802.1ag - Connectivity Fault ManagementTutorial – Part 1

Dinesh Mohan

July 12, 2004

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802.1ag PAR Overview

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802.1ag Scope

• “This standard specifies protocols, procedures, and managed objects to support transport fault management. These allow discovery and verification of the path, through bridges and LANs, taken for frames addressed to and from specified network users, detection, and isolation of a connectivity fault to a specific bridge or LAN”

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802.1ag Purpose

• “Bridges are increasingly used in networks operated by multiple independent organizations, each with restricted management access to each other’s equipment. This standard will provide capabilities for detecting, verifying and isolating connectivity failures in such networks”

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802.1ag Reason for Standardization

• Growing interest in the use of Fault Management tools within enterprise and provider networks

• Such tool needed for established operational practices

• Existence of similar tools e.g. – ATM’s “continuity check”, “Loopback” and “multiple Loopback” and – IP’s “ping” and “traceroute”

• Interest and activities within ITU-T and MEF have further highlighted the need for these fault management tool

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OAM Framework

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Ethernet OAM Layering

CE U-PE U-PEN-PEN-PE CEB B P P P PDevice View

Ethernet Layer

Eth Access MPLS Core MPLS Access

Customer CustomerService Provider

• Example: network/service with Ethernet & other technologies

• The Ethernet Layer implies the visibility to Ethernet frames– BUT Flat! Difficult to manage and identify accountability

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OAM Domain – Service/Network

Eth Access MPLS Core MPLS Access

Customer CustomerService Provider

Customer Domain

Provider Domain

Operator Domain Operator Domain

Operator Domain

• Solution: OAM Domains

• Domains necessary to bound OAM Flows & OAM responsibilities

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Maintenance Entity Points (MEP) & Maintenance Intermediate Points (MIP)

Network OAM

Service OAM

Customer Domain

Provider Domain

Operator Domain Operator Domain

Operator Domain

Eth Access MPLS Core MPLS Access

Customer CustomerService Provider

MPLS Domain MPLS Domain

Maintenance Entity PointMaintenance Intermediate Point

PW/MPLS OAM

• MEPs initiate/terminate/react to all OAM flows

• MIPs react to some OAM flows [Optional]

• MEPs & MIPs dependent on Business Models & Deployment Scenarios

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Ethernet MEPs & MIPs

CustomerEquipment

CustomerEquipment

Operator ABridges

Operator BBridges

ETH

ETY

1 2 3 4 5 6 7 8 9

• Another representation for positioning of MEPs and MIPs on devices with consideration for ingress and egress.

Maintenance Entity PointMaintenance Intermediate Point

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Maintenance Entities Mapped

• Example MEs identified– 2 Service Providers (SP1 & SP2)– SP2 has two domains (operators)– MEs 1,2,3,4 are required for Business relationship– MEs 5,6 are required for convenience

Customer CustomerService Provider

1. UNI_C-UNI_C ME2. UNI_N-UNI_N ME3. UNI ME 3. UNI ME

SP 1 SP 2 SP 2

4. E-NNI ME

5. Inter-domain ME (SP)

6. Intra-domain ME 6. Intra-domain ME6. Intra-domain ME (Operator)

UNI UNIE-NNI

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End-to-end OAM – 2 Models

• Provider End-to-end OAM? CE-CE (terminating UNIs)– 2 Possible Models

Strong-Trust E-NNI• ME (3) + ME (2) + ME (3)

Weak-Trust E-NNI• ME (3) + ME (6) + ME (4) + ME (5) + ME(3) or• ME (3) + ME (6) + ME (4) + ME (6) + ME(3)

Customer CustomerService Provider

1. UNI_C-UNI_C ME2. UNI_N-UNI_N ME3. UNI ME 3. UNI ME

SP 1 SP 2 SP 2

4. E-NNI ME

5. Inter-domain ME (SP)

6. Intra-domain ME 6. Intra-domain ME6. Intra-domain ME (Operator)

UNI UNIE-NNI

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Maintenance Entities – P2P Case

• All MEs may not be needed always

• MEPs realize Maintenance Entities (MEs)

