📄 rfc3133.txt
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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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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RFC 3133 Terminology for Frame Relay Benchmarking June 2001
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