Ethernet OAM Overview

Operations, Administration & Maintenance Standards

Ethernet Operations, Admin & Maintenance

OAM standards developed to make Ethernet carrier grade

Protocols developed to enable operationally efficient carrier

Ethernet services over multi-vendor, multi-operator networks

Key Functions

Proactive network and service monitoring

Rapid fault detection & isolation

Performance / Service Level Agreement (SLA) parameters

measurement: on-demand or continuously

Service usage measurement for billing & capacity management

When Deployed End-to-End

Ethernet becomes carrier grade, capable of carrying real-time,

critical services with high availability and QoS

Ethernet OAM Standards Overview

Core Access

10/100/GbE

Base TX / FX /

LX / SX

MEF & ITU-T Y.1731 Service

802.1ag, Y.1731, MEF Connectivity

IEEE 802.3ah Link

Access OAM Layer

Customer

Network

Customer

Network

Transport

Network

Demarcation

Point

Standards

OAM Layer Function / Focus

Service end-to-end service (customer) view, reflected in SLAs

Connectivity Network & service connectivity & performance monitoring, topology-aware, multi-domain

Link focused on single-hop links, 1st mile transport

802.3ah Link Layer OAM

Designed for 1st mile / single-hop links

Typically Provider Edge (PE) to Customer Edge (CE)

Does not propagate beyond the link

Key functions:

Discovery: demarcation point device discovery & loopback capability

Remote failure indication: dying gasp, link fault & critical events

Fault isolation: customer or provider network, unidirectional failures

Port-level loopback: remote or locally activated, layer 1 only, disruptive

Performance & Status Monitoring with threshold alarms

ProvidersNetwork

1st Mile

% frame errors

# coding symbol errors

Unrecoverable error(e.g. power: dying gasp)

LOS (directional)

Critical events

stats

alarms

OAMPDUs:

- Loopback

- Continuity

Connectivity & Service OAM

End-to-End Ethernet Service OAM

IEEE 802.1ag, ITU-T Y.1731 and MEF

OAM standards are based on a common

multi-domain network model

Model reflects services delivered by

multiple providers at different levels

Goal is to ensure OAM is contained

within pre-defined maintenance levels

Customer

Site 1

Operator 2Operator 3

Provider

CustomerCustomer

Site 2

Operator 1

Access Links, 802.3ah(fail-over link in grey)

Service Demarc

802.1ag

Maintenance Intermediate Point (MIP)

Maintenance Endpoint (MEP)

CPE CPE

Provider Domain

Operator A Bridges

Customer OAM Level

Provider OAM Level

Operator OAM Level

Link OAM

Layer 2

Data Path

Operator B Bridges

Multi-Domain Network Model

OAM Management Entities & Components

Maintenance Intermediate Point (MIP)

Maintenance Endpoint (MEP)

Acronym Description

MEP Maintenance Endpoint

MIP Maintenance Intermediate Point

ME Management Entity (relationship between 2 MEPs)

MA / MEG Maintenance Assc (802.1ag) / Entity Group (Y.1731)

Logical Group of MEs at same level

on same S-VLAN

Pt-to-Pt or Multipoint EVC

Operator A

Operator B

Service Provider (S)

B

SS

B

B

B

B

B

B

BS

B

AA

A A

A

A

Operator A MEG

Operator A ME

S

A A

S

S

A

802.1ag / Y.1731 Connectivity Fault Management (CFM)

Fault Detection using Continuity Check Messages

EVC

Failure

Alarm

CCM

NOCCCM Timeout

Alarms

Fault Verification Using Loopback Messages (Ping)

EVC

Failure

LBR

LBM

Fault Isolation Using Linktrace Messages

EVC

Broken Link

LTR

LTM

Fault Notification, Alarm Indication Signal (Y.1731 only)

EVC

Broken Link

AIS

Per Service

Alarms

Can also be used to loopback a test traffic stream

(e.g. throughput measurement)

802.1ag

Unicast only

Y.1731

Unicast & multicast

Y.1731 Performance Monitoring (PM)

DMM time-stamped packet sent to far-end

Far-end device responds with DMR

carrying original timestamp

Originating device compares timestamp to

current time to calculate delay

No clock-sync required between endpoints

Frame Loss Ratio Using CCM (dual-ended)

EVC

Broken Link

Tx / Rx Counters

CCM

Frame Delay (FD) / Delay Variation (FDV)

Measurements, 1-Way

1DM time-stamped

packets

Synchronized Clocks

DMR

DMM

EVC

DMM

DMR

Frame Delay (FD) / Delay Variation (FDV)

Measurements, Round-Trip

Connectivity & Services OAM Summary

Accedian Networks has also developed in-service throughput testing

based on Y.1731 LBM / LBR frames (patent pending)