ETH_TFPETH_FP ETH_FP

ETHFPPLink ETH_FP

ETH_TFPETH_FP

ETHFPPLink

Service provider Y

User X User X

UNI_C to UNI_C maintenance entity

UNI_N to UNI_Nmaintenance entity

IntraDomain ME

UNI UNI

Access Link ME Access Link ME

NetworkOperator B

ETHFPP Link

NNI

InterDomain ME

IntraDomain ME

NetworkOperator AETH_TFP

ETH_FP ETH_FP

ETHFPPLink ETH_FP

ETH_TFPETH_FP

ETHFPPLink

Service provider Y

User X User X

UNI_C to UNI_C maintenance entity

UNI_N to UNI_Nmaintenance entity

IntraDomain ME

UNI UNI

Access Link ME Access Link ME

NetworkOperator B

ETHFPP Link

NNI

InterDomain ME

IntraDomain ME

NetworkOperator A

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Maintenance Entities – MP2MP Case

ETH_TFPTH_FP ETH_FP

ETHLink ETH_FP ETH_FP

ETHLink

ETH_TFPETH_FP

ETHLink

ETH_FPETHLink

Service Provider Y

Network Operator BNetwork Operator AUser X User X

UNI NNI UNI

UNI

ETH_TFPETH_FP

ETH_TFPETH_FP

ETHLink

UNI

ETH_FP ETH_FP

UNI_C to UNI_C maintenance entities

UNI_N to UNI_N maintenance entities

Intra Domain MEs Intra Domain MEs

Access Link MEs Access Link MEsInter Domain ME

ETH ETH

• All MEs may not be needed always

• MEPs realize Maintenance Entities (MEs)

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Maintenance Entities – CPE based Network Demarcation Access

• All MEs may not be needed always

ETH_FP

Service. Provider YNetwork Operator B

User X

UNI_C to UNI_C ME

UNI_N to UNI_N ME

Access Link ME

ETH_TFP ETH_FP

User X

Access Link ME

Extension Link ME

User Location

UNI_NP to UNI_NP ME

UNI ETH_FP

ETH Link

Private NNI

ETH_FP

Network Operator A

ETH Link

NNIETH_FP ETH_FP ETH_FP

ETH FPP Link

UNI

ETH FPP Link

ETH_TFP ETH_FP

NDD

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Maintenance Entities – CPE based Network Demarcation Access

• All MEs may not be needed always

1 2 3 4 5 6 7 8 9

ETH_FP

Service. Provider YNetwork Operator B

User X

ETH_TFP ETH_FP

User X

User Location

UNI ETH_FP

ETH Link

Private NNI

ETH_FP

Network Operator A

ETH Link

NNIETH_FP ETH_FP ETH_FP

ETH FPP Link

UNI

ETH FPP Link

ETH_TFP ETH_FP

NDD

NDD

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Service/Network OAM – How does it come together?

Ethernet link OAM

PW/MPLSOAM

EoSONET OAM

Other OAM

Network OAM

Service OAM

Transport Links

Network

Services

• OAM Interworking possible to utilize OAM across Layers

• However, each layer must support OAM capabilities independently

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Connectivity Fault Management Functions

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CFM Functionality

• a) CC – Continuity Check• Multicast unidirectional heartbeat • Use: Fault Detection

• b) Loopback• Unicast bi-directional request/response• Use: Fault detection, verification

• c) Traceroute• Multicast request/unicast responses• Use: Fault Isolation

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Other OAM Functionality (out of scope for .1ag)

• d) Discovery– i) Service

• e.g. discover all PEs supporting common service instance

– ii) Network• e.g. discover all devices (PE and P) common to a domain

• e) AIS/RDI• Use: E<->W Fault propagation, Alarm Suppression

• f) Performance Management

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CFM Functions mapped to MEs

Customer CustomerService Provider

1. a, b, c2. a, b, c

• Note: Specifically for ME (3) and ME (4)– IEEE 802.3ah OAM can be used for network/link OAM when UNI/E-NNI is an Ethernet link– When single service carried across a link, network OAM can map to service OAM

3. a, b, c, e

SP 1 SP 2 SP 2

3. a, b, c4. a, b, c

5. a, b, c

6. a, b, c 6. a, b, c6. a, b, c

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Summary

• Ethernet moving into Provider Networks

• Providers require fault management tools to manage their networks

• High Industry interest in Ethernet connectivity fault management tools