful  payload octets received to attempted
 payload octets transmitted.  Attempted payload octets transmitted are
 referred to as DataOffered.  Successfully delivered payload octets
 are referred to as DataDelivered.  These loads are further
 differentiated as being within the committed information rate or as
 burst excess.
 Three data relay ratios may be reported:
 Data Delivery Ratio (DDR):
        (DataDelivered_c + DataDelivered_e   DataDelivered_e+c
   DDR = --------------------------------- = -----------------
        (DataOffered_c + DataOffered_e)    DataOffered_e+c
 Data Delivery Ratio (DDR_c) for load consisting of frames within the
 committed information rate:
           DataDelivered_c
   DDR_c = -------------
           DataOffered_c
 Data Delivery Ratio (DDR_e) for load in excess of the committed
 information rate:
           DataDelivered_e
   DDR_e = ---------------
           DataOffered_e
 where
 DataDelivered_c: Successfully delivered data payload octets within
 committed information rate,
 DataDelivered_e: Successfully delivered data payload octets in excess
 of CIR,
 DataDelivereD_e+c: Successfully delivered total data payload octets,
 including those within committed information rate and those in excess
 of CIR,
 DataOffered_c: Attempted data payload octet transmissions within
 committed information rate,
 DataOffered_e: Attempted data payload octet transmissions in excess
 of CIR
 and

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 DataOffered_e+c: Attempted total data payload octet transmissions,
 including those within committed information rate and those in excess
 of CIR
 Each direction of a full duplex connection has a discrete set of data
 delivery ratios.
 Discussion: Data delivery ratio measurements may not be
 representative of data delivery effectiveness for a given
 application.  For example, the discarding of a small frame containing
 an acknowledgement message may result in the retransmission of a
 large number of data frames.  In such an event, a good data delivery
 ratio would be reported while the user experienced poor performance.
 Measurement units: dimensionless.

2.2.2.2. Frame Delivery Ratio (FDR)

 Definition: The FDR service level parameter reports the networks
 effectiveness in transporting an offered frame relay load in one
 direction of a single virtual connection.  The FDR is a ratio of
 successful frame receptions to attempted frame transmissions.
 Attempted frame transmissions are referred to as Frames Offered.
 Successfully delivered frames are referred to as Frames Delivered.
 These loads may be further differentiated as being within the
 committed information rate or as burst excess.
 Frame Delivery Ratio (FDR):
 Frame Delivery Ratio (FDR):
        (FramesDelivered_c + FramesDelivered_e)  FramesDelivered_e+c
   FDR = ------------------------------------- = -------------------
        (FramesOffered_c + FramesOffered_e)   FramesOffered_e+c
 Frame Delivery Ratio (FDR_c) for load consisting of frames within the
 committed information rate:
           FramesDelivered_c
   FDR_c = -----------------
           FramesOffered_c
 Frame Delivery Ratio (FDR_c) for load in excess of the committed
 information rate:
           FramesDelivered_e
   FDR_e = -----------------
           FramesOffered_e

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 where
 FramesDelivered_c: Successfully delivered frames within committed
 information rate,
 FramesDelivered_e: Successfully delivered frames in excess of CIR,
 FramesDelivered_e+c: Successfully delivered total frames, including
 those within committed information rate and those in excess of CIR,
 FramesOffered_c: Attempted frame transmissions within committed
 information rate,
 FramesOffered_e: Attempted frame transmissions in excess of CIR
 and
 FramesOffered_e+c: Attempted total frame transmissions, including
 those within committed information rate and those in excess of CIR.
 An independent set of frame delivery ratios exists for each direction
 of a full duplex connection.
 Discussion: Frame delivery ratio measurements may not be
 representative of frame delivery effectiveness for a given
 application.  For example, the discarding of a small frame containing
 an acknowledgement message may result in the retransmission of a
 large number of data frames.  In such an event, a good data delivery
 ratio would be reported while the user
 Measurement units: dimensionless.

2.2.2.3. Frame Discard Ratio (FDR)

 Definition: The number of received frames that are discarded because
 of a frame error divided by the total number of transmitted frames in
 one direction of a single virtual connection.  Frame errors are
 defined as follows:
 1) frames that are too long or too short,
 2) frames that are not a multiple of 8 bits in length,
 3) frames with an invalid or unrecognized DLCI,
 4) frames with an abort sequence,
 5) frames with improper flag delimitation,
 6) frames that fail FCS.

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 The formal definition of frame discard ratio is as follows:
         sum {i=1 to N} fr_i
   FDR = -------------------
         sum {i=1 to N} ft_i,
 where
 fr_i is the number of successfully delivered frames for a particular
 DLCI at second i
 and
 ft_i is the total number of attempted frame transmissions within the
 committed plus extended information rate for a particular DLCI at
 second i.
 Discussion: Frame discards can adversely effect applications running
 on IP over FR.  In general, frame discards will negatively impact TCP
 throughput; however, in the case of frame discard due to frame error,
 frame discard will improve performance by dropping errored frames.
 As a result, these frames will not adversely effect the forwarding of
 retransmitted frames
 Measurement units: dimensionless.