OAM Function 802.1ag Y.1731 Method

CFM

Fault Detection CCM

Fault Verification /

Loopback LBM / LBR (Ping)

Fault Isolation LTM / LTR

Discovery LTM / LTR & Multicast LBM*

Fault Notification AIS / RDI

PM

Frame Loss CCM, LTM / LTR

Frame Delay DM (1 way), DMM / DMR

Delay Variation DM (1 way), DMM / DMR

* Y.1731 only

Incorporating 802.1ag/Y.1731 into Service Endpoints

802.3ah (link OAM) not interoperable with 802.1ag / Y.1731 (Connectivity OAM) -

some vendor-specific methods & emerging MEF 17 standard

802.3ah lacks: performance monitoring, fault propagation beyond 1st mile (link

faults not sent end-to-end), link trace & loopback response for fault verification &

isolation, L2/3 & per-flow traffic loopback.

NIDs enable 802.1ag / Y.1731 OAM functionality end-to-end

Demarcation

Point

CPE CPE

802.3ah

or no OAM

802.3ah

or no OAM

Demarcation

Point

CPE CPE

802.1ag / Y.1731 OAM

802.1ag / Y.1731 OAM

ProvidersNetwork

ProvidersNetwork

SukhoiHighlightNetwork Interface Device

Ethernet OAM is a good start but not sufficient

ProvidersNetwork

Over 100 remote base

stations homing into the

MSC

MSC / BSC

Challenging OAM PERFORMANCE of

High speed/high capacity pipes with 100s of

service flows handed-off at MSCs.

Ethernet OAM/PMs is often only supported

on a per-port or low-count VLAN basis and

only in a round-trip fashion.

Aggregation Network Elements having a

hard time computing high-accuracy/high

granularity one-way OAM/PMs for several

100s of flows on a single high speed port.

NE-based Ethernet OAM/PM currently

unusable for throughput verification, a key

SLA component

Forklift upgrades often required

Service Assurance vendors supporting

advanced, standards-based Ethernet

OAM/PM often brought-in to the rescue

Single 1G or 10G pipe

with hundreds of service

flows.Aggregator

OAM Function

ImplementationSoftware based implementation

(network processor)Dedicated silicon packet processing, hardware-based, real-time

Delay / Delay Variance

Measurement

~1 ms resolution, variable accuracy

not sufficient to monitor real-time

services and SLAs

1 s delay / jitter measurement resolution with < 20 s accuracy

One-Way Delay

Measurements

Typically only provides round-trip

measurements. SLAs commonly

specify one-way delay requirements.

Provides both one-way and round-trip measurements in multi-flow,

multi-site, multi-service and multicast configurations.

Multi-Flow MonitoringNEs can monitor A Few Flows -varies by network element & traffic load

Up to 100 Concurrent Flows / SLAs with no performance hit

Loopback Testing

Limited OAM loopback packet

processing capacity; delay added to

loopback traffic. No throughput testing.

Hardware-based architecture enables advanced, in-service throughput

testing of CIR, EIR up to full wire-speed

Frame Loss

Measurement

Standards provide synthetic frame loss based only on OAM frames

In-line, hardware-based packet processing provides Real Frame Loss

(RFL) - orders of magnitude more precise than Synthetic

measurements. RFL is required to validate high-performance SLAs.

OAM Uniformity over

Multi-Vendor / Carrier /

Technology Networks

Interoperability, OAM version and

feature support uneven.

Enables an overlay of the latest , full OAM functionality and advanced

complementary testing end-to-end without network element upgrades

Service creation,

traffic conditioning &

OAM alignment

Many access platforms do not support

advanced rate limiting, filtering and

shaping to optimize QoS.

OAM should be established at the service endpoints to provide valid

results. NIDs provide service mapping, OAM and conditioning at the

service demarc for complete end-to-end coverage.

802.1ag / Y.1731

Reach

OAM in access platforms limits visibility

of the problematic last mile, leaving this segment unmanaged.

OAM enabled in NIDs at the demarc point provide connectivity and

service OAM visibility directly to the customer site

Deploying 802.1ag/Y.1731 using NIDs vs. NEs

Ethernet OAM, Conclusions

Establishing end-to-end OAM is a key part of delivering

high-performance, carrier-grade Ethernet services.

OAM CFM provides operational efficiency, rapid per-

service fault identification, verification and isolation for

high availability services over multi-operator networks.

OAM Performance Monitoring provides means to

monitor and report key SLA and service usage metrics.

Standards are evolving: multi-vendor interoperability

issues and varying levels of feature support is common.

Establishing OAM using NIDs provides uniform, end-to-

end service management over any network topology.

Hardware-based NIDs also enable highly scalable

service creation and assurance functionality directly at

the service endpoints.