Accedian Networks - Ethernet OAM Overview.pdf

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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 Demarcation Point

10/100/GbE Base TX / FX / LX / SX

Transport Network

Customer Network

Standards

Access

Core

Customer Network

Access

OAM Layer

MEF & ITU-T Y.1731

Service

802.1ag, Y.1731, MEF

Connectivity

IEEE 802.3ah

Link

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 OAMPDUs: - Loopback - Continuity

Provider’s Network

 % frame errors  # coding symbol errors  Unrecoverable error

alarms

1st

 Key

stats

Mile

(e.g. power: dying gasp)

 LOS (directional)  Critical events

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

Connectivity & Service OAM Multi-Domain Network Model Provider Domain Operator A Bridges

Maintenance Intermediate Point (MIP) Maintenance Endpoint (MEP)

Operator B Bridges

CPE

CPE

Customer OAM Level Layer 2 Data Path

Provider OAM Level

Operator OAM Level Link OAM

End-to-End Ethernet Service OAM Access Links, 802.3ah







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

(fail-over link in grey)

Service Demarc

Customer Customer Site 1

Customer Site 2

Provider Operator 1 802.1ag

Operator 2

Operator 3

OAM Management Entities & Components Service Provider (S) Operator A Operator B

S A

A A

A

A

A

S

S

A

B

S B

B B

B B

Operator A MEG

B B

A

S B

S

Operator A ME A

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)

Maintenance Intermediate Point (MIP) Maintenance Endpoint (MEP)

 Logical Group of MEs  

at same level on same S-VLAN

 Pt-to-Pt or Multipoint EVC

802.1ag / Y.1731 Connectivity Fault Management (CFM) Fault Detection using Continuity Check Messages

Fault Verification Using Loopback Messages (“Ping”) Can also be used to loopback a test traffic stream (e.g. throughput measurement)

NOC

CCM Timeout Alarms

EVC Failure CCM Alarm

Fault Isolation Using Linktrace Messages

802.1ag Unicast only Y.1731 Unicast & multicast

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

EVC Broken Link LTM LTR

EVC Failure LBM LBR

EVC Broken Link AIS

Y.1731 Performance Monitoring (PM) Frame Delay (FD) / Delay Variation (FDV) Measurements, 1-Way

Frame Loss Ratio Using CCM (dual-ended)

Synchronized Clocks 1DM time-stamped packets

EVC Broken Link CCM Tx / Rx Counters

Frame Delay (FD) / Delay Variation (FDV) Measurements, Round-Trip



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

DMM

DMR EVC DMM DMR

Connectivity & Services OAM Summary

OAM Function

CFM

802.1ag

Y.1731

Fault Detection





CCM

Fault Verification / Loopback





LBM / LBR (“Ping”)

Fault Isolation

 

LTM / LTR

Fault Notification

  

AIS / RDI

Frame Loss



CCM, LTM / LTR

Frame Delay



DM (1 way), DMM / DMR

Delay Variation



DM (1 way), DMM / DMR

Discovery

PM



* Y.1731 only

Method

LTM / LTR & Multicast LBM*

Accedian Networks has also developed in-service throughput testing based on Y.1731 LBM / LBR frames (patent pending)

Incorporating 802.1ag/Y.1731 into Service Endpoints

802.3ah or no OAM

802.3ah or no OAM Provider’s Network

CPE

CPE 802.1ag / Y.1731 OAM

Demarcation Point

Demarcation Point

Provider’s Network CPE

CPE 802.1ag / Y.1731 OAM



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

Ethernet OAM is a good start but not sufficient 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

Over 100 remote base stations homing into the MSC

Provider’s Network Single 1G or 10G pipe with hundreds of service flows. Aggregator

MSC / BSC

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

OAM Function Implementation

Software 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 μs delay / jitter measurement resolution with < 20 μs 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 Monitoring

NEs 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

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 perservice 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-toend service management over any network topology.



Hardware-based NIDs also enable highly scalable service creation and assurance functionality directly at the service endpoints.

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