2.2.2.4. Frame Error Ratio (FER)

 Definition: The number of received frames that contain an error in
 the frame payload divided by the total number of transmitted frames
 in one direction of a single virtual connection.
 The formal definition of frame error ratio is as follows:
         sum {i=1 to N} fe_i
   FER = -------------------
         sum {i=1 to N} ft_i,
 where
 fe_i is the number of frames containing a payload error for a
 particular DLCI at second i
 and
 ft_i is the total number of attempted frame transmissions within the
 committed plus the extended information rate for a particular DLCI at
 second i.  This statistic includes those frames which have an error

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 in the Frame Check Sequence (FCS).  Frame errors in the absence of
 FCS errors can be detected by sending frames containing a known
 pattern; however, this indicates an equipment defect.
 Discussion: The delivery of frames containing errors will adversely
 effect applications running on IP over FR.  Typically, these errors
 are caused by transmission errors and flagged as failed FCS frames;
 however, when Frame Relay to ATM Network interworking is used, an
 error may be injected in the frame payload which, in turn, is
 encapsulated into an AAL5 PDU (see RFC 2761 for a discussion of AAL5
 related metrics).
 Measurement units: dimensionless.

2.2.2.5. Frame Excess Ratio (FXR)

 Definition: The number of frames received by the network and treated
 as excess traffic divided by the total number of transmitted frames
 in one direction of a single virtual connection.  Frames which are
 sent to the network with DE set to zero are treated as excess when
 more than Bc bits are submitted to the network during the Committed
 Information Rate Measurement Interval (Tc).  Excess traffic may or
 may not be discarded at the ingress if more than Bc + Be bits are
 submitted to the network during Tc.  Traffic discarded at the ingress
 is not recorded in this measurement.  Frames which are sent to the
 network with DE set to one are also treated as excess traffic.
 The formal definition of frame excess ratio is as follows:
             sum {i=1 to N} fc_i
   FXR = 1 - -------------------
             sum {i=1 to N} ft_i,
 where
 fc_i is the total number of frames which were submitted within the
 traffic contract for a particular DLCI at second i
 and
 ft_i is the total number of attempted frame transmissions for a
 particular DLCI at second i.
 Discussion: Frame discards can adversely effect applications running
 on IP over FR.  Specifically, frame discards will negatively impact
 TCP throughput.
 Measurement units: dimensionless.

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2.2.2.6. Frame Loss Ratio (FLR)

 Definition: The FLR is a ratio of successful frame receptions to
 attempted frame transmissions at the committed information rate, in
 one direction of a single virtual connection.  Attempted frame
 transmissions are referred to as Frames Offered.  Successfully
 delivered frames are referred to as Frames Delivered.
 The formal definition of frame loss ratio is as follows:
            FramesDelivered_c
   FLR = 1- -----------------
            FramesOffered_c,
 where
 FramesDelivered_c is the successfully delivered frames within
 committed information rate for a given DLCI
 and
 FramesOffered_c is the attempted frame transmissions within committed
 information rate for a given DLCI
 An independent set of frame delivery ratios exists for each direction
 of a full duplex connection.
 Discussion: Frame delivery loss measurements may not be
 representative of frame delivery effectiveness for a given
 application.  For example, the loss of a small frame containing an
 acknowledgement message may result in the retransmission of a large
 number of data frames.  In such an event, a good data delivery ratio
 would be reported while the user
 Measurement units: dimensionless.

2.2.2.7. Frame Policing Ratio (FPR)

 Definition: The number of frames received by the network and treated
 as excess traffic and dropped divided by the total number of received
 frames, in one direction of a single virtual connection.  Frames
 which are sent to the network with DE set to zero are treated as
 excess when more than Bc bits are submitted to the network during the
 Committed Information Rate Measurement Interval (Tc).  Excess traffic
 may or may not be discarded at the ingress if more than Bc + Be bits
 are submitted to the network during Tc.  Traffic discarded at the
 ingress is recorded in this measurement.  Frames which are sent to
 the network with DE set to one are also treated as excess traffic.

Dunn & Martin Informational [Page 19] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

 The formal definition of frame excess ratio is as follows:
            sum {i=1 to N} fr_i
   FPR = 1- -------------------
            sum {i=1 to N} ft_i,
 where
 fr_i is the successfully delivered frames for a particular DLCI at
 second i
 and
 ft_i is the total number of attempted frame transmissions for a
 particular DLCI
 at second i.
 Discussion: Frame discards can adversely effect applications running
 on IP over FR.  Specifically, frame discards will negatively impact
 TCP throughput.

