Filter
Top Products
11-4
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 11 ITU-T Y.1731 Performance Monitoring
Information About ITU-T Y.1731 Performance Monitoring
When the sender MEP receives this frame, it records RxTimeStampb, where RxTimeStampb is the
timestamp of the time at which the frame containing ETH-DM reply information is received.
Two-way frame delay is calculated as:
Frame delay = (RxTimeStampb-TxTimeStampf)-(TxTimeStampb-RxTimeStampf)
Note Discard the frame delay and frame-delay variation measurements when known network topology
changes occur or when continuity and availability faults occur.
For more information on ITU-T Y.1731 performance monitoring, see Configuring IP SLAs
Metro-Ethernet 3.0 (ITU-T Y.1731) Operations in the IP SLAs Configuration Guide.
Frame Loss Ratio
Ethernet Frame Loss Ratio (ETH-LM: FLR), also known as frame loss, measures the availability of
synthetic frames in the network. Availability is defined in terms of the ratio of frames lost to frames sent,
or Frame Loss Ratio (FLR).
Ethernet Synthetic Loss Measurement (ETH-SLM) is used to collect counter values applicable for
ingress and egress synthetic frames where the counters maintain a count of transmitted and received
synthetic frames between a pair of MEPs.
ETH-SLM transmits synthetic frames with ETH-SLM information to a peer MEP and similarly receives
synthetic frames with ETH-SLM information from the peer MEP. Each MEP performs frame loss
measurements, which contribute to unavailable time. A near-end frame loss refers to frame loss
associated with ingress data frames. A far-end frame loss refers to frame loss associated with egress data
frames. Both near-end and far-end frame loss measurements contribute to near-end severely errored
seconds and far-end severely errored seconds, which together contribute to unavailable time. ETH-SLM
is measured using SLM and SLR frames.
There are the two methods of frame loss measurement, defined by the ITU-T Y.1731 standard ETH-LM
and ETH-SLM. However, the Cisco ASR 901 router supports only single-ended ETH-SLM.
Single-ended ETH-SLM
Each MEP transmits frames with the ETH-SLM request information to its peer MEP and receives frames
with ETH-SLR reply information from its peer MEP to carry out synthetic loss measurements.
On-Demand and Concurrent Operations
On-demand IP SLAs SLM operations enable users without configuration access to perform real-time
troubleshooting of Ethernet services. There are two operational modes for on-demand operations: direct
mode that creates and runs an operation immediately and referenced mode that starts and runs a
previously configured operation.
• In the direct mode, a single command can be used to create multiple pseudo operations for a range
of class of service (CoS) values to be run, in the background, immediately. A single command in
privileged EXEC mode can be used to specify frame size, interval, frequency, and duration for the
direct on-demand operation. Direct on-demand operations start and run immediately after the
command is issued.