2.2.2.8. Frame Transfer Delay (FTD)

 Definition: The time required to transport frame relay data from
 measurement point 1 to measurement point 2.  The frame transfer delay
 is the difference in seconds between the time a frame exits
 measurement point 1 and the time the same frame enters measurement
 point 2, in one direction of a single virtual connection.  The formal
 definition of frame transfer delay is as follows:
    FTD = 1/N * sum {i=1 to N} t2_i - t1_i,
 where
 t1_i is the time in seconds when the ith frame leaves measurement
 point 1 (i.e., frame exit event),
 t2 is the time in seconds when the ith frame arrives at measurement
 point 2 (i.e., frame entry event)
 and
 N is the number of frames received during a measurement interval T.
 FTD is computed for a specific DLCI and a specified integration
 period of T seconds.  The computation does not include frames which
 are transmitted during the measurement period but not received.

Dunn & Martin Informational [Page 20] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

 Discussion: While frame transfer delay is usually computed as an
 average and, thus, can effect neither IP nor TCP performance,
 applications such as voice over IP may be adversely effected by
 excessive FTD.
 Measurement units: seconds.

2.2.2.9. Frame Transfer Delay Variation (FTDV)

 Definition: The variation in the time required to transport frame
 relay data from measurement point 1 to measurement point 2.  The
 frame transfer delay variation is the difference in seconds between
 maximum frame transfer delay and the minimum frame transfer delay, in
 one direction of a single virtual connection.  The formal definition
 of frame transfer delay is as follows:
    FTDV = max {i=1 to N} FTD_i - min {i=1 to N} FTD_i.
 where
 FTD and N are defined as above.
 Discussion: Large values of FTDV can adversely effect TCP round trip
 time calculation and, thus, TCP throughput.
 Measurement units: seconds.

3. Security Considerations

 As this document is solely for providing terminology and describes
 neither a protocol nor an implementation, there are no security
 considerations associated with this document.

4. Notices

 Internet Engineering Task Force
    The IETF takes no position regarding the validity or scope of any
    intellectual property 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; neither does it represent
    that it has made any effort to identify any such rights.
    Information on the IETFs procedures with respect to rights in
    standards-track and standards-related documentation can be found
    in BCP-11.  Copies of claims of rights made available for
    publication and any assurances of licenses to be made available,
    or the result of an attempt made to obtain a general license or

Dunn & Martin Informational [Page 21] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

    permission for the use of such proprietary rights by implementors
    or users of this specification can be obtained from the IETF
    Secretariat.
    The IETF invites any interested party to bring to its attention
    any copyrights, patents or patent applications, or other
    proprietary rights, which may cover technology that may be
    required to practice this standard.  Please address the
    information to the IETF Executive Director.
 Frame Relay Forum
    Copyright Frame Relay Forum 1998.  All Rights Reserved.
    References FRF, FRF.5, FRF.8 and FRF.13 and translations of them
    may be copied and furnished to others, and works that comment on
    or otherwise explain it or assist in their implementation may be
    prepared, copied, published and distributed, in whole or in part,
    without restriction of any kind, provided that the above copyright
    notice and this paragraph are included on all such copies and
    derivative works.  However, these documents themselves may not be
    modified in any way, such as by removing the copyright notice or
    references to the Frame Relay Forum, except as needed for the
    purpose of developing Frame Relay standards (in which case the
    procedures for copyrights defined by the Frame Relay Forum must be
    followed), or as required to translate it into languages other
    than English.

Dunn & Martin Informational [Page 22] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

5. References

 [DN]     Private communication from David Newman, Network Test, Inc.
 [FRF]    Frame Relay Forum Glossary, http://www.frforum.com, 1999.
 [FRF.5]  Frame Relay Forum, Frame Relay/ATM PVC Network Interworking
          Implementation Agreement, December 1994.
 [FRF.8]  Frame Relay Forum, Frame Relay/ATM PVC Service Interworking
          Implementation Agreement, April 1995.
 [FRF.13] Frame Relay Forum, Service Level Definitions Implementation
          Agreement, August 1998.
 [FRMIB]  Rehbehn, K and D. Fowler, "Definitions of Managed Objects
          for Frame Relay Service", RFC 2954, October 2000.

6. Editors' Addresses

 Jeffrey Dunn
 Advanced Network Consultants, Inc.
 4214 Crest Place
 Ellicott City, MD 21043 USA
 Phone: +1 (410) 750-1700
 EMail: Jeffrey.Dunn@worldnet.att.net
 Cynthia Martin
 Advanced Network Consultants, Inc.
 4214 Crest Place
 Ellicott City, MD 21043 USA
 Phone: +1 (410) 750-1700
 EMail: Cynthia.E.Martin@worldnet.att.net

Dunn & Martin Informational [Page 23] RFC 3133 Terminology for Frame Relay Benchmarking June 2001

Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Dunn & Martin Informational [Page 24]